Advances in Parasitology Volume 09

Advances in

PA RASlTOLOGY

VOLUME 9

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Advances in

PARASITOLOGY Edited by

BEN DAWES Professor Emeritus, University of L o d n

VOLUME 9

ACADEMIC PRESS, INC. IHarcourl B r a t r IovanovIc h, Publishrrrl

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ACADEMIC PRESS INC. (LONDON) LTD. Berkeley Square House Berkeley Square London, W1X 6BA U.S. Edition published by ACADEMIC PRESS, INC.

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Copyright 0 1971 by ACADEMIC PRESS INC. (LONDON)LTD

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Library of Congress Catalog Card Number: 62-22124 ISBN: 0-12-031709-5

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9 8 7 6 5 4 3 2

CONTRIBUTORS TO VOLUME 9 *EDER L. HANSEN,Clinical Pharmacology Research Institute, Berkeley, California, U.S.A. (p. 227)

I. G. HORAK,MSD ( P T Y )LTD, 142 Pritchard Street, Johannesburg, Republic of South Africa (p. 3 3 ) W. GRANTINCLIS,South Australian Museum, Adelaide, South Australia 5000 (P. 185) J. B. JENNINCS, Department of Zoology, University of Leeds, England (p. 1)

THOMAS A. MILLER, Jensen-Salshery Laboratories, Division of RichardsonMerrell Inc., Kansas City, Missouri, U.S.A. (Q. 153) RALPHM ULLFR, London School of Hygiene and Tropical Medicine, London WCI, England (p. 73) *PAULH. SILVERMAN, Department of Zoology, University of Illinois, Urbana, Illinois, U.S.A. (p. 227)

* Authors in the section “Short Rrvicus” V

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PREFACE This volume contains reviews on various topics by experts, working in Leeds and London, England; Urbana, Illinois and Kansas City, Missouri, U.S.A.; Johannesburg, South Africa; and Adelaide, South Australia. J. B. Jennings has written about Parasitism and Commensalism in Turbellaria, Ivan G. Horak on Paramphistomiasis of Domestic Ruminants, Ralph Muller on Dracunculus and Dracunculiasis (hitherto known as Dracontiasis), Thomas A. Miller on Vaccination against the Canine Hookworm Diseases, and W.Grant Inglis on Speciation in Parasitic Nematodes. In the one updated review, Paul H. Silverman has been assisted by Miss Eder L. Hansen in dealing with in vitro Cultivation Procedures for Parasitic Helminths. The origins of parasitism in helminths may be sought in turbellarians, for in every one of the five orders commonly recognized some representatives live in close association with other animals, mainly echinoderms, crustaceans and molluscs but less commonly annelids, sipunculids, xiphosura and coelenterates, teleost fishes and elasmobranchs, not to mention other turbellarians. Turbellaria participating in these close partnerships belong to at least 27 families, and only freshwater and terrestrial triclads are entirely freeliving in habit. Notably, these associations often show host-type specificity, related forms of a single family tending to associate with one type of host, as most Umagillidae associate with echinoderms. However, in only a few out of many such associations are the turbellarians truly parasitic, the majority living as commensals, Parasitic turbellarians do not represent the climax of commensalism and Temnocephalids entered into an ancient association with crustaceans without developing parasitism. However, the wide variety of associations with other animals range from ecto- and endo-commensalism to true parasitism, and Jennings takes the five great groups of Turbellaria in turn in considering such relationships in some detail. The salient emergent conclusion is that remarkably few turbellarians are parasitic in the usually accepted sense of the term; most of them are Rhabdocoela such as the genera Acholades, Fecampia, Glanduloderma, Kronborgia and Oikiocolax. All these forms get all their nourishment from the host, and their alimentary system is much reduced by comparison with the typical rhabdocoele condition. Kronborgia and Oikiocolax bring about castration of the hosts, and the former is lethal to the hosts. Forms which live in the “kidneys” and their ducts (e.g. Grafllla) and subcutaneous tissue dwellers (e.g. Ichthyophaga) may also be parasitic, but more information must be sought about modes of life and metabolism of species which are apparently parasitic. Asexual reproduction such as occurs in trematodes and cestodes is little known in turbellarians, although Microstomum produces chains of zooids, and transverse fission is seen in Dugesia and other genera. The loss of epidermis and development of cuticle is worthy of study in greater (ultrastructural) detail in Temnocephalids, and it would no doubt be interesting to know why large deposits of glycogen vii

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Vlll

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occur in con~mensalssuch as Syiidc~snzis.The various associations studied, we are told, probably arose from chance contacts which provided food and shelter, thus conveying selective advantage. Intensifications of such contacts could have given rise to many different degrees of commensalism and in some instances to parasitism. Ivan G . Horak notes that paramphistomiasis is caused by massive infection of the small intestines of sheep, goats, cattle and water buffalo, and is characterized by sporadic epizootics of acute gastro-enteritis which may cause high mortality, especially in young animals. Various paramphistomes have been incriminated in this respect but most of our knowledge concerns Paramphistomum microbothrium in Africa and Israel, P. ichikawai in Australia and Cotylophoron cotylophorum in India. The disease is caused by sexually immature worms, and this adds to the difficulty of specific identifications. After dealing with outbreaks of disease in Africa, Asia, Australasia, Eastern Europe, Russia and the Mediterranean countries, Horak goes on to consider the life cycle characteristics of P . microbothrium, P. ichikawai, Cotylophoron cotylophorum and Calicophoron calicophorum, and then subsequent development in definitive hosts. One point made is that in cattle paramphistomes grow larger, migrate more rapidly, mature sooner, live and produce eggs for a longer period, and survive migration in greater numbers than occurs in either sheep or goats. Most readers will not need reminding about the outstanding difficulties of experimental work with such large hosts as these. Much field work has been carried out and is considered in the particular area of immunology, and it is shown that previous infection in adult cattle can supply a degree of resistance to subsequent massive infections such as produce paramphistomiasis in the field. Multiple infections in sheep result in partial immunity, but the worms can excyst and attach in the small intestines, whereas in cattle subsequent infections are eliminated. There is an interesting parallel, I might point out, with the elimination of flukes in cattle in fascioliasis. However, Horak has reported successful immunization of sheep, goats and cattle against massive infections of P . microhothrium. He has also shown that immunity to paramphistomiasis, especially in sheep, depends on such factors as the number of metacercariae ingested and thus the number of young flukes which excyst and attach themselves to the mucosa of the small intestines. Immunity does not depend on the number of worms present in the rumen, and cattle or sheep with numerous flukes in thc rumcn may be susceptible, while other hosts with smaller numbers of flukes in the rumen may be immune. This is true when X-irradiated metacercariae are used to produce immunity: many young flukes excyst and attach to the intestinal wall, but many are lost during or after migration to the rumen, leaving small fluke burdens in the rumen, and yet cattle are then completely immune to reinfection. In sheep, immunity seems to depend on the continued presence of flukes, and anthelmintic treatment lowers the degree of immunity achieved. Horak also discusses the effects of immunity on the flukes, and one effect is retardation of growth in immune hosts. Some observations on serology have also been made and pathological studies include notes on clinical signs,

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ix

clinical pathology and pathological anatomy. Pathogenesis is studied in relation to worm burden and fatal acute paramphistomiasis is produced in stabled sheep with P . microbothrium in numbers greater than 40000: in stabled cattle the corresponding number is about 160 OOO flukes. Epizootiology of the disease is also considered in detail : the intermediate snail hosts (Bulinus tropicus and B. truncutus) are prolific breeders found in streams, ponds, pools, water troughs, marshes and other locations at any altitude up to 6800ft. They can produce more than sixteen eggs per day for an experimental period of thirty days. The eggs start hatching after seven days and young snails in turn lay eggs when about four weeks old. Within the snails a massive multiplication of P . microbothrium may occur, cercariae being shed for many months. In late African summer the grass seeds become unpalatable; only green grazing surrounds natural water masses where sheep, cattle and calves become heavily infected with amphistomes. In other countries conditions vary. Treatment is also considered and a number of anthelmintics are effectual against adult parasites, notably hexachlorophane, hexachloro-ethane-bentonite suspension, tetrachloridifluoro-ethane, bithionol and combinations of certain drugs. Since 1962, remedies against immature forms have been available and some are effectual in sheep but none has proved effectual in cattle. This problem is discussed in some detail, after which methods of control are considered, although methods for the prevention of paramphistomiasis have not yet been devised. Many of the measures used are based on practical observations which are treated in great detail. At present, control depends on keeping livestock away from potentially dangerous areas when climatic conditions produce massive concentrations of infected snails and myriads of metacercarial cysts. Ralph Muller notes that Drucunculus has been known from ancient times as an agent of the disease dracontiasis (or, as he would prefer to call it, dracunculiasis). This is a disease characterizing human poverty mainly in tropical rural communities which lack suitable water supplies. In spite of the hideous culmination as the female’s body emerges from an ulcer on arms, legs, breasts or other parts of the body, this is not a lethal disease when there are no pathological complications, although these are not uncommon and produce crippling effects. Muller first deals with the morphology of both sexes of the parasite, notes the paucity of our knowledge on physiology and then considers the life history. The mature female worm may liberate into water more than one half million embryos, and smaller numbers thereafter, about three millions being available in her body. Development continues in some species of Cyclops, in which two moults yield a third stage larva that can be activated by the action of acids. In experimental animals larvae occur in the duodenum four hours after infection in drinking water and are soon commencing a long migration through the tissues of the body to widely separated regions. The route of migration is difficult to determine, especially in the early stages when the young worms are microscopically small, and special techniques which can be used are noted. The female worms emerge, usually in the extremities, 10-14 months after infection, giving an approximately annual life cycle. Much useful information is given on maintenance

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PREFACE

of Dracunculus in the laboratory, in both the intermediate and definitive hosts. Various species are characterized and discussed in terms of the species problem within the genus. The greater half of the review deals with dracunculiasis, one section with epidemiology, geographical distribution, the economic effects of disease, the effect of climate and water sources on seasonal incidence in ponds and wells, and the species of Cyclops that serve as vectors of the disease. Another section is concerned with pathogenesis including sites of emergence, numbers of worms emerging, clinical symptoms, the simple course of the disease, secondary infection and the failure of worms to emerge. Diagnosis is considered from clinical, parasitological and immunological points of view, with information bearing on the surgical removal of adult females. Chemotherapy is not overlooked, and mention is made of the transformation of treatment brought about by the use of niridazole (“Ambilhar”) and thiabendazole (“Mintezol”). Lastly, there is an account of methods of prevention and the control of dracunculiasis by various means, notably chemical treatment of ponds and wells and the general improvement of water supplies. Thomas A. Miller considers that hookworm disease of dogs has been neglected by comparison with the same disease of Man, text book accounts agreeing with one another largely because of the deficiency of recent work. Yet there may be four species of hookworms which produce disease in dogs, namely Ancylostoma caninum, A . braziliense, A . ceylanicum and Uncinaria stenocephala. The three species of Ancylostoma are tropical or subtropical forms but U.stenocephala occurs in wild Canidae and Vulpidae north and south of the tropical hookworm belt and even in near Arctic regions. The life cycle of all species is direct, but transport hosts have been noted but are unnecessary, so enormous is the biotic potential of the canine hookworms. A heavily infected pup may pass five million eggs of A. caninum per day for more than four weeks. Miller describes the life cycles in detail in the dog, and he deals with prenatal-colostral infection although in experimental infections less than 2 % of parasites were acquired by the intra-uterine route. The term “colostral” is also considered unsatisfactory for the reason that larvae have been recovered from the milk of bitches up to twenty days after parturition. There is also some information dealing with abnormal hosts; in the mouse, third stage larvae of A. caninum accumulate and persist almost throughout life. In discussing canine hookworm diseases (the plural indicates that it is necessary to qualify about the species concerned), the mechanisms by which anaemia is caused are various; intravascular haemolysis, myelotoxins and depressed erythropoiesis, intoxication from worm metabolic products, and secondary microbial infection. During the last decade only, it has been proved that one of these factors only (i.e. intestinal haemorrhage) can be regarded as the primary cause of pathogenesis. In dealing with specific hookworm disease, Miller shows that the signs of infection are related to its intensity, the age of the host, nutritional states, and the presence of acquired and age resistance. The question of immunity is dealt with in detail in respect of age, infection with normal and with attenuated larvae, and vaccination. One section of the review is devoted to the practical use of the newly instituted

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xi

Canine Hookworm Vaccine. Immunity against infection does not usually include destruction of the larvae or complete elimination of entire intestinal challenge infections. The demonstration of hookworm eggs in faeces should not be the prime criterion of diagnosis of clinical hookworm disease; more accurate diagnosis is based on haematological observations and clinical examinations. The review of W. Grant Inglis, which contains ten sections between Introduction and Conclusions, is concerned with the extent to which speciation in parasitic nematodes has been dependent upon or independent of their hosts in the light of recent studies of speciation in free-living animals. He defines speciation as a process of multiplication by which one genetical population divides into two such populations between which genetic interchange is not possible. In this sense, speciation is the crucial process upon which evolution depends, and the problem is to explain the process by which or in consequence of which the genetic continuity between the members of one population can be broken, i.e. how the members of once interbreeding populations can become and remain distinct in reproductive processes and so protect their genetic integrity. After he has devoted a section to species, Inglis in later sections discusses species characteristics, speciation in freeliving animals, speciation and the origin of parasitism, and the analysis of speciation in parasites. He then devotes other sections to speciation in the genus Parathelandros (parasites of reptiles and amphibians, but in consideration here are parasites of Australian frogs), speciation in the oxyuridae of primates, species flocks, speciation and host specificity, and general speciation. To try to outline here the ideas discussed by Inglis would be futile but is unnecessary, but final discussion is interpreted in terms of an hypothesis of sympatric speciation. As a general case Inglis assumes one parasite occurs in a range of diverse hosts characterized only by a common ecology and common feeding habits. If that host group divides and the parasite is also divided the parasites can speciate. If or when the host groups come together, the two parasites can divide the total host environment between them, either by each occupying a distinct part of the body of each host, or by each occupying a restricted range of hosts. By a continuous series of speciations and niche diversifications the host range of each species would become increasingly restricted and increasingly diversified taxonomically. However, the author does not depend on this model, and he considers less strict hostparasite parallelisms which give the impression that parasites have speciated and radiated to occupy each environment as it appeared. And, in conclusion, there is an interpretation of parasite speciation in terms of an hypothesis of allopatric speciation, which explains the presence of flocks of parasites and intra-host restricted distribution of taxonomically similar parasites, as well as explaining all those other features covered by an hypothesis of hostdependent speciation. In bringing up to date his review on in v i m cultivation procedures for parasitic helminths (1965), Paul H. Silverman has been assisted by Miss Eder L. Hansen. Together and in respect of recently published works they have analysed closely all available data, indicating areas in which some

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additional research is desirable. They have also emphasized the application of in vitro methods to the elucidation of’ problems coiicerning parasite physiology and development. In applying in vitro techniques to helminths there are several limitations. So far, only very few species out of an enormous assemblage have been studied, and few of the studies made have been sufficiently sustained to warrant adequate generalizations, or even to certify the reproducibility of a particular technique. Marked differences in in vitro cultural requirements seem to exist, and no obligate helminth parasite has been cultured through successive generations. Because such limiting factors exist, the writers have considered axenic culture of free-living and insect or plant parasitic nematodes when necessary. Environmental conditions considered include host stimuli and trigger mechanisms, precise conditions that are required during successive stages of development, factors that influence development and organogenesis as distinct from maintenance or survival, immunological inhibition, the toxicity and elimination of metabolic waste products and protreatment factors acting on the parasite before cultivation. Separate sections deal with techniques, trigger mechanisms of various kinds, media and various conditions, recent studies concerning trematodes, cestodes and nematodes, and applications of metazoan in vitro cultivation procedures. In a concluding statement there is mention of considerable progress in recent years, “guideposts” having been set up to assist future researchers in this field. Experimental biologists can now utilize culture systems to obtain basic information on the parasite’s development and interaction with the host, which could lead to new ideas concerning the host-parasite relationship. Finally, I can once more express my gratitude and thanks not only to all the contributors to this volume who have set aside the excitement of research or their leisure hours for the tedium of writing, but also to the members of staff of Academic Press who attend to a thousand important details in the preparation of such a volume as this. I can only hope that they have produced another useful and informative book. “Rodenhurst” 2 Meadow Close Reedley Drive REEDLEY, Nr Burnley Lancashire, England

BENDAWES Professor Emeritus: University of London December 1970

CONTENTS CONTRIBUTORS TO VOLUME 9 ............................................................... PREFACE ..........................................................................................

v vii

Parasitism and Commensalism in the Turbellaria J . B . JENNINGS

I. Introduction ........................................................................... I1. Acoela., .................................................................................. 111. Rhabdocoela ........................................................................... IV. Alloeocoela ........................................................................... V. Tricladida .............................................................................. VI. Polycladida ........................................................................... VII . Discussion .............................................................................. References ..............................................................................

1

2 4

18 19 21 23 27

Paramphistomiasis of Domestic Ruminants I . G . HORAK

I. Introduction .............................. ........................................ ........................................ I1. Pathogenic Species of Paramphistom 111. Life Cycie .............................................................................. IV. Development in the Definitive Hosts............................................. V. Immunity .......................................................... VI . Pathology .............................................................................. VII . Epizootiology .............................................................. ... VIII . Diagnosis .............................................................................. IX . Treatment .............................................................................. X . Control ................................................................................. Acknowledgements .................................................................. References ..............................................................................

33 34 36 40 46 52

63 65 66 68 70 70

Dracunculus and Dracuncdiasis RALPH MULLER

I . Introduction ........................................................................... I1. Dracunculus: Structure and Biology ............................................. I11. Dracunculiasis ........................................................................ Acknowledgements .................................................................. References ..............................................................................

...

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73 75

104 140 140

xiv

CONTENTS

Vaccination Against the Canine Hookworm Diseases

. .

.

THOMAS A MILLER

I Introduction ........................................................................... I1 The Canine Hookworms............................................................ 111. Life Cycles .............................................................................. IV The Canine Hookworm Diseases ................................................ V Immunity to Infection with Hookworm.......................................... VI. Practical Use of CanineHookworm Vaccine.................................... References ..............................................................................

. .

153 154 155 158 165 178 180

Speciation in Parasitic Nematodes .

W GRANT INCLIS

185 I . Introduction ........................................................................... 187 I1 Species .................................................................................. 189 111 Species Characteristics ............................................................... 190 IV. Speciation in Free-living Animals ................................................ 192 V Speciation and the Origin of Parasitism.......................................... 195 VI The Analysis of Speciation in Parasites.......................................... 198 VII Speciation in the genus Puruthelundros (Geographic Speciation) VIII Speciation in the Oxyuridae of Primates (Phyletic Speciation)............ 200 202 IX Species Flocks ........................................................................ 208 X Speciation and Host Specificity ................................................... 211 XI General Speciation .................................................................. 215 XI1 Conclusions ............................................................................ 218 'References..............................................................................

. . . . . . . . . .

.........

SHORT REVIEWS Supplementing Contributions of Previous Volumes

In vitro Cultivation Procedures for Parasitic

Helminths: Recent Advances

. . I . Introduction ........................................................................... I1. Techniques .............................................................................. I11. Trigger Mechanisms.................................................................. IV. Media and Conditions............................................................... V. Recent Culture Studies............................................................... VI. Applications of Metazoan in virro Cultivation Procedures.................. PAUL H SILVERMAN AND EDER L HANSEN

.

VII Concluding Statement ............................................................... References ..............................................................................

AUTHOR INDEX ................................................................................. SUBJECT INDEX .................................................................................

227 228

230 232 240 241 251 252

259 269

Parasitism and Commensalism in the Turbellaria J. B. JENNINGS

Department of Zoology, University of Lueds, England I. Introduction ....................................................................................... 11. Acoela ............................................................................................. 111. Mabdocoela ....................................................................................... A. Lecithophora: Dalyellioida ..................... .................................. B. Lecithophora:Typhloplanoida ........... C. Temnocephalida ............................. ....................................... IV. Allaocoela ....................................................................................... V. Tricladida .......................................................................................... VI. Polycladida ....................................................................................... VII. Discussion.......................................................................................... References ..........................................................................................

1 2 4 6 13 14 18 19 21 23 21

I. INTRODUCTION The Turbellaria are predominantly free-living predators but each of the five orders contains families with representatives living in association with other animals. The commonest partners with which these associationshave been established are echinoderms (Asteroidea, Ophiuroidea, Echinoidea, Holothuroidea and Crinoidea), crustaceans (Isopoda, Amphipoda and Decapoda), and molluscs (Lamellibranchiata and Gastropoda). Less common are associations with annelids (Polychaeta), sipunculids and arachnids (Xiphosura), and a very few species have become associated with coelenterates (Anthozoa), other turbellarians (Alloeocoela)and lower vertebrates (Elasmobranchiiand Teleostei). The Turbellaria concerned in these associations come from at least twentyseven different families and represent all the major subdivisions of the class, with the exception of the freshwater and terrestrial triclads which are entirely free-living in habit. One striking feature of the associations is the great extent to which they show “host-type” specificity,in that the members of one family tend to be associated With a single type of host organism. Virtually all of the rhabdocoel family Umagillidae, for example, are found in association with echinoderms, and the remaining members occur only in sipunculids. Although a fairly large number of turbellarian species have entered into associations with other animals, relatively few have become parasitic. The others show a range of different types of relationships, and many of these are 1

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difficult to define in strict terms. As a general descriptive term “commensal” is perhaps the most convenient and generally applicable. In many instances the literal interpretation of the term, as implying the sharing of the same food by the turbellarian and its partner, is not entirely valid. In the temnocephalids, for instance, the food consists of various freshwater organisms in addition to particles of the host’s food, and in species like the umagillids other commensal organisms such as ciliate protozoans may form a significant proportion of the diet, Nevertheless the concept of commensalism provides a useful background against which most turbellarian associations can be considered, and it will be used in this way in the present review. It might be thought that the parasitic turbellarians represent a climax to the gradual intensification of the relationship between commensal species and their particular partners, and that the other types of relationship found represent stages in the evolution of the parasitic habit. This may well be correct, but on the other hand there can be no doubt that some of the associations between turbellarians and other animals represent nothing more than end points in the development of those particular associations. The temnocephalids, for example, occur principally on freshwater decapod Crustacea in Central and South America, Madagascar, New Zealand, Australia and some of the islands of the South Pacific. This distribution is interpreted by Baer (1951) as indicating the very ancient nature of the association between flatworm and crustacean since these habitats, originally united by the Palaeoantarctic continent during the early Cretaceous when ancestral parastacid Crustacea were appearing, were separated from each other by the oceans in the middle of the Tertiary period. Despite its long-standing nature, however, this particular association has not developed further towards parasitism. The fact remains, however, that members of the Turbellaria have become involved in a whole variety of associations with other animals, ranging from ecto- and ento-commensalism to true parasitism. They are members of a phylum which is predominantly parasitic in habit, and even if some or all of the associations involving turbellarians are incapable of evolving further, a study of them may well indicate possible ways in which parasitism has become established as the principal mode of life in their phylum. In the present review, therefore, the occurrence of parasitism and commensalism in the Turbellaria will be surveyed systematically throughout the class, and particular attention will be given to any modifications in structure, physiology or life history which appear to be related to the transition from the basic free-livinghabit. 11. ACOELA The Acoela are small worms, one to several millimetres in length, exclusively marine, and generally regarded as the most primitive living turbellarians. Primitive features include the absence of an excretory system and of a permanent lumen to the gut. The food of free-living species consists of bacteria, Protozoa, unicellular algae and similar microscopic particles, and digestion occurs in temporary vacuoles within the syncytial endoderm (Jennings, 1957). Only a few genera (summarized in Table I) have formed associations with

PARASITISM A N D COMMENSALISM IN T H E T U R B E L L A R I A

3

other organisms and so little is known of their biology, and especially of their physiology, that it is impossible to define their exact relationship with the host. A single species, Ectocotylupuguri, is described by Hyman (1951) as living ectocommensally with hermit crabs on the Atlantic coast of North America. There is some doubt, however, whether or not this species is in fact an acoelan and De Beauchamp (1961) places it within the family Monocoelididae (order Alloeocoela) because of the arrangement of the reproductive system and the plicate form of the pharynx. Other salient features of E.puguriare a “degenerate TABLE I Genera of Acoela living commensally with other organisms

Genus

Host

Authority

Fam. Anaperidae Avagina A. glandulifera A . incola A . vivipara

Echinoidea Spatangus purpureus Echitiocardium javescens S. purpureus Echinocardium cordatum

Westblad, 1953 Leiper, 1902; 1904;

Westblad, 1953 Hickman, 1956

Fam. Convolutidae Aphanastoma A. sanguineum A . pallidurn

Holothuroidea Chirodota laevis Myriotrochus rinkii

Beklemischev, 1915 Beklemischev, 1915

Fam. Hallangiidae Aechmalotus A. pyrula

Fam. Otocelididae

Holothuroidea Eiipyrgus scaber

Beklemischev, 1916

Holothuroidea

Otocoelis Chirodota Iaevis 0. chirodotae Acoela of uncertain affinities: Crustacea Ectocotyla hermit crabs E. paguri

Beklemischev, 1916 Hyman, 1951

Suborder Nernertoderrnida Meara M. stichopi

Holothuroidea Stirhopus trernulus

Westblad, 1949

intestine”, which De Beauchamp admits is indicative of acoelan affinities,and a posterior adhesive disc reminiscent of that of the temnocephalid rhabdocoels. The caudal disc is clearly an adaptation for an ectocommensal, or at least epizoic, mode of life, but nothing is known of the diet or feeding mechanism. Thus until the systematic position of the genus Ectocorylu is clarified and more is known of its general biology it is impossible to say categorically whether or not the acoelan grade of organization has proved adaptable to ectocommensalism, whereas that of other turbellarian orders clearly has been capable of such adaptation. Entocommensalism, however, has arisen in a number of acoelan genera, usually with holothurian echinoderms as hosts. Such accounts as are available of these genera tend to be restricted to taxonomic descriptions, but the general

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impression gained from them is that the acoels are truly commensal and not parasitic forms. Westblad (1 949) describes in some detail Meara stichopi, which he found in the intestine and body cavity of the holothurian Stichopus tremulus and, in one instance only, in the body cavity of the related Mesothuria intestinalis. He found no evidence of injury to the host’s tissues, but observed the remains of copepods and diatoms in the acoel’s gut and concluded therefore that M . stichopi is “a harmless commensal”. From the appearance of fixed specimens he deduced that the acoel feeds by protruding a portion of the intestine through the mouth and engulfing its food in an amoeboid fashion, in precisely the same manner as described by Jennings (1957) for the free-living acoel Convolutaparadoxa (= C. convoluta). M . stichopi differs from the free-living acoels in that the epidermis is thicker, lacks rhabdites and has a reduced complement of mucous glands. The brain is reduced also, and the intestine is cellular rather than syncytial. These differences cannot be related to the mode of life, however, since most are shared with the related free-living genus Nemertoderma (Westblad, 1937). Other Acoela from holothurians include Otocoelis chirodotae, from the oesophagus of Chirodota laevis; Aphanostoma sanguineum, from the intestine of C. laevis; A . pallidum, from the intestine of Myriotrochus rinkii; and Aechmalotus pyrula, from the intestine of Eupyrgus scaber (Beklemischev, 1915). All four of these species appear to be commensal with their hosts and their presence does not cause any obvious damage. Three species of Acoela are reported from echinoids. Avagina incola was described by Leiper (1 902,1904) from the intestine of Echinocardiumflavescens, and later by Westblad (1953) from both E.Jlavescens and Spatanguspurpureus. The latter echinoid also harboured Avagina glandulijiera. No information is available as to the gut contents or feeding habits of these two species, so that no valid comment can be made as to their precise status within the host. In A . vivipara from the oesophagus of Echinocardium cordatum, however, the gut contains diatoms, indicating that the acoel is using the same type of food as free-living species (Hickman, 1956). These three species show no significant structural differences from free-living forms, but A . glandulijiera does produce a much greater number of eggs-a feature which Westblad noted as “usual amongst parasites”. A . incola in the same habitat, however, shows no such modification of its reproductive physiology. 111. RHABDOCOELA

The rhabdocoel Turbellaria are small worms like the acoels, but somewhat more complex in internal structure. The gut is saccate, with a permanent lumen and with the anterior region differentiated into a pharynx (simple, bulbous or rosulate) which is an important component of the feeding mechanism. The food in free-living species ranges from protozoa through various small invertebrates, which are swallowed intact, to crustaceans on which species with an eversible bulbous pharynx feed by sucking out body ffuids (Jennings, 1957). Feeding by this latter method may on occasion leave the prey alive and capable of recovery.

P A R A S I T I S M A N D C O M M E N S A L I S M I N THE T U R B E L L A R I A

5

TABLEI1 Commensaland parasitic genera of Rhabdocoela (excluding Dalyellioida: Umagillidae and the Temnocephalida) Genus

Host

SUBORDER LECITHOPHORA: DALYELLIOIDA Fam. Acholadidae Asteroidea Acholades Coscinasterias colamaria A. asteris Fam. Fecampiidae Fecampia F.erythrocephala

F. spiralis F. xanthocephala

Clanduloderma G. myzostomatis Kronborgia

K.amphipodicola K. caridicola Fam. Graffillidae Grafilla G. brauni G. buccinicola G. muricicola G. mytili G. parasitica Paravortex P.cardii

Decapoda and Isopoda Cancer pagurus, Pagurus bernhardus, Carcinus maenas Serotis schytei Idotea neglecta

Authority

Hickman and Olsen, 1955 Giard, 1886; Caullery and Mesnil, 1903; Southern. 1936; Southward, 1951 Baylis, 1949 Caullery and Mesnil, 1903

myzostomid Annelida Myzostomum brevilobatum Jagersten, 1942 M. longimanum Amphipoda and Decapoda (Natantia) Ampelisca macrocephala, Christensen and A, tenuicornis Kanneworff, 1964 Eualus machilenta, Kanneworff and i Lebbeus polaris, Christensen, 1966 Paciphaea tarda Gastropoda and Lamellibranchiata marine lamellibranchs Buccinum undatum Murex sp. Mytilus edulis marine lamellibranchs Lamelli branchiata Cardium edule

Von Graff, 1904-08 Dakin, 1912 Jhering, 1880 Von Graff, 1904-08 Von Graff. 1904-08 Hallez, 1909; Atkins, 1934 Linton, 1910; Ball, 1916

P.gemellipara Modiolus plicatulus Fam. Provorticidae Oikiocolax Turbellaria 0.plagiostomorum Plagiostomum sp. Reisinger, 1930 Fam. Pterastericolidae Pterastericola Asteroidea P.fedotovi Pteraster sp. Beklemischev, 1916 SUBORDER LECITHOPHORA : TYPHLOPLANOIDA Farn.Typhloplanoidae l)phlorhynchus Annelida T. nanus Nephthys scolopendroides Laidlaw, 1902

J . B. J C N N I N G S

6

The epidermis is usually uniformly ciliated except in the sand-dwelling and terrestrial species, where the dorsal ciliation is reduced, and in the ectocommensal temnocephalids where the body is covered with a cuticle-like integument. The rhabdocoels fall into four suborders (Hyman, 1951),viz.: 1. Notandropora or Catenulida (free living, freshwater).

3. Lecithophora or Neorhabdocoela (marine, freshwater and terrestrial, free living, commensal or parasitic) (a) Dalyellioida (b) Typhloplanoida (c) Kalyptorhynchia.

2. Opisthandropora or Macrostomida (free living, marine and freshwater). 4. Temnocephalida (freshwater, commensal).

Rhabdocoels living i n association with other organisms occur in the Lecithophora, and almost entirely in the marine Dalyellioida, apart from a single instance in the Typhloplanoida, and in the Temnocephalida. They constitute the majority of those turbellarians following this mode of life and host organisms include other turbellarians, annelids, sipunculids, molluscs, crustaceans and echinoderms. The distribution of the better-known species within these host organisms is summarized in Tables 11, 111 and IV. Table I1 deals with rhabdocoel species other than umagillids and temnocephalids, i.e. Lecithophora : Dalyellioida, families Acholadidae, Fecampiidae, Graffillidae, Provorticidae, and Pterastericolidae ; and Lecithophora : Typhloplanoida, family Typhloplanoidae. Table 111 summarizes the Lecithophora: Dalyellioida, family Umagillidae, and Table 1V summarizes the Temnocephalida. A.

LECITHOPHORA : DALYELLIOIDA

The dalyellioid rhabdocoels are characterized by their possession of a bulbous doliiform pharynx, paired testes, an armed penis, single or paired germovitellaria or separate ovaries and yolk glands, often a seminal or copulatory bursa, uterus and common gonopore (Hyman, 1951). Five families have members associated with other animals and two of these, the Fecampiidae and the Provorticidae, are the only turbellarian groups shown conclusively to be parasitic. The others are entocommensal, in a few instances with tendencies towards parasitism in that host tissues may occasionally be used for food. 1. Acholadidae Only one species is known from this family. Hickman and Oisen (1955) describe the new genus and species Acholades asteris which lives encysted within the connective tissue of the tube-feet of the starfish Coscinusterias calamaria, in Tasmanian waters. A . asteris is remarkable in that eyes, mouth, pharynx and intestine are all lacking, as also are rhabdites and subepidermal mucous glands.

