National Library Bibliothèque nationale of Canada du Canada Acquisitions and Direction des acquisitions et Bibliographie Services Branch des services bibliographiques 395 Wellington Street 395, rue Wellington Ottawa, Ontario Ottawa (Ontario) K1AON4 K1A0N4 NOTICE AVIS The quality of this microform is La qualité de cette microforme heavily dependent upon the dépend grandement de la qualité quality of the original thesis de la thèse soumise au submitted for microfilming. microfilmage. Nous avons tout Every effort has been made to fait pour assurer une qualité ensure the highest quality of supérieure de reproduction. reproduction possible. If pages are missing, contact the S'il manque des pages, veuillez university which granted the communiquer avec l'université degree. qui a conféré le grade. Sorne pages may have indistinct La qualité d'impression de print especially if the original certaines pages peut laisser à pages were typed with a poor désirer, surtout si les pages typewriter ribbon or if the originales ont été university sent us an inferior dactylographiées à l'aide d'un photocopy. ruban usé ou si l'université nous a fait parvenir une photocopie de qualité inférieure. Reproduction in full or in part of La reproduction, même partielle, this microform is governed by de cette microforme est soumise the Canadian Copyright Act, à la Loi canadienne sur le droit R.S.C. 1970, c. C-30, and d'auteur, SRC 1970, c. C-30, et subsequent amendments. ses amendements subséquents. Canada • PLAGIORCHIS ELEGANS FROM CERCARIAE TO INFECTIVE METACERCARIAE: FACTORS AFFECTING TRANSMISSION, REQUIREMENTS FOR DEVELOPMENT, AND BEHAVIOURAL RESPONSES OF INTERMEDIATE HOSTS TO INFECTION. by CARL A. LOWENBERGER • Institute of Parasitology l\1:cGill University, Montreal, Québec August 1993 A Thesis submitted to the Faculty of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Doctor of Philosophy © Carl A. Lowenberger, 1993 National Library Bibliothèque nationale 11+1 of Canada du Canada Acquisitions and Direction des acquisitions et Bibliographie Services Br<'nch des services bibliographiques 395 Wellington Slleel 395. rue Wellington Ottawa, Ontario Ottawa (OntR;rio) K1A ON4 K1AON4 The author has granted an L'auteur a accordé une licence irrevocable non-exclusive licence irrévocable et non exclusive allowing the National Librâry of permettant à la Bibliothèque Canada to reproduce, loan, nationale du Canada de distribute or sell copies of reproduire, prêter, distribuer ou his/her thesis by any means and . vendre des copies de sa thèse in any form or format, making de quelque manière et sous this thesis available to interested quelque forme que ce soit pour persons. mettre des exemplaires de cette thèse à la disposition des personnes intéressées. The author retains ownershi:.> of L'auteur conserve la propriété du the copyright in his/her t~lesis. droit d'auteur qui protège sa Neither the thesis nor substantial thèse. Ni la thèse ni des extraits extracts from it may be printed or substantiels de celle-ci ne otherwise reproduced without doivent être imprimés ou his/her permission. autrement reproduits sans son autorisation. ISBN 0-315-91709-1 Canada Plagiorchis elegans: transmission, development, and host behaviour. Il • AB8TBACT Plagiorchis elegans is a typical digenean parasite that cycles through aquatic molluscs and insects as intermediate hosts. During emergence of P. elegans cercariae, infected snails moved to the top of the water column where they remained immobile for 2-3h. Consequently, the cercariae fOlmed a dense cloud which disp'rsed slowly. The infectivity of cercariae was <20% upon emergence and peaked at 76% 4-6h later. This delay in reaching maximum infectivity may be an adaptation to prevent superinfection and the associated mortality of insect hosts. Cercariae transformed into metacercari.ae aftE'r penetrating Aedes aegypti larvae, the experimental insect hosto Overall development oîmetacercariae, and excystment of • infective metacercariae in vitro, was temperature dependent. However, there was an initial 8-hour period of obligatory host-parasite ~ontact that was temperature independent. This may represent a period of major nutrient acquisition since young metacercariae were more active metabolically than older metacercariae, as measured by the in vitro uptake of 3H-glucosamine and 3H-Ieucine. Mosquitoes may have mechanisms to .r<::duce lasses of larvae to parasites. Oviposition by adult A. aegypti wab reduced in waters that had previously contained P. elegans-infected larvae. We propose that this selective oviposition was due to the production of an oviposition deterrent compound produced by parasitized larvae that serves to reduce oviposition in sites detrimental to larval development. • III • ABRéGé Le