UNESCO-IHE INSTITUTE FOR WATER EDUCATION Prevalence and pathology of protozoan and monogenean parasites from fry and fingerlings of cultured Clarias gariepinus (Burchell, 1882) in Uganda Akoll Peter MSc Thesis (ES 05.17) October 2005 Prevalence and pathology of protozoan and monogenean parasites from fry and fingerlings of cultured Clarias gariepinus (Burchell, 1882) in Uganda Master of Science Thesis by Akoll Peter Supervisors Dr. Robert. Konecny (Institute of Ecology, Department of Limnology, University of Vienna, Althanstraße 14, 1090 Vienna, Austria) Dr. Justus. Rutaisire (Faculty of Veterinary Medicine, Department of WARM, Makerere University Kampala, P.O. Box 7062, Kampala, Uganda) Examination committee Prof. J. O’keeffe, PhD (UNESCO-IHE, Delft), Chairman Dr. R. Konecny, PhD, MSc (University of Vienna, Austria) Dr. J.J.A. van Bruggen, PhD, MSc (UNESCO-IHE, Delft) This research is done for the partial fulfilment of requirements for the Master of Science degree at the UNESCO-IHE Institute for Water Education, Delft, the Netherlands Delft October 2005 The findings, interpretations and conclusions expressed in this study do neither necessarily reflect the views of the UNESCO-IHE Institute for Water Education, nor of the individual members of the MSc committee, nor of their respective employers. This work is dedicated to my beloved parents Richard and Rita Masai and above all God for the strength He gave me till now. Abstract Aquaculture is considered the best option for the dwindling capture fisheries in Uganda. Among the economically important aquaculture fish species with very successful breeding technologies is African catfish, Clarias gariepinus. However, farmers are constraint with massive fry and fingerling mortalities, especially in intensive culture system. Despite the fact that parasites and diseases are reckoned to be the causes of these mortalities, little has been done to authenticate this claim in Uganda. Therefore this study investigated the cause of mortalities with the aim of establishing information on the prevalence and pathology of Protozoa and Monogenea parasites occurring on C. gariepinus. Using routine parasitological and histological techniques, a total of 334 fry and fingerlings of cultured C. gariepinus from three hatcheries were examined for parasite infestations. Five ectoparasites and one endoparasite species were recorded. Of these, the protozoan Trichodina sp. and the monogenean Gyrodactylus sp. were the dominant parasites. The major routes of entry of parasites into the hatcheries were through surface water supply and possibly via the semi aquatic organisms like amphibians. During initial stages of infection, the prevalence, mean intensity and mean abundance of these parasites increased with fish age. At the later stage, Trichodina sp. declined probably due to host resistance and competition for space with Gyrodactylus sp. Trichodina sp appeared less susceptible to the 40ml/l formalin treatment than Gyrodactylus sp. Major pathological changes observed were oedema and hyperplasia in the gills, infiltration of melanomacrophage centers into the skin epidermis and mild epidermal cell hypertrophy of parasitized fish. Hyperplasia and oedema of gill and subsequent gill fusion seem to have interrupted respiration and hence caused death of the host. Concomitant occurrence of Trichodina sp. and Gyrodactylus sp. aggravated pathological effects on fish thus increasing mortality. Epistylis sp., Apiosoma sp. and Trichophrya sp. were considered less pathogenic. The results were discussed in relation to parasite occurrence and parasite induced fish mortalities. i Keywords: Uganda, Clarias gariepinus, Trichodina sp., Gyrodactylus sp., histopathology, aquaculture. ii Acknowledgements The successful completion of this study greatly gained contribution from the good will of many people. First and foremost, my sincere gratitude go to my supervisors, Dr. Robert Konecny and Dr. Justus Rutaisire for their tireless efforts in guiding during field study, providing of literature and editing my work. Special thanks go to Dr. Helmut Sattmann, Director of the Department of invertebrates, Natural History Museum, Vienna, for the support, good hospitality and above all provision of enormous amounts of literature from the commencement of this research project to the end. Thanks go to Dr. Oskar Schachner of the Department of Fisheries, Reptiles and Amphibians, University of Veterinary Medicine Vienna for providing practical support in preparations for sampling and helping in histopathological analysis. Michael Schabuss of University of Vienna for sparing his time to receive me at the airport and editing of my work is greatly acknowledged I am very grateful to Dr. G. Mbahinzireki, Officer in