PARASrTlSM AND COMMENSALJSM IN THE TURBELLARIA

7

Nothing is known as to how the flatworm gains its nourishment, but from the absencc of an alimentary system it seems likely that it absorbs soluble substances through the integument.

I

2. Fecampiidae The family Fecampiidae comprises three genera, Fecampia, Glanduloderma and Kronborgia. They are known best from European waters and are wholly parasitic in habit. Fecampia erythrocephala was first described by Giard (1886), who found it in the haemocoel of the decapod crustaceans Cancer pagurus, Pagurus bernhardus and Carcinus maenas. A second species, F. xanthocephala, was reported from the isopod Idotea neglecta by Caullery and Mesnil (1903). Both these species are from the French coast but Baylis (1949) described a third one, F. spiralis, from the Antarctic isopod Serotis schytei. The life cycles of F. erythrocephala and F. xanthocephala have been described in some detail by Caullery and Mesnil (1903). The young individuals possess eyes, mouth, buccal tube, pharynx and intestine. The epidermis is uniformly ciliated and the flatworm superficially resembles a free-living rhabdocoel. By some means as yet undiscovered it enters the crustacean host and settles in the haemocoel where it grows and becomes sexually mature, losing in the process the eyes, mouth, buccal tube and pharynx. Nothing is known about the mode of feeding during this stage, but nutrients can obviously only be obtained at the expense of the host. The mature Fecampia then leaves the host, again by an unknown method, and produces bottle- or flask-shaped cocoons which are cemented to the substratum. The parent then dies. Each cocoon contains two eggs and masses of yolk cells, and eventually two ciliated larval forms develop, leave the cocoon and become the motile juvenile stages. No obvious adverse effect on the host has been reported and the relationship between Fecampia and the crustaceans, therefore, is presumably long-established. F. spiralis differs from the other two species in that the cocoons have a tubular spiral form and are deposited on the body surface of the host (Baylis, 1949). Glanduloderma myzostomatis was described by Jagersten (1942) from Japanese myzostomid annelids (Myzosfomum brevilobafum and M . longimanum). The life cycle is not known, but the sexually mature worm lives in the mesenchyme of the host and, like the comparable stage in Fecampia, lacks mouth and pharynx. The epidermis shows no modification, being uniformly ciliated and possessing well-developed rhabdites and mucous glands. The third genus of the Fecampiidae, Kronborgia, occurs in the body cavity of crustaceans in northern European waters, K. amphipodicola in the amphipods Ampelisca macrocephala and A . tenuicornis, and K. caridicola in the shrimps Eualus machilenta, Lebbeus polaris and Paciphaea tarda (Christensen and Kqnneworff, 1964, 1965; Kanneworff and Christensen, 1966). Kronborgia is one of the few dioecious Turbellaria so far described, and amongst these it is unique in possessing pronounced sexual dimorphism. The males are 4-5 mm long, whilst the females are 2&30 rnm in length and can elongate during movement up to 45 mm. Both sexes lack eyes, mouth, pharynx and intestine at all

8

J. B . JENNINGS

TABLE I11 The principal genera of Umagillidae (Rhabdocoela: Lecithophora Dalyellioida), with some details of their species and hosts

Genus ____.-

___

-___

Host

Anoplodiera Holothuroidea A. voluta Stichopus tremulus Anoplodium Holothuroidea A. evelinae, A. gracile, Holothuria spp. and A. grafi, A. longiductum, S. tremulus, A. mediale, A. parasita, S. japonicus A. ramosum, A , stichopi, A. tuberiferum

Authority Westblad, 1930 Schneider, 1858; Monticelli, 1892; Wahl, 1909,1910; Bock, 1925a; Ozaki, 1932; Marcus, 1949; Westblad, 1926, 1930, 1953

Bicladus Crinoidea B. metacrini Metacrinus rotundus Coilastoma Sipunculida C. monorchis Phascolosoma vulgare C. minuta Physcosoma granulatum C. eremitae Phascolosoma eremitae C. pac$ca Dendrostoma pyroides Cleistogamia Holothuroidea C. holothuriana Holothuria sp. C. loutfa Holothuria sp. Desmota Crinoidea D. vorax Holothuria sp. Macrogynium Holothuroidea M . ovalis Stylochus sp. Marcusella Echinoidea M . atriovillosa Spatanguspurpureus M . paliida Echinocardium cordatum Monticellina Holothuroidea M . longituba H. impatiens, H. polii Notothrix Holothuroidea N.inguilina Mensamaria thompsoni Orametra Holothuroidea 0.striata Stichopus mollis 0.arborum S.japonicus (0.arborum wrongly as Xenometra by Ozaki, 1932, corrected by Marcus, 1949) Syndesmis Echinoidea S. antillarum Diadema (= Centrechinus) antillarum (wrongly as S.franciscana by Jennings and Lytechinus variegatus Mettrick, 1968; corrected by Mettrick and Jennings, 1969)

Kaburaki, 1925 Dorler, 1900 Wahl, 1909,1910 Beklemischev, 1916 Kozloff, 1953 Baer, 1938 Khalil-Bey, 1938 Beklemischev, 1916 Meserve, 1934 Westblad, 1953 Hickman, 1956 Westblad, 1953 Hickman, 1955 Hickman, 1955 Marcus, 1949

Stunkard and Corliss, 1951

Mettrick and Jennings, 1969

PARASITISM A N D COMMENSALISM IN THE TURBELLARIA

9

TABLE 111 (continued) -

Genus ___

Host

Authority Stunkard and Corliss,

S. dendrastorum

Dendraster eccentricus

S. echinorum

Silliman, 1881; Echinus sphaera, Franwis, 1886 E. acutus Strongylocentrotus lividus RUSSO, 1895 E. esculentus Shipley, 1901

S. evelinae

(Caribbean, host unknown)

Marcus. 1968

S.franciscana (wrongly

Strongylocentrotus franciscanus S. purpuratus Lytechinus variegatus

Powers, 1936; Stunkard and Corliss, 1951 ; Hyman, 1960 Mettrick and Jennings,

1951

as Syndesmis franciscanus by Lehman, 1946, corrected by Stunkard and Corliss, 1951)

S. glandulosa

S.punicea

Umagilla I/. elegans U.forskali Wahlia W. macrostylifera

1969

Diadema (= Centrechinu antillarum)

(Madagascar,echinoid) Heliocidaris eryfhrogramma Amblypneustes ovum

Hyman, 1960 Hickman, 1956

Holothuroidea Stichopus tremulus H . forskali

Westblad, 1930 Westblad, 1953

Holothuroidea Stichopus tremulus

Westblad, 1930

stages of the life cycle and Christensen and Kanneworff conclude, therefore, that food is absorbed in soluble form through the body wall. The life history of K. amphipodicola, parasitic in the tube-building amphipod Amphiscela macrocephala, has been described in detail by Christensen and Kanneworff (1965). The mature males live in the extreme anterior end of the body cavity, whilst the females occupy the rest of the available space and are generally coiled upon fhemelves along the length of the intestine (Fig. IA). They eventually emerge from the host at the posterior end (Figs 1 B, 1C) and during this process the host suddenly becomes immobile and then dies. The cause of this paralysis and subsequent death in the host is not known, but Christensen and Kanneworffimply that it is somehow achieved by the parasite. Since emergence of the female may occupy several minutes they see the paralysis as distinctly advantageous, preventing damage to the flatworm whilst it is still partially within the host. Immediately after emerging the female begins to secrete a cocoon around herself, and the base of this is anchored to the inside of the tube formed by the host during its lifetime. The cocoon is 4-6 cm in length and protrudes from the host tube for 2-3 cm (Fig. ID). The free end of the cocoon remains open and males enter here, pass down to the female (Fig. 1C) and fertilize her. They then leave the cocoon and die. The female eventually deposits several thousand

EXPLANATION OF THE FIGURE FIG.1. Schematic representation of the lifc cycle of Kronlxwgin amphiporlicolu in the tubebuilding amphipod Atipilescu /tiucro,czpliulu. Malcs and females are not always present in the same host specimen as indicated hcrc. From Cliristensen and Kanneworff (1965): for explanationlsee text on pages 9.and 11.

PARASITISM A N D COMMENSALISM I N THE T U R D E L L A R I A

11

capsules, each containing two fertilized eggs and a number of yolk cells, within the cocoon, and then she too leaves it and dies. Development occupies 50-60 days, each egg giving rise to a small ciliated larva (Fig. 1E). The larvae eventually leave the cocoon, seek out a new host and encyst on the carapace (Fig. 1G). The larva moves freely within its cyst for a time, but eventually bores a conical hole 4-8 p in diameter in the carapace and passes through it into the haemocoel (Fig. IG). Christensen and Kanneworff believe that the boring is achieved chemically since the larva does not possess any means of puncturing the carapace mechanically. The ciliated larva then enters the haemocoel, where it develops within a year into either a mature male or female. In the early stages of growth the larvae swim freely in the fluid of the haemocoel, but as they grow they slow down, come to rest near the gut and assume the adult form. The principal effect on the host whilst the parasites are maturing is atrophy of the gonads and both sexes of the host amphipod are rendered sterile by the presence of the rhabdocoels. Finally, the parasite kills the host as it emerges. Christensen and Kanneworff (1967) describe six types of cocoons similar to those formed by K. amphipodicola but collected from various waters offAlaska, Greenland, Java, Thailand and the Philippines. All the cocoons can be referred to the K . amphipodicola type and the authors interpret this as evidence for the existence of more species of Fecampiidae, as yet undiscovered and from tropical as well as temperate and polar seas.

3. Grafillidae This family comprises three genera, namely the free-living Bresslauilla and the commensal Crafilla and Paravortex. Species of Gra@lla live in the kidneys and kidney ducts of various gastropods, examples being G. muricola in Murex (Jhering, 1880), and G.buccinicola in Buccinum, where it may also occur in the mantle cavity and various parts of the gut (Dakin, I91 2). Von Graff ( I 904-1 908) listed three further species, G. parasitica, G . brauni and G. mytili, but did not give details of the precise location in the host. Little is known of the biology of all these species, but there is no evidence of their presence having any deleterious effect on their hosts. The known species of Paravortex occur in lamellibranchs, P. gemellipam in Modiolus plicatulus on the New England coast (Linton, 1910; Ball, 1916) and P. cardii in Cardium edule in European waters (Hallez, 1909; Atkins, 1934). Leigh-Sharpe (1933) reported on “Grafllla gemellipara” from C. edule at Plymouth, England, but according to Atkins the specimens observed were in fact P. cardii. Both P . gemellipara and P . cardii are viviparous. The adult P . cardii lives in the stomach of the host and when fertilized eggs appear in the reproductive system they become enclosed, usually in pairs and surrounded by masses of yolk cells, within thin-walled capsules. The capsules then pass into the mesenchyme, often in considerable numbers, and development occurs there. The capsules and the gravid parent then eventually rupture and the embryos are freed at an advanced stage of development. They pass onwards from the stomach into the intestine and develop there, in three to four days, into the

12

J . B. J E N N I N G S

adult form. Hallez believes that at ths stage copulation occurs, after which the worms pass out with the faeces and are swept out of the mantle cavity in the exhalent current. Presumably the life cycle is completed when the mature fertilized worm is taken in by the feeding current of another cockle and passes to the stomach. Occasionally capsule formation may begin in the intestinal stage, before the worm leaves the first host. As with Grafilla spp., no deleterious effect on the host has been reported in infections of P. gemellipara and P. cardii, and Atkins (using material at Plymouth) refers to “apparently healthy cockles” which were quite heavily infected, bothas individualsand as a population, with P. cardii. The viviparous habit appears to be characteristic of the Graffillidae,the freeliving Bresslauil(ahaving the eggs developinginto young forms in the intestine of the adult, so that it cannot be interpreted as related to the mode of life or regarded as the forerunner of the asexual multiplicative stages seen in the Trematoda and Cestoda. So far as is known there are no further modifications of structure, physiology or life history of note in the family. 4. Provorticidae The Provorticidae include marine, freshwater and terrestrial species. Oikiocolax plagiostomorum is the only parasitic representative, and lives in the mesenchyme of the alloeocoel Plagiostomum (Reisinger, 1930). Details of its nutrition and general physiology are not known, but infected Plagiostomum consistently shows degeneration of the ovaries, presumably resulting from abstraction of nutrients by the rhabdocoel. The pharynx is much reduced, when compared with that of free-livingspecies such as Provortex sp., indicating, perhaps, some modification in the mode of ingestion or in the particle size of the food.

5 . Pterastericolidae Only one species, Pterastericola fedotovi, is known from this family. It is reported by Beklemischev (1916) to live in starfishes of the genus Pteraster in northern European waters, but nothing further is known of the relationship.

6. Umagillidae All the umagillid rhabdocoels live in either the coelom or digestive tract of other animals, with holothurian and echinoid echinoderms as the commonest hosts. The principal genera and species so far described are summarized in Table 111, together with their hosts and the authors describing them. Stunkard and Corliss (1951) revised the family and provided a useful key for identification of the species. It can be seen from Table I11 that the genera are remarkably specific in their association with certain types of hosts, Anoplodium, for example, occurring only in holothurians, Collastoma in sipunculids, and Syndesmis in echinoids, Only two genera (Bicladus and Desmote) occur in crinoids, and none has been reported from asteroids or ophiuroids. There is no evidence that any of the umagillids cause significant damage to their hosts, or that the association between flatworm and host is at all

PARASITISM AND COMMENSALISM I N T H E T U R B E L L A R I A

13

deleterious to the latter i n terms of competition for ingested food in those instances where the flatworm lives in the host’s gut. The general concensus of opinion is that the umagilligs are harmless commensals,but so little is known of their biology that firm judgement is impossible. In one instance a tendency towards the use of host tissues for food has been described. Jennings and Mettrick (1968) reported that Syndesmis antillarum (described by them as S. franciscana but subsequently re-identified as S. antillarum by Mettrick and Jennings, 1969)feeds mainly upon ciliate protozoa present in the gut and coelom of the host Lytechinus variegatus. This diet is supplemented, however, by host coelomocytes apparently ingested by chance along with the normal food. The host suffers no obvious ill-effects, but it is clear that a shift in emphasis in the diet could lead to a fully parasitic existence. Syndesmisfranciscana, from the intestine of Strongylocentrotusjianciscanus and S. purpuratus, feeds entirely on ciliates commensal in the same habitat. The digestive physiology of both this species and Syndesmis antillarum resembles that of free-living flatworms, as described by Jennings (1957, 1962) in that endopeptidases, exopeptidases, lipases, and acid and alkaline phosphatases are involved, and in that at least the final stages of digestion are intracellular. The two species differ markedly, however, from free-living turbellarians in the nature and amount of their food reserves. Both form extensive reserves of glycogen (15-19 % of the dry weight) and in Xfranciscana these are supplemented by lipid reserves amounting to just over 25 % of the dry weight (Jennings and Mettrick, 1968; Mettrick and Jennings, 1969). These values are much more akin to those reported for endoparasitic helminths than for free-living species (Von Brand, 1966) and, further, over 85 % of the glycogen present in S. franciscana exists in the soluble lyo form, again as in endoparasitic helminths. Nothing is known of the nutritional or general physiology of other umagillid species. The life cycles of the Umagillidae remain unknown. Only adult stages have been described, from within the particular host, and whilst it would appear that the eggs of speciesliving in the host intestine can simply pass out with the faeces it is not known how eggs laid in the coelom can reach the exterior. Presumably free-swimming larval stages are ingested by fresh hosts, or else actively seek these out, but details are not known. B.

LECITHOPHORA : TYPHLOPLANOIDA

Typhloplanidac Only one representative of the Typhloplanoida lives in permanent association with another animal. Typhlorhynchus nanus (Typhloplanidae) occurs on the body surface of the polychaete Nephthys scolopendroides (Laidlaw, 1902), attaching itself to the host by means of a posterior adhesive region. This is somewhat flattened and expanded but is not organized into a definite sucker. The anterior end is produced into a kind of tactile snout which bears small papillae. Eyes and otolith are absent but apart from these features the organiza-

14

J . B. J E N N I N G S

tion does not differ significantly from that of other typhloplanids. Nothing is known of the food, feeding habits or general physiology. C. TEMNOCEPHALIDA

The Temnocephalida are here considered as a suborder of the Rhabdocoela, following Fyfe (1942) and Hyman (1951) and recognizing their dalyellioid affinities.They are entirely freshwater, and are the only turbellarians from this habitat living in association with host organisms. The temnocephalids are all ectocommensal on freshwater hosts, mainly decapod, isopod and a few other crustaceans but occurring also on turtles, molluscs and, very rarely, on freshwater hydromedusae (Table IV). They generally inhabit the external surface, the gills, or the lining of the branchial chamber of the host. Geographically they occur mainly in Australia, New Zealand and South America, but some species occur also in India and Ceylon, Madagascar, Indonesia, Central America and various islands of the South Pacific. In Europe a few species occur, sparingly, in the Balkans. The morphology and general biology of the group has been described by Hyman (1951) and Baer (1961). Baer (1931) reviewed the taxonomy of the species known at that time, giving all known synonyms and including details of the host organisms and their geographical distribution. Of all the commensal and parasitic Turbellaria the Temnocephalida are the ones most obviously modified for their mode of life. They are small, flattened organisms, distinguished from other rhabdocoels by the possession of anterior tentacles and an adhesive organ. The tentacles are five, six or twelve in number, except in Scutariella, Monodiscus and Caridinicola, which possess only two, and Actinodactylla which has twelve distributed along the body. The adhesive organ is generally posterior and may be pedunculate; it is saucer-shaped and muscular but considerably simpler in structure than the type of sucker found in the Trematoda. In a few instances there is an anterior adhesive organ, in addition to the posterior one. The tentacles can also be used for adhesion, and most species move briskly about on their hosts in a leech-likemanner by looping over and attaching tentacles and adhesive organ alternately. The epidermis is syncytial, with a clear distal border which resembles a cuticle, and ciliation is either lacking or very sparse. Rhabdites are present only anteriorly, and mucous glands tend to be concentrated posteriorly to supply the adhesive organs. The eggs are laid enclosed in thick capsules which are cemented on to the surface of the host and they hatch as miniature adults. Since the majority of the hosts are crustaceans and moult periodically there is obviously the possibility that eggs will sometimes be laid on material which will be shed from the host before they hatch. This is probably only a minor consideration, though, since the temnocephalids are reported to produce considerable numbers of eggs over an extended period. More intriguing, however, is the question as to how the temnocephalids themselves survive host ecdysis and achieve their transference on to the newly exposed exoskeleton. It is known that some species can survive and even breed away from their hosts (Gonzales, 1949; Hickman, 1967;

PARASITISM A N D COMMENSALISM I N THE TURBELLARIA

15

TABLEIV The principal genera of Temnocephalida, with some details of their species, hosts and geographical distribution (for synonyms see Baer, 1931)

~-

__

__.

Fam. Actinodactylellidae Crystacea Actinodactylella A. blanchardi Engoeusfossor Crustacea Fam. Craspedellidae . Craspedella C. spenceri Paracheraps bicarinatus Fam. Scutariellidae Crustacea Scutariella S. didactyla A tyaephyra desmarestii Monodiscus M . parvus Caridina nilotica Caridinicola C. indica Caridina spp. Fam. TemnoCrustacea, Mollusca, cephalidae Chelonia, Hydrornedusae Craniocephala C. biroi Sesarma gracillipes Dactylocephala D. madagascariensis Astacoides madagascar iensis Temnocephala T. aurantica Astacopus sp. T. axenos Aeglea laevis T. brenesi Macrobrachimi americanirni T.bresslaui Aeglea castro T. brevicornis Hydromedusa maximilliani, H. platanensis, Hydrupsis gibbu T. caeca T. chaerapis T. chilensis T. cita T. comes T. detirlyi

Geographical location

Host

Genus

Phreatoicopsis terricola Chaerapspreissii Aeglea sp. Parasfarus sp. Parastacoides tasmanicus Astacopsis serratus Paracheraps bicarinarru

~

~

_

Authority _ -_. .

Australia

Haswell, 1893

Australia

Haswell, 1893

Yugoslavia Mrazeck, 1906 (Lake Scutari) Ceylon

Plate, 1914

India

Annandale, 1912

New Guinea

Monticelli, 1905

Madagascar

VayssBre, 1892

Tasmania Brazil Costa Rica

Haswell, 1900 Monticelli, 1899 Jennings, 1968a

Brazil Brazil, Venezuela

Australia

Gonzales, 1949 Monticelli,l899; Pereira and Cuocolo, 1940 Caballero and Zerecero, 1951 Haswell, 1900

Australia Chile

Hett, 1925 Wacke, 1905

Tasmania

Hickman, 1967

Australia Australia

Haswell, 1893 Haswell, I893

TABLEIV (continued) Genus

T.digitafa

Host

Geographical location

Authority

Brazil

Monticelli, 1902

Australia Australia Tasmania

Haswell, 1893 Haswell, 1887 Hickman 1967

T.jheringi

Palaemonetes argentinus Engaeus fossor Astacopsis serratus Parastacoides tasmanicus Ampullaria sp.

Brazil

T. lanei

Trichodactylussp.

Brazil Brazil Mexico Brazil

Haswell, 1893; Hyman, 1955a Pereira and Cuocolo, 1941 Monticelli, 1913 Vayssibre, 1898 Monticelli, 1903

Australia

Haswell, 1887

New Zealand

Haswell, 1887; Fyfe, 1942 Hickman, 1967 Haswell, 1887 Merton, 1913 Weber, 1889 Rohde, 1966 Haswell, 1900

T. engaei T.fasciala T. fulva

Telphusa sp. Cambarus digueti Trichodactylus orbicularis Paracheraps T. minor bicarinafus T. novae-zeelandiae Paranephrops neo-zelandicus Astacopsis gouldi T. pygmaea Astacopsisfranklini T. quadricornis Cheraps arvanus T. rouxi Potamon spp. T.semperi P . raflesi Astacopsis franklini T. tasmanica tasmanicus T.travassosfilhoi Trichodactylus petropolitanirs Aeglea sp. T. tumbesiana T. lutzi T. mexicana T. microdactyla

Tasmania Tasmania Isles Aru Indonesia Malaya Tasmania Brazil Chile

Pereira and Cuocolo, 1941 Wacke, 1905

-

Jennings, 1968a) and it is possible, therefore, that a brief free-living stage is a normal, or at least a tolerable, stage in the life history. The temnocephalids are agile animals and would appear to have every chance of seeking out new hosts iffor any reason they become separated from their first one. Support for this suggestion that part of the life history may be spent away from the host comes from Jennings (1968a), who studied the occurrence of Temnocephala brenesi on the gills of the freshwater shrimp Macrobrachium americanud in Costa Rica, Central America. Fifty-five per cent of the hosts examined were infested, with an average of eight temnocephalids per host. The gills generally carried clusters of the flatworm’s eggs and many more eggs than adults dpre found consistently, with in some cases over 150 eggs occurring on gills but yielding only three adults, Laboratory observations showed that development occupies 21-24 days, and that adults it1 vitro produce one egg every 3 4 days Thus when the rate of egg production and the time span of development are considered together and against the numbers of adults normally found on any one host, it is clear that a larger number of adults could reasonably be expected on any one host than was ever found. Further, recently-laid eggs are occasionally found on gills and these do not yield adults, even when examined immediately on removal of the host from the natural habitat, and from hosts which

PARASITISM AND COMMENSALISM I N THE TURBELLARIA

17

have obviously not moulted for some timc (Jennings, unpublished observations). Thus it seems possible that T. breriesiat least, normally spends some time away from its host, but exhaustive searches of the pools and backwaters favoured by M. arnericanum failed to reveal any free-living temnocephalids. It is generally accepted that the temnocephalids do not feed on host tissues, except in the case of Scutariella didactyla which apparently ingests the host’s body fluids (Mrazeck, 1906). Most species appear to use the host largely as a substratum for attachment and to feed on materials present in the surrounding water or, in the case of species living on host gills or in the host’s branchial chamber, on particles swept over them by the host’s respiratory current. The free-living rhabdocoels feed on protozoa, rotifers, nematodes and small oligochaetes and crustaceans (Jennings, 1957, 1968b), and the few temnocephalid species whose nutrition has been studied (T. bresslaui, T. brenesi and T. novae-zealandiae)have precisely the same diet in nature, as judged from the gut contents of freshly collected specimens, and they survive well when fed upon these organisms in the laboratory (Gonzales, 1949; Jennings, 1968~). The digestive physiology, too, of T. brenesi and T. novae-zealandiae is of the type characteristic of the free-living flatworms, with extra- and intracellular stages being achieved by endo- and exopeptidases, lipases and acid and alkaline phosphatases which are secreted in sequence from either specialized gland cells or the cytoplasm of non-glandular columnar intestinal cells. The food reserves similarly resemble those of free-living rhabdocoels as regards their nature and location, as also do those of Caridinicola indica and Monodiscus parvus (Fernando, 1945), and the entire pattern of nutrition shows no significant variation from that found in other rhabdocoels. The egg-laying activities of T. brenesi are of interest in that they create conditions favouring the growth of the smaller food organisms upon which newly-hatched specimens feed (Jennings, 1968~).Eggs are laid in rows of five to ten, and the empty capsules remain attached to the gill lamellae after the eggs have hatched. Small particles of detritus gather between and around the capsules as soon as they are laid, and form a substratum which soon develops a rich growth of diatoms, protozoa and rotifers. The resultant brownish patches on the gills are easily visible to the naked eye and afford a ready indication of a past or present infestation. The rich microflora and fauna of the patches form the principal food of newly-hatched and juvenile T. brenesi and their ready availability probably permits rapid growth. A similar situation has been observed on the gills of the crayfish Ataephyra desmarestii from Yugoslavia, where the feeding activities of Branchiobdella hexadonta (Annelida : Branchiobdellida) causes lesions and scars in the host tissue. Diatoms and Protozoa collect around these, and are subsequently ingested by the branchiobdellid (S.R. Gelder, personal communication). Both of these instances, in T. brenesi and B. hexadonta, are reminiscent of the situation in the digenetic trematode Fasciola hepatica whose feeding activities, according to Dawes (1963), set up inflammatory reactions within the biliary system of the host to produce “a ‘pasture’ of hyperplastic epithelium and connective tissue” upon which the trematode then feeds. Apart from this effect on the gills, incidental to egg-laying and insufficient

18

1.

n.

JINNlNCS

to cause any significant blockage or diversion of the respiratory current, the presence of T. brenesi appears to have no adverse effect on the host crustacean and this seems to be true of all other associations between teninocephalids and their hosts, apart from the one case of Scutariellu already cited. 1V. ALLOEOCOELA The Alloeocoela are in many ways intermediate between the Acoela and Tricladida. They tend to be larger than the acoels or rhabdocoels and are predominantly marine. A number of species extend into brackish and fresh waters and members of one family, the Prorhyncidae, are also found in moist terrestrial habitats. TABLEV Commensul und parasitic geireru of Alloeocoela ~~~

_____

Genus ~

~

Host - .- -~

__

Authority ~

- -- __ -

.

SUBORDER CUMULATA (= HOLOCOELA) Lamellibranchiata Fam. Cylindrostomatidae CyIindrostoma

C. cyprinae

Fam. Hypotrichinidae Hypotrichina (= Genostoma) H . tergestinum H . marsiliensis Zchthyophuga I. subcufanea Urastoma U.frausseki

Fam. Plagiostomidae Plagiostoma P. oyense

various European species Hyman, 1951 of lamellibranchs Lamellibranchiata, Crustacea, Teleostei Nebalia spp. Nebulia spp.

Von Graff, 1904-1908 Von Graff, 1904-1908

Teleostei Bero sp., Hexagramma sp. Syriamiatnikova, 1949 Mytilus edulis Modiolus mod;olus (and

Dorler, 1900 Westblad, 1955

free-living) Crustacea Idotea sp.

De Beauchamp, 1921 ;

Naylor, 1952; 1955

The group falls into four subordcrs, the Archoophora, Lecithoepithelia, Cumulata (= Holocoela) and the Seriata. Only the Cumulata contains species regarded as ectocommensal or parasitic, living on gastropod and lamellibranch molluscs, crustaceans and, rarely, teleosts (Table V). Monocelis, in the Seriata, is occasionally found within the shell valves of the barnacle Ealunus bdanoides, or beneath the shell amongst the pallial gills of Patella vulgaris (Gastropoda), but this seems to be a purely temporary association during the low water period and the flatworm leaves the “host” when both are submerged by the incoming tide. Nevertheless, this temporary association conferring on the Monocelis protection from desiccation may well illustrate how more permanent associations have been established.

PARASITISM A N D COMMENSALISM I N TllC TURRELLARIA

19

Of the Cumulata. Cyliiidrorostonia cypririae occurs on the gills of various marine lamellibranchs in European waters, whilst Hypotrichina (= Genostoma) tergestinum and H. marsiliensis live on the surface of Nebaiia spp. in the Mediterranean (Von Graff, 1904-1908; Hyman, 1951). Little is known of their physiology, and their precise relationship with their host is consequently difficult to define. H. tergestinum and H . marsiliensis have reduced ciliation and possess an anterior adhesive disc, but these features are found to varying extents in some free-living alloeocoels and cannot be related specifically to the mode of life. Urasromafrausseki lives in the mantle cavity and on the gills of the Iamellibranchs Mytiius eduiis and Modioius modiolus (Dorler, 1900; Westblad, 1955), but the relationship appears to be entirely facultative because Westblad reported finding free-living individuals fairly frequently amongst sea-weeds and in general detritus. Zchthyophagasubcutanea is one of the few turbellarians living on vertebrates. It is also one of the few that is almost certainly parasitic. Syriamiatnikova (1949), who discovered this species living subcutaneously in the anal and branchial regions of the teleosts Bero and Hexagramma, describes it as red in colour, and since the gut occupies most of the body the red coloration probably comes from ingested host blood. The pharynx is of the bulbous type, quite highly muscular and suitable for rupturing small vessels and sucking in blood, and reminiscent of the pharynx of monogenetic trematodes. The epidermis is uniformly ciliated, however, and eyes are present anteriorly, both features which could be expected to have been lost during the evolution of the parasitic habit, I. subcutanea is often found enclosed in cysts which are apparently of host origin, and this evidence of host reaction, together with the retention of eyes and ciliation by the parasite, suggests that the association with teleosts may be a relatively recent development. In the PlagiostomidaePlagiostoma oyense lives on the surface of the isopod crustacean Zdotea (De Beauchamp, 1921 ;Naylor, 1952, 1955). The association is a permanent one, with the flatworm producing cocoons and cementingthese on to the host’s cuticle. De Beauchamp reports that the intestine often contains the empty cuticles of rotifers, however, so that it would appear that P. oyense is living in much the same fashion as the temnocephalids, and uses the host merely as a substratum whilst continuing to feed as a predator in the usual turbellarian fashion.

V. TRICLADIDA

The Tricladida are mostly fairly large flatworms, ranging in size from 2 or 3 mm up to 50 cm, and are easily distinguished from other turbellarians by the plicate pharynx and tripartite intestine. They occur in salt, brackish and fresh water, and in moist terrestrial habitats, and fall into three suborders in which there is marked correspondence between the type of habitat and taxonomy. These are the Maricola (marine and brackish), Paludicola (freshwater) and Terricola (terrestrial). All three groups are carnivorous and prey on a wide variety of organisms including annelids, molluscs, crustaceans and insect 2

20

J . 13. J L N N I N G S

larvae (Hyman, 1951; Jennings, 1957, 1968b; Reynoldson and Young, 1963). The prey may occasionally be swallowed intact, if it is small enough, but usually the plicate pharynx is thrust through the prey's body wall to suck out the body contents. The Paludicola and Terricola are entirely free-living, apart from a single unnamed species quoted by De Beauchamp (1961) as living commensally in the mantle cavity of the gastropod Cyclophorus. The Maricola contain three genera ectocommensal on the horse-shoe crab Limulus (Arachnida: Xiphosura) and one ectocommensal on elasmobranchs (Table VI). Bdelloura, Syncoelidium and Ec:'cplana all live on the gill lamellae of Limu1u.r and are gcncrally believed to be commensal, feeding on particles of the host food drifting back from the mouth-parts in the respiratory current, or upon small marine organisms in the surrounding water. Some host tissue may also be taken, since Ryder (1 882) describes a species of Bdelloura (probably B. cundidu) as causing perforations in the gill lamellae, but it is difficult to envisage the use of the plicate pharynx in this type of feeding. The digestive processes and food reserves in B. cundida resemble those of free-living triclads (Jennings, 1968b), TABLEVI Commensal and parasticic genera of Tricladida

Genus

Host

SUBORDER MARICOLA Fam. Bdellouridae

Xiphosura

Bdelloura B. candida B. wheeleri B. propinqua Syncoelidium S. pellucidum

Fam. Procerodidae Ectoplana sp.