digénien Plagiorchis elegans est un parasite type qui se développe dans les gastéropodes et les insectes, ses hôtes intermédiaires. Lorsque les cercaireR de Plagiorchis elegans émergent des escargots infectés, ces derniers se déplacent vers la surface de l'eau, où ils restent immobiles de deux à trois heu.res. Ceci permet aux cercaires fonr.ant un nuage dense de se disperser lentement. Le pouvoir infectieux des cercaires à l'émergence est de moins d~ 20% et atteindra, quatre à six heures plus tard, un maximum de 76%. Cette capacité infectieuse maximale tardive est probablement une adaptation prévenant une surinfection associée à la mortalité des insectes hôtes. Par la suite, les cercaires pénètrent les larves d'Aedes aegypti, l'insecte expérimental utilisé, et se transforment en métacercaires. In vitro, le développement des métacercaires et leur capacité • de se libérer de leur kyste est relié à la température. Par contre, la période initiale de huit heures où le parasite et l'hôte sont en contact ne l'est pas. Cette période semble correspondre à une activité d'absorption en éléments nutritifs. Les jeunes métacercaires ont une activité métabolique plus élevée que les métacercaires plus vieux. Cette activité a été mesurée par l'absorption de 3H-glucosamine et de 3H-Ieucine in vitro. Les moustiques ont des mécanismes pour réduire la mortalité chez leurs larves causée par le parasite. L'oviposition des adultes Aedes aegypti est moindre dans les eaux ayant contenues préalablement des larves infectées avec Plagiorchis elegans. Cette oviposition sélective semble être le résultat de l'émission d'une substance par les larves parasitées empêchant celle-ci. De cette façon, l'oviposition est réduite aux endroits défavorables au développement des • larves. IV • SUGGESTED SHORT TITLE Plagiorchis elegans: transmission, development, and host behaviour. • • " ACKNOWLEDGEMENTS l have been helpecl, prodded, pushed and restrained (ûut never bribed) by many people over the course of this study. l thank my supervisory commlttee of Drs. Manfred Rau, Marilyn Scott, and Gary Dunphy for their il'lt'lrest, suggestions, guidance, and help dù"Ïng my tenure at the Institute of Pnrasitology. l thank Dr. Kris Chadee for assistance in the design and implementation of the study using radiolabelled materials. l also thank my former supervisor Dr. John Webster for his support and comments on several aspects of the studies presented here. My laboratory co:npanions have provided intense debate and discussion over several aspects of the rese?rch reported here. These include Charles Kimoro, Philippe Jacobs, Manon Bombardi<'r, SylvainPoirier, and Julie • Riddock. Others from the Institute who have helped me through their friendship and help over the last 4 years include (in alphabetical order) Jenny Anderson, Gord Bingham, Pierre Bourassa, Darren Campbell, Mark Fielding, Janet Forrester, Peter Gatongi, Kathy Keller, Marc LaBerge, Silvie Labrecque, Mary LaDuke, Carlos Lanusse,. Sharon McGee, Shirley. Mongeau, Roy Nare, Christine Noronha, Siva Ranjan, Sharon Rutherford, Rosanne Seguin, Stephanie Tremblay, Christiane Trudeau, Sil-King Tse, Bernie Wright, to name but a few. In particular l am indebted to Kathy Keller and Sylvain Poirier for close friendship, inspiration, and help whenever l needed it; and sometimes when l didn't. l thank Dr. Jim Smith for help with the computers. l thank the students of the Illstitute for • allowing me the invaluable experience of representing them during staff VI • meetings and as their represent:J.tive on the Curricuhm and Computer c.omnrittees. My parents have a.lW'iYs supported Ilie in my entieavours and 1 am indebted to them for constant enc1JUragement and love. Megan has been my mainstay during our sojourn in Montreal. ~hroughout the stormy periods she provided the voice of reason and stability. Without her support, encouragement, and recriminations, f :s thesis would never have been completed. Dr. 'Tristan ha3 become the light of our lives. His arrivaI and subsequem inclusion into my personal supervisory committee, and his constant commentary on my research has allowed me to put aspects of this reseal"ch, and life in general, in its proper perspective. • Major funding for this research was obtained through grants from the Natural Sciences and Engineering Research Council (NSERC) and the Fonds pour 18. formation de chercheurs et l'aide à la recherche (FCAR) of Québec to M.E.R. Personal support was provided by the Walter M. Stewart Foundation, the Lynden Laird Lyster award, and the M. Gowans support fund. .. • VII • TABLE OF CONTENTS TITLE PAGE . ABSTRACT ........................................................ .. ii ABRéGé. ............................. .. ............................ iii SUGGESTED