Fam. Micropharyngidae Micropharynx M . parasitica M. murmanica

Authority

Limulirs polyphemus Limulus polyphemus Limulus polyphemus

Girard, 1850; 1852 Wilhelmi, 1909 Wheeler, 1894a

L. polyphemus

Wheclcr, I894a

Xiphosura Limulus sp. Elasniobranchii

Kaburaki, 1922

Ruju batis, R. cluvata,

Jiigerskiold, 1896; Averinzev, 1925

and the mode of life does not appear to have caused any significant physiological changes. Morphologically, however, Bdelloura differs from the freeliving Maricola in having a caudal adhesive disc and a somewhat elongated and pointed anterior end, which may well be an adaptation for penetrating between the gill lamellae. Syncoelidium and Ectoplana, though from the same habitat, lack specialized caudal adhesive zones (Wheeler, 1894a; Kaburaki, 1922) and presumably retain their grip on the substratum by means of their marginal adhesive glands, in the typical triclad fashion, All three genera deposit their eggs in capsules which are cemented to the host

P A R A S I T I S M A N D COM,MENSALISM I N THE T U R B E L L A R I A

21

gill lamellae. According to Wheeler, who studied Bdelloura and Syncoelidium on 15.polyphemus on the coast of Massachusetts, the different species vary somewhat in the areas selected for oviposition and also in the breeding season. B. candida deposits its egg capsules randomly over the entire surface of the gill lamella, B. propinqua selects the basal region and Syncoelidium prefers a small area near the edge of the lamella. The eggs of B. candida are deposited in May and early June, when the host returns from deep water to sandy beaches to breed. Wheeler believes that the prolonged copulation of the hosts favour migration of the triclads from one to another. B. propinqua and Syncoelidium lay eggs later, in late July and early August, by which time the eggs of B. candida have hatched and the young forms have moved towards the basal joints of the cephalothoracic appendages. Wheeler gave no data in support of his observations, but did give an interesting description of the co-existence of related species living in the same habitat and apparently utilizing the same foods, but with separate reproductive patterns; the ecology of these species would repay further study. The only other genus of triclad living in association with a host organism is Micropharynx, which lives on the dorsal surface of the skates Raja batis, R. clavata and R. radiata (Jagerskitjld, 1896; Averinzev, 1925). M. parasitica and M . murmanica both lack eyes but possess posterior adhesive zones with which they attach themselves securely to the host. Nothing is known of the feeding habits and general physiology of either species, and once again their precise relationship with the host is difficult to define.

VI. POLYCLADIDA The Polycladida, apart from a single freshwater species, are entirely marine. There are no parasitic species but a number live in permanent or semipermanent association with other organisms, principally molluscs and hermit crabs (Table VIl). Many species, too, seek shelter in empty mollusc shells, and the associations with hermit crabs have probably developed by chance from this habit. Others live either on or in close proximity to the food organisms upon which they feed as free-living predators. The cotylean Cycloporus papillosus, for example, is generally found adhering to the surface of tunicate colonies (Botryllus and Botrylloides), and it feeds on these by thrusting its plicate pharynx downwards into the colony and sucking out individual zooids. In contrast to this somewhat sedentary manner of feeding some of the Acotylea capture motile animals such as annelids and crustaceans and either swallow them intact or, if they are too large for this, envelop them in the protruded ruffledplicatepharynx. Digestivejuices are then poured on to the prey to break it into smaller pieces, and these are then ingested (Jennings, 1957). Occasionally this capacity for extracorporeal digestion is utilized in attacking relatively large but sedentary animals, with the prey generally surviving the initial attack but eventually dying after repeated attacks. Species of Stylochus, for example, feed in this way on oysters, which are manifestly too large to be killed and eaten by a polyclad at a single attempt. Stylochus.frontalis(= inimicus), the "oyster leech" of the Florida coast, creeps between the shell valves of the oyster when these

22

J. R . JENNINGS

TABLE VII The principal genery of Polycladida living in association with other organisms

Genus

Host

SUBORDER ACOTYLEA Fam. Apidioplanidae

Gorgonacea

Apidioplana A . mira

Melitodes spp.

Fam. Emprosthopharyngidae Emprosthopharynx E. opisthoporus E. rasae

Fam. Hoploplanidae Hoploplana H. inquilina

Fam. Latocestidae Taenioplana T. teredini

Farn. kptoplanidae Euplana (= Discoplana) E, takewakii Stylochoplana S. parasitica

Fam. Stylochidae

Authority

Bock, 1926

Crustacea

Petrochinis californiensis Calcinus latens

Bock, 1925b Prudhoe, 1968

Gastropoda Busycon canaliculatum, Thais haemastoma, Urosalpinx cinerea

Wheeler, 1894b; Marcus, 1952; Hyman, 1967

Lamellibranchiata Teredo spp.

Hyman, 1944

Ophiuroidea Ophiuroid spp.

Kato, 1935a

Amphineura Chiton spp.

Kato, 1935b

Echinoidea

Discostylochus D. parcus Stylochus S. zebra

Colobocentrotus atratus

Bock, 1925b

Crustacea various hermit crabs

Hyman, 195 1

SUBORDER COTYLEA Fam. Prosthiostomidae Euprosthiostomrrm sp.

hermit crabs

Bock, 1925b

are open and gradually ingests the mollusc over a considerable length of time, remaining between the shell valves and periodically taking in meals of oyster tissue (Pearse and Wharton, 1938). Other polyclads normally found in association with other animals appear to gain only shelter from their host, whilst continuing to feed as predators on smaller organisms present in, or straying into, the microhabitat. Most of these are members of the suborder Acotylea, characterized by the absence of any type of adhesive organ, the lack of marginal eyes and possession of a voluminous, ruffled plicate pharynx. Apidioplana miro, a species living on gorgonians (Melitodes spp.), is exceptional in that the pharynx is more like the tubular plicate type found in the Cotylea and Tricladida. Further, the pharynx is directed anteriorly rather than ventrally and this may well be an advantage in feeding if, as is suspected, the polyclad feeds by sucking out individual polyps i n a manner comparable to Cyclop0ru.v feeding on tunicatc zoodids. In both

P A R A S I T I S M A N D COMMENSALISM I N THE TURBELLARIA

23

these instances the “host” organism is colonial, so that the use of only parts of the colony as food by the polyclads could conceivably be regarded as parasitization, but it seems more logical to regard the process as predation since entire individuals, albeit colonial, are destroyed. The association of any one polyclad with a host species is sometimes remarkably specific. Emprosthopharynx rasae, for example, lives in shells of Trochus sandwichensis occupied by the hermit crab Calcinus latens, but is never found in T. sandwichensis shells occupied by C. laevimanus or Clibanarius zebra (Prudhoe, 1968). C. latens extends further from the beach into the sub-tidal zone, however, and this may be in some way advantageous to the polyclad and responsible, therefore, for the evolution of this “host specificity”. In contrast to this restriction of a polyclad species to a single host species, others of the group show a wider range of host selection, e.g. Hoploplana inquilina has been reported from the mantle cavities of a number of gastropods, notably Busycon canaliculatum, Thais haemastoma and Urosalpinx cinerea, and Euplana takewakii occurs in the genital bursae of various species of ophiuroids. A characteristic feature of the life cycle in polyclads is the occurrence of a free-swimming ciliated larva, which acts as a dispersal stage. There is no evidence to suggest that larvae seek out prospective hosts, and in species living commensally the larvae appear to metamorphose in the same way as in totally free-living species, and then the immature adults take up the association with a partner of the appropriate species, VII. DISCUSSION

The salient feature emerging from this survey of turbellarian species which live in association with other animals is that remarkably few of them are parasitic in the generally accepted sense of the term. These few are all rhabdocoels, apart from one instance in the alloeocoels, and include Acholades, Fecampia, Glanduloderma,Kronborgia and Oikiocolax. They are truly parasitic in that they apparently derive all their nourishment from the host, since the typical rhabdocoel alimentary system is considerably reduced or absent in these genera, and in the cases of Kronborgia and Oikiocolax the host suffers parasitic castration, in the former case eventually dying. Grafilla, with species living in the kidneys and kidney ducts of the host, may also be parasitic but not enough is known of its biology to permit precise definition of its status. Ichthyophaga, the alloeocoel living in the subcutaneous tissue of teleosts, also appears to be entirely parasitic judging from its situation in the host, but even less is known of its biology than in the case of Grafilla. In all these parasitic species so little information is available about their metabolism that it is difficult to compare them with the trematodes or cestodes as regards physiological adaptation to their mode of life. Structurally their principal modifications lie in the reduction of the gut and a general tendency to increase the size and fecundity of the female part of the reproductive system. Increased production of eggs is an obvious advantage, probably a necessity in entoparasitic and entocommensal animals to ensure dispersal and continuity ofthe species, and this is shown in most of those Turbellaria which follow these

24

J . B. J E N N I N G S

modes of life (Hyman, 1951). This is the limit, though, to which modification of the life cycle is taken. Asexual multiplicative stages, which are a dominant feature in trematode and some cestode life cycles, have not been evolved, and each adult individual is the sole product of one fertilized egg. Asexual reproduction does occur in the Turbellaria, however, with some free-living freshwater rhabdocoels such as Microstomum undergoing transverse fission into chains of zooids. Each zooid becomes well differentiated towards the normal adult form before breaking free from the chain. Similarly, some freshwater triclads multiply by transverse fission (Dugesiu, Phugocutu, Polycelis), thus the potential for this type of increase in numbers is well established in the class, but it has not been utilized in the parasitic species. Asexual multiplication in the digenetic trematodes and in the Cestoda is closely linked with the occurrence of primary, secondary or even tertiary hosts in the life cycle. In the parasitic rhabdocoels, in contrast, the life cycle is simple and never includes more than one host species. Establishment of young individuals in new hosts is apparently direct, the flatworm or a free-swimming larval stage seeking out the host, as in Kronborgiu, and not utilizing the host’s food chain as a means of securing entry to its body. Morphological changes, in addition to the reduction of the gut, found in these parasitic species include tendencies towards reduced ciliation, a lack of rhabdites and pigment in the epidermis and the absence in some cases of eyes. It is difficult, however, to relate these particular changes to the mode of life since similar conditions are often found in free-living species. Conversely the alloeocoel Zclzthyophugu, living subcutaneously, retains apparently normal ciliation, possesses eyes and also has a normal type of alimentary system. The overall absence of extreme modifications of structure, physiology (so far as is known) and life history in the parasitic Turbellaria may be a demonstration of the fact that the turbellarian grade of organization, as seen in modern forms, is incapable of such modifications and this may be the basic reason for the relative rarity of the fully parasitic habit. In contrast, the commensal habit is much more common but again relatively few modifications in structure or function can be directly related to it. It is difficult to see why parasitism in the Turbellaria should not, therefore, be equally common. One possible reason is that the fully parasitic habit in some way puts so much stress on the host, and reciprocally on to the parasite, that the latter requires advantageous modifications in its physiology and life cycle in excess of those needed for simple commensalism, if it is to enjoy any significant amount of biological success. The few genera living parasitically obviously show that the turbellarian type of organization does permit this mode of existence, but their small numbers demonstrate its limitations. The commensal Turbellaria may show a greater range of structural modifications than do the parasitic forms, but again the life cycle remains simple, there are no specific methods for gaining access to new hosts and a number of species are capable of a free existence in virro and occasionally in natural circumstances also. Here may be recalled the species of Temnocephaluwhich have been reared in the laboratory away from their hosts (Gonzales, 1949; Hickman, 1967; Jeilnings, I968a) and the alloeocoel Urnstoiiia found by Westblad (1955) to live

PARASITISM A N D COMMENSALISM I N T H E TURBELLARIA

25

both commensally in the mantle cavity of laniellibranch hosts and quite freely and independently am9ngst algae in the littoral zonc. Structural modifications related to the commensal life generally take the form of adhesive areas or organs. These range from simple concentrations of adhesive mucous glands, generally posteriorly, to the development of sessile or pedunculate cup-shaped suckers, Nowhere, though, does the development of suckers or adhesive organs reach the level found in the Trematoda and Cestoda. Adhesive areas are common also in free-living turbellarians ; the posterior adhesiveglands of acoels such as Convofutaand of many rhabdocoels, and the marginal adhesive glands of the triclads, are well-known examples. Suckers, too, occur in the cotylean polyclads so that these, like many other characteristics of the commensal turbellarians, can be regarded as basic turbellarian features rather than as specific modifications for one way of life. Nevertheless,adhesive organs are commoner in the ectocommensal Turbellaria than in the free-living ones and are obviously important in preventing the flatworms from being swept from their substratum. This is probably particularly true in those species living on the gills or in the branchial cavities of the host, where there is a constant current of water passing over them. In the rhabdocoels Temnocephala spp., from crustacean gills primarily, have welldeveloped posterior suckers and adhesive anterior tentacles, and the triclads Bdelloura and Syncoefidium on the gills of Limufus possess suckers in addition to the usual triclad marginal adhesive glands. The temnocephalids also show modifications of the integument, the epidermis having lost its ciliation and developed a fairly tough cuticle-like covering. The adaptive significanceof this is obscure, and it would be more reasonable to expect such structures in entocommensal forms. Its presence throughout the temnocephalids, though, and the occurrence of specialized adhesive organs, make this group of rhabdocoels the most highly modified of all the commensal Turbellaria. The parasitic habit, in those Turbellarja possessing it, appears to have exerted a profound effect upon the diet and the means of obtaining food. The tendency towards reduction of the alimentary system can only be interpreted as reflecting a tendency towards uptake of nutrients by absorption through the body surface, and the inherent difficulties of this method of feeding may well be a further factor restricting the number of parasitic species. In the Trematoda, which exploit to the full the possibilities of the parasitic life, the vast majority of both Monogenea and Digenea retain a well-developed gut and digestive physiology and digest their food for themselves, even though it is partially or wholly of host origin (Jennings, 1968b). The Cestoda, of course, rely entirely on absorption through the integument and are extremely well adapted in both structure and physiology to this way of life. The commensal Turbellaria, in marked contrast to the parasitic ones, show relatively few changes in the alimentary system and, so far as is known, in their diet, digestive physiology and food reserves. Their nutrition, in fact, is remarkably similar to that of the equivalent free-living species, and provided the new habitat offers suitable food organisms few problems are encountered. This fact offers a possible explanation for the predominance of echinoderms amongst

26

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the host organisms, and particularly holothurians ilnd cchinoids. Ciliate protozoa form an important component of the diet in many free-living acoels and rhabdocoels and they are also extremely common as commensals in the gut and coelom of holothurians and echinoids (Hyman, 1955b). Consequently acoels and rhabdocoels able to make other necessary adjustments to life in these habitats find a readily available food supply and can utilize it with little or no modification of their feeding mechanism and digestive physiology. The mantle cavities of gastropod and lamellibranch molluscs similarly contain commensal micro-organisms, and organic particles gathered by the host’s own feeding mechanism, so that here too food of an appropriate size and nature is readily available. There is some evidence that one of the umagillid rhabdocoels from echinoids, Syndesmis antillarum, supplementsits diet of ciliates by chance ingestion of host coelomocytes (Jennings and Mettrick, 1968) and this illustrates how the parasitic habit could arise from commensalism, needing only a shift in dietary preferences. An interesting parallel exists here in the case of the digenetic trematode Diplodiscus, parasitic in the frog rectum. D. temeratus and D. subclavatus feed on blood drawn from the capillaries of the rectal wall, but also ingest large quantities of the bacteria, entamoebae and ciliates normally present in the rectal contents (Hazard, 1941 ; Halton, 1967a). The food reserves of an animal are often closely related to the mode of life, as regards their nature and the amounts stored. The free-living Turbellaria have the reserves typical of free-living predators, storing fat and to a small extent glycogen (Jennings, 1957). Endoparasitic helminths, in contrast, lay great emphasis on storage of glycogen. This reflects their emphasis on carbohydrate metabolism generally and the release of energy by anaerobic glycolysis, which is of obvious value in endoparasites living in anaerobic or potentially anaerobic surroundings (Von Brand, 1966). What little is known of the food reserves of the commensal and parasitic Turbellaria tends to support this hypothesis of a close correlation between food reserves and mode of life. The ectocommensal temnocephalids, for example, form reserves very similar to those of free-living flatworms, and this affords a further demonstration of how little their nutritional physiology is modified from the basic turbellarian pattern. Entocommensals such as Syndesmis antillarum and S. franciscana, in contrast, do form large reserves of glycogen. The significance of this in their case, however, is obscure, since their habitat is far from anaerobic and the explanation used to account for large deposits of glycogen in cestodes, for example, cannot apply here. Nevertheless, there does appear to be some correlation between life within another organism and the deposition of large amounts of glycogen, as similar cases have been reported where the oxygen tension of the environment cannot be the deciding factor. In the Digenea, for example, species parasitizing the frog lung may have a high glycogen content (Halton, 1967b), despite the aerobic situation. Possibly the emphasis on carbohydrate metabolism in these cases is related to the increased production of eggs, or to some other factor as yet unknown. The various associations between Turbellaria and other organisms reviewed here probably arose originally from chance contacts which conferred immediate

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selective advantages in terms of food or shelter, or both. From such contacts a gradual intensification of the relationship would give rise to all the different degrees of commensalism seen in modern forms, and culminate in a few instances in the complete dependence upon the host seen in the parasitic species. It is conceivable that the evolution of the Trematoda and Cestoda in its earliest stages followed a similar pattern, with ancestral forms arising from a stock common to these groups and to the Turbellaria but becoming associated primarily with molluscs, some other invertebrates and eventually the vertebrates rather than with echinoderms. Further evolution paralleling that of the host organisms and modifying the structure, physiology and life cycles of the ancestral forms, to allow full exploitation of the potentials of the parasitic life, would then give rise to the trematodes and cestodes as they are known today. REFERENCES

Annandale, N. (1912). Curidiiticola, a new type of Temnocephaloidea. Rec. Indian MUS.7,232-243.

Atkins, D. (1934). Two parasites of the common cockle Curdiumedule; a rhabdocoele Paravortex cardii Hallez and a copepod Paranthessius rostratus (Canu). J. mar. biol. Ass. U.K.19, 669-676. Averinzev, S. (1925). Uber eine neue Art von parasitaren Tricladen (Micropharynx). Zool. Anz. 64,81-84. Baer, J. G. (1931). Btude monographique du groupe des Temndphales. Bull. biol. Fr. Belg. 55, 1-57.

Baer, J. G. (1938). On the anatomy and systematicstatus of Cleisfogamiaholofhuriana Faust, 1924. Rec. Indian Mus. 40, 159-168. Baer, J. G, (1951). “Ecology of Animal Parasites.” Univ. Illinois Press, Urbana. Baer, J. G. (1961). Classe des Temnoc4phales. In “Trait6 de Zoologie” 4 (Ed. P-P. GrassC), pp. 213-241. Masson et Cie, Paris. Ball, S. J. (1916). Development of Paravortex gemellipara. J. Morph. 27,453-557. Baylis, H. A. (1949). Fecampia spiralis, a cocoon-forming parasite of the antarctic isopod Serolis schyfei.Proc. Linn. SOC.Lond. 161,64-71. Beklemischev, W . (1915). Sur les TurbellariCs parasites de la c6te Mourmannes. I. Acoela. Trav. de la SOC.imp. des narur. de Petrograd. Zool. er Physiol. 43, 103-172.

Beklemischev, W. (1916). Sur les turbellariis parasites de la c6tc Mourmannes. 11. Rhabdocoela. Trud? leningr. Obshch. Estesf.45, 1-59. Bock, S. (1925a). Anoplodium stichopi, ein neuer Parasit von der Westkiiste Skandinaviens. Zool. Bidr. Upps. 10, 1-30. Bock, S . (1925b). Papers from Dr. Th. Mortensen’s Pacific Expedition 1914-16. XXV. Planarians. Parts 1-111. Vidensk.Meddr dansk nafurh.Foren. 19, 1-84 and 97-1 84.

Bock, S. (1926). EinePolyclademit muskulosen Driisenorganen rings um den Korper, 2001. Anz. 66, 133-138.

Caballero, E. and Zerecero, C. (1951). Presencia de Temnocephala brevicornis Monticelli, 1889, en crustaceos venezolanos. Revta Med. vet. Parasit., Caracas 10, 110-117.

Caullery, M. and Mesnil, F. (1903). Recherches sur les Fecumpia Giard, TurbellariCs Rhabdocoeles, parasites internes des Crustacks. Annls Fac. Sci. Marseille 13, 13 1-1 68.

28

J . B. J E N N I N G S

Christensen, A. M. and Kanneworff, B. (1964). Kronborgia amphipodocola gen. et sp. nov., a dioecious turbellarian parasitizing ampeliscid amphipods. Opheliu 1, 147-1 66. Christensen, A. M. and Kanneworff, B. (1965). Life history and biology of Kronborgia amphipodicola Christensen and Kanneworff (Turbellaria, Neorhabdocoela). Ophelia 2, 237-25 1. Christensen, A. M. and Kanneworff, B. (1967). On some cocoons belonging to undescribed species of endoparasitic turbellarians. Ophelia 4,2942. Dakin, W. (1912). Buccinirm. Proc. Trans. Lpool biol. SOC.26, Mem. NO. 2. Dawes, B. (1963). Hyperplasia of the bile duct in fascioliasis and its relation to the problem of nutrition in the liver fluke, Fasciola hepatica L. Puraritology 53, 123-133. De Beauchamp, P. (1921). Sur quelques Rhabdocoeles des environs de Dijon. C. R. Assoc. franc. Av. Sci., Congr. Strasbourg, 1921. De Beauchamp, P. (1961). Classe des TurbellariCs. I n “Traite de Zoologie” 4 (Ed. P-P. Grassk), pp. 35-212. Masson et Cie, Paris. Dorler, A. (1900). Neue und wenig bekannte rhadocole Turbellarien. Z . wiss. Zool. 68, 1-42. Fernando, W. (1945). The storage of glycogen in the Temnocephaloidea. J. Parasit. 31, 185-190. Francois, P. (1886). Sur le Syndesmis, nouveau type de Turbellaries dCcrit par M. W. A. Silliman. C. R. Acad. Sci. Paris 103,752-754. Fyfe, M. L. (1942). The anatomy and systematic position of Temnocephala novaezealandiae Haswell. Trons. R. Sac. N.Z. 72, 253-267. Giard, M. A. (1886). Sur un rhabdocoele nouveau, parasite et nidulant (Fecampiu erythrocephala). C. R. Acad. Sci. Paris 103,499-501. Girard, C. (1850). Two marine species of Planariae. Proc. Boston SOC.nuf. Hisr. 3, 264. Girard, C. (1852). Descriptions of two new genera and two new species of Planariae. Proc. Boston SOC.nut. Hist. 4, 210-212. Gomales, M. D. P. (1949). Sobre a digestlo e respiracfio des Temnocephalas (Temnocephalus bresslarri spec. nov.). Bol. Fac. Filos. Ciinc. Univ. SGo Paul0 (Zool.) 14, 277-323. Hallez, P. (1909). Biologie, organization, histologie et embryologic d’un rhabdocoele parasite du Cardiim edule L., Paravortex cardii n. sp. Archs Zool. exp. gkn. Ser. 4 9, 1047-1049. Halton, D. W. (1967a). Observations on the nutrition of digenetic trematodes. Parasitology 57, 639-660. Halton, D. W. (1967b). Studies on glycogen deposition inTrematoda. Comp. Biochem. Physiol. 23, 113-120. Haswell, W. A. (1887). On Temnocephala, an aberrant monogenetic trematode. Q. J f microsc. Sci. 28, 279-303. Haswell, W. A. (1893). A monograph of the Temnocephaleae. I n “Macleay Memorial Volume”, pp. 94152. Proc. Linn.SOC.N.S. W., Sydney. Haswell, W. A. (1900). Supplement to a monograph of the Temnocephaleae. Prac. Linn. SOC. N.S. W. 25,430-434. Hazard, F. 0. (1941). The absence of opalinids from the adult green frog Ram clamitans. J. Parasit. 27, 513-516. Hett, M. L. (1925).On anew species of Temnocephola(T. chaerupis)fromW .Australia. Proc. zool. SOC. Lond., 569-575 (1 925). Hickman, V. V. (1955). Two new rhabdocoel turbellarians parasitic in Tasmanian holothuroids. Pap. Proc. R. Soc. T a m . 89, 81-97.

PARASITISM A N D COMMENSALISM I N T H E T U R B E L L A R I A

29

Hickman, V. V. (l956), Parasitic Turbellaria from Tasmanian Echinoidea. Pap. Proc. R. SOC. Tasm. 90,169-181. Hickman, V. V. (1967). Tasmanian Temnocephalidae.Pap. Proc. R. SOC.Tasm.101, 227-250. Hickman, V. V. and Olsen, A. M. (1955). A ncw turbellarian parasite in the sea-star Coscinasterias calamaria Gray. Pap. Proc. R. SOC. Tasm. 89, 55-63. Hyman, L. H. (1944). A new Hawaiian polyclad flatworm associated with Teredo. Occ. Pap. Bernice P. Bishop Mus. 18,73-75. Hyman, L. H. (1951). “The Invertebrates: 2, Pfatyhelminthes and Rhynchocoela.” McGraw-Hill, New York. Hyman, L. H. (1955a). Miscellaneous marine and terrestrial flatworms from South America. Am. M u . Novit. No. 1742, 1-33. Hyman, L. H. (1955b). “The Invertebrates: 4, Ekhinodermata”. McGraw-Hill, New York. Hyman, L. H. (1960). New and known umagillid rhabdocoels from echinoderms.Am. MUS.Novit. NO. 1984, 1-14. Hyman, L. H. (1967). “The Invertebrates: 6,Mollusca: 1.” McGraw-Hill,New York. Jagerskiold, L. A. (1896). Ueber Micropharynx parasitica, n. g., n. sp., eine ectoparasitische Triclade. Ofv. Vet. Akad. Forhandl. Stockholm 53,707-715. Jagersten, G . (1942). Zur Kenntnis von Glanduloderma myzostomatis n. gen., n. sp., einer eigentiimlichen,in Myzostomiden schmarotzendenTurbellarienforrn. Ark. ZOO!. 33, NO. 3, 1-24. Jennings, J. B. (1957). Studies on feeding, digestion and food storage in free-living flatworms. Biol. Bull. 112,63-80. Jennings, J. B. (1962). Further studies on feeding and digestion in triclad Turbellaria. Biol. Bull. 123, 571-581. Jennings, J. B. (1968a). A new temnocephalid flatworm from Costa Rica. J. nut. Hist. 2, 117-120. Jennings, J. B. (1968b). Platyhelminthes: Nutrition. In “Chemical Zoology” 2 (Eds M. Florkin and B. T. Scheer), pp. 303-326. Academic Press, New York. Jennings, J. B. (1968~).Feeding, digestion and food storage in two species of temnocephalid flatworms (Turbellaria: Rhabdocoela). J. Zool., Lond. 156, 1-8. Jennings, J. B., and Mettrick, D. F. (1968). Observations on the ecology, morphology and nutrition of the rhabdocoel turbellarian Syndesmis franciscana (Lehman, 1946) in Jamaica. Caribb. J. Sci. 8, 57-69. Jhering, H. von (1880). Grafilla muricolu, eine parasitische rhabdocoele. 2.wiss. ZOO^. 34,147-1 74. Kaburaki, T. (1922). On some Japanese Tricladida Maricola, with a note on the classification of the group. J. Coll. Sci. imp. Univ. Tokyo 44, 1-54. Kaburaki, T. (1925). An interesting alloeocoel infesting the alimentary canal of Metacrinus rotundus P.H.C. Annotnes 2001. jap. 10,299-310. Kanneworff, B. and Christensen, A. M. (1966). Kronborgia caridicola sp. nov., an endoparasitic turbellarian from North Atlantic shrimps. Ophelia 3,65-80. Kato, K. (1935a). Dkcoplana takewakii sp. nov., a polyclad parasitic in the genital bursa of the Ophiuran. Annotnes zoo!.jap. 15,149-1 56. Kato, K. (1935b). Stylochoplanaparasitica sp. nov., a polyclad parasitic in the pallial groove of the Chiton. Annotnes 2001. jap. 15, 123-129. Khalil-Bey, M. (1938). Cleistogamiu loutfia (Khalil-Bey et Azim, 1937) Khalil-Bey, 1937; a redescription. J. Egypt. med. Ass. 21, 285-287. Kozloff, E. N. (1953). Collastoma pacifca sp. nov., a rhabdocoel turbellarian from the gut of Dendrostomapyroides Chemberlin. J. Parasit. 39, 336-34.

30

J . B. JENNINGS

,

Laidlaw, F. (1902).Typhlorhynchus nunus. Q.JI niicrosc. Sci. 45,637-652. Lehman, H. E. (1946). A histological study of Syndisyrinx franciscanus, gen. et sp. nov., an endoparasi tic rhabdocoel of the sea urchin Strongylocentrotirsfranciscanus. Biol. Bull. 91,295-311. Leigh-Sharpe, W. H. (1933). Note on the occurrence of Grafila geniellipara Linton (Turbellaria) at Plymouth. Parasitology 25, 108. Leiper, R. T. (1902). On an acoelous turbellarian inhabiting the common heart urchin. Nature, Lond. 66.641. Leiper, R. T. (1904). On the turbellarian worm Avagina incola, with a note on the classification of the Proporidae. Proc. 2001. SOC.Lond. 1,407411. Linton, E.(1910).On a new rhabdocoele commensal with Modiolusplicatulus. J. exp. Z001.9,371-386. Marcus, E. (1949). Turbellaria Brasileiros (7). Bol. Fac. Fil. C i h . Letr. Univ. Srio Paula, zool. 14,7-155. Marcus, E. (1952).Turbellaria Brasileiros (10).Bol. Fac. Fil. C i h . Letr. Univ. Srio Paulo, zool. 17,5-188. Marcus, E. (1968). A new Syndesmis from Saint-BarthClerny, Lesser Antilles. (Neorhabdocoela). Stud. Fauna Curacao 26,139-42. Merton, H. (1913). Beitrage zur Anatomie und Histologie von Temnocephala. Abh. senckenb. naturforsch. Ges. 35, 1-58. Meserve, F. G. (1934). A new genus and species of parasitic Turbellaria from a Bermuda sea cucumber. J. Parasit. 20,270-276. Mettrick, D. F. and Jennings, J. B. (1969).Nutrition and chemical composition of the rhabdocoel turbellarian Syndesmis franciscana (Lehman, 1946), with notes on the taxonomy of S. antillarum Stunkard and Corliss, 1951.J, Fish. Res. Bd Can. 26,NO. 10, 2669-2679. Monticelli, F. S. (1892). Notizia preliminare intorno ad alcuni inquilini degli Holothuroidea del Golfo di Napoli. Monifore zool. Ital. 3,248-256. Monticelli, F. S. (1899). Sulla Temnocephala brevicornis Mont. 1889 e sulle Temnocefale in generale. Boll. SOC.Nut. Napoli 12,72-127. Monticelli, F. S. (1902). Temnocephala dkitata n. sp. Boll. SOC.Nut. Napoli 16,309. Monticelli, F. S. (1903) Temnocephala microdactyla n. sp. Boll. Musei 2001.Anat. comp. R. Univ. Torino 18,1-3. Monticelli, F. S. (1905). Di un Temnocephala della Sesarma gracillipes. Ann. Mus. M t . Hung. 3,21-24. Monticelli, F. S. (1913). Brevi communicazione sulle Temnocefale. Boll. SOC.Nut. Napoli 26,7-8. Mrazeck, A. (1906). Ein Europaischer Vertreter der Gruppc Ternnocephaloidea. Sber. K. bohm. Ges. Wiss. 36, 1-7. Naylor, E. (1952). On Plagiostomum oyense de Beauchamp, an epizoic turbellarian new to the British Fauna. Ann. Rep. Mar. biol. Sra. Port Erin 64 (1951). Naylor, E. (1955). The seasonal abundance on Idotea of the cocoons of the flatworm PIagiostomum oyense de Beauchamp. Ann. Rep. mar. biol. Sta. Port Erin 67 (1954). Ozaki, Y.(1932). On a new genus of parasitic Turbellaria “Xenometra” and a new species of Anoplodium. J. Sci. Hiroshima Univ. (Zool.),Ser. B. Dib. 1, 1,81-89. Pearse, A. S. and Wharton, G. W. (1938). The oyster “leech” Stylochus inimicus Pdomli, associated with oysters on the coasts of Florida. Ecol. Monogr,, Durham, N. C. 8,605-655. Pereira. C. and Cuocolo, R. (1940).ContribuiCHo para o conhecimento da morfologia, bionomia e ecologia de “Temnocephala brevicornis Monticelli 1 889”. Archos Znst. biol., S. Paula 11.367-398.

PARASITISM AND COMMENSALISM I N THE TURBELLARIA

31

Pereira, C. and Cuocolo, R. (1941). Estudos sobre “Temnocephalidae Monticelli, 1899”, com estabelecimento de dois novos gheros australianos e descriGlo de duas novas espkies neotr6picas. Archos Znst. biol., S. Paul0 12, 101-127. Plate, L. (1914). Uber zwei ceylonischeTemnocephaliden. Jena. 2. Med. Naturw. 51, 707-722.

Powers, P. B. A. (1936). Studies on the ciliates of sea urchins. Rep. Tortugas Lab. 29,101-103.

Prudhoe, S . (1968). A new polyclad turbellarian associating with a hermit crab in the Hawaiian Islands. Pat$ Sci. 22,408-41 1. Reisinger, E. (1930). Zum ductus genito-intestinalis Problem. i. Uber primiire Geschlechtstraktdarmverbindungen bei rhabdocoelen Turbellarien. 2. Morph. ‘ C)kol. Tiere 16,49-73. Reynoldson, T. B. and Young, J. 0.(1963). The food of four species of lake-dwelling triclads. J. Anim. Ecol. 32, 175-191. Rohde, K. (1966). A Malayan record of Temnocephala semperi,ectocommensalon the freshwater crab Potamon raflesi Roux. Med. J. Malaya 20,356. Russo, A. (1895). Sulla morfologia del Syndesmis echinorum FranGois. Ric. Lab. Anat. norm. R. Univ. Roma 5,43-68. Ryder, J. A. (1882). Observations on the species of planarians parasitic on Limulus. Am. Nut. 16,48-51. Schneider, A. (1858). Uber einige Parasiten der Holothuria tubulosu. Mull. Arch. Anat. Physiol. Berlin. Shipley, A. E. (1901). On some parasites found in Echinus esculentus. Q . JI microsc. Sci. 44,281-296. Silliman, W. A. (1881). Sur un nouveau type de Turbellairies. C. R. Acad. Sci.,Paris 93,1087-1089.

Southern, R. (1936). Turbellaria of Ireland. Proc. R. Zr. Acad. 43, B, 61-62. Southward, A. J. (1951). On the occurrence in the Isle of Man of Fecampia erythrocephala Giard, a platyhelminth parasite of crabs. Ann. Rep. mar. biol. Sta. Port Erin 63 (1950). Stunkard, H. W. and Corliss, J. 0. (1951). New species of Syndesmis and a revision of the family Umagillidae Wahl, 1910 (Turbellaria: Rhabdocoela). Biol. Bull. 101, 319-334.

Syriamiatnikova, I. P. (1949). A new turbellarian parasite of fish, Zchthyophagu subcutanea n.g. nov. sp. (In Russian.) C. R. Acad. Sci., Moscow n.s. 68, NO. 2. Vayssitre, A. (1892). Btude sur le Temnocdphale parasite de I’Astacoides madugascariensis. Annls Fac. Sci. Marseille 2, 1-23. Vayssitre, A. (1 898). Description du Temnocephala mexicana, nov. sp. Annls Far. Sci. Marseille 8, 227-235. Von Brand, T. (1966). “Biochemistry of Parasites.” Academic Press, New York. Von Graff, L. (1904-1908). Acoela und Rhabdocoelida. Zn “Klassen und Ordnungen des Tier-Reichs” 4,1. 1 (Ed. H. G. Bronn), pp. 1-2599. Wacke, R. (1905). Beitrage zur Kenntniss der Temnocephalen (T. chilensis. T. tumbesiana und T. novae-zelandiae).Zool. Jb. Supp. Bd. VI (Fauna Chilensis , Bd. 111). 1-116. Wahl, B. (1909). Untersuchungen Uber den Bau der parasitischen Turbellarien aus der Familie der Dalyelliiden (Vorticiden), 1-111. Sber. Akud. Wiss. Wien, Mathnafurwiss.118, 943-965. Wahl, B. (1910). Beitragezur Kenntnis der Dalyelliiden und Umgilliden. In “Festchr. fiir R. Hertwig”, pp. 39-60. G. Fischer, Jena. Weber. M. (1889). Ueber Temnocephala Blanchard. In “Zool. Ergeb. einer Reise in Niederlandisch Ost-Indien”. 1, 1-29.

-

32

J.

n.

JENNINCS

Westblad, E. (1926). Parasitische Turbellarien von der Westkuste Skandinaviens. ZOO^. Attz. 61, 323-333. Westblad, E. (1930). Anop/odiera volufu und Wahlia rnacrostyliyera, zwei neue parasitische Turbellarien aus Sticliopus tremuliis. Z. Morph. L)kol. Tiere 19, 397-426. Westblad, E. (1937). Die Turbellarien-Gattung Nemcrtodcrma SteinbBck. Actu SOC. Fauna Flora,fenn. 60,45-89. Westblad, E. (1949). On Meara stichopi (Bock) Westblad, a new representative of Turbellaria archoophora. Ark. Zool. 11. ser. 1, no. 5,43-57. Westblad, E. (1953). New Turbellaria parasites in echinoderms. Ark. Zool. n. ser. 5, no. 2,269-288. Westblad, E. (1955). Marine alloeocoels (Turbellaria) from N. Atlantic and Mediterranean coasts. Ark. Zool. n. ser. 7,491-526. Wheeler, W. M. (1894a). Syncoelidium pellucidum, a new marine triclad. J. Morph. 9,167-194. Wheeler, W. M. (1894b). Plunoceru inquilina, a polyclad inhabiting the branchial chamber of Sycorypus cunaliculatus, Gill. J . Morph. 9, 195-201. Wilhelmi, J. (1909). Tricladen. Fauna und Flora des Golfes von Neapel u. d. angr. Meeresabschnitte. Monographie 32, Berlin.

Paramphistomiasis of Domestic Ruminants . .

I G HORAK

M S D (PT Y )LTD. 142 Pritchard Street. Johannesburg. Republic of South Africa I . Introduction .................................................................................... I1 Pathogenic Species of Paramphistome ................................................... A . Africa .................................................................................... B. Asia ....................................................................................... C. Australasia ................................................................................. D Eastern Europe and Russia ............................................................ E. The Mediterranean Countries ......................................................... 111. Life Cycle ....................................................................................... A . Paraniphistomum microbothriuni ................................................... B. Paramphistomum ichikawai ............................................................ C. Cotylophoron corylophorum ......................................................... D. Calicophoron ca[icophorum ............................................................ 1v. Development in the Definitive Hosts ...................................................... A . A Comparison of the Life Cycle in Sheep. Goats and Cattle ..................... B. The Effects of Massive Infection on the Life Cycle .............................. V . Immunity .......................................................................................... A Field Observations ........................................................................ B. Multiple Infections ..................................................................... C. Immunization ........................................................................... D. The Effects of Immunity on Paramphistomes .................................... E . Serology ................................................................................. VI . Pathology ....................................................................................... A . Clinical Signs .............................................................................. B. Clinical Pathology ...................................................................... C. Pathological Anatomy .................................................................. D. Pathogenesis .............................................................................. VII. Epizootiology .................................................................................... v111. Diagnosis .......................................................................................... 1x. Treatment ....................................................................................... A Adult Paramphistomes .................................................................. B. Immature Paramphistomes ............................................................ X . Control .......................................................................................... Acknowledgements ........................................................................... References .......................................................................................

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33 34 34 35 35 35 36 36 36 38 39 40 40 40 44 46 46

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47 50 51 52 52 53 56 61 63 65 66 66 66 68

70 70

I . INTRODUCTION Infections by adult members of the family Paramphistomatidae may be found in sheep. goats. cattle and water buffalo in countries situated around the globe . The disease paramphistomiasis. caused by massive infection of the small intestine with immature paramphistomes. is however. confined to Africa. 33

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Asia, Australasia, Eastern Europe and Russia and some of the Mediterranean countries. Paramphistomiasis is characterized by sporadic epizootics of acute parasitic gastro-enteritis with high morbidity and mortality rates, particularly in young stock. Although various paramphistomes have been incriminated as the aetiological agents of this disease none has been studied as extensively as Paramphistomum microbothriumin Africa and Israel, Paramphistomum ichikawai in Australia and Corylophoron cotylophorum in India. Consequently this review will to a large extent discuss our present knowledge of these three paramphistomes and the role they play in the aetiology of the disease. At the same time findings concerning the other paramphistomes responsible for paramphistomiasis will be presented. 11. PATHOGENIC SPECIESOF PARAMPHISTOME

The various genera of the family Paramphistomatidae are difficult to identify from the systematic point of view. Nasmark (1937) has discussed this difficulty fully and attempted to overcome it by histiological examination of median sagittal sections in which particular attention is directed to the structure of the acetabulum, pharynx and genital atrium. Dawes (1946, 1956, 1968) considered that the majority of species of Paramphistomum are synonyms of either P. cervi (Zeder, 1790) or P. explanatum (Creplin, 1849). Subsequent workers have considered that some of these species are in fact valid (Durie, 1951; Swart, 1954; Lengy, 1960). In this text the species names used are those listed by Yamaguti (1958); where species names have been changed the most recent name is used with the name appearing in the particular publication given as a synonym in brackets. Although numerous species of paramphistome exist, outbreaks of paramphistomiasis are confined to massive infections by certain species only. Because the worms responsible for disease are sexually immature, specific identification is made even more difficult and the investigator may have to rely on the dubious procedure of identifying a few adult worms which may be present in the rumen of the diseased animal. With these reservations in mind the following species have been incriminated as the cause of paramphistomiasis in domestic ruminants in various countries around the globe. A.

AFRICA

Deaths in cattle as a result of paramphistome infection have been reported by Simson (1 926), Butler and Yeoman (1 962) and Horak (1 967) and in sheep by Simson (1926), Le Roux (1930), Eddin (1955), Roach and Lopes (1966) and Horak (1 967). Dinnik (1964) stated that in all cases of paramphistomiasis in Africa, where the paramphistome species responsible has been identified, the disease was was caused by P. niicrobothrium. In the outbreaks described by Le Roux (1 930) the paramphistome responsible was originally named C. cotyfophortrm but was later identified by Dinnik (1965) as P . microhothriuni.

P A R A M P H I S T O M I A S I S OF DOMESTIC R U M I N A N T S

35

In an outbreak in sheep in Kenya described by Roach and Lopes (1966) both P. microbothrium and Paramphistomum daubneyi were incriminated. This outbreak, however, was also complicated by the presence of liver fluke. B. ASIA

Infection has been recorded in buffaloes by Patnaik (1964); outbreaks of paramphistomiasis have been reported in cattle by Pande (1935), DSouza (1948) and Ramakrishnan (1950); in sheep or goats by Baldrey (1906), Walker (1906), Haji (1935), Bawa (1939), Mudaliar (1945), DSouza (1948), Katiyar and Varshney (1963), Katiyar and Garg (1965) Sharma Deorani and Katiyar (1967). A review on paramphistomiasis in domestic ruminants in India was published by Alwar (1948). Investigating a number of outbreaks in sheep and goats in Uttar Pradesh, India, Katiyar and Varshney (1 963) found the amphistomes responsible for the disease in order offrequency to be Gastrothylaxcrumenifer, C . cotylophorum, P. cervi, Fischoederius elongatus and P. explanatum. Ramakrishnan (1 950) investigated an outbreak in young and adult cattle caused by Fischoederius cobboldi and G. crumenifer, while D’Souza (1948) incriminated C. cotylophorum and G. crumenifer as causing the disease in cattle and sheep and Patnaik (1964) recovered P. explanatum from infected buffaloes. In Ceylon, Dewan (1966) reported the death of a cow owing to massive infection with Cotylophoron sp. and Lee (1967) recorded a high incidence of infection with several species of adult paramphistomes in cattle and buffaloes in West Malaysia. C. AUSTRALASIA

In Australia paramphistomiasis occurs in cattle (Edgar, 1938; Boray, 1959) and in sheep (Boray, 1959, 1969a, 1969b). According to Durie (1956) one of the most common paramphistomes occurring in cattle is Calicophoron calicophorum but no record can be found of this species being pathogenic for cattle. Boray (1969a, 1969b) has described an outbreak in sheep caused by P . ichikawai. In New Zealand Whitten (1955) described the disease, probably caused by C . calicophorum [syn. Calicophoron ijimai] in a flock of 250 ewes of which 35 died as a result of infection. D. EASTERN EUROPE AND RUSSIA

Because of language difficulties the major portion of the discussion under this heading has been obtained from various abstracting journals and not from the original publications. I . Bulgaria. Clinical paramphistomiasis in adult cattle, probably caused by P . cervi, has been described by ViSnjakov and Ivanov (1964). 2. Hungury. A detailed description of an outbreak of paramphistomiasis in young cattle was given by Boray (1959) and two species of paramphistome,

36

I. G. HORAK

namely P. microbothrium and Paramphistomum microbothroides, have been described from cattle by Kotlan (1958). 3. Poland. Infection with P. cervi resulted in clinical symptoms, particularly in young cattle with a mortality rate probably not exceeding 10% (Anczykowski and Chowaniec, 1955). 4. Russia. The disease appears to occur mainly in the Ukraine where climatic conditions probably closely approximate those in Eastern Europe. Paramphistomiasis has been reported in cattle by Podberezski (1951), Orlova (1953), Deusov (1955), Tsvetaeva (1959) and Mereminskii and Gluzman (1967). The latter authors identified P. cervi as the cause of one outbreak of acute paramphistomiasis amongst calves. E. THE MEDITERRANEAN COUNTRIES

1. France. Guilhon and Priouzeau (1945) reported on the occurrence of paramphistomiasis in four cattle. Although the symptoms were similar to those of acute intestinal paramphistomiasis the authors were able to recover P. cervi only from the rumen of the affected animals. It is possible that the immature paramphistomes responsible for the disease had already migrated to the rumen by the time the animals were slaughtered. 2. Israel. Acute paramphistomiasis has occurred in cattle in the form of sporadic outbreaks (Nobel, 1956). Lengy (1960) identified the pathogen in one such outbreak as P . microbothrium. 3. Itah. Paramphistomiasis in cattle caused by P. cervi has been described by Bonini (1963). 4. Sardinia. An outbreak of acute paramphistomiasis in goats caused by P . cervi described by Deiana et al. (1 962), while Dinnik (1964) identified young specimens of P. inicrobothrium in a collection of paramphistomes made by le Roux in Sardinia. 5. Turkey. Kurtpinar (1955) reported the death of ten cattle in an outbreak of acute paramphistomiasis. No specific identification of the fluke involved was made. 6. Yugoslavia. Cvetkovic (1968) identified P. microbothrium as the cause of an outbreak of acute paramphistomiasis in a flock of sheep. During the course of approximately 1 month 30 % of the sheep and 77 % of the lambs died. Employing the number of publications directly concerned with outbreaks of paramphistomiasis as an extremely arbitrary indication of the extent of the problem, it would appear that India is the most severely affected followed by the eastern half of Africa and the Russian Ukraine and that P. microbothrium, P . cervi and Cytolopltoron spp. are responsible for the majority of outbreaks.

ur. A.

LIFECYCLE

PARAMPHISTOMUM MICROBOTHRIUM

The eggs laid by the adult paramphistomes present in the rumen are evacuated with the faeces of the host. If temperature and moisture conditions

P A R A M PHISTOMIASIS OF DOMESTIC RUMINANTS

i

37

are adequate, development of the miracidium within the egg can start once the egg has been freed from the faecal mass (Swart and Reinecke, 1962b). Miracidia hatch from eggs after incubation at 27°C for 12 days (Swart and Reinecke, 1962b) or after 14-16 days when incubated at 2628°C (Dinnik and Dinnik, 1954) or on the 17th day at 28°C (Lengy, 1960). The hatching of the miracidium is triggered off by exposing full term eggs to light (Lengy, 1960). The newly-hatched miracidia generally swim in straight lines; in the vicinity of snails, however, most miracidia become excited and swim in short elliptical courses. Two species of snail serve as intermediate hosts for P. microbothrium. These are Bulinus tropicus in Kenya (Dinnik and Dinnik, 1954) and South Africa (Swart and Reinecke, 1962a); and Bulinus truncatus in Israel (Lengy, 1960) and Iran (Arfaa, 1962). The miracidia penetrate the snail after entering the respiratorycavity (Dinnik and Dinnik, 1954;Lengy, 1960).They apparently do not penetrate through the head, foot or tentacles of the snail and all B. iruncatus snails are equally well infected irrespective of age or size (Lengy, 1960). Swart and Reinecke (1962b), however, found that only 12.4% of 800 adult B. tropicus became infected, whereas all snails of this species 7-21 days old could be infected. Lengy (1960) studied the early development of the sporocyst in the snail and found embryonic rediae developing within the sporocyst on the 3rd day of infection, the first redia leaving the sporocyst on the 10th day. Both Dinnik and Dinnik (1954) and Lengy (1960) found that the rediae give rise to daughter rediae, then to cercariae and then again to rediae, the daughter rediae following the same pattern. The cercariae emerge from the rediae while they are still immature and require a further period of maturation, which takes place in the hepato-pancreas of the snail. The first free cercariae are recovered from the tissue of the snail on the 26th day of infection (Lengy, 1960) or on the 30th day (Dinnik and Dinnik, 1954). The first cercariae emerge from infected snails on the 37th day (Lengy, 1960) or 43rd to 46th day (Dinnik and Dinnik, 1954). The slower rate of development recorded by the latter authors is probably due to the fact that their snails were kept at a temperature of 18-22°C compared with28"C by Lengy (1960). At the MSD Veterinary Research and Development laboratory in South Africa cercarial emergence has been recorded as early as the 30th day after infection in snails kept at 2428°C. The cercariae, which each have a pair of eyespots, are stimulated to emerge by exposing the infected snails to light, and the greater the light intensity the more cercariae will emerge (Lengy, 1960). The majority of cercariae are shed within 4 h of exposure to light (Dinnik and Dinnik, 1954; Lengy, 1960; Swart and Reinecke, 1962b). Infected snails can live and shed cercariae for 10 months, (Swart and Reinecke, 1962b), or 1 year (Dinnik and Dinnik, 1954). After emerging from the snail, cercariae swim actively and congregate near the surface of the water where the light is most intense (Dinnik and Dinnik, 1954). They start encysting shortly after emergence and favour surfaces with a yellow or green colour (Lengy, 1960). The process of encystment has been described by Lengy (1960). When about to encyst the cercaria comes to rest on its ventral surface; strong contractions

38

1. G . H O R A K

and extensions coupled with side movements of the body follow. Cystogenous matter, which is granular in nature, then begins to exude from pores all over the body and the cercarial tail breaks off. The cercaria slowly rotates within the cystogenous matter which has formed a brown ring and cystogenousrods are released through the cuticle into the surrounding matter. The movements of the cercaria shape the exuded material into a dome-like cyst, which develops an outer clear and inner opaque layer. The cercaria then contracts sharply and becomes spherical and the cuticle is detached forming a third layer within the cyst. By the end of 20 min a definite cyst has formed around the cercaria, which continues rotating for another 8-12 h, apparently completing the inner wall, before coming to rest. The metacercariae so formed require a period of maturation of at least 24 h before the majority are capable of excystment, and may remain viable for at least 29 days if kept moist at room temperature (Horak, 1962a). After ingestion by the final host excystment is accomplished during passage through the rumen, abomasum and small intestine with consequent exposure to ruminal fluid then pepsin and hydrochloric acid, followed by trypsin and bile salts in an alkaline medium (Horak, 1962a). Excystment and early attachment takes place in the first 6 m of the small intestine (Horak, 1967). The young paramphistomes grow rapidly and those which are attached behind the first 3 m portion of small intestine migrate to the anterior portion within the first 10 days after infection. Migration to the rumen commences on about the 10th day after infection and can be complete by the 39th day, but may continue for several weeks. On reaching the rumen the paramphistomes migrate to their predilected sites on the dorsal surface of the anterior ruminal pillar and the dorsal and ventral aspects of the posterior ruminal pillar (Horak, 1967). They continue growing and reach their maximum size in cattle 5-9 months after infection (Dinnik and Dinnik, 1962). The eggs of P . microbothrium are recovered from the faeces of cattle, goats and sheep, 56, 69 and 71 days after infection respectively (Horak, 1967). These prepatent periods are considerably shorter than the 89 days given for cattle by Dinnik and Dinnik (1962) and sheep (Lengy, 1960) and correspond to the 69 days given by Arfaa (1962) for sheep. The minimum period required for P . microbothriumto completethe entire life cycle in cattle is 98 days and about 113 days if sheep or goats are the final hosts. B. PARAMPHISTOMUM ICHIKAWAI

The life cycle of this paramphistome was described by Durie (1953) and Kisilev (1967). The miracidia hatch after 12 days of incubation at 27"C, light serving as a stimulus for hatching (Durie, 1953). Kisilev (1967) reported that the eggs hatched after 5 days of incubation at 33-39°C. Durie (1953) found that the behaviour of the miracidium and penetration of the intermediate snail host Segnitilia alphena are similar to those described for miracidia of P. microbothrim. The sporocyst becomes established and matures in what appears to be a small pocket in the tissue of the mantle, rediae are first released 8 days after infection. Cercariae are liberated from the rediae 15 days after

PARAMPHlSTOMlASIS O F DOMESTIC R U M I N A N T S

39

infection and require a further 10days of maturation in the snail’s tissue before being released on the 25th day. The shedding of cercariae is stimulated by light and the cercariae are attracted to yellow light. Encystment normally takes place within 30 min of liberation from the snail host. 32 % of metacercariae allowed to stand for 6 months under water were still viable (Durie, 1953). The eggs of P. ichikawai are recovered from the faeces of sheep 49 days after infection. Kisilev (1967) recovered sexually mature paramphistomes from sheep and cattle 42-51 days after infection, The minimum period to complete the entire life cycle if sheep serve as the final hosts is 86 days. C. COTYLOPHORON COTYLOPHORUM

’

The life cycle has been described by Srivastava (1938), Sinha (1950) and Varma (1961). Miracidia hatch from the eggs after 18-21 days of incubation at 27-32°C (Srivastava, 1938), 7-9 days at Indian summer room temperature (Sinha, 1950) or 15 days at 28-30°C (Varma, 1961). The miracidia seem to be attracted to the intermediate snail host Indoplanorbis exustus and after penetration develop into sporocysts (Varma, 1961). The first free rediae are found after 6 days (Varma, 1961) or 10 days (Sinha, 1950), and the development of daughter rediae may take pIace (Srivastava, 1938). The cercariae leave the rediae while still immature and require a further period of maturation in the tissues of the snail (Srivastava, 1938). The first cercariae are shed after 26 days (Varma, 196I), 30 days (Sinha, 1950) or 30-35 days (Srivastava, 1938). The cercariae leave the snail under the stimulus of light (Srivastava, 1938; Varma, 1961) and encyst on vegetation with a smooth surface in preference to that with a hairy or spiny surface (Varma, 1961). Srivastava (1938) found that the metacercariae remain viable for about 4 months if kept moist. Sinha (1950) stated that these paramphistomes took about 3 months to mature in the final host, but he gave no data to verify this. An interesting theory on the reasons for the intestinal phase in the life cycle of C. cotylophorum was put forward by Sharma Deorani and Jain (1969). They suggested that the young worms after excystment are unable to withstand the effects of the acid abomasal pH and consequently cannot migrate directly to the rumen. The worms are thus forced to remain in the small intestine for a certain amount of development before migration can commence. This development requires attachment and nourishment but as the superficialmucosa of the infected intestine undergoes constant desquamation this is not a suitable site and the worms enter the submucosa. Here they feed on the epithelial cells lining Brunner’s glands and grow, so that even though they are not mature when leaving the mucosa they are able to withstand the acid pH of the abomasum during their migration to the rumen. Krull (1933, 1934) and Bennett (1936) also described the life cycle of C. cotylophorum, but doubt on the validity of their identification of this paramphistome has been expressed by Price and McIntosh (1944) who considered it to be P . microbothriodes. Lengy (1960) expressed doubts as to the validity of P. microbothriodes as a separate species and argued that it should be considered as synonymous with P. microbothrium, the latter name having priority.

40

I . G . 11ORAK D. CALICOPHORON CALICOPHORUM

This paramphistome is commonly encountered in cattle in Australia (Durie, 1956) and South Africa (Swart, 1954). Durie (1956) described its life-history in naturally infected snails of the species Pygmanisus pelorius and consequently the rate of development of the various intermediate stages could not be determined. The larval stages and their development, however, appear to be similar to those of P . ichikawai as described by Durie (1953). The cercariae are attracted to and readily encyst on, a yellow illuminated surface. The prepatent period in an artificially infected lamb was 80-95 days. IV. DEVELOPMENT IN THE DEFINITIVE HOSTS Observations made during the investigation of either natural or artificial paramphistome infections in domestic livestock have indicated that the species of the final host has an influence on both the life cycle and pathogenicity of the various paramphistome species. Le Roux (1930) noted that cattle, grazing the same camps as sheep which died from paramphistomiasis, did not appear to be affected by the disease. Dinnik and Dinnik (1954) found that the percentage recovery of P. microbothrium was lower in artificially infected goats than in cattle and that the paramphistomes recovered from these goats were smaller than those in cattle. Deiana et al. (1962) found that P . cervi were larger in goats infected per 0s with live paramphistomes than in sheep infected at the same time in a similar manner. Katiyar and Varshney (1963) recorded higher mortality and morbidity rates in goats than in sheep infected with various paramphistome species. In an outbreak caused by Homalogaster poloniae, in which seven cattle died, Muchlis (1964) stated that buffaloes kept under similar circumstances showed a better adaptability to the environment. To clarify the position as far as P . microbothrium is concerned Horak (1967) conducted a series of comparative experiments in artificially infected sheep, goats and cattle. A.

A COMPARISON OF THE LIFE CYCLE IN SHEEP, GOATS AND CATTZE

Horak (1967) infected sheep, goats and cattle with identical small numbers of metacercariae of P . microbothrium. These animals were slaughtered at various times after infection; the small intestine was divided into 3 m portions and the worms were recovered from these portions and the other gastro-intestinal organs by sieving the contents. The worms were counted and 30 from each animal were measured. In those infections which were allowed to mature before slaughter faecal worm egg counts were performed at regular intervals. The percentage takes, i.e. the number of worms recovered expressed as a percentage of the number of metacercariae dosed are illustrated in Fig. 1. The takes in sheep and goats slaughtered 4 and 10 days after infection varied between 60.0 and 74.1 %, while those in cattle were 55.5 and 55.0 %. At 20 days the takes in sheep and goats were 72.1 and 53.1 % respectively while that in

PARAMPHISTOMIASIS O F DOMESTIC R U M I N A N T S

Y Q)

0

4

10

20 and 21

34 and 35

48

97

41

487 Age of infection in days

FIG.1. The percentage take in sheep, goats and cattle (Reprinted with permission from

Horak, 1967).

cattle at 21 days was 49.1 %. Thereafter the percentage take in sheep and goats declined erratically until at 487 days it was 2.8 % and 0-4% respectively, that in cattle, however, remained reasonably constant between 36.0 and 54-4%, the take at 487 days being 44.7%. This indicates a greater longevity for P . microbothrium in cattle than in either sheep or goats. Using the external breadth of the acetabulum as an indication of size it was possible to determine that the paramphistomes in cattle generally grow more rapidly than those in goats, in which they usually grow faster than in sheep. The frequency distributions of these measurements are illustrated in Fig. 2. Migration of the paramphistomes towards the rumen was determined by the shift in the percentage of worms present in the small intestine to the abomasum and then to the forestomachs. These percentage distributions are summarized in Table 1.

42

1. C . H O R A K

50

-

20 10

0.4

f

0.0

20

4

-

1.5

10

6Or

7

A 0'3

05

2.1

24

A

10 days

20

1

0-0.

12

15

18

20 10

Acetabular rnaasuramants in mm.

FIG.2. The acetabular size of paramphistomes recovered from sheep, goats and cattle (Reprinted with permission from Horak, 1967).

In the 4 days old infections most of the worms were concentrated in the first 3 m portion of the small intestine, but a fairly large percentage was found in the second and third 3 m portions. At 10 days nearly all these latter worms had migrated to the first 3 m of small intestine where they remained until migration to the rumen commenced, when the diameter of the acetabulum or posterior sucker was about 0.56 mm. This size is reached sooner in cattle, migration towards the rumen begins sooner and is completed sooner in this host species than in either sheep or goats. Massive migration commenced a t about 21 days and was virtually complete at 35 days in cattle, nearly as far advanced at 34 days in sheep, but in goats it had only just commenced at 34 days. At 48 days it was complete in cattle and very nearly so in sheep and goats. It is during and after this migration that worm loss occurs in sheep and goats, thus reducing the percentage take. The first paramphistome eggs were recovered from the faeces of infected

TABLE I Percentage take and worm distribution in sheep, goats and cattle V

Host

Age of infection in days

Worm distribution expressed as a percentage No. of No. of Small intestine First Second metacercariae worms Percentage Foredosed recpvered take Stomachs Abomasum 3 m 3m Remainder

> w

>

z

V

z

v)

Sheep Goat Bovine Sheep Goat Bovine Sheep Goat Bovine Sheep Goat Bovine SkP Goat Bovine Sheep Goat Bovine

4 4 4 10 10 10 20 20 21

34 34 35 48 48 48 97 97 97

10 000 10 000 10 000 10 000 10 000 10 000 10 000 10 000 10 000 10 000 10 000 10 000 5000 5000 5000 5000 5000 5000

6292 5955 5551 7411 6324 5501 7207 5306 4914 1088

2904 3602

384 950 2381 77 237 2721

_,

62.9 60.0 55.5 74.1 63.2 55-0 72.1 53.1 49.1 10-9 29.0 36-0 7-7 19.0 47-6 1.5 4.7 54.4

0.00 0.00 0.00 0.00 0.00 0.00 0-89 0.02 0.18 98-53 1-48

4-77 0.00 1-08 0.27 0-63 2.18 5-26 1.34 7-29 0.28 18-46

99.34 97 - 92 98.85 100-00 97-40 100*00 100.00

0-26 0.21 0.00 2-60 0.00 0.00

0.30

83-39 88-51 72.83 98-18 98-74 96-86 93-70 98 38 92-27 1.19 76-72 0.28 1-30 0.00 0.00 0.00 0.00 0.00

-

6.20 7.96 21-17 1-28 0.57 0-78 0.10 0.07 0.18 0.00 1*27 0.05 0.00 0.84 0.00 0.00 0.00

5.64 3.53 4.92 0.27 0.06 0.18 0.05 0.19 0.08 0.00 2.07 0-03 0.52 0.10 0.00

Extracted with permission from Horak (1967) P

w

44

I . G . FIORAK

cattle after 56 days while in shecp and goats this period was 71 and 69 days respectively. In both sheep and goats infections with 5000 metacercariae resulted in higher faecal worm egg counts than infections with 2000 or 10 OOO metacercariae. In cattle the highest egg count was obtained after infection with 10 000 metacercariae. After reaching peak levels egg counts remain at a high level in cattle, but decline with increasing age of infection in sheep and goats. Dinnik (1964) stated that two calves infected with P. microbothrium were still passing about 100 eggs per gram of faeces 7 and 10 years later. The highest concentration of eggs in the faeces of laboratory-housed sheep, goats and cattle fed at 8 a.m. and 2 p.m. occurred between 12 noon and 2 p.m. (Horak, 1967). To summarize briefly, the worms in cattle grow larger, migrate more rapidly, mature sooner, live and produce eggs for a longer period and a greater number survive migration than in either sheep or goats. B.

THE EFFECTS OF MASSIVE INFECTION ON THE LIFE CYCLE

Although in nature light infections are the rule, acute paramphistomiasis is caused by massive infections with immature worms affecting both the host and the parasite. Horak (1967) investigated the effects of massive experimental infection on the life cycle ofP. microbothrium in sheep and cattle. The animals were infected with 2000-305 OOO metacercariae and slaughtered at varying times thereafter. In sheep the percentage take was generally higher in heavily infected animals than in more moderately infected animals carrying infections of the same age. The reason for this was usually that in the moderate infections migration to the rumen had commenced and part of the worm burden was lost during this migration thus reducing the percentage take, while in the heavy infections migration and hence worm loss, was delayed. The percentage take in cattle with few exceptionsremainedat30 %-60 %irrespectiveof thedegreeof infection. In sheep with infections less than 21 days old, and in excess of 70 OOO worms most worms were recovered from the first 3 m of small intestine, but a fair number were present in the second 3 m portion. In older infections only a few were recovered from the latter site irrespective of the magnitude of the infection. In cattle with infections in excess of 50 OOO worms large numbers were recovered from the second 3 m portion of small intestine and even further back, for as long as 40 days after infection. Paramphistomes were frequently recovered from the gall-bladders of sheep and cattle with massive infections. The size of the worms in heavily infected sheep or cattle was smaller than that of worms of the same age in moderately or lightly infected animals. The frequency distributions of the acetabular measurements of paramphistomes recovered from cattle with moderate or heavy infections of approximately the same age are illustrated in Fig. 3. Because of the retardation in size, migration to the rumen was delayed in heavily infected animals. It was not complete 50 days after infection in a sheep harbouring 20 891 worms, while in a bovine with 72 252 worms most of the worms were still in the small intestine 52 days after infection.

PARAMPHISTOMIASIS OF DOMESTIC R U M I N A D T S

4cL

‘qP\/

-

2oI 0

A /:,’

i

,/; , A

Large wor m burden Small w o r m burden

A-A

A-A A

A

45

813, 2 0 days 83. 21 clays

I

I

I

I

I

I

I

I

I

I

I

FIG.3. The acetabular sue of paramphistomes recovered from cattle with light and heavy infections (Reprinted with permission from Horak, 1967).

Once having reached the rumen, the worms from numerically large infections in sheep, goats and cattle are generally smaller than paramphistomes from numerically smaller infections (Fig. 3). This retardation in size may also affect egg production, a sheep and a goat harbouring 2568 and 2338 worms had lower faecal worm egg counts than a sheep and goat harbouring 2157 and 634 worms of the same age. Although the above findings are based on single artificial infections in laboratory housed animals, field observations confirm the delay in migration in the massive infections encountered in outbreaks of paramphistomiasis. Boray (1959) investigating an outbreak in cattle in Hungary found large numbers of immature worms in the intestine of affected cattle slaughtered one month after removal from the source of infection. In Tanganyika Butler and Yeoman (1962) found immature P . microbothrium still present in the small intestine of a calf 72 days after removal from an infected swamp. In an outbreak of paramphistomiasis in sheep in Australia, caused by P. ichikawai, Boray (1969b) found that worms did not migrate to the rumen in substantial numbers for 4 months after infection and that the total body length of the fluke did not change during this period. By contrast, in light infections the prepatent period of this paramphistome is 7 weeks (Durie, 1953). The delayed migration is due to retarded growth which in its turn is caused by overpopulation of the small intestine resulting in competition for space and probably food. This delay in the small intestine contributes to the prolongation of the disease and will be discussed in Section VI D.

46

I . G . HORAK

V. IMMUNITY A.

FIELD OBSERVATIONS

The findings of several authors who have investigated natural outbreaks of paramphistomiasis suggest that previous infection or perhaps age of the host supplies a degree of immunity capable of protecting animals from reinfection and its effects. Edgar (1938) reported annual losses of 20 %-30 % in young dairy calves, but made no mention of disease or deaths in adult cows grazing the same pasture in New South Wales, Australia. Young cattle in Hungary affected by acute paramphistomiasis harboured large numbers of immature worms but no adults at autopsy. Adult cows grazing the same pasture evacuated paramphistome eggs in their faeces, but exhibited no signs of infection. Boray (l959), who investigated this outbreak, concluded that the disease rarely occurs in adult cattle, presumably because they have experienced an earlier infection and developed some immunity. Similar observations were made in cattle in Tanganyika by Butler and Yeoman (1962). Cows purchased from an outside source and homebred calves 4-14 months of age were put out to swampy grazing previously used by local cattle. Of the 76 calves 73 died from paramphistomiasis, while only six of the 131 cows died. In Australia, Boray (1969b) found that during an outbreak of paramphistomiasis in young sheep, aged ewes similarly exposed to massive infection harboured adult P. ichikawai, but had very few immature worms and were not affected by the disease. D’Souza (1948), however, noted that sheep that had suffered from paramphistomiasis and recovered in the preceding year, died from acute paramphistomiasis the following year when exposed to massive natural infections. It has been suggested by Horak (1967) that cattle can play an important role in the epizootiology of outbreaks of paramphistomiasis in sheep without developing the disease themselves. He based this assumption on the outbreaks in sheep reported by Le Roux (1930), Whitten (1955)and himself wherecattle either grazed with or preceded the introduction of the sheep to the infected pasture, these cattle, probably the source of infection, being apparently unaffected by the disease. These observations indicate that previous infection, particularly in adult cattle, is liable to supply a degree of resistance capable of withstanding the massive infections required to produce paramphistomiasis in the field.

B.

MULTIPLE INFECTIONS

Assuming that infection in the field is normally acquired by the regular or irregular ingestion of small or large numbers of metacercariae, Horak (1967) attempted to simulate these conditions in the laboratory, infecting sheep and cattle at regular intervals with known numbers of metacercariae of P. microbot/rriz/tn for vnrioiis periods of time. When the number of metacercariae

PARAMPHISTOMIASIS O F DOMESTIC RUMINANTS

47

given to sheep daily or on 6 days per week exceeded 6O00 per day, death supervened. The time of death from the commencement of infection was inversely related to the number of metacercariae administered daily. Metacercariae dosed at a daily rate of 4000 on 6 days per week did not result in death. The percentage take of paramphistomes in all the sheep generally declined as the length of the infection period increased. The reason for this could be either overcrowding in the small intestine with consequent elimination, or the development of resistance to further infection. In two cattle infected either with lo00 or 1500 metacercariae three times per week for periods of 189 and 181 days the percentage takes were reduced to 6.0% and 2.3 % respectively. In three sheep similarly infected with 500, 1OOO and 1500 metacercariae for periods varying from 151 to 182 days the respective takes were 30.5%, 14.9 % and 18.0%. When the sheep receiving multiple infections were slaughtered 22 %-97 % of the paramphistomes recovered were present in the small intestine. In the cattle nearly all the worms were present in the rumen, only one worm being recovered from the small intestine of one of them, the other harbouring none at all in its intestines, although these animals had received 9000 and 12 000 metacercariae during the 3-week period precedingslaughter. Thus, in sheep, multiple infections result in a partial immunity to reinfection as shown by reduced percentage takes, but the worms are nevertheless able to excyst and attach in the small intestine. In cattle this immunity is virtually complete and the worms from subsequent infections are eliminated.

C.

IMMUNIZATION

Horak (1965a, 1967) reported on the successful immunization of sheep, goats and cattle against massive artificial infections with P. microbothrium. 1. Sheep Provided that sheep are over 1 year old they can be successfully immunized against subsequent massive reinfection. Three sheep were immunized by the oral administration of 40000metacercariae either as a single dose or two equal, divided doses. These sheep were challenged with an average of 201 OOO metacercariae and harboured a mean challenge worm burden of 428 at slaughter. The challenge infection was administered to one of these three sheep 1075days after immunization and the sh ep harboured only 85 worms at slaughter. Thus immunity in this sheep was stii highly effective nearly 3 years after immunization. Four sheep were immunized by the administration of multiple small doses of metacercariae over a prolonged period of time. These sheep were challengedwith an average of 200 500 metacercariae and at slaughterharboured a mean burden of 2285 worms resulting from the challenge infection. Five susceptible sheep were infected with an average of202 200 metacercariae. Three of these sheep died from paramphistomiasisand the other two were slaughtered. Theaverage burden in these fivesheep was 91 736paramphistomes.The findings for sheep, goats and cattle are summarized in Table 11.

f

I. G . HORAK

48

TABLE I1 The immunization of sheep, goats and cattle

Challenge Average No. of Average No. metacercariae of worms dosed recovered

-

No. of animals Sheep 3 4 5 Goats 2 2 Corrle 4 7

3 1 5

Immunization procedure 40 000 Metacercariae

Multiple small infections Controls 40 OOO Metacercariae

Controls 40 000 to I00 OOO Metacercariae 40 OOO Metacercariae X-irradiated at 2 kr Multiple small infections Multiple small infections

Controls

201 OOO 200 500 202 200

2 285 91 736

198 500 200 OOO

1238 78 857

165 250 250 OOO 249 667 1 573 OOO 262 200

337 115 362 182 127 473

428

Extracted with permission from Horak (1967).

If the immunizing infection in sheep consisted of a single dose employing numbers of metacercariae lesser or greater than 40000, immunity to subsequent challenge was either poor or absent. The development or maintenance of immunity in sheep can be interfered with by the effects of pregnancy and parturition or by anthelmintic removal of the immunizing infection (Horak, 1967). 2. Goats Two adult goats were successfully immunized by infection with 40 OOO metacercariae either as a single or two equally divided doses. Subsequent challenge infections with 199 000 and 198 OOO metacercariae produced 84 and 2392 worms respectively. Two susceptible goats each infected with 200 OOO metacercariae died from paramphistomiasis 23 and 29 days later, harbouring 86 135 and 71 579 worms.

3. Cattle Adult cattle are the most suitable subjects for immunization. Four cattle were immunized by the administration of a single dose of metacercariae varying in number from 40000 to 100000. These animals were challenged with an average of 165 250 metacercariae and harboured an average of 337 paramphistomes at slaughter. The immunizing infection in two of these four animals was 40 000 metacercariae and the challenge infection which was administered 28 or 35 days later consisted of 101 OOO metacercariae. At slaughter these animals harboured 29 and no worms of the challenge infections respectively. thus indicating that immunity to reinfection in adult cattle was

P A R A M P H I S T O M I A S IS 0 I: D 0 M EST1 C R U MI N A N TS

49

already effective four weeks after immunization. Two cattle each infected with 2500 metacercariae failed to develop immunity to subsequent challenge.

Seven cattle were immunized by a single or equally-dividedinfection consisting of 40 OOO metacercariae exposed to X-irradiation of 2 kr. These animals were challenged with an average of 250 0oO non-irradiated metacercariae and harboured at slaughter an average of 115 paramphistomes originating from the challenge infections. Four cattle were immunized by the administration of multiple small doses of metacercariae over a prolonged period of time. Three of these animals were challenged with an average of 249 667 metacercariae administered as a single dose and harboured an average of 362 paramphistomes originating from the challenge infections at slaughter. The fourth animal was challenged 376 days after the completion of immunization with 792 OOO metacercarae irregularly administered over 18 days followed by 781 OOO metacercariae 38 days later. Of the total of I 573 OOO metacercariae administered as a challenge only 182 worms were recovered at slaughter. The results in this animal indicate that immunity in cattle is probably effective for at least a year after immunization. Five susceptible adult cattle were infected with an average of 262200 metacercariae, and two of these animals died from paramphistomiasis. An average of 127 473 worms was recovered from these five cattle at slaughter. Thus, immunity in sheep, goats and cattle resulted not only in a marked reduction in the worm burdens originating from the challenge infections, but protected the hosts from the lethal effects of these infections. 4. Factors governing immunity The development of an effective immunity to paramphistomiasisparticularly in sheep, is dependent upon a number of factors (Horak, 1967). It is dependent upon the number of metacercariae dosed initially as an immunizing infection and thus on the number of young worms which excyst and attach in the smallintestine. Immunityisnot dependentupon the number of worms present in the rumen, as sheep or cattle with relatively large ruminal burdens may be entirely susceptible while other animals with small ruminal burdensare immune.Thisappliesparticularly where X-irradiated metacercariae are used to produce immunity; these metacercariae are capable of excystment and attachment in the small intestine, but large numbers are lost during or after migration to the rumen, leaving small ruminal burdens (Horak, 1967). Cattle immunized in this way, however, are virtuallycompletely immune to reinfection (Table 11). Immunityinsheep at least seems to be dependent upon the continued presence of worms, for if the worms resulting from the immunizing infection are removed by anthelmintic treatment the degree of immunity is reduced. Immunity is dependent upon the immunizing infection completing the normal life cycle in the final host, for if this is by-passed by dosing adult viable paramphistomesper as, which then attach in the rumen, immunity to infection with metacercariae does not develop.

50

1. C . H O R A K

Attempts to immunizesheep less than 1 year old, suckling kids and 14 day old calves were disappointing. None of the sheep developed immunity, one of the two kids used developed a reawnably solid immunity and the calves because of their poor condition at the start of the experiment were not suitable subjects. It is thus possible that age may play a role in the ability of an animal to develop immunity to paramphistomes. Whether large-scaleimmunization would ever be practically possible depends entirely on whether the considerable numbers of metacercariae required for immunization could be produced. To immunize 100 cattle simultaneously with 40 000 metacercariae each would require 4 million metacercariae and these would have to be produced within a period of 60 days because thereafter their viability decreases with age (Horak, 1967). Swart and Reinecke (1962b) found that loo0 snails infected with P. microbothrium produced 41 OOO metacercarinae daily. Under optimal conditions this could possibly be raised to 100000 daily. Thus theoretically a colony of lo00 infected snails could produce sufficient metacercariae to immunize 100 cattle in a 40-day period. D. THE EFFECTS OF IMMUNITY ON PARAMPHISTOMES

The findings discussed under this heading are based on the observations made by Horak (1967) on the paramphistomes recovered from laboratory housed ruminants which had been immunized against P. microbothrium. Excystment of the metacercariae used as a challenge infection is not inhibited. This is confirmed by the fact that most of the metacercariae recovered from the faeces of newly-challenged animals have excysted, or if an immune sheep is slaughtered very soon after challenge immature paramphistomes will be recovered from the intestine. The continued attachment of the newly-excysted paramphistomes is prevented and these worms are evacuated. This probably takes place immediately after excystment in cattle or after a few days in sheep. Although this elimination is seldom complete it is very nearly so and the residual worm burdens resulting from challenge are negligible. Because of this marked reduction in numbers the pathogenic effects of the challenge infection are absent. The growth-rate of the paramphistomes in immune animals, particularly cattle, is severely retarded. The acetabular measurementsof worms from susceptibleand immune cattle are given in Table 111. Six immune cattle harboured an average challenge burden of only 355 worms 18-51 days after reinfection. The average acetabular breadth of these few worms was scarcely more than half that of worms from a mean burden of 5208 in two susceptible cattle with 10-21 day old infections or that of worms from an average burden of 59,786in three susceptiblecattle with 14-27 day old infections. This stunting is probably caused by a hostile intestinal environment which has already caused the elimination of the major portion of the worm burden and now inhibits the growth of the few remaining worms. A large proportion of the residual challenge infection in immune cattle is attached behind the first 3 m of the small intestine. This may be either because the first 3 m portion, which is their normal intestinal habitat, is now unsuitable

P A R A M P H I S T O M I A S IS 0 F I)O

M EST I C: R U M I N A N TS

51

for their attachment or because the growth of the paramphistomes which attach posteriorly is so retarded that they are unable to commence migration to the first 3 m portion of the small intestine. TABLE 111 The cr8i.ct of immtrriity or1 worm size No. of cattle

Average age of Average acetabular Average No. breadth in mm infection in days (Range) of worms recovered (Range) -

Siucqitibli~c ~ r t t l cndtli ~ smoll worm brrrderis 2 1 5 . 5 (10-21) 5 208 St4scq1tible~cuttlii wit11 Iqqe worm burtiem 59 786 3 20(14 27) Cttallerigc~irt/ktiorts in inimiirte cut tie 6 32 (18-51) 355

0 . 5 3 (0.334.72)

0.52 ( 0 . 2 6 4 . 6 8 ) 0 . 3 2 (0.15-0.64)

Extracted with permission from Horak (1967)

Migration from the small intestine to the rumen is delayed. This may be an actual delay, in that the worms are so stunted that the acetabular size only reaches 0.56 mm after a considerable sojourn in the small intestine (this is the acetabular size at which migration normally takes place). Alternatively, the delay in migration may only be apparent in that the paramphistomes start migrating, but are then evacuated before reaching the rumen; thus at slaughter the residual challenge worm burden is confined to the intestine, giving the impression that migration has been delayed. I n sheep and in calves that have been immunized a number of the worms originating from the immunizing infection, which is now situated in the rumen, are also eliminated when these animals are challenged with a large number of nietacercariae. This, however, does not occur in adult cattle on challenge. The niechanism ofthis elimination must be interesting, for it requires that a newly-excysted challenge worm burden, harboured entirely in the small intestine, can trigger a reaction in the rumen which will eliminate part of a pre-existing worm burden entirely ruminal in habitat. I!.

SEROLOGY

Animals suffering from paramphistomiasis. or infected with paramphistomes, or immune to reinfection develop certain responses which can in some cases be measured serologically. 1. The inirudertiiul allergic ir.st Katiyar and Varsliney (1963) triturated 3 g of saline washed adult param-

phistomes in 90 ml of rectified spirit in a glass pestle and mortar. After standing at room temperature for 12 h the filtrate was evaporated and the residue dissolved in 10 ml of distilled water. Twenty-two affected sheep were injected 3

52

I. Ci. HORAK

intradermally i n a shaved area on the side of the neck and compared with five ;ilTected sheep similarly iqjected with distilled water. No significant changes i n the thickness ofthe skin or the body temperature of the two groups of sheep were observed. Horak (1967) prepared three antigens, one of which was a saline extract of immature piirampliistonies, another a similar extract of metacercariae and [lie third ii boiled, alcohol-precipitated antigen made from immature and adult paramphistomes. Sheep were injected intradermally in the hairless axillary region. A positive reaction caused the appearance, within I to 30 min of injection. ol'a dark red to purple area at the site of the injection surrounded by a large oedematous weal. Not one of the three antigens was specific, since positive reactions also occurred i n sonic sheep infected with nematodes, Fusu'olu lieputicu or Srlristosorrru riiattlroci. The saline extracts of immature worms or metacercariae, howcvcr. gavc the inore reliable results.

2 . 7 k c~oirrpli~rrii~irt,fi.\otic~ir trst As the shocp scra uscd i n his tests were markedly anti-complementary Horiik (1067) resorted to a modification of the complement fixation test. The potency o f a serum was assessed in terms of its index ratio, as this method of assessment takes the anti-complementary activity ofa serum into consideration. Using a boiled alcohol-precipitated antigen made from adult or immature paramphistomes, low index ratios were obtained for the sera of uninfected sheep, infected sheep shortly after anthelmintic treatment and sheep suffering the acute efl'ects of paramphistoniiasis. High index ratios were obtained in acutely infected sheep and i n immune sheep. Because of the involved nature ofthis test and the difficult interpretation of results it is not a practical method for use a s ;I diagnostic aid.

3. Srmrrir prwipitatPs aroiirid IiiYrig j)urar,ij~lristonres Hornk (1967) collected living adult and immature paramphistomes and incubated these at 38°C i n the sera of sheep, goats and cattle. The most striking results were obtained when adult worms were incubated in the sera of immune iind infected cattle. Precipitates formed within 2: h particularly at the excretory pore. genital citrittiii and on the cuticle of the anterior portion of the worm. The precipitates which i'ormed around worinb incubated in the scra of immune sheep and an ini'ected goat were only slighl. The rapidity with which this test can be read makes it a useful laboratory diagnostic aid in the case ofcattle. A positive result. however. does not difl'erentiate between an infected animal requiring treatment or an animal immune to reinfection. VI. A.

PAI1101.0GY

C'L.INI('AL. SIGNS

Baldrey ( 1906) was probably the first to associate the disease paramphistomiasis with iictual paramphistome infection. However. he considered the

I ' A R A M P H I S T O M I A S I S O F DOMI<STIC R U M I N A N T S

53

presence of the immature worms in the small intestine as exaggerating a pre-existing condition rather than its primary cause. Although not recognizing the cause of the disease Walker (1906) gave an excellent description of the clinical signs. The clinical signs of acute paraniphistomiasis in sheep, goats and cattle have been described by Walker ( I 906), Simson ( I 926), Le Roux ( I 930), Pande (1935), Haji(1935). Edgar(1938). Bawa(1939). Mudaliar(1945), Alwar(1948), Ramakrishrian (1950), Boray (1959, 1969a, 1969b). Butler and Yeoman (1962), Deiana ef a / . (1962), Horak and Clark (1963), Katiyar and Varshney (1963), Horak (1 966, 1967), Roach arid Lopes (1966) and Cvetkovic ( 1 968). Affected animals are listless and a progressive decrease in appetite develops terminating in complete anorexia. Small quantities of water are taken frequently and the animals may stand with their muzzles in the water for long periods of time. Diarrhoea develops 2-4 weeks after infection, the faeces are extremely fluid and foetid and may contain immature worms. In particularly severe cases the diarrhoea is projectile, this being especially noticeable i n cattle. As the disease progresses the rectal contents leak out involuntarily, soiling the hind limbs. I n chronic cases the continued straining may lead to rectal haeniorrhage and fresh blood can be seen in the faeces. Submandibular oedema has been noted in a large number of outbreaks. Anaemia has frequently been described, but has not been observed in artificial infections with . , P. tnicrobo tlir iuri I . The course of the acute disease is about 5-10 days in sheep and goats and 2-3 weeks in cattle and buffaloes (Alwar, 1948). Morbidity and mortality rates are high. Le Roux (1930) reported a mortality rate of 30% in a flock of 275 sheep. In young cattle in New South Wales Edgar (1938) recorded a mortality rate of 30':/;, and Pande (1935) found mortality rates of 21 "/, to 37.4% i n cattle on three tea estates in India. In Tanganyika 73 of 76 calves put out to swampy grazing died of paramphistomiasis (Butler and Yeoman, 1962). The average percentage morbidity and mortality in sheep in Uttar Pradesh, India. during 1953 to 1959 was 41.54 and 57.62 and i n goats 68.59 and 75.54 respectively (Katiyar and Varshney. 1963). If death does not occur marked loss of condition and live weight persist for a considerable length of time. The latter condition is often referred to as chronic paramphistomiasis. n.

CLINICAL PATliOI.O(;Y

The clinical pathology of the acute disease i n artificially infected sheep has been studied by Lengy (1962) and Horak and Clark (1963). Many of their findings have been substantiated by observations made during field outbreaks of paramphistoniiasis in sheep. When Lengy (1962) infected a sheep with approximately 75000 metacercariae of P. t~lic'robofhriutu,thc resultant worm burden produced clinical changes, but not death. At slaughter about 2700 adult paramphistomes were recovered from the rumen of this sheep. Severe diarrhoea lasting for I week occurred at the end of the 3rd week of infection, thereafter it became more mild and ceased at the end of the following week. No decrease in appetite

54

I. G . HORAK

was noted. A slight drop in haemoglobin concentration, packed cell volume and erythrocyte count took place, and the lowest values were recorded when the experiment was terminated 16 weeks after infection. Eosinophile counts rose during the 1st week of infection, dropped slightly during the 3rd week and then reached a peak in the 4th week to decrease gradually to normal levels by the 11th week. An apparent rise in blood sugar concentration occurred during the 4th week of infection, but this returned to normal by the 12th week. The total plasma protein concentration and albumin-globulin ratio fluctuated within normal limits throughout the period of observation. Horak and Clark (1963) infected each of six Merino sheep bred and reared under worm-free conditions with 170 OOOf5000 metacercariae of P . microbothrium. These infections resulted in burdens of 40 039-87 768 paramphistomes and death from acute paramphistomiasis 22-36 days after infection. In addition they infected two sheep with 171 500f2500 metacercariae of P . microbothrium, but treated these animals with nicofosamide (Lintex: Bayer) at a dosage rate of 50 mg/kg liveweight at the height of the reaction to infection. These sheep were reinfected with 202 000f2000 metacercariae 31 and 24 days after treatment. The one died from paramphistomiasis 28 days after reinfection harbouring 53 476 paramphistomes resulting from the challenge infection. The other exhibited no symptoms and was slaughtered 32 days after reinfection, harbouring 18 162 worms of the challenge infection. Feed intake decreased in all the sheep on the 7th to 8th day after infection and progressed to complete anorexia within 16-27 days.The anorexia persisted until death in the untreated sheep. Water intake remained more or less constant, As sheep on a low feed intake usually consume correspondingly less water, the water intake during the period of anorexia can be considered abnormally high. These sheep frequently stood for long periods of time with their muzzles submerged in the water troughs. This finding confirms the observations of Walker (1 906) who was probably the first to notice polydypsia in sheep suffering from paramphistomiasis. Butler and Yeoman (1 962) made similar observations in infected calves which they found would eat only a little hay and yet take water and milk avidly. A severe, fluid, foetid diarrhoea developed 16-28 days after infection and persisted until death in the untreated sheep. Live weight decreased by 1.3 to 3.6 kg during infection. Total plasma protein concentrations were reduced markedly from the 14th day of infection. This fall was almost entirely due to a lowering of plasma albumin concentration. The average plasma protein concentrations of three sheep prior to and during infection are shown in Fig. 4. The average plasma albumin concentration of these three sheep prior to or just after infection was 2.93 g %. whereas the average value just prior to death was only 0*76g%. A decrease in plasma volume occurred in some of the infected sheep in the terminal stages of the disease. This decrease in plasma volume accompanied by the decrease in plasma albumin concentration results in a severe reduction in the total weight of circulating plasma albumin. This was particularly noticeable in one of the sheep treated with niclosamide. The blood and plasma volumes and plasma protein concentrations of this sheep are shown in Fig. 5.

I'h

R A M 1' H I STOM I A S IS

0 1: I)O M I: LI.1C'

K U MI N A NI'S

55

Days o t t e r infei.lion

FIG. 4. The effect of parainphistome infection on plasma protein concentration (Reprinted with permission from Horak and Clark, 1963).

f

3

08 06 04

0 2

6 Averoqr normal

9

; W

4 (onceritrotion

2 0

Days after Infestahan Days after treatment Days after remfestatlan Globulin

0 cz and /3

globulins

0Albumin

FIG. 5. Blood and plasma voluiiics and plasma protein concentration in an inliectcd sheep (Reprinted with permission from Horak and Clark. 1963).

56

I . Ci. IIORAK

This sheep had a pre-infection plasma volume of 1-16 I. and a corresponding plasma albumin concentration of2.8 g';:,and thus atotal of32.5 gofcirculating plasma albumin. These values just prior to treatment were: plasma volume 0.75 I.. plasma albumin concentration 1.5 g:,; and 11.3 g ofcirculating plasma albumin. This is a reduction of 65.8 ;,{) in the amount of circulating plasma a I bum i 11. During the terminal stages of the disease an increase in the packed red cell voluiiie, red cell count, haenioglobin concentration and total volume of circulatiilg erythrocytes occurred in many of the sheep. The rise in the volume of circulating red cells is well shown in Fig. 5 just prior to anthelmintic intervention. The initial volume of circulating red cells in this particular sheep was 400 in1 and this had increased to 550 ml .just before treatment. Thus instead of anaemia, ii liaemoconcentration with an actual increase in the total volume of circulating erythrocytes developed. During this phase of the disease eosinophi les disappeared from the peri phera I blood. The plasma calcium concentration fell with the plasma albumin concentration. The average initial calcium value for six sheep was 10.9 nig% and the terminal value 7.5 mg%. This confirms the findings of Le Roux (1930), that the calcium content of the blood of five sheep suffering from acute naturally acquired paramphistome infections was much reduced. The feed intake of the two sheep treated with niclosamide improved rapidly after treatment and reached normal levels within a week. Diarrhoeadisappeared within three days. Total plasma protein and plasma albumin concentrations reached pre-infection levels 24 to 3 I days after treatment. Upon reinfection the one sheep was conipletaly susceptible and total plasma protein and plasma albuinin levels fell rapidly (Fig. 5). This sheep died 28 days after reinfection. The only reaction noted to reinfection i n the other sheep was an increase in the plasma gamma-globulin concentration. Boray (l969b) confirmed the rapid recovery of sheep suffering from paraniphistoniiasis after treatment with niclosaniide. He treated sheep during ;in outbreak of paramphistomiasis caused by P. ichikaicui and noted that diarrhoea ceased 24 h after treatment and that theappetite returned to normal 2 to 3 days later. The difference between the findings of Lengy (1962) and those of Horak and Clark (1963) can be attributed to the fact that Lengy was studying a sub-lethal infection, while Horak and Clark had produced infections more typical ofthose encountered in the acute naturally occurring disease. C.

P A ' l t l O l ~ O G l C A L ANATOMY

I . Macro-piillioloR.~, The macroscopic pathology of' paramphistomiasis in domcstic ruminants has been described by Baldrey ( 1906). Simson (1926), Le Koux ( I 930), Pan& (l935), Bawa (1939). Maqsood (l943), Mudaliar (1945), D'Souza (1948). Raniakrishnan (1950). Boray (1959, 1969b). Butler and Yeoman (1962), Deiana Pt (11. (19621, Horak and Clark (19631, Katiyar and Varshney (1963), Horak (1966, 1967) Roach and Lopes (19661, Dewan (1966) and Sharma

P A R A M I ’ H I S T O M I A S I S OF D O M F S T I C R U M I N A N T S

57

Deorani and Katiyar (1967). Their observations may be combined to give the following picture: (a) Adult Paramphistomes. Infections with adult worms result in no outward signs of parasitism. When the rumen is opened large numbers of paramphistomes are found attached to the epithelium and papillae of the ruminal pillars. The papillae appear anaemic, being off-white in colour when compared with the grey-green of the surrounding tissue. Owing to pressure necrosis, caused by the acetabula of the numerous paramphistomes attached at the bases of the papillae, these are frequently atrophied and their tips slough off. If the paramphistomes are dislodged prominent buds of mucosa mark the sites of their recent attach men t. (b) Immature Paramphistomcs. When death is due to infection with immature paramphistomcs, soiling of the hind limbs with fluid, foetid faeces is a common observation. Autopsy of affected animals in acute infections with P. microbothrium shows dark red and viscous blood flowing from severed blood vessels. Possibly,

FIG.6. Marked oedeniatous thickcning of thc abomaral spiral folds in an infected bovine (Reprinted % i t t i pcrrnis\ion from Horak, 1967).

58

I . G. H O R A K

FIG.7. The corrugated appearance 0 1 afPected intestinal mucosa. Large numbers of parainphistoiiics can be seen between the folds (Reprinted with permission from Horak, 1967).

infection by other species may cause the blood to appear anaemic. Subniandibular ocdemn may occur. Depending on the duration of infection the carc;iss may be i n fair condition or extremely emaciated. If the animal is in fair condition the adiposc tissue may show signs of necrosis, in more chronic cases the fatty tissues undergo serous atrophy. Oedema of the lungs, hydrothorax, liydropericardiutn, and ascites arc generally present. In chronic cases splenicatrophy, runiinal atony and atrophy and muscularatrophyareobserved. The niesenteric lymph glands are oedematous and the first 2-3 m of the small intestine are hyperaeniic and the larger blood vessels extremely congested. The niesenteric fat is absent or replaced by clear serous fluid at the site of attachment of the niesenterium to the aflected intestine. Immature paramphistonies niay penetrate the intestinal wall to just below the serosa and can be seen from the peritoneal side of tlie intestine. On rare occasions they perforate the intestine and are found in the abdominal fluid. The small intestine beyond the infected portion is distended with fluid and the wall extremely thin. The bile-duct may be enlarged and tlie gall-bladder distended. When the gastro-intestinal tract is opened, immature paramphistomes may be found attached to the mucosa of the rumen and omasum. The rumen contains little solid ingesta and niuch fluid. The walls and spiral folds of the aboniasuni are oedematous. These folds niay be so enlarged in cattle that the aboninsal lumen i s virtually occluded (Fig. 6 ) . Paramphistomes are found attached to the abomiisd iiiucosii which generally exhibits shallow erosions and petechiae. The wall oftlie lirst 2--3ni of the small intcstine is hypertrophied, oedematous,

P A R A M P H I S T O M I A S l S OF I>Oh.l I:STl(' R U M I N A N T S

59

the mucosa corrugated and often covered by a catarrhal exudate. Large numbers of dark brown to pink paramphistomes are attached to the surface and deeply embedded in the mucosa (Fig. 7). Many paramphistomes are dislodged when the intestine is opened, and are found in the ingesta as clusters of pink worms, tightly adherent to one another. Numerous erosions, petechiae and ecchymoses are present in the intestinal mucosa, and the ingesta, which is extremely fluid, may be slightly haemorrhagic. Few paramphistomes are found posterior to the first 6 m of small intestine in sheep and goats, but large numbers can be present in cattle. Caecal and colonic ingesta are extremely fluid, and in those cases which exhibited prolonged diarrhoea, rectal haeniorrhages are not uncommon. A few paramphistomes may be found attached to the wall of the gall-bladder. The bile is frequently thick and, viscous and superlicial necrosis of the gall-bladder epithelium is noticeable. 2. Micro-pathology The histopathology of the parasitized rumen in sheep was described by Mukherjee and Sharma Deorani (1962). They found a proliferation of the epithelium in the vicinity of the worms, but no evidence of cellular infiltration, vascular congestion or haemorrhage in the mucosa. A marked proliferation of the stratified squamous epithelium of the papillae and hypertrophy of the stratum corneuni was evident. The distal extremities of the papillae frequently showed signs of degeneration and sloughing. CankoviC and Batistid (1963) found oedema of the epithelial layer and lymphocytic infiltration in the propria and sometimes in the epithelium and submucous layer of the parasitized rumen. The histopathology of acute intestinal paramphistomiasis in sheep and goats has been described by Mudaliar (1945), Varma (1961), Katiyar and Varshney (1963), Sharma Deorani and Katiyar (1967), Horak (1967) and Boray (1969b). I n cattle it has been described by Nobel (1956). Boray (1959), Tsvetaeva (1959) and Dewan (1966) and i n the buffalo by Patnaik (1964). (a) Paratphistonturn microbothriinn. The histopathology of the acute disease caused by this paramphistome in cattle in Israel has been described by Nobel (1956). This paramphistome was originally identified as P. cervi, but I have taken the liberty of naming it P. niirrohofhriurn;Lengy (1969, personal communication) informed me that all the specimens in the Hebrew University up to 1961 were named P. cerri, but were in fact P. niicrohofhrium and that in his surveys, albeit on a limited scale. this was found to be the only species present i n cattle in Israel. In the duodenum the superficial epithelial layer and the crypts of Lieberkuhn are desquamated and necrotic; the capillaries of the villi are congested, distended and sometimes ruptured. Necrosis affects Rot only the superficial layers of the mucosa. but often reaches the muscularis mucosa. The tissue surrounding Brunner's glands is oedematous and infiltrated with eosinophils, lymphocytes and plasma cells. The glands of Brunner are distended and a large number of paramphistomes are embedded between these glands and the

60

I . (;. I I O R A K

muscularis mucosa, or may cveii be found adjacent to the inner longitudinal muscle layer ofthe intestine. No rcaction, apart from congestion, was observed around the worms in the deep tissues. The lumen of the jejunum is packed with necrotic epithelial cells mixed with polyniorphs, lymphocytes and numerous paramphistonies. The mucosa and subniucosa are diffusely infiltrated with lymphocytes, plasma cells, eosinophils and polyniorphs. The lumen is reduced because of oedema of the tissue. Worms are embedded in the tunica propria mucosa down to the muscularis mucosa. Plugs of mucosa can be seen in the acetabular cavities of these paramphistomes (Fig. 8), while there is no tissue reaction surrounding them.

FIG. 8. A paraniphistome deeply embedded in the mucosa of the small intestine with a plug of tissue drawn into its acetabulum ( x 75) (Reprinted with permission from Horak, 1967).

Nobel (1956) stated that the pathogenicity of paramphistomiasis is directly proportional to the number of worms and that the pathogenic action of the immature paramphistomes in the small intestine is mechanical and toxic. (b) Coty/ophoro/, spp. Sharnia Deorani and Katiyar (1967) descrihe three phases in the micro-pathology of naturally occurring paramphistomiasis in sheep and goats caused by worms resembling Cotylophoron spp. In the mucosal phase the young flukes attach to the superficial duodenal mucosa causing epithelial proliferation and cellular infiltration. When they enter the mucosa the tissue surrounding the sites of entry is hypertrophied, infiltrated with mononuclear cells and superficial parts of the mucosa exhibit mild necrotic changes. Once the worms have entered the mucosa there is hypertrophy, superficial necrosis and desquamation of the mucosa and signs of traumatic destruction of tissue around the paramphistomes. The mucosa

P A R A M P H 1STO M I A S 1S 0 F D O M CS TI C R U M I N A N TS

61

is congested and infiltrated with macrophages and haemorrhagic spots develop, while a marked increase in the number of goblet cells takes place. When many young worms enter the mucosa at one site traumatic desquaniation of the mucosa occurs. The paramphistomes in this phase do not appear to feed on the intestinal tissue, since neither epithelial cells nor erythrocytes are observed in their oral cavities or intestinal caeca. The paramphistomes in the sub-mucosal phase of the infection break through the muscularis mucosa and invade Brunner’s glands. Much of the superficial mucosa is desquamated at this stage and hypertrophy of the glands occurs. The mucosa and submucosa are infiltrated with mononuclear cells and a few eosinophils are seen in the submucosa. Initially only certain glands are affected but eventually when large numbers of glands have been invaded there is little submucosal connective tissue left between the glands and the musculature. Virtually all the subrnucosa is then occupied by hypertrophied glands while at the same time there is a massive infiltration of mononuclear cells and eosinophils. The worms probably start feeding and developing in these sites as epithelial cells can be found in their oral cavities and intestinal caeca. In the post-migration phase the worms have moved back to the lumen of the intestine; reorganization of the submucosa and regeneration of the mucosa then take place. Varma (1961) artificially infected lambs with C. cotylophorum. He observed that the immature worms in the submucosa of the small intestine were surrounded by a zone of ceilular infiltration, the cells being predominantly those of the mononuclear wandering type and a few giant cells. The mucous layer was thickened and the submucosa swollen. Desquamation of the mucosa from the underlying layers and of the submucosa from the muscular layer beneath were evident. Dewan (1966) noted that the intestinal villi of a cow naturally infected with Cotylophoron sp. were fairly uniformly eroded. (c) Paramphistomum ichikawai. The histopathology of the parasitized intestine of sheep has been described by Boray (1969b). The newly excysted flukes penetrate deeply into the mucosa reaching as far as the muscularis mucosa. In severe infections they remain deeply embedded in the mucosa for a considerable time. SmalI pieces of the mucosa or muscularis mucosa are drawn into their acetabula, causing strangulation and necrosis of the cells and resulting in erosions of the villi. A diffuse cellular infiltration and plasma exudate occurs amongst the villi. Oedema and loosening of the tissues raises areas of the mucosa from the deeper layers. As the worms grow they emerge from the mucosa and the larger worms are found attached to the surface of the mucosa before migrating to the rumen. D.

PATtlOGEN1:SIS

The magnitude of the worm burden is the most important factor in the pathogenesis of the disease. In stabled sheep artificially infected with P. nticrobothrium burdens in excess of 40 000 paramphistomes are required to produce acute fatal paramphistomiasis (Horak and Clark, 1963). In stabled cattle this figure is about 160 000 (Horak, 1967).

62

I . . nicdinensis. D . oesophageus and possibly other

I04

RALPH MULLER

species if more specimens are examined, this feature should be viewed with caution. There is no constant character which will serve to separate the forms occurring i n mammals from those in reptiles on morphological grounds. To confuse the issue still further, it is by no means clear that D . medinensis was originally a parasite of man. Infection in a wide range of animals has been reported from many parts of the world, i n some of which the disease in humans does not occur or has been eradicated (Table IX),and this suggests that there are reservoir hosts maintaining the infection. The fact that records of infection in animals are so geographically widespread and yet so sporadic, indicates how easily the parasite may be missed, and it is probable that infection is considerably more common than is usually supposed. This is demonstrated by recent studies at the University of Guelph by Crichton and Beverley-Burton, who found developing stages of Dracirncirhrs sp. on dissection in 81 of otters, 36 of mink and 14",:, of r;moons rrom Southern Ontario (197Qpersonal communication).

x,

I 11. A.

DRACUNCULIASIS I:PI I)EMIOLOGY

I . Crographic~aldistribution An extensive list of references concerning the distribution of the disease prior to 1920 was given by Stiles and Hassall (1920). The present distribution is shown in Fig. 17.

FIG.17. Geographical distribution of dracunculia\is.

(a) Wtwern Honisphcw. Until recently the disease occurred in the West lndies (Chisholm, 1815) and in the Bahia Province of Brazil, presumably brought by slaves from West Africa. I t appears to have died out spontaneously in the last fifty years (Costa, 1956). The situation i n North America is rather confused. Infection is widely

I ) K A C U N C U 1. US A N 1) I)R A C U N C U L I A S 1 S

105

distributed in carnivores in the United States and the south of Canada but does not occur in man (Chitwood, 1933). although worms are sometimes seen in X-rays of patients in the eastern United States (Michelson, 1969-personal communication) and have been removed at operation (Spiers and Baum, 1953). Some reports list the parasite in carnivores as Dracunculus medinensis (Benbrook, 1932; Chitwood, 1933; Mirza, 1957; Medway and Soulsby, 1966), but it is usually regarded as belonging to a closely related species D . insignis (Chandler, 1942; Chitwood, 1950. See section IID). (b) East Indies. Guinea worm infection has been encountered occasionally in Arab and Indian visitors (Brug, 1930; Marjitno and Essed, 1938). One possibly autochthonous case in a dockyard worker was reported from Java (Van Heutz, 1926). (c) Korea. A single worm was found by Hashikura (1926) at Fusan emerging from an ulcer on the breast of a Korean who had never left the country. Typical embryos were expelled from the uterus of the worm. (d) Burma. A few cases were reported in 1939 (Simmons el a/., 1944-51). (e) Ceylon. Infection was described at Orniusz by Lindschoten (16lO)and Tennent ( I 868) but no longer occurs there (Gooneratne, 1969). (f) India. Dracunculiasis is probably more widespread in this country than in any other. The overall distribution was described by Turkhud (1920) and that in various regions by Moorthy (1932a); Rice (1959); Datta el a/. (1964); Rao and Reddy (1965); Singh and Raghavan (1957); Patnaik and Kapoor (1967); and Reddy ct a / . (1969a). Turkhud (1919) described the most heavily infected areas as Mysore (3973, Maharashtra (28 y;), Andra Pradesh ( I 2 y,’,), Madhya Pradesh (10.6 %) and Rajasthan (LO 7;). Stoll (1947) estimated that about 25 million cases occurred annually but Singh and Raghavan (1957) thought that only 5 million people were at risk; this figure was made up of 2.3 millions i n Rajasthan, 0.9 million in Madras, 0.9 million in Andhra Pradesh, 0.4 million in Madhya Pradesh and Madhya Bharat, 0.2 million in Bombay, 0.3 million in East Punjab, 0-2 million in Saurashtra, 0-1 million in Hyderabad, 0.1 million in Jammu, 0.03 million in Mysore and 0.02 million in Kutch. Datta eta/. ( I 964) found only two infected villages in Pondicherry Settlement with a 1-37”infection rate, and Megaw and Gupta (1927) found that Assam and Orissa were completely free from infection. Patnaik and Kapoor (1967) reported that the highest incidence occurred in Rajasthan (0.062 and other heavily infected areas were Maharashtra (0.049 Orissa (0-034 Madras (0.025 7 0 , Uttar Pradesh (0.024 Andhra Pradesh (0.018‘%,)and the Andaman and Nicobar Islands (0.098‘%,). The very low figures given by these authors of 847-1243 ca\es per 1000o0 population during 1950-1958 and 8.78-27.84 per 100 000 during 1959-1964 (which would give a total for all India of about 71 OOO cases for the years 1950-1958 and of 140000 cases for the years 1959-1964) do not represent a great decline in incidence since previous estimates, but reflect the fact that their rates were based largely on hospital and dispensary records, a notoriously unreliable index for a disease of this nature.

x),

x)

x),

x),

I06

R A L P H MULLER

From a detailed study of four villages, and from knowledge of similar wells i n many others, Reddyctal. (1969a)estimated that there were about 0.5 million people at risk in the Kurnool district of Andhra Pradesh alone and concluded that previous surveys had considerably underestimated the problem in India. (g) Iran. The endemic area is probably confined to the very dry Laristan region bordering the Persian Gulf. Lindberg (1936) reckoned that there was from 15 to 20 infection at Bastak, 10 ‘%, at Lar and 1 %at Lingeh. However, the infection has been much reduced in recent years (Sabokbar, 1968). ( h ) /<ussia.The infection wasdescribed t’romTurkestan by Fedchenko(l871), Yakiniolr (1914) and lssajev (1934a). A very good account of the historical literature on infection in Bokhara, Tashkent and Samarkand was given by Lindberg ( I 950), who stated that the disease had been eradicated. However, worms are still observed in dogs (Chun-Sun, 1958). (i) Iray. Denecke (1954) said that dracunculiasis was contracted by bedouin from ponds in the western desert regions and was present in the low-lying areas bordering the Tigris and Euphrates. (j) Y m e n . Reported from the marshy areas around Suda (Katzenellenbogen, 1950), from San’ a Tihama (Lindberg, 1950) and from Haggia and Beit el Faglinh in the Hodeida area (Egidio, 1955). (k) Suidi Arabia. The infection was common up to 1954 in the area south of Djeddah but may not be so common since tube wells were constructed in the area (Zarah, 1968-personal communication). Lindberg (1950) described the disease from the coast of the Red Sea, Djeddah, Hadramut and Muscat, and Reinhard (1961) found many calcified worms by X-ray. (I) East Afiica. Guinea worn1 is common in the south of Sudan, particularly in Equatoria, Bahr el Ghazal, Blue Nile and Kordofan Provinces (Wenyon, 1908; Davis, 1931 ; Simmons rt a/., 1951), and occurs in the north of Uganda (Bradley, 1968). A focus was rediscovered recently at the village of Keru in Ethiopia (Eritrea) on the trade route from Sudan (Ten Eyck, 1970-personal communication), and cases occur in Somalia (Ricci, 1940). Occasional non-autochthonous cases have been found in Indians: in Nairobi and South Africa (Selkon and Latham, 1952),and infection has been reported from South West Africa and Botswana (Simmons eta/., 1951). (m) West and North Afiica. The infection is widely distributed over the Guinea and Sahel Savannah areas north of the equator but its distribution and incidence have not been recorded for many countries. Portirgiwse Giiinea. An infection rate of 23.5 of the population was found in five villages in the Susana zone (Ferreira and Lopes, 1948). Ivory Coast. Infection was reported from the high Sassandra region by Blanchard (191 1) and found to be very common around Bouake by Raffier ( I 965). Ghana. I n the M o district of North-West Ashanti, Scott (1960) found that about a quarter of the population were infected during the course of each year and that more than half were infected before the age of 10. Dracunculiasis is also widespread in the Northern region north of Tamale and around Sunyani and Wa in the Upper region.

x,

I>R A C U N C U L US A N D D R A C U N C U LI A S I S

107

Nigeria. The disease was found to bc common i n the north (Ramsay, 1935) and in the west, where 641 of 5865 children examined (lO.9xJ were infected (Onabamiro, 1952). The disease is still common in the west and 6 % of the population was found to be infected i n 1969 in three villages north of the city of I badan. Orher areas. The disease occurs in the area of Ouagadougo in Upper Volta, in Guinea (Carayon r t al., 1961), i n Senegal (Carayon er al., 1961 ; Schneider, 1964; Gretillat, 1965), Mali (Schneider, 1964), Tidjikja in Mauritania (Camm616ron, 1907), Agouagon in Dahomey (Roubard, 1913), Adrar in Algeria (Rousset, 1952) arid in N.W. Liberia, Togo, Niger, Chad and Northern Cameroun (Simmons rt a/., 1951). (n) Pakistan. The most important endemic area is the Tharparkar district of Hyderabad region. The disease appeared in this area in 1948 after a long interval free from infection (caused, according to an old inhabitant, by a drought in the 1930's) and was introduced by the migration of people after partition. 1 found that in 1968 there was a 19.2% infection rate in secondary school children in the town of Chachro (population 6-7000), in the centre of the endemic area. Ansari and Nasir (1963) found an infection rate of 9 % in boys and 7 2, in girls in the town. The disease may now be severely limited or have vanished again owing to lack of rainfall in 1968, and may not reappear as there is no longer migration from the contiguous endemic zone in the Rajasthan desert in India (according to official sources). Dracunculiasis has been reported from the north around the lndus basin at Attock, Dera Ghazi Khan, Muzaffargarh, Mianwali and former North West frontier province (Ansari and Nasir, 1963), and there were 203 I cases reported from Karachi in 1966 (Ahmed, 1968-personal communication). These last may not have been autochthonous as many people have moved recently from the Rajasthan area of India.

2. Econottric rflkfsof'rlisrasr Dracunculiasis is typically a disease of rural communities far from medical centrss, making it difficult to know the true morbidity figures. although it is likely that in the past they have usually been underzstimated. There are no accurate national figures but some measure of the extent of distress caused by the disease can be gauged from various small scale epidemiological surveys. In four villages north of the city of Ibadan (Western Nigeria) the infection rate in March 1966 was 53%, and nearly half of the patients in the I5 to 40 age group (i.e. of active working age) were incapacitated for at least I0 weeks (Wennen, 1966-personal communication). In this area, as in many regions of Africa and India. the maximum incidence of disease coincides with the planting season, a matter of great concern to an agricultural community (Rao. 1942; Singh and Raghavan, 1957; Rao and Reddy, 1965). In a survey of two villages with a 1.3 '%, infection rate in Pondicherry Settlement, Datta ef d.( I 964) found that worms took 1-3 months to emerge fully and led to an average lpss of 119.8 working days by malys and 78.1 days by females. In four villages in the Kurnool district of South India, where the infection rate varied from 11-69 to 53.75:'(,, 703 out of 1709 patients suffered

-

0 X

TABLE VI Region

Transmission szason

P a l . transnission

Rainy season

Authority

Date 1946b 1930 1957 1924b 1967 I969a 1965 1942 1935 1967 1969

~~

INDIA

Rajasthan Bombay Mysore Madras Andhra Pradesh (H ydera bad) Gujarat Madhya Pradesh PAKISTAN Tharparkar

May-October February-Ma! February-J ul;, March-Jux Febrirar) -.iiine February-May April-Junc October-Jill! Januar! -Mac May-July

May March March-May June March

July-September July-September J une-Sep tember J une-September

Lindberg Pradhan Singh and Raghavan Fairley and Liston Patnaik and Kapoor Reddg er el. Rao and Reddy Rao Lindberg Patnaik and Kapoor Bildhai>a rf 01.

J une-0c:ober

September

J une-Septem ber

Ansari and Nasir

1963

March-August

June hlay-J uly DecEmber-February

November-February May-August

Lindberg Sabok bar Roubrird

I936 1968 1913

April

June-Septem ber May-September

Onaba m i ro Rarnsay

1952 1935

June

July March March-May M ay May

June-September J une-Oc t ober July-September J ul y-September July-September July-September -

C

1R A N

Larestan

DAHOMEY NIGERIA w. State N. States GHANA G ambaga N.W. Ashunti ALGFRIA Adrar

3

J a n t w - Junc May-Oc'totKr Mainl) November-June

April

May-August May-August

Graham Scott

I905 I960

May-Septenibcr

September

September-November

Rousset

1952

I) R A C U N C U L U S A N D I>R A C U N C U L 1A S I S

109

for 1 month while 565 had the infection for 31-360 days (Reddy er at., 1969a). Other studies have found that most patientswere physically disabled for about a monthprovidedcomplicationsdid notoccur(Rao,I942; Rao and Reddy, 1965). The proportion of sufferers who became permanently disabled was four out of 624 (0.64 %) in one survey (Rao and Reddy, 1965) and one in 200 in another (Singh and Raghavan. 1957). The fatality rate is low, 0.1 (Williams, 1899) or 0.03 (Patnaik and Kapoor, 1967), according to studies of medical records in India, but in view of the high infection rate in endemic areas, not negligible.

3. Efect of climatc and Ir’atcr sources on scwsonal incidence There have been very few determinations of the infection rate in cyclops and none giving the monthly variation. Estimates of season transmission, therefore, have to be based on the human infection rate the following year, and assume that the female takes exactly a year to mature. (a) Ponds In desert regions, exemplified by the Rajasthan/Sind deseri area of India and Pakistan, water is obtained from wells for most of the year but from ponds (known as “tarais”) during the rainy season. In the desert focus in Pakistan there are very deep draw wells but while there is water in the ponds it is used in preference; this is partly because well water has to be paid for from professional water carriers, partly because it is slightly saline, but also for rzligious reasons. Each village or town has oneor two ponds. which may be up to 30 m in diameter and 5 m deep at the height of the rainy season. Transmission is confined to the months when the ponds have water, most cases occurring in September just before they become completely dry (Table VI). A unique type of habitat is the desert focus in the south of Iran. All running water in this area is saline and rain water for drinking is collected in large cisterns, known as “birkehs”, some of which are very ancient. There are many cisterns in towns and villages and they are also found along all caravan routes (Figs 18 and 19). They rarely dry up completely but transmission occurs principally during the dry season (Lindberg, 1936). Peak transmission (as measured by the proportion occurring in the same month the following year) occurs when the cisterns are still half full and transmission almost ceases for thc 2 months before the rains (Table VI). This is unlike the situation in which drinking water is obtained from permanent ponds, where transmission builds up to a peak just before the rains. In both cases, as in step wells, there is little transmission in the rainy season owing to the large volume of water present and because its turbidity reduces the density of cyclops. The transmission season in savannah regions depends on the rainfall. In Sahel savannah areas of Africa, where the annual rainfall is less than 75 cm per year the ponds dry up for much of the year, as in desert areas. This occurs in Northern Nigeria (Ramsay, 1935; Onabamiro, 1952) and probably in Upper Volta, Niger, Chad, Mauritania, Sudan and Senegal, and results in infection being confined to the rainy season and the following months until the ponds dry LIP(Fig. 20). I n the Guinea \avannah areas of We\t Africa. with an annual rainfall of

I10

RALPH MULLER

FIG. 18. A cistern (hirkeh) near Bandar Abbas (Iran). The writing states that it had recently been chlorinated.

FIG.19. A cistern at Lingeh (Iran) destroyed by an earthquake and being replaced by a piped water supply.

L)R A C U N

C U L U S A N I) I) K A C U N C U LI A S l S

FIG.20. Pond in the Mabauu area of Sudan in the Sahel savannah zone (courtesy of Dr J . F. E. Bloss).

111

112

RALI’I1 M U L L E R

more than 150 cni (Guinea, Togo, Ghana, Ivory Coast, Dahomey, Southern Nigeria), the ponds have water all the year. However, during the rainy season there is little or no transmission as there is so much surface water that many of the ponds turn into small streams, all become very turbid and often unsuitable for cyclops host species, and there are many alternative sources ofdrinking water. For instance, in the village of lwoye in Western Nigeria, during the rainy season water is obtained from a well, from rain water butts, and from two ponds, but only the ponds have water in the dry season ; infection was found to be confined entirely to the dry season (Onabamiro, 1952). There is also the factor that infected cyclops sink to the bottom of a pond (Onabamiro, 1954), and so are more likely to be picked up when the level is low. However, this may not be of great importance as the bottom is normally thoroughly stirred when water is obtained (Fig. 21).

FIG.21. An infected pond in Western Nigeria during dry season in derived Guineasavannah

zone.

In the savannah regions infection is confined to areas which are away from rivers, and which rely on shallow ponds for drinking water (Onabamiro, 1954; Scott, 1960). (b) Wells In endemic areas where draw wells arc in use they appear to be of little importance in transmission (Lindberg, 1946a; Onabamiro, 1952; Scott, 1960; Ansari and Nasir, 1963),as they are usually surrounded by a parapet. However, Ahmed ( I 969---personal communication) found infected cyclops

I)R A C U N C'lJ L U S A N D D R A C U N C: U L I A S I S

113

in a sample of well water from Chachro in the Sind desert taken during the rainy season when the level was high. Step wells, which provide the main source of drinking water i n many rural areas of India, are ideally situated for the transmission of Dracw1ci4lirs (Lindberg, 1946a). These wells are often a few metres in diameter with steps going down into the water, so that affected Iimbsare often immersed when dipping a water container into the well (Fig. 22).

FIG.

22. Infected step well at Kantarvos, near Khcrwara, India (courtesy of Dr A. Banks).

4. Specics of cJv.lops at.1it ig as

iir t crt r iivliat E liosts The most important factor determining whether a particular cyclops will transmit Dracirnciiliis is its mode of life; unless it is a predatory species it will not ingest embryos i n the water. In general. larger forms tend to be carnivorous

1 I4

RALPH MULLER

and smaller species (particularly members of the subgenera Microcyclops and Eucyclops) herbivorous (Fryer, 1957). The species of cyclops which have been found to act as intermediate hosts in various parts of the world are shown in Table VII; the cosmopolitan species C. (Mesocyclops) kcuckarti acts as a host in all parts of the world if present in a particular habitat, but may not be the most important agent. Only one or two species of cyclops have been found naturally infected in each endemic region, although there are usually other species present in the same habitat which can be easily infected experimentally; the explanation is unknown. There are some species of cyclops in which the embryos will not develop after ingestion, and the sluggish or disintegrating embryos can be found in the gut for a few days after ingestion. The inability to penetrate the gut wall may be due to physiological resistance or because the feeding habits of the cyclops cause damage to the embryos. That true resistance does occur is indicated by the fact that in the laboratory Cyclops vcrnalis americanus can be easily infected, while development of larvae in the haemocoel of C. vernalis s. str. occurs in only a few specimens; but, when infected, these commonly have many larvae (Table VI11). TABLE V11 Spcicies of Cyclops fourtd rraturally infected with D.

Authority

Species

- ...

NrcERiA (Western Region) Cyclops kcrickorti (Claus) C. ltwcliarti aeyiiotoriolis (Kiefer) C. riigericuiiiu (Kiefer)

C. irtopirtiis (K iefer)? C. varicatis subaeqiialis (Kiefcr)?

C.hyalitiiis (Rehberg)

IVORY COAST(Bouake) C.coronatiis= C ../iscii.s (Jurinc)*

~

Onabamiro Muller Onabamiro Onabam iro Muller Onabamiro Onabamiro Muller

medinensis Year

__

-..-

1952 I968a I952 I952

unpublished 1952 1952

unpublished

Raffcr

I966

Roubard

1913

DAHOMEY (Agouagon) C. Ieiickrtrti

GHANA (Wa) C. lerickarti

Muller

unpublished

PORTUGUESE GUINEA (Susana) C. leuckarti aequatorialis

Ferreira and Lopes

1948

Li nd berg

1950

lssajev

1934b

MIDDLEEAST C. kcuckarti C. rylovi vertrtifir (Lindberg) C. rylovi s.str. (Smirnov)? C. niicrospinulosiis (Lindbcrg)? C. titictus (Lindberg)*

RussrA (Samarkand) C. oitliorioitks (Fr iesl and)*

I) K A (' U N C U L U S A N 1)

1)

K A C' U N C U L I A S IS

I I5

TAMI V I I ( w / / / i w w d )

Species

Authority

Year

-~~

IRAN(Larestan) C. iranicus (Lindberg) PAKISTAN (Tharparkar) C. hisrtosus (Rehberg)* INDIA (Deccan) C. leuckarti C. vermijer (Lindberg)

~

Lindberg Muller

~.

1936 unpublished

Lindberg Lindberg

1935 1939

Moorthy and Sweet

I936b

Lindberg

1946b

Rao and Reddy

1965

INDIA(Mysore) C. leuckarti C. hyalinus C. decipiens (Kiefer)? C .fimhriatus (Fixher)? C. karvei (Kiefer and Moorthy)?

INDIA(Rajasthan) C. leuckarti C. hyalinus* C. varicans (Saw)*

(Andhra Pradesh) C . leuckarti* C. hyalirius*

Not found naturally infected but assumed to act as an intermediate host on epidemiological grounds and capable of experimental infection. t Occurs together with proved host species and can be experimentally infected.

Embryos seldom penetrate the gut wall of a species of cyclops and then fail to develop. Many of the reports of this occurring can probably be attributed to the temperature of incubation being too low (Manson, 1895; Southwell and Kirshner, 1938). Nothing is known of the number or density of infected cyclops necessary for continued transmission in a particular habitat. In four ponds in the village of Iwoye in South-West Nigeria there were 76-506 specimens of C . nigeriunus in each 10 litres of water during the maximum transmission season in April, and it was estimated that each inhabitant ingested an average of 75 infected cyclops per annum (Onabamiro, 1951). The infection rate in cyclops varied from 4.7% to I0.5%, with an average of just over one larva per litre of water. However, no infected cyclops were found during the rainy season in September. Uninfected C. nigeriunils undergo a vertical diurnal migration (Onabamiro, 1952), but after about 6 days of infection this is reduced and by the 14th day thecyclops areconfined to the bottom few inches o f a pond (Onabamiro, 1954). This effect is probably a result of the physiological action of the larval moults and it may be of importance in confining transmission to man to the months when the water level is low. 5 . Rcwrvoir Hosls Infection with guinea worm has been reported from a wide variety of animals in many parts of the world (Table IX). Early records were reviewed by Bartet (1909), Leiper (1910) and Turkhud ( I 920), and more recent ones by Hinz (1965). 5

TABLEVIII Species of Cyclops used for experimental infections outside an endemic area

Species .-

~

____

Region

Result

Cyclops quadricortiis C. viridis (Jurine) C. riridis C. leuckarti C. prasinrrs (Fischer) C. magnus C. leuckarti C. serrulatus = C. agilis (Koch) C. ternis C. leuckarti C. vernalis (Marsh) C. vernalis americanus (Fischer) c.sp.

Authority _

~~

_

~~~~

Year

~- -

~~

London Paris Algeria

Partial development No development No development

Manson Roubard Chatton

1895 1920 1918

Peking

Full development in a few

Hsii and Watt

1933

Java Liverpool London Paris

Full development Partial development Full development Full development

Brug Southwell and Kirshner Muller Golvan and Lancastre

1930 1938 1968a 1968

1) R A C U N C U L U S A N 1)

117

D R A C U N C U LI A S I S

TABLEIX Records of natural infections itr animals

Region

Host

Author

Year .-

Primates Cercopithecus aethiops Papio hamadryus Macaca mulatta Carnivores Acitionyx jrihatri.\ Aonyx ciiwriw Canis,fumilicrris

Timbuctu India India Kordofan Malaya Buenos Aircs China (Pgking) Egypt

Kasachstan India

Ivory Coast Timbuctu Tanzania Panthera pardus Wolf Jackal and Wolf Felis domestica Herbivores Bos taurus

Gazella bennetti Equiis caballiis

Zambia Egypt Egypt Israel India

West Africa Arabia India India

Cazalbou (in Bartet, 1909) Turkhud London School collection Valencienncs RaruS and Moravcc Hussem Hsii and Watt Blanchard Griffith Piot Cinotti Leiper Chun-Sun Smyttan Forbes Gaiger Mitter Stiles and Hassall Turkhud Sharma and H ussain Sankaranarayanan et a/. Anantaraman Raffier Cazalbou (in Bartet, 1909) Truscott (persbnal communication) Leiper Blanchard Piot Wi tenberg Turkhud Anan taraman Bartet Blanchard Brook-Fox Forbes Clarkson Cobbold Batliwala

1920

1856*

1969 1771* J 933 1890 1888* 1889* 1906 1910 1958 1825* 1837* 1910a 1910 1920 1920 1946 1965 1966 1969b 1956 1910 1890 1889* 1951

1920 1966 1909 1 890 1913t

1838* 1845* 1881* 1893*

118

RALPH MULLER

TABLE 1X (continued) Region

Host Eq 1lll.S c*aDtrIll IS

India

E. tJSitrflS

I ran

* In

Author Gaiger Turkhud Anantaraman Sabokbar

Year 1910b 1920 1968 1968 unpublished

Leiper. 1910.

t Vcry unlikcly 10

haw been Dracrmc.rr/rrs.

The fact that most reports have been from dogs may reflect the close relationship of this animal to man rather than any particular susceptibility. In other areas and especially in wild animals the adult female worms are not likely to be noticed unless they are emerging, a process which may be over very quickly. Reports of Dracunculus infection from mammals in North America have not been included in Table I X but weregiven separately i n Table IV. This is because, although many of the reports refer to the parasites as D. medinensis, they are inore likely to belong to the related species D.insignis. Some reports from other parts of the world might also refer to a non-human species but there is no evidence to support such a view. Despite the sporadic findings of Dracunculus in animals, it is not known whether there arc animal reservoir hosts capable of maintaining the infection in the absence of nian anywhere in the world. However, records of D. medinensis from places where human infection does not occur, such as Tanzania, Zambia, China and Malaya, or where it has been eradicated from man, as in Russia, make it a likely supposition. The situation in the formerly endemic foci in Russia is particularly suggestive. as out of 213 dogs examined in Kasachstan in 1955-1956, 25 (1 1.7 7;) were found to be infected (Chun-Sun, 1958). U.

PATHOGLNESIS

I . Sitr of’niiergcnci~ All investigators have found that most worms emerge from the lower limbs, although occasionally worms may be found almost anywhere in the body. The distribution of lesions found in various surveys is given in Fig. 23 which shows that there are no significant geographical differences in the sites of emergence. I t has often been stated that the female worms migrate to those parts ofthe body which frequently come into contact with water-the emergence of worms from the back of the neck of water carriers who carry water on their heads was reported by Harrington (1899) and Manson (1905)-but this may have been merely coincidence. Worms rarely emerge from the hands and in exprimentally infected rhesus monkeys most worms emerge from the lower limbs, even though the animals have never been in contact with water. I n these hosts the outline of pre-emergent worms can often be made out and they can be seen to migrate down to the limbs about 9 months after infection (Muller, 1968a).

1)

R A C U N C U L U S A N D DR A C U N C U 1.1 A S 1 S

119

Head and neck

Thigh 7.0 o 6.3d 2 8 e

Knee 74.5 81 6 93 4

FIG.23. Percentage distrihution of guinea worm lesions on the body. Bold figures refer to a survey of 267 patients in villages north of lbadan (Nigeria) in 1967. Other sources: (a) from Fairley (1924); (b) from Lindberg (1946); ( c ) from Ferreira and Lopes (1948); (d) from Onabamiro (1958); (e) from Rao and Reddy (1965).

It is possibly a geotactic response, but the mechanisms by which parasitic nematodes reach preferred sites are not clear (e.g. the adults of Onchocerca gutterma are found near the nuchal cartilages of the cow, while microfilariae are found only in the skin of the umbilical region). 2. Numhpr of‘ 1i’ort17sem>rging. Usually one to three worms emerge at one time but in the occasional patient

1 20

RALPH MULLER

there may be multiple infection with up to 40 worms in one season (Blacklock and O'Farrell, 1919; Gore, 1932; Rao, 1942: Lindberg, 1948; Ferreira and Lopes, 1948; Onabamiro, 1951 ; Lucas ct a/., 1969; Raffier, 1969~;Reddy etal., 1969a). Two surveys have been made in India based on a large number of patients: Rao ( I 942) found that in 3 I29 cases, 2086 (65.5 :(,) had one worm, 650 (22 %) had two, 193 ( 6 x ) had three, 85 (2.8)l.i) had four, and I 1 5 (3.7%) had more; Reddy et a/. (1969a) found that of 1759 cases, 1052 (61 had one worm, 234 (I5 had two, 183 (1 I :h) had three, 91 (5 had four, and 134 (8 %,)had from five to 40. I n West Africa most patients have only one worm emerging at a time: eighty-five per cent of cases in three villages in Portuguese Guinea (Ferreira and Lopes, 1948); 374 (58.3x,) with one worm, 143 (22.4%) with two, 55 (8.6x) with three and 69 (10.7 with more in 641 infected children in Western Nigeria (Onabamiro. 1958); in another 158 cases i n Western Nigeria, 136 (86%) had one worm, sixteen (10%) had two, and six (4%) had three (Muller, 1969--unpublished observations); and, out of 101 patients in Ghana, 61 had a single worni (Litvinov, 1968).

x)

x)

x)

x,)

3. Clinicalsytnptoms There are three ways in which infection with guinea worm may first become apparent: by the recognition of a palpable sometimes moving worm; by allergic symptoms; or by the formation of a bleb. Reddy eta/. ( I 969a) found that only 37% (812 out of 2193) of patients were aware that they were infected beforea blister appeared. The majority of these discovered the presence of a worm 8-10 days before the blister formed, although a few (63) were aware a month before. Other investigators have found that a generalized urticaria is the first indication of infection i n 30-80 of their patients, and this is sometimes accompanied by fever, giddiness, gastro-intestinal symptoms and dyspnoea (Duke, 1895; Fairley, 1924a; Carayon et a / . . 1961). The urticaria1 eruption may be accompanied by infra-orbital oedema; it may appear up to 8 days before the blister forms but commonly the day before. and lasts only for a few hours (exceptionally up to 96 h according to Fairley, 1924a). Occasionally chronic infection with non-emergent worms may cause an allergic pruritis (Hodgson and Barrett, 1964). In many patients (61 in Fairley's series, 63 '%, of those of Reddy rt ul.) the local blister is the first sign of infection. The blister is minute when first noticed but may grow to a few cm in diameter before it bursts, usually in I--3 days (Fig. 24). The blister fluid consists ofa bacteriologically sterile serum containing monocytes, eosinophils and usually embryos; polymorphs were also reported by Fairley but this was thought to be a tnistakc by Reddy rt a/. (1970). The formation of the blister is accompanied by local itching and often an intense burning pain, which may be relieved by immersion of the infected portion in cold water. It is at this stage that topical treatment with concoctions of leaves, roots, vegetable oils or even kerosene is often used to ameliorate the pain. The formation of thc blister is often stated to be due to a necrotizing fluid produced by the adult worni but may be caused by the liberation of embryos into the tissues. This was thought to be unlikely by Fairleyand Liston(1924b),

x

:,;

121

I ) I< A C U N ('U L U S A N I) I I R A C U N C U L I A S I S

FIG.24. A blister in process of bursting. There has been a n unusually Severe tissue reaction rcsulting in a very large blister with a free length of worm in the blister fluid. I

I

I

I

5-9

10-14

15-19

1

\

0

'3-4

I

I

-

I

0

1

1

I

.

20-29 30 -39 40-49 5 0 - 5 9

I

.

60+

Age groups

FIG.25. Age incidence o f dracunculiasis in 1393 people from three villages in W. Nigeria during April 1969. The open circles show the perccntage that each agegroup representsofthe total population in the area (data from Barber, 1966).

I22

RALPH MULLER

since intradermal and subcutaneous inoculation of thousands of embryos into human volunteers produced a pus-filled abscess but not a typical blister nor allergic manifestations. However, soluble extracts of embryos cause shock when injected intravenously into “uninfected” rhesus monkeys and, if this release of embryos is the mechanism by which the blister is formed, it would help to explain the complications that so often occur (Muller, unpublished observations). The highest infection rate is found between the ages of 10 and 20 (Fig. 25): above I 1 according to Scott, 1960; 16-25 according to Rao and Reddy, (1965). There is no evidence that immunity develops, however, and some individuals are infected year after year. Most surveys have found that the sexes were about equally infected (Rao, 1942; Scott, 1960; Reddy et al., 1969a) but in India more infections have been found in males (Lindberg, 1964a; Rao and Reddy, 1965; Bildhaiya et al., 1969). 4. Sintple course of the disease A portion of the uterus of the worm is extruded through the ulcer, which is formed by the bursting of the blister, the edges of which consist of pinkish granulation tissue. After a few days the anterior end of the worm is exposed by sloughing of the white central eschar of the ulcer and more of the worm protrudes, particularly after immersion in water (Fig. 26). Once embryos have been expelled, about 5 cm of the flaccid portion of the worm can usually be drawn out each day and the exposed part of the worm dries up. The surrounding epithelium grows over the ulcer leaving a small hole through which the worni protrudes (Fig. 27) and, when all the worm has been extracted or has been spontaneously expelled, the ulcer heals rapidly. The complete expulsion of the worm occurs on average in 4 weeks and, provided that there have been no complications, the presence of a worm causes little pain or incapacity. The worm in the subcutaneous tissues is surrounded by a thin fibrous sheath, which does not adhere to the cuticle and so the worm is able to move freely through it. However, when the worm has partially emerged, adhesion of the tissues of the host often makes extraction difficult (Fig. 28). 5. Secondary infection

Jn their detailed account of the disease, Fairley and Liston (1924a) gave a list of the complications observed in cases of dracunculiasis, which included acute abscess, cellulitis, arthritis, synovitis, epididymo-orchitis, bubo, chronic ulcerations, fibrous ankylosis of joints and contractures of tendons. They stated that almost without exception these resulted from secondary bacteriai infection. The most common organisms cultured from the lesions were Staphylococcus aureus. Eschericliiu coli and streptococci. They described how the female worm withdraws into its connective tissue sheath if it is broken during extraction, drawing bacteria into the tissues. I n areas without adequate hospital or dispensary care sccondary infcction of lesions is very common (Fig. 29). I n an examination of 273 lesions in patients from two villages in Western Nigeria, I found that SO‘%, showed evidence of

FIG.26. Ulcer on the foot of a child (the end of the worm has been cut; it would normally dry up). FIG.27. Worm on leg being wound out through the small hole left after closure of ulcer (this illustrates an uncomplicated case).

FIG.28. Scction of adult worn1 with surrounding tissuc' reaction, including foreign body giant cells. caused in t h i \ case by release ofenihryos into tlic ticsues (cross-sectionsofembryos can be seen outside thc cuticle or'the adult).

124

RALI'tI M U L L E R

sepsis; not surprisingly lesions on the feet and ankles were much more likely to become secondarily infected (Table X). In a very few cases fatalities have followed septicaemia (Carayon et a/., 1961) or gangrene.

FIG.29. Secondarily infected lesion on leg showing evidence of treatment with palm oil. TAH1.E

x

Proportioii oJIi~.tioiisJho wing evidcncr of sepsis

Site of lesion

N ti iii ber

Foot

I I4

Ankle

69

Leg Other Total

48 42 373

found

Number septic -

90 31 13 2 136

Percentage septic 79 45

27

4.8

50

Data froin paticnts in the village5 oI'1hbil-c: mid Apapa (W. Nigeria) during April, 1969.

I) K A C U N C U L U S A N 1) I)

R A C U N C U I. 1 A SJS

125

Fairley and Liston's contention. Ihllowcd by standard text books, that bacterial infection is necessarily involved i n thc coniplications of the disease has been challenged i n rccent years (Kothari v ~ n l .196%; , Reddy and Sivaraniappa, 1968; Muller, 1970e; Muller. P/ al., 1970b), principally because of the lack of success of antibiotic therapy and the converse quick healing of a secondarily infected ulcer or abscess. once the worm is removed. The risk oftetanus as a sequel to guinea worm infection is very real. Lauckner cf a/. (1961). i n an anctlysis of medical admissions to University College Hospital, Ibadan. Nigeria, observed that in 1958 tetanus was the most important cause of'death and that a guinea worm ulcer was the third commonest portal of entry of the tetanus spores. Pirame and Becquet (1963) believed that 15 out of 21 1 cases of tetanus in Upper Volta resulted from Dracunculus infection, and Pirame (1963) advised that all guinea worm patients should be vaccinated against tetanus. An isolated case of tetanus following guinea worm infection was reported by Labegorre ct al. (1969). 6 . Norwiiiergellccwceqf'Mwrrns The female worn1 frequently fails to rsach the surface and discharge its larvae. I n the majority of such cases the worms become encysted and calcify (Fig. 30); their presence is shown only by X-ray (Rolleston, 1892; Selkon and Latham. 1952; Ramdas. 1953; Egidio, 1955; Roussel, 1928; Smith and Siddique, 1965; Patel and Anand, 1960; Carayon and Camain, 1961 ; Donges, 1966; Redtfy c v a/., 1968. Fig. 31). Encystment, followed by absorption or calcification (Cohen. I959), is the normal fate of the male worm (Fig. 32). Reddy PI ul. (1968) examined 10 032 X-rays taken for other ailments at the Kurnool University College Hospital in South India, and found that 460 of them, mostly from the 26-SO year age group, showed the presence of calcified worms. Over halfof the X-raysshowed the presence of morethan one worm, and one showed 50 worms. The pelvis and abdomen were the most common sites

FIG.30. Calcifying female guinea worni in a cyst removed from the abdominal mcsenterie\ (I'rom DBnges, 1966).

126

RALPH MULLIR

FIG.3 I . X-ray of calcified worm in the hand (from Muller, 1973b).

FIG.32. Section of encysted inale worm 5 months after infection (from rhesus monkey).

1)

R A C' U N C' U L U S

AN

D D R A C UN C U L I A SI S

127

I'or calcitied worms, followed by the region orthe kneejoint. Out of 100 patients contacted, 89 were unaware of the presence ofthe worms, while ten had chronic arthritis with a calcified worm by the side of the joint. However, these workers do not believe that the calcified lesion had anything to do with the synovitis inside thejoint. Occasionally the encysted worm causes more serious symptoms if it is in an unusual site: Donaldson and Angelo (1961), Reddy and Vasanta Valli (1967), and Mitra and Haddock (1970) described a total of five cases of paraplegia caused by the presence of guinea worms in the extradural space, one of which ended fatally; Kinare et al. (1962) reported that a worm in the thoracic cavity caused constrictive pericarditis; Raffi and Dutz (1967) described three urinogenital cases.

FIG.33. A large guinca worm abscess.

Sometimes when worms do not emerge they form a large pus-filled abscess (Figs. 33 and 34) which may occur in many sites in the body (Dejou, 1951 ; Reddy et al., 3969d) but, if near a joint, can lead to arthritis. This abscess should be differentiated from the septic condition resulting from bacterial infection of the pathway of an emerging guinea worm. I f the condition is due to a necrotic reaction to the worm itself, the question arises why it should occur only in about 10 of patients harbouring non-emergent worms. As mentioned in the preceding section, Fairley and Liston (1924b) ascribed practically all complications except calcified worms to secondary infection. However, Fairley (1924a) remarked that a deeply-seated abscess, which was sterile on culture, could result from premature escape of embryos into the

>
D K A C U N C U L1 A SI S

I39

tions of a chemical with no residual action (such as bleaching powder) could be eflective; the first application to be given 4 weeks after the ponds refill, and a second 4 weeks later if necessary. This timing is based on the assumption that it will be at least 2 weeks after the ponds have refilled (or after treatment) before there are enough cyclops present for transmission to occur, and that the larvae take a minimum of 12-14 days to reach the infective stage in cyclops (page 83). In areas with a long transmission period, a compound with residual action would be of great advantage, particularly where there are numerous scattered water sources. The 1 '%, sand granule formulation of Abate might be suitable under these conditions, because at a concentration of 1 ppm in the laboratory it was found to be lethal to cyclops for up to 12 weeks (Muller, 1970a). It is at present undergoing field evaluation i n step-wells in India and in ponds in Ghana.

2. Improvement of water supplies (a) Piped water. With the introduction of a piped water supply the incidence of dracunculiasis falls dramatically in a year or two. Examples are provided by the towns of Fiditi and Igbo-Ora in Western Nigeria, each with a population of 30 000. The incidence was over 20% in grammar school children in Fiditi and over 60 % in the general population of Igbo-Ora prior to the completion of piped water systems in 1963 and 1965, but no cases were reported two years after completion, although the disease is still endemic in the surrounding areas. When cases do occur in a large town with a proper water supply it is always found that the patient has travelled from the country. The disease still occurs frequently in the city of Ibadan in Western Nigeria, with a population of about three-quarters of a million, because so many of the inhabitants have land in the surrounding countryside which they farm for about a month of the year, and they drink pond water during this time. (b) Bore wells and tube wells. Where these are technically and economically feasible they can provide a constant supply of pure water. The water is not liable to the contamination which can occur in draw wells when full and, if used with an elevated tank, can provide the convenience of a piped water supply with taps. A tube well is being installed in the town of Chachro (population about 6000) in the centre of the endemic focus in the Tharparkar region of Pakistan, and it will be of great interest to see its effect on the incidence of dracunculiasis. (c) Improvements to existing supplies. Many of the sophisticated methods of water supply are not feasible in the poor rural areas where the disease occurs. However much can still be done to prevent the transmission of dracunculiasis. I n three villages in the Rajasthan area of India the replacement of the traditional step wells by draw wells has resulted in a dramatic fall in the number of cases (Johnson, 1969; Banks, 1969-personal communication), and similar conversions in an area of Andhra Pradesh have reduced the number of infected villages from 103 in 1957 to 52 in 1961 (Rao and Reddy, 1965). This was the measure that was mainly responsible for eradicating the disease from Samarkand and Tashkent in the 1940's.

I 40

R A 1. I’ I4 M U L 1.17 R

The use of raised edges and concrete surrounds to draw wells helps to prevent contamination of the water. With cisterns in Iran, three of the doorways have been sealed off and a barrier placed across the fourth to prevent the emerging embryos from reaching the water (Fig. 18). However, a gap must be left at the bottom for rain water to run in, and the barriers were sometimes unpopular and have been destroyed. In some areas the provision of wells does not solve the problem. In the town of Chachro there are numerous draw wells, and people who drink only from these d o not become infected (Ansari and Nasir, 1963). However, pond water is preferred by many people when available; this is partly because well water has to bebought,partly because it tastes brackish, but also for religious reasons. In the village o f Akufo in Western Nigeria the annual incidence ofguinea worm infection is nearly 26 yL (Gilles and Ball, I964), even though a properly designed well was built a few years ago; pond water is apparently still used because of the extra effort involved i n drawing well water. ACKNOWLEDGEMENTS The work of the author was supported by a grant from the Tropical Medicine Research Board of the M.R.C. and the Ministry of Overseas Development. Thanks are due t o Dr A. Banks for Fig. 22, D r J. F. E. Bloss for Fig. 20, Professor D. B. Jelliffe and Edward Arnold Ltd. for Fig. 31 and G. Thieme Verlag for Fig. 30 from 2. Tropenmd Parasit. Also to M r C . J. Webb and staff of the Visual Aids Dept. a t the School. REFERENCES Acton, H. W. and Rao, S. S. (1933). The pathology of elephantiasis of filarial origin. Indian med. Cur. 68, 305-3 14.

Ambroise-Thomas, P. ( 1 969). “6tudc sero-imniunologique de dix parasitoses par les techniques d’immuno-fluorescence.” Faculte de Medccine de Lyon (mimeo). Anantaraman, M. (1966). Dracontiasis in animals. Proc. f s f fnfernut. Conxr. Parusirology (Rome, 1964). Vol. 2, pp. 798-799. Pergainon, Milan. Anantaraman, M. (1968). Epidemiological viewpoints in parasitic zoonoses in India. Bull. ftidiun SOC.Mal. 5, 270-214. Ansari, A. R. and Nasir, A. S. (1963). A survey of guinea worm disease in the Sind Desert (Tharparkar district) of West Pakistan. Pukist. J . Hlth 13, 152-167. Balfour, A. (1903). Eosinophilia in bilharzia disease and dracontiasis. Lancer ii, 1649. Bandyopadhyay, A. K. and Chowdhury, A. B. (1965). Preliminary observations on the effect of prolonged hypothermia on Dracunculus medinensis. Bull. Culcutta Sch. trop. Med. Hyg. 13, 49-50.

Barber, C. R. (1966). “Igbo-Ora, a town in transition.” Oxford University Press, Ibadan. Bartet, A. J. A. L. (1909). “Le Dragonneau (Ver de Guinde, Filaire de Medine).” A. Maloine, Paris. BaruS, V. and Moravec, F. (1969). Three interesting nematodes from Aonyx cinerea (carnivora) from Malaya. Fohn Parasitol., Praha 16, 235-236. Benbrook, E. A. (1932). Qracrrncirlus medinensis (Linnaeus 1758) appears in the United States as a parasite of the fox. J . A m vet. Med. Ass. 34. 821.

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Benbrook, E. A. (1940). The occurrence of the guinea worm in a dog and in a mink, with a review of this parasitism. J. Am. vet. med. Ass. 96,260-263. Bhajekar, M. V. (1951). A note on the treatment of guinea-worm infection. Indian men. Gar. 86, 193- I 96. Bildhaiya, G. S., Marwaha, S. M. and Patidar, S. R. (1969). An epidemiological assessment of dracontiasis. J. Indiati med. Ass. 52, 67-71. Billet, A. (1896). Eosinophilie dans un cas de filariose sous cutanee de Medine. C. r. Seanc. SOC.Biol. 9, 18. Blacklock, B. and O’Farrell, W. R. (1919). Note on a case of multiple infection by Dracunculus medinensis. Ann. trop. Med. Parasit. 13, 189-194. Blanchard, R. (1890). “Traite de Zoologie medicale.” Vol. 2, Paris. Blanchard, M. (191 1). Note sur le Ver de GuinCe dans la region du Haut-Sassandra (Cbte d’Ivoire). Bull. Soc. Path. exot. 4. 206-209. Brackett, S. (1938). Description of the life history of the nematode Dracunculus ophidensb n. sp. with a redescription of the genus. J . Parasit. 24, 353-361. Bradley, D. J. (1968). In “Uganda atlas of disease distribution” p. 836. Ministry of Health, Uganda. Brook-Fox, E. (1913). Chinkara suffering from guinea-worm. J. Bombay nut. hist. SOC.22, 390. Brug, S. L. (1930). Dracrmculirs rnedinensb in the Dutch East Indies. Mededeel Dienst. Volksgezondheid Nederl-Indi2 19, 153-1 57. Bueding, E. and Oliver-Gonzalez, J. (1950). Aerobic and anaerobic production of lactic acid by the filarial worm Drnruncrrlirs insignis. Br. J. pharmac. Chemother. 5, 62-64. Bueding, E. and Fisher, J. (1969). Biochemical effects of schistosomicides. Ann. N.Y. Acad. Sci. 160, 536-543. Canimeleron ( 1907). L‘nierreu de Tidjikja (Mauritanie), Urticarie d‘origine filarienne. Ann. Hyg. Med. Colon. 10, 379. Carayon, A. and Camain, R. (1961). Migration habituelles, aberrantes ou manquks de la filaire de Medine. Presse MPd. 69, 1599-1600. Carayon, A., Camain, R., Guiraud, R. and Havret, P. (1961). Aspects chirurgicaux des helminthiases en Afrique de I’ouest (ascaridiose, dracunculose, filariose, bilharziose). IT. Pathologie de migrations habituelles, aberrantes ou manqukes de la filaire de Medine (A propose de 25 localisations chirurgicales). MPd. Trop. 21. 538-549. Casile, M. and Saccharin, H. (1953). L’intradermo-reaction dans la filariose de Bancroft en Guyane Francaise. Bull. SOC.Path. exot. 46,137-144. Chabaud, A. G. (1960). Deux nematodes parasites de serpents Malgaches. Mem. Inst. scienl. Madugascar (ser. A) 14, 95-103. Chaddock. T. T. ( I 940). Diseases of Mink. Am. Fur Breeder 12, 8 (quoted by Ewing and Hibbs, 1966). Chandler, A, C. (1942). The guinea-worm Dracunculus insignis (Leidy, 1858), a common parasite of raccoons in East Texas. Am. J. Trop. Med. 22, 153-157. Charles, R. H. (1892).“Acontribution on the life-history of the male Filariamednensis removed from abdominal cavity of man.” Scientific memoirs by medical officers of the army of India, Calcutta (quoted by Mirza, 1929). Chatton, E. (1918a). Observations sur le ver de Guinee preuve expkrimentale de I’infestation des Cjdops par voie digestive. Bull. SOC. Path. exot. 11, 338. Chatton, E. (1918b). Observations et preuve expkrimentale a Gab& sur le ver de GuinCe preuve experimentale de I’infestation de Cyclops par voie intestinale. Arch. Insr. Pnstew. Tunis 10. 158.

142

RALPH MULLER

Cheatuni, E. L. and Cook, A. H. (1948). On the occurrence of the North American guinea worm in mink, otter, raccoon and skunk in New York State. Cornell Vet. 38, 421. Chisholm, C. (1815). On the Malis Dracunculus or Guinea-Worm (in Grenada). Edin. Med. Surg. Journal 9, 145-1 64. Chitale, P. K. (1912). Observations on three hundred cases of Guinea-worm. Indian med. Gaz. 47, 3 18-320. Chitwood, B. G. (1933). Does the guinea-worm occur in North America? J. Am. med. Ass. 100, 802. Chitwood, B. G. (1950).'The male of Dracunculus insignis (Leidy, 1858) Chandler 1942. Proc. helminth. Soc. Wash. 17, 14-15. Chun-Sun, F. (1958). Dracimculirs infection in dogs in Kasachstan [in Russian]. Mecl. Purazitoi. Moskva 27, 219. Cinotti, F. (1906). Si di un caso di Filuria medinensis nel cane. Nuovo Ercolani 11,466. Cohen, G.(1959). The radiological demonstration of Drucuncirlus medinensis. South African med: J . 33, 1094-1095. Connor, F. P. (1922). Some surgical aspects of filarial disease. Br. J. Surg. 10,253. Costa, 0. R. (1956). Contribuiqdo ao connecimento da filariose na Amaz6nia. Riv. Serv. Especid Saude Publ. 8, 329-422. Cowper, S. G . (1966). A review of helminthiasis in the Western region of Nigeria with special reference to the lbadan area. W. Afr. Med. J. 15, 3-1 1. Crites, J. L. (1963). Dracontiasis in Ohio carnivores and reptiles with a discussion of the dracunculid taxonomic problem. Ohio J. Sci. 63, 1-6. Datta, S. P., Stanislas, L. and Veeraraghavan, M. (1 964). Dracontiasis in Pondicherry Settlement. Bull. Indian Soc. Mal. I , 11-18. Davis, J. L. (1931). A note on some experiments with agents lethal to cyclops. Trans. Roy. Soc. trop. Med. Hyg. 24, 631-633. Dejou, L. (1951). Les localisations profundes de la dracunculose (ptritonCales et juxta-peritoneales en particulier). M i d . trop. 11, 645-652. Denecke, K. ( I 954). Die Trinkwasserversorgung in Mesopotamien. Arch. Hyg. 138, 628-638. Deshmukh, P. G. (1969). Two new species of the genus Dracrrnculus Reichard, 1759, from snakes. Folia Parusitol., Praha 16, 105-1 10. Desportes, C. (1 938). Filariu oesophagea Polonio, 1859, parasite de la couleurre d'ltalie, est in Dracrmculirs trCs voisin de la filaire de Medine. Annls Parasit. hum. comp. 16, 305-226. Dickmans, G. (1948). Another case of guinea-worm, Dracunculus sp., infestation in a dog in the United States. Proc. helminth. Soc. Wash. 15, 39-40. Donaldson, J. R. and Angelo, T. A. (1961). Quadriplegia due to guinea worm abscess. J. Bone and Joint Surg. 43A, 197-1 98. Donges, J. (1966). Parasitare abdominalcysten bei Nigerianern. Z . Tropenmed. Parasifol. 17, 252-256. Dudgeon, L. S. and Child, F. J. ( I 903). Eosinophilia associated with dracontiasis. J. trop. Med. 6, 253-254. Duke, J. ( I 895). Note on the symptoms of Filaria medinensis or guinea worm. Indian med. Gaz. 30, 64-65. Egidio, M. di (1955). Aspetti radiologici di Drarunculus medinensis calcificato. Arch. Ital. Sci. Metl. trop. 36, 5-23. Elder, C.(1954). Dracunculiasis in a Missouri dog. Am. vet. metl. Ass. 124, 396-391. Elliott, M. (1942).A new treatment for dracontiasis. Trans. Roy. So(../rap. Med. / f y g . 35, 29 I --30I .

DRACUNCULUS A N D DRACUNCULIASIS

143

Erickson, A. B. (1946).Incidence of worm parasites in Minnesota mustelidae and host lists and keys to the North American species. Am. Midl. Natural. 36, 494-509. Ewing, S.H.and Hibbs, C. M.(1966). Dracunculus insignis (Leidy. 1858)in dogs and wild carnivores in the great plains. Am. Midl. Natural. 76, 515-519. Fairley, N.H.(1924a).Studies in dracontiasis. 1V: the clinical picture-an analysis of 140 cases. Indian J. med. Res. 12,351-367. Fairley, N. H. (1924b). Studies in dracontiasis. V: Observations and reflections on intravenous medication with special reference to tartar emetic. Indian J. med. Res. 12,369-374. Fairley, N. H. and Liston, W. G. (1924a). Studies in the transmission of Dracunculus medinensis: a negative experiment. Indian J. med. Res. 12,93-103. Fairley, N. H.and Liston, W. G. (1924b).Studies in the pathology of dracontiasis. Indian J. med. Res. 11, 915-932. Fairley, N. H.and Liston, W. G. (1924~).Studies in dracontiasis. 111. A note on various local Indian remedies. Indian J. med. Res. 12,347-349. Farmer and Witter (1952). J. small Anim. Med. 1, 174 (quoted by Schwabe et al., 1956). Fedchenko, A. P. (1871). On the formation and increase of Filaria medinensis L. [In Russian.] Isvest.Imp. Obsh. tlub. Estestrozn., Moskva, 1869170 8, 71-82. Ferreira, F.C . and Lopes, E. M. R. (1948).Aspectos clinicos e epidemiol6gicos durn foco endernico de dracontiase na GuinC Portuguesa. An. Znst. Med. trop., Lisboa 5, 71-86. Floch, H.(1954).L’intradermo-riaction chez les filariens: Etude compartk de deux antigkns: D. medinensiset D. immitis. Arch. Inst. Past., Guyanefranc. 15,1-6. Fontanilles, F. (1969). Risks versus benefits in antischistosomal therapy. Ann. N.Y. Acad. Sci. 168, 81 1-820. Fryer, G . (1 957).The food of some freshwater cyclopoid copepods and its ecological significance. J. anim. Ecol. 26, 263-286. Gaiger, S.H.( I 9 I Oa). Filuriu medinensis in the dog. J. trop. vet. Sci. 5 , 48I , Gaiger, S. H. (191Ob).A preliminary check list of the parasites of Indian domesticated animals. J. trop. vet, Sci, 5, 65. Gandhi, N. J. (1962). Unusual manifestations of dracunculosis. Br. med. J. i, 1206. Gideon, P. W. (1942).Experiments in the control of guineaworm infection in stepwells by means of carnivorous fish, Rasbora doniconius, and chlorogen (abst). Proc. 28th Indian Sci. Congr. p. 225. Gilles, H. M. and Ball, P. A. J. (1964).Guinea-worm infection and gastric function. Ann. trop. Med. Parasit. 58, 78-72. Goble, F. C . (1942).The guinea worm in a Boneparte weasel. J. Mammal. 23,221. Golvan, Y-J. and Lancastre, F-A. (1968). Developpement des larves de Dracunculus medinensis chez les Cyclops de l’lle-de-France. Annls Parasit. hum. romp. 43, 705-710. Gooneratne, B. W. M. (1969).An additional historical note on the transmission of Dracunculus medinensis. Trans. Roy. SOC.trop. Med. ffyg. 63, 546 (corr.). Gore, K. B. (1932). Cases of Dracunculus medinensis. J.R. Army med. Corps 58, 288-289. Graham, W. M. (1905). Guinea-worm and its hosts. Br. med. J. ii, 1263-1266. Greenwood, B. M.(1968).Guinea-worm arthritis of knee joint. Br. med. J. i, 314. Gretillat, S. (1965).Le dimethyldithiocarbarnate de zinc dans la prophylaxie de la dracunculose. Mgd. Afrique Noire, Dakar 12,93-96. Hamilton, W. J. and Cook, A. H. (1955).The biology and management of the fichcr in New York. New York Fish und Game Journal 2, 13-35. Harrington, V. (1899).A note on Drucunc~tlirsmeclinen.ris. Br. med J . i, 146-147.

144

RALPH MULLER

Hashikura, T. (1926). A case of Filaria medinensis in Chosen [in Japanese]. Chosen igakka Zasshc 68. Quoted by Kobayashi, H. (1926). Acta Medicinalia Keijo 11, 43-58. Helmboldt, C. F. and Jungherr, E. L. (1955). Distemper complex in wild carnivores simulating rabies. Am. J. vet. Res. 16,463-467. Hinz, E. (1965). Der gegenwartige Stand der Kentnisse iiber die Infektion von Saugetieren mit Dracirnculus medinensis als Grundlage fiir einen Modellversuch zur Priifung chemotherapeutischer Substanzen. Z. Troprnmed. Parasit. 16, 90-105. Hodgson, C. and Barrett, D. F. (1964). Chronic dracunculosis. Br. J. Dermatol. 76, 21 1-217. Hoeppli, R. (1959). “Parasites and parasitic infections in early medicine and science.” University of Malaya Press. Hsii, H. F. (I933). On Dracrrnrrdirs hoiirlemcJrin. sp., Dracunculus globocephalus and Drucicnculrrs medinensis. %. Purasitenkde 6, 101-1 18. Hsu, H. F. and Watt, J. Y. C. (1933). Dracunculus medinensis infection in two dogs in Peiping--experimental infection of cyclops. Chinese Med. J. 47, 1326-1 330. Huard, P. and Tran Anh (1950). L’intradermo-reaction chez les filariens de Hanoi. MPd. Trop. 10, 858-864. Hugghins, E. J. ( I 958). Guinea worms from carnivores in South Dakota and Minnesota, with a review of the distribution and taxonomy of dracunculid worms in North America. Proc. South Dakota Acad. Sci. 37,4046. Issajev, L. M. (1934a). Experimental dracunculiasis in the dog. [In Russian.] Med. Parazit., Moskva 3, 231-238. Issajev, L. M. (1934b). On the penetration of Dracunculus medinensis larva in cyclops. [In Russian.] hied Parazit., Moskva 3, 212-230. Issajev, L. (1934~).A simple method of demonstrating nematode larvae in crustacea. [In Russian.] Med. Parazit., Moskva 3,238-240. Jain, R. C. and Gupta, 0. P. (1966). Electrophoretic pattern of serum proteins in dracunculosis. Indian J. med. Sci.20, 71 3-715. Jeanselme, E. (1919). Note sur un cas de ver de Guinee radicalement gueri par novarsenobenzol en injections intraveneuses. Bull. Acad. Med. 81, 156. Johnson, M. F. (1968). Guinea-worm arthritis of knee joint. Br. med. J. i, 314 (corr.). Kagan, I. G. (1963). A review of immunologic methods for the diagnosis of filariasis. J. Parasit. 49, 773-798. Katzenellenbogen, 1. (1 950). Dracontiasis among immigrants from Yemen. Ifarejiuah 39, 80. Kinare, S. G., Parulkar, G. B. and Sen, P. K. (1962). Constrictive pericarditis resulting from dracunculosis. Br. mcd. J. i, 845. Kothari, M. L., Pardanani, D. S. and Anand, M. P. (1968a). Niridazole in dracunculiasis. Am. J. trop. Med. Hyg. 17, 864-866. Kothari, M. L., Pardanani, D. S. and Anand, M. P. (1968b). Guinea-worm arthritis of knee joint. Br. med. J. iii, 435, 6 (corr.). Kothari, M. L., Pardanani, D. S., Anand, M. P., Mehta, L., Kothari, D. L. and Dastur, P. (1969a). Role of secondary infection in dracontiasis. Trans. Roy, SOC. Trop. M e d Hyg. 63, 687 (corr.). Kothari, M. L., Pardanani, D. S., Mehta, L. and Kothari, D. L.(1969b). Niridazole in dracontiasis: a controlled study. Trans. Roy. SOC.trop. Med. Hyg. 63, 60861 2. Kiichenmeister, F. and Ziirn, F. A. (1878-81). “Die Parasiten des Menschen.” 2nd ed. pp. 419-425, Leipig. Labegorre, J., Pelloux, t i . , Piacentini, M. and Grimaldi, A. (1969). Le tetanos de I’adulte a Cotonou - a propos de 353 cas. MLd. Trop. 29, 702-710.

I ) R A C U N C U L U S A N I)

D R A C U N C U LI A S l S

145

Lauckner, T. R., Rankin, A. M . and Adi, t . C. ( 1961). Analysis ofmedical adniissions to University College Hospital, Ibadan. W . Afr. mecl. J . 10, 3. Layne, J. N., Birkenholz, D. E. and Griffo, J. V. (1960). Records of Dracunculus insignis (Leidy, 1858) from raccoons in Florida. J . Parasit. 46, 685. Le Dentu, K. (1923). Le traitement du ver de Guinee par les injections intraveneuses d’emetique. Bidl. SOC.Path. exot. 16, 566-567. Leidy, J. (1858). Contributions to helminthology Proc. Acud. Nut. Sci. Philudelphiu (1850-1851)10, 110-112. Leiper, R. T. (l906a). Some results of the infection of monkeys with Guinea worm. Rep. Br. Ass. Adv. Sci. 76, 600. Leiper, R. T. (1906b). The influence of acid on guinea worm larvae encysted in cyclops. Br. med. J. i, 19-20. Leiper, R.T. (1907).Theetiologyand prophylaxisof dracontiasis. Br. med. J. i, 129-1 32. Leiper, R. T. (1910). Guinea-worm in domesticated animals with a note on its discovery, by Mr. Charles Grey, in a leopard. J. trop. Med. Hyg. 13,65, and J. trop. vet. Sci.5, 414. Leiper,R.T.(1911). Amethod fordealingwith townwellsinfected withGuineaworm. J. Lond. School. trop. Med. 1, 28-30. Leiper, R. T. (1926). Discussion of the validity of certain generic names at present in use in medical helminthology. Arch. SchiJi-u. Tropenhyg. 3 0 , 4 8 4 9 1 . Leiper, R. T. (1929). Landmarks in Medical Helminthology. J. Helminrh. 7 , 101-1 18. Lindberg, K. (1935). Remarques sur I’tpidemiologie de la dracunculose dans I’Inde brittanique. Bull. SOC.Path. exot. 28, 866-875. Lindberg, K. (1936). Dracunculo$e en Iran. Arch. Srhifs-u. Tropenhyg. 40,330-342. Lindberg, K. (1939). Infestation naturelle de Mesocyclops vermqer Lindberg par les embryons du ver de Medine dans un puit du Deccan (Inde). Bull. SOC.Path. exot. 31,816-821. Lindberg, K. (1946a). Enqubte ej$demiologique sur les dracunculose dans un village du D e a n (Inde). Bull. SOC.Path. exot. 39, 303-3 18. Lindberg, K. (1946b). Dracunculose dans I’etet de Djodhpour (Radjpoutana), Inde. Bull. Soc. Path. exot. 39, 3 18-328. Lindberg, K. (1948). Seconde enquete Cpidemiologie sur la dracunculose dans un village du Deccan (Inde). Bull. Soc. Path. exot. 39, 303-318. Lindberg, K. (1950). La dracunculose en Asie, particulierement Moyen-Orient avec liste des cyclopides teceullis dans des regions enddmiques. Rev. palud. M i d . trop. 8, 87-1 11. Lindschoten, J. H. van (1610). “Histoire de la navigation de J.H.L.”. Amsterdam. Liston, W. G. (1914). “Report of the Bombay Bacteriological Laboratory for 1913.” Government Central Press, Bombay. Litvinov, S. K. (1968). On the clinical picture and treatment of dracunculosis. [In Russian.] Med. Parazit., Moskva 37,401406. Lucas, A. 0.. Oduntan, S. 0. and Gilles, H. M. (1969). Niridazole in guinea worm infection. Ann. N. Y. Acad. Sci. 160, 729-739. Macario, C. (1965). Traitement de la dracunculose par le 9955 R.P. ou Me1 W en injection unique essai en vue du traitement de masse (premiers resultats clinique). Bull. SOC.Path. exot. 58, 1089-1 103. McClaren, D. J. (1970). Preliminary observations on the sensory structures in adult filariae. Trans. Roy. SOC.trop. Med. Hyg. 64, 191-192 (cow.). Macfie, J. W. S. (1920a). Intravenous injection of tartar emetic in Guinea-worm infections. Lancet i, 654-656. Macfie, J. W. S. (1920b). Tartar emetic in Guinea-worm infections. Ann. trrjp. Med. Ptirasit. 14, 127-147.

146

KALPII MULLER

Mackin, J. G. ( I 927). Dracri/rc~rrlrisglohoerip/ru/r~sn. sp. from C/relydru sc~rperrtitru. J. Parasit. 14, 9 1-94. Manson, P. ( I 895). On the guinea-worm. Br. nretl. J. ii, 1350- I35 I . Manson, P. (1903). The life-span of Filaria n~i~tlitrerrsis. Br. nzed J. ii, 10. Manson, P. (1905). “Lectures on Tropical Diseases.” A. Constable, London. Marjitno, M. and Essed, W. F. R. (1938). Meded. dienst. VolksgesorrdheidNeder1.Indit27, 141-146. Medway, W. and Soulsby, E. J. L. ( I 966). A probable case of Dracurrculi~smedinensis (Linn., 1758) Gallandant, 1773, in a dog in Pennsylvania. J . Am. vet. med. Ass. 149, 176. Megaw, J. W. D. and Gupta, J. C. (1927). The geographical distribution of some of the diseases of India. Indiun med. Gaz. 62,299-313. Mirza, M. B. (1929). Beitriige zur Kenntnis des Baues von Dracunculus medinensis Velsch. 2.Parasi/enkde 2, 129- 156. Mirza, M. B. (1957). On Dracuncirbis Reichard 1759, and its species. 2.Parasitenkde 18, 44-47. Mirza, M. B. and Basir, M. A. (1937). A report on the guinea worm found in Varanus sp. with a short note on Dracirnculus medinensis. Proc. Indian Acad. Sci. 5 , 26-32. Mirza, M. B. and Roberts, L. S. ( I 957). A redescription of Dracunculus from a snake Natrix sipedon Linn. 2. Parasitenkde 18, 40-43. Mitra, A. K. and Haddock, D. R. W. (1970). Paraplegia due to guinea-worm infection. Trans. Roy. Soc. trop. Med. Hyg. 64, 102-106. Mitter, S. N. (1910). Cutaneous filariasis in a dog. Journ. Irop. vet. Sci., Calcutta 5 , 41 1414. Moorthy, V. N. (1932a). An epidemiological and experimental study of dracontiasis in Chitaldrug district. Indian Med. Gaz. 67, 498-504. Moorthy, V. N. (1932b). Treatment and prophylaxis of dracontiasis. Indim med. Gar. 67. Moorthy, V. N. (1935). The influence of fresh bile on guinea-worm larvae encysted in cyclops: a preliminary report. Indian med. Gaz. 70, 21. Moorthy, V. N. (1937). A redescription of Dracuncuhis medinensis. J. Parasit. 23, 220-224. Moorthy, V. N. (1938). Observations on the development of Drtlcunculus medinensis larvae in cyclops. Am. J. Hyg. 27,437460. Moorthy, V. N. and Sweet, W. C. (1936a). A biological method for the control of dracontiasis. Indian rned. Gaz. 71, 565-568. Moorthy, V. N. and Sweet, W. C. (1936b). Guinea worm infection of cyclops in nature. Indian med. Gar. 71, 568-570. Moorthy, V. N. and Sweet, W. C. (1936~).A note on the experimental infection of dogs with dracontiasis. Indian med. Gar. 71,437. Moorthy, V. N. and Sweet, W. C. (1936d). A peculiar type of guinea-worm embryo. Indian J. med, Res. 24, 53 1-534. Moorthy, V. N. and Sweet, W. C. ( I 938). Further notes on the experimental infection of dogs with dracontiasis. Am. J. Hyg. 27, 301. Moravec, F. (1966). The first record of dracunculosis in the Anaconda Euirnectes muriniis L. Folia Purasitol., Praha 13, 281-283. Mueller, J. F. (1959). The laboratory propagation of Spirometra munsonoide,s as an experiniental tool. 11. Culture and infection of the copepod host, and harvesting of the procercoid. Trans. Am. Micrusc. Sop. 78, 245-255. Muller, R. (1967a). A historical note on the transmission of Draclmciilus. Trrm.s.Roy. Sac. trop. Med. Hyg. 61, 747-750 (corr.).

D R A C U N C U L US

A N I) I) R A C U NCCI L I A S IS

I47

Muller R. ( I 967b). The development of Drcrcwncmlris ttiat1itretw.s in the intennediate host after deep freezing (demonstration). Truns. Ruy. Soc. trop. Med. Hyg. 61, 45 1452. Muller, R. (1968a). Studies on Drucunculus mea‘inensis (Linnaeus). I . The early migration route in experimentally infected dogs. J. Helminth. 42, 331-338. Muller, R. (1968b). Experimental dracontiasis in animals. Parasitology 58, 7p-8p. Muller, R. (1968~).Studies on the serological diagnosis of dracontiasis. VIIIth Internar. Cotrgr. trup. Med. Ma/. (Teheran) Abst 940-941. Muller, R. (197Oa). Laboratory experiments on the control of cyclops transmitting Dracutreiilus. Bull. Wld Hlth Org. 42, 563-567. Muller, R. (1970b). In “Diseases of children in the subtropics and tropics.” 2nd ed. (D. B. Jelliffe, ed.) pp. 893-898. Edward Arnold, London. Muller, R. ( I97Oc). Development of Draciinculus medinensis after deep freezing. Nature, Lond. 226, 662. Muller, R. (1970d). Dracuncuhis medinensis: diagnosis by indirect fluorescent antibody technique. Expl Parasit. 21, 357-361. Muller, R. (1970e). Egg division in Dracunculrrs medinensis (demonstration). Trans. Roy. Soc. trop. Med. Hyg. 64,473. Muller, R., Ellis D. S. and Bird, R. G. (1970a). Electron microscope studies of the phasmids in Dracunculus medinensis larvae (demonstration). Trans. Roy. Soc. trop. Mecl. Hyg. 64, 24. Muller, R., Furse, H. and Duckett, V. (l970b). Pathology and chemotherapy of Dracrinculus infection in rhesus monkeys (demonstration). Trans. Roy. Soc. trop. Med. Hyg. 6 4 2 4 . Neumann, G . (1895). Sur un Filaire (Filuria rlahomensis n. sp.) du python, de Natal, voisine de la Filaire de Medine. Bull. Soc. zool. Fr. 20, 123-127. NgQyen-Van-Ai (1963). Apercu sur la faune helminthologique au sud-Vii5tnam. Rap. Ann. Fonction Techn. Inst. Pasteur. ViCt-Nam 3-1 0. Nugent, D. A. W., Scott, D. and Waddy, B. B. (1955). Effect of water-point treatment with DDT on the incidence of guinea-worm infection. Trans. Roy. Soc. trop. Med. Hyg. 49,476. Oduntan, S. O., Lucas, A. 0. and Gilles. H. M. (1967). Treatment of dracontiasis with niridazole. Laticel ii, 73-75. Onabaniiro, S. D. (1950). A technique for studying infection of Dracunculus in Cyclops. Nature, Lonrl. 165, 3 1. Onabamiro, S. D. (1951). The transmission of Dracwwlus medinensii by Thermocyclops trigeriunus as observed in a village in south-west Nigeria. Ann. trop. Med. Parasit. 45, 1-10. Onabaniiro, S. D. (1952). The geographical distribution and clinical features of Dracuncuhis mditrensis in south-west Nigeria. W . Ajr. med. J . 1, 159. Onabamiro, S. D. (1954). The diurnal migration of cyclops infected with the larvae of Dracrincdus medinensis (Linnaeus), with some observations on the development of the larval worms. W. Afr. med. J . 3, 189-1 94. Onabamiro, S. D. ( I 956a). The early stages of the development of Dracunculus medinensis (Linnaeus) in the mammalian host. Ann. frup. Med. Purud. 50, 157-166. Onabamiro, S. D. (1956b). The effects of hetrazan (banocide) diethylcarbamazine on the larval form of Dracunculus medinensis. W . Afr. med. J. 5, 64. Onabamiro, S . D. (1958). In “Diseases of children in the subtropics and tropics.” 1st ed. (eds. H. C. Trowell and D. B. Jelliffe) pp. 815-821. Edward Arnold, London. Pardanani, D. S. and Kothari, M. L. (1970). Metronidazole in dracunculosis. A preliminary report of a therapeutic trial. Ind. J. med. Sci. 24, 359-360. 6

I48

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Parekh, G. and Kulkarni, D. R. (1958). A clinical and therapeuticstudy indracontiasis (guineaworni) infection. J.J.J. Hosp. Grunt med. Coll. 3, 22. Patel, C. V. and Anand, A. L. (1960). Seltene FIlle von multipler MedinawurmVerkalkung. ffuururzr 11, 326-327. Patnaik, K . C. and Kapoor, P. N. (1967). Incidence and endemicity of guinea-worm in India. Indian J . med. Res. 55, 123 I -I 242. Pirame, Y. (1963). Aspect du tetanos en Haute-Volta. A propose de 211 cas observes en 2 ans. Presse Mid. 71, 1043-1047. Pirame, Y. and Becquet, R. (1963). Dracunculose et tttanos. A propos de 15 observations. Bull. Soc. Path. exot. 56,469474. Plehn, F. (1898). “Die Kanierun-Kuste. Studien zur Klimatologie, Physiologie und Pathologie in der Tropen.” pp. 363. August Hirschwald, Berlin. Polonio, A. F. (1859). “Prospectus helminthum qui in reptilibus et amphibiis faunae italicac conticntur.” pp. 10. Bianchi, I’adua. Powell, A. (1904). The life span of the Guinea-worm. Br. med. J . i, 73. Powell, S. J., Wilmot, A. J. and Elsdon-Dew, R. (1969). The use of niridazole alone and in combination with other amoebicides in amoebic dysentery and amoebic liver abscess. Airri. N . Y. Aiad S’ci. 160, 749- 754. Pradhan, Y . M. ( 1930).Observations on cxperiments designed to combat dracontiasis in an endemic arca by Col. Morison’s method of “liming wells”. Indiun J . med. R ~ s18,443-465. . Raffi,P. and Dutz, W. (1967). Urogenital dracunculiasis: review of the literature and report of 3 cases. J . Urol. 97, 542-543. Raffier, G. (1965). Note prelimhaire sur I’activite du ClBA 32644-Ba dans la dracunculose. Acta. Tropica 22, 350. Raffier, G. (1966). Preliminary note on the activity of a new anti-helminthic agent in dracunculosis. Mid. Trop. 26, 3 9 4 6 . Raffier, G. (1967). Activite du thiabendazole dans la dracunculose. Mid. Trop. 27, 673-678. Raffier, G. (1968). Drdcunculosis: Recents developpements en epidemiologie, traitement et controle. XIlIth Inter. Coiigr. trop. Mod. Mal., Teheran (abst) p. 936-937. Raffier, G. (1969a). ActivitC du thiabendazole dans la dracunculose. Bull. Soc. Path. exot. 62, 581-593. Raffier, G. (1969b). Eficacy of thiabendazole in the treatment of dracunculiasis. Texas Reports on Bio1og.v arid Medicine 27 (suppl. 2), 601-609. Raffier, G. (1969~).Activity of niridazole in dracontiasis. Ann. N . Y. Acad. Sci.160, 720-728. Raghavan, N. G. S. (1958). Diagnosis of early dracontiasis. Bull. nut. Soc. Jndiu Mu/. 6, 155-162. Ramakrishnan, N. R. and Rathnaswamy, G. K . (1953). Use of DDT for control of cyclops breeding and as an anti-dracontiasis measure. fndiun med. GUZ.88, 386-390. Ramdas, A. (1953). Chronic encysted guinca-worm lesion. lndiun mrd. Gar. 88, 391. Ramsay, G . W. St. C. (1935). Observations on an intradermal test for dracontiasis. Trans. Roy. Soc. rrop. M e d Hyg. 28, 399404. Rao, S. S. (1936). The effect of gastric juice and of bile on cyclops infected with guinea-worn1larvae. Med. Res. 24, 535-540. Rao, S. R. (1942). Some epidemiological factors of guinea-worm disease as noticed in a recent survey of the Osmanabad district. f.Indian mecl. Ass. 11, 329-337. Rao, C. K. and Reddy, G. V. M. (1965). Dracontiasis in West Godavari and Kumool districts, Andhra Pradesh. B d l . Ind. Soc. Mal. Corn. Dis. 2. 275-293.

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Reddy, C. R. R. M. and Vasanta Valli, V. (1967). Extradural guinea-worm abscess Am. J. trop. Med. Hyg. 16,23-25. Reddy, C. R. R. M. and Sivaramappa, M. (1968). Guinea-worm arthritis of knee joint. Br. med. J. i, 155-156. Reddy, C. R. R. M., Sivaprasad, M. D., Parvathi, G . and Chari, P. S. (1968). Calcified guinea worm: clinical, radiological and pathological study. A m . trop. Med. Farasit. 62, 399406. Reddy, C. R. R. M..Narasaiah, 1. L. and Parvathi, G. (1969a). Epidemiological studies on guinea-worm infection. Bull. Wid HIth Org. 40,521-529. Reddy, C. R. R. M., Parvathi, G. and Sivaramappa, M. (1969b). Adhesion of white blood cells to guinea-worm larvae. Am. Jorrr. trop. Med. Hyg. 18, 379-381. Reddy, C. R. R. M., Rcddy, M. M. and Sivaprasad, M. D. (1969~).Niridazole (Ambilhar”’) in the treatment of dracunculiasis. Am. J. trop. Med. Hyg. 18, 5 16-5 19. Reddy, C. R. R. M., Reddy, N. V., Reddy, M.and Sulochana, G. (1969d). Scrota1 dracunculiasis. J . Urol. 101, 876-880. Reddy, C. R. R. M., Prasantha Murthy. D., Sita Devi, C., Lakshmi, S.and Sivaramappa, M. (1970). Pathology of acute guinea-worm synovitis. J. trop. Med. Hyg. 73,28-32. Reinhard, Jr. M. C. (1961). Calcified guinea worm simulating intrapulmonary calcification. J. Am. merl. Ass. 175, 53-55. Ricci, M. (1940). Elmintologia umana dell’Africa Orientale. Riv. biol. Colon., Roma 3, 241-295. Rice, D. T. (1959). Guinea worm in Semrd (M.P). Indian J. Pub. Hlth 3, 289293. Richards, W. G. ( I 922). Note on Dracitncrilrts medinensis. Parasi!ology 14, 307-308. Rolleston, H. D. (1892). Guinea-wormembedded for 21 years under the skin of the calf of the leg. Tr. Path. Soc., Lond. 43, 152. Rosa (1794). (Quoted by Valenciennes, M.A. 1856. C. R. Acad. Sci. 43, 259.) Roubard, E. (I91 3). Observations sur la biologie du ver de Guinee infection intestinale des cyclops. Bull. SOC.Path. exot. 6, 28 1-288. Roubard, E. (1920). Nouvelle contribution A I’histoire du ver de Guinee. Bull. Soc. Path. exo!. 13, 254-260. Roussel, B. (1928). Radiographie du Ver de Guinee (Filaire de Medine) a p r b injection intrasomathique de Lipiodol. Bull. Soc. Pa/h. exot. 22, 103-104. Rousset, P. (1952). Essai de prophylaxie et de trdilement de la dracunculose par la notezine en Adrar. Bull. SOC.mid. Alr. Ow. Jrunc. 9, 35 I . Sabokbar. R. (1968). Dracunculose en Iran. Vlllth Internat. Congr. Trop. Med. Ma/., Tehran (abstr.) 938-939. Sankaranarayanan, M.V., Ramamirtham, S. and Lashminarayanan, K. S. (1965). Record of the guinea worm Dracimculus medinensis in an Alsatian bitch. Indian ve!. J. 42, 972-973. Schneider, J. (1964). Problhmes diagnostiques et therapeutiques de medecine tropicale dans la pratique medicale courante en France. Bid/. SOC.Path. exot. 57, 669-71 5. Schuurmans Stekhoven, Jr. J. H. (1937). Parasitic Nematoda .In “Exploration du Parc National Albert. Mission G. F. de Witte (1933-35).” Fasc. 4, Bruxelles. Schwabe, C. W., Meier, H. and Bent, C. F. (1956). A case of dracontiasis in a New England dog. J. Parasit. 43, 65 1. Scott, D. (1960). An epidemiological note on guinea-worm infection in north-west Ashanti, Ghana. Ann. trop. M e d Pnrosi!. 54. 32-43. Selkon, J. M. and Latham, W. J. (1952). Calcified guineaworms in a South African Indian. S. At). med. J. 26, 918.

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Sharma, G. K. and Hussain, A. (1946). A note on guinea-worm disease in dogs. Indioti J. vet. Sci. arid Anind Hushunrlry 16, 3 1-32. Shastry, T. S. (1946). Guineaworm. J . Inr/iuti rned. Ass. 15, 362-364. Siegler, H. R. (1946). Guinea worm infestation of raccoons in new Hampshire. J. Mamniul. 27. 179. Simmons, J . S., Whayne, T. F., Andcrson. G . W. and Horack, H . M. (194451). “Global cpidciniology.” Vol. I : Asill (1944). Vol. 2 : Africa (1951). Lippincolt, Philadclphia. Singh, J. and Raghavan, N. G. S. (1957). Dracontiasis in India, its public health importance and its control. B d . narrrfn.SIX. India Ma/. 5, 141-158, Sivaramappa, M., Reddy, C. R. R. M., Sita Devi, C., Reddy, A. C., Reddy, P. K. and Murthy, D. P. (1969). Acute guinea-worm synovitis of the knee joint. J. Bone Joint Siirg. 51, 1324-1 330. Sita Devi, C., Sankaraiah, D., Nardsiah, 1. L., Reddy, C. R. R. M. and Rao, V. (1969a). Role of gastric acidity in guinea-worm infection. Indian J. med. Res. 57, 1850-1855.

Sita Devi, C. S., Murthy, D. P. and Reddy, C. R. R. M. (1969b). Development of enzyme activity in the guinea-worm larvae. Indian J. merl, Res. 57, 20922097. Smith, D. J. N. and Siddique, F. H. (1965). Calcified guinea worm in the broad ligament of a pregnant mother. J. Obstet. Cynaec. Br. Commonw. 72, 808. Southwell, T. and Kirshner, A. (1938). Some observations on guinea worm larvae. Ann. trop. Me(/.Parasit. 32, 193-196. Spiers, R. E. and Baum, A. H. (1953). Dracunculosis. J. Kansas med. SOC.54, 553554. Stefanopoulo, G.J. and Daniaud, J. (1940). Reaction de fixation d u complkment et intrddermo-reaction au course de la filariose humaine a Dr. medinensis. Bull. Soc. Putli. exot. 33, 149- 153. Stiles, C. W. and Hassall, A. (1920). “Index catalogue of medical and veterinary zoology.” U.S. Hyg. Lab. Bull. No. 114, Washington. Stoll, N. R. (1947). This wormy world. J . Parasit. 32, 1-18. Striebel, H. P. (1969). The effects of niridazole in experimental schistosomiasis. Ann. N . Y. Acad. Sci. 160,491-518. Tennent, Sir J. E. (1868). “Sketches of the Natural History of Ceylon.” Longmans, Green, Reader and Dyer, London. Tournier, E. (1922). Le traitement du Ver de G u i d e par les sels d’antimoine. Bull. SOC.Path. exot. 15, 809415. Travassos, L. (1934). Drariincitlus fuelleborni n. sp. parasito de Di(le(diis uurita Wied. Mem. b i s t . Osw. Criiz. 28, 235-237. Trewn, H. S . (1937). Guinea-worm. fndiarz med. Gaz. 72, 606-609. Turk, R. D. (1950). Guinea worm (Dracunculus insignis Leidy 1858) infection in a dog. J. Am. vet. mecl. Ass. 117, 21 5-2 16. Turkhud, D. A. (1919). Prophylaxis of dracontiasis. India J. med. Res. (spec. Indian Sci. Congress number) pp. 217. Turkhud, D. A. (1920). Dracontiasis in animals; with notes on a case ofguinea-worm in a cobra. Indian J. rned Res. I, 127-734. Vad, B. G. ( I 963). Drucuncu1u.v medinensi.s (Guinea-worm). Muhorashfra med. J., Poona 10,475-483. Van Heutz (1926). Verslag der Afd. Sumatra’s Oostkust. CPILTiid.srhr. Y . Ned.-lndik 66, 35 (quoted by Brug, 1930). Velschius, G. H. ( 1674). “Exercitationcs dc Vcna medinensis ct de vcrmiculiscapillaribus infantium.” Augsburgh.

D R A C U N C U L U S A N I) I) R A C U N C U L I A SI S

151

Wenyon, C. M.(1908). Report of travelling pathologist and zoologist (Dracontiasis). 3rd. Rep. Wellcome Res. Lab., Khartoum 132-1 35. Williams, C. L. (1899). The prognosis of guinea-worm in its relation to the assurance of native lives in India. Indian med. Gaz. 34, 242-243. Wilson, W. D. (1958). The guinea worm Dracunculus insignis (Leidy, 1858) Chandler, 1942, in a raccoon, Procyon lotor from Michigan, a new location. Am. M i d . Natur. 59, 256.

Witenberg, C. (1951). Some unusual observations on helminthiasis in Israel [in Hebrew, English summary]. Harefuah 41, 178-180. Wurtz, R. and Sorel, F. (1912). Note sur la duree de I’incubation du Ver de Guinee. Rev. Med. Hyg. trop. 9, 123.

Yamaguti, S. (1961). “Systema Helminthum.” Vol. 111. Academic Press, New York and London. Yakimoff, W. L. (1914). Recherches sur les maladies tropicales humaines et animales au Turkestan, VI. La formule leucocytaire du sang des maladies renfermant Filaria medinensis. Bull. SOC.Path. exot. 7 , 192.

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Vaccination Against the Canine Hookworm Diseases THOMAS A. MILLER

*Jensen-Salsbery Laboratories, Division of’Richardson- Merrell lnc., Kansas City, Missouri, United Slates of’America

1.

Introduction

....

1 I. The Canine Hookworms

I[[.

............................................................... .....................................................................

..........................................

B. Distributions .............................................................................. Life Cycles ....................... ................................................... A. In theDog .................................................................................

........................................

C . In Abnormal Hosts ..................................................................... 1V. The Canine Hookworm Diseases ............................................................ A. “Hookworm Disease” .................................................................. B. Specific Hookworm Disease ......................................................... V. Immunity to Infection with Hookworm .............................. A. Age Resistance ........................................................................... B. Acquired Resistance after Infection with Normal Hookworm Larvae ...... C. Acquired Resistanceafter Infection with Attenuated Hookworm Larvae ... D. Vaccination to Prevent Prenatal-Colostral Infection in the next Generation VI. Practical Use of Canine Hookworm Vaccine .......................................... A. Indications ................................................................................. B. Use of Vaccine ...................... ..................................... C. Interpretation of Post-Vaccinatio .................................... References ........................... .....................................

153 154 154 154 155 155

157 157

158 158 158 165 165 166 166 175 178

I78 179

180 180

I . 1NTRODUCTION Compared to its medical counterpart, canine hookworm disease has been rather neglected as a subject for study and publication. There are descriptions of the “disease” in all of the standard textbooks on veterinary helminthology and parasitology (Monnig, 1947; Soulsby, 1965; Lapage, 1968; Georgi, 1969). The uniformity of these descriptions is remarkable. With minor exceptions, the descriptions appear to have been repeated faithfully and largely unaltered over the last 40 years. This is not an indication, however, of the uniformity of repeated experimental and clinical observations but is rather an illustration of their deficiency. The life cycles, signs, and pathogenesis of the three species have been assumed to be almost identical, one with the other. They have even been assumed to be identical with the respective aspects of the related worms

* Part of this review was written and most of the experiments were completed while the author was at the Wellcome Laboratories for Experimental Parasitology, University of Glas\ gow. Scotland. 153

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which infect man. Prenatal infection of pups has been assumed to occur in all species, whereas it has recently been shown that the amount of infection achieved by the intra-uterine route is minimal and that it occurs only in one species of hookworm. Suffice it to note, without continuing extensively in this rnthcr ncgntivc approach. that thc authors of the standard tcxtbooks through lack of published information havc bccn laboring itnder considcrablc handicaps in the past. I t is the object, therefore, now to collect in one article most of the relevant recent information on the subject of the canine hookworm diseases, for there are at least two distinct disease syndromes. I t is also intended to show how these diseases may be prevented by vaccination. I I . THECANINE HOOKWORMS A . SPECIES

After the initial descriptions and identification of the two more common hookworms of dogs, Ancylostoma caninum (Ercolani, 1859) and Uncinaria s/enocephula (Railliet, 1884), there was little further dissention on this aspect. An exception was the continuing argument over whether worms identified as A . cuninum from dogs and cats comprised host-adapted strains of the same parasite (Scott, 1929a, b) or constituted two separate species, A. caninum in dogs and Ancylostoma fubaeforme (Zeder, 1800) in cats (Biocca, 1954; Burrows, 1962). The latter opinion has now superceded, although weak evidence that the feline strain or species may accommodate and be adapted to a limited degree to the heterologous host is on record (Scott, 1930). Disagreement on classification of the third canine hookworm, Ancylostoma braziliense (de Faria, 1910), in the matter of its differentiation from, or relationship to, Ancylostoma ceylanicum (Looss, 191I), has also continued until recent years (Leiper, 1913; Lane, 1922; Darling, 1924; Biocca, 1951; Biocca and LeRoux, 1958). However, the work of Rep et al. (1968a) has shown conclusively that these are two distinct species. It is at present not known whether the latter, A . ceylunicum, is naturally a parasite of man, of dogs and cats, or of all three hosts. Although Rep's strain of A . ceylanicum was isolated from man (Rep, 1964), he succeeded in establishing this parasite in dogs and cats (Rep, 1966a). He also showed that the final criterion for species separation, i.e. failure of fertile cross-breeding experiments between A . braziliense and A . ceylanicum, was satisfied (Rep et al., 1968a). Unfortunately, there is almost no information on the differential frequencies and distributions of A. ceylanicum and A . braziliense in the human, canine or feline populations, because the species were until recently considered as a single entity. There may, therefore, be four distinct species of hookworms which occur naturally in dogs, if A . ceylanicum, being distinct from A . braziliense, occurs commonly in nature. For the most part these two species will be considered together. B.

DISTRIBUTIONS

With the exception of I/. stenocephala, the hookworms that infect dogs are tropical and subtropical in their distribution. A . caninurn occurs in almost all

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155

suitable areas, while A . hrazilienseappears to be limited to distinct geographical areas (Rep, 1963). In the latter areas, mixed infections of the two species are common. Uncinuriu stenocephala has lower temperature requirements and occurs around the world to the north and south of the tropical hookworm belt. Its distribution extends into near Arctic regions in populations of wild Canidae and Vulpidae. At the junction of the distribution areas of the temperate hookworm, U . stenocephala, and the tropical species, A . caninurn, mixed infections occur. The distributions are restricted largely by the environmental temperatures, although an equal requisite is that of humidity since hookworm distributions rarely extend into the arid regions of the world. However, even this statement is qualified by the finding of A . duodenale infection in desert bushmen (Heinz, 1961). I I I. A.

Lll.1. CY. I’.---scc Prasantha Murthy, D. Myers, Ci. S., 203, 221 MYW, It. F., 232,236,238, 240,252,255 Mykytowycz, R., 203, 210, 2/9, 221

265

AUTHOR INDEX

Patnaik, M. M., 35, 59, 71 N Narasaiah, I. L., 85, 86, 105, 106, 107, Pattanayak, S.,238, 253 Pavlovski, E. N., 196, 222 108, 120, 122,149, 150 Peacock, R., 167,182 Nasir, A. S., 107, 108, 112, 140, 140 Pearse, A. S.,22, 30 ‘Nlsrnark, K. E., 34, 71 Pelloux, H., 125, 144 Naylor, E., 18, 19, 30 Pcreira, C., 15, 16, 30, 31 Neilson, J. T. McL., 242, 255 Perez-Gimenez, M. E., 158, 182 Nemec, P., 229, 251, 252 Perez-Mendez, G., 236, 240, 252 Neumann, G., 97, 98, 103, 147 Petrushevski, G. K.. 213,222 Newton, W. L., 229, 258 Petter, A. J., 200,203,204,205,206,207, Ngiiyen-Van-Ai, 97,147 210, 213, 218,222 Nicholas, W. L., 228, 229, 256 Philippon, F., 234, 256 Nielsen, K., 164, 182 Piacentini, M., 125, 144 Nobel, T. A., 36, 59, 60, 62, 71 Pirarne, Y.,125, 148 Noble, E. R., 216, 222 Plate, L., 15, 31 Noble, G. A., 216, 222 Plehn, F., 90, 91, 148 Nugent, D. A. W., 137,147 Podberezski, K. N., 36, 71 Podger, K. R., 242, 257 Pogorelyi, A. I., 66, 71 0 Poinar, G. 0. Jr., 232, 236, 238, 254 Oduntan, S. O., 120, 134, 135, 145, 147 Poll, M., 203, 222 O’Farrell, W. R., 78, 120, 129, 141 Polonio, A. F., 99, 148 Okoshi, S.,155, 182 Powell, A., 87, 148 Oliver-Gonzalez, J., 77, 141 Powell, S.J., 136, I48 Olsen, A. M., 5, 6, 29 Powers, P. B. A,, 9,31 Olsen, 0. W., 66, 71 Poynter, D., 167, 182, 242,257 Onabamiro, S. D., 81, 83, 84, 86, 87, 88, Pradhan, Y.M., 108, 137,148 89,90,91, 107, 108, 109, 112, 114, 115, Prasantha Murthy, D., 85, 120, 128, 119, 120, 134, 147 149, I50 Orions, G. H., 204, 222 Price, E. W., 39, 71 Orlova, K. V., 36, 62, 71 Priouzeau, M., 36, 71 Osche, G., 193, 195, 201. 212, 213, 217, Prisco, E. di, 158, 182 222 Prudhoe, S., 22, 23, 31 Otto, G. F., 166, 180, 182 Purchase, H. S.,66, 70 Ozaki, Y.,8, 30 Ozerol, N. H., 232, 242, 255 Ozoux, L. L., 208, 220

R

P Pande, P. G., 35, 53, 56, 65, 71 Pantelouris, E. M., 232, 255 Pardanani, D. S., 125, 129, 134, 135, 137, 144, 147 Parekh, G., 134, 148 Parulkar, G. B., 127, 144 Parvathi, G., 85, 105, 106, 107, 108, 120, 122, 125, 128, 129, 149 Patel, C. V.. 125. 148 Patidar, S. P., 108, 122, I41 Patnaik, K. C., 105, 108, 109, 148

Kactliffe, L. H., 233, 239, 255 Raffi, P., 127, I48 RafTier, G., 88, 106, 114, 117, 120, 134. 135, 136, 137, I48 Raghavan, N. G . S.,105, 107, 108, 109, 131, 148, 150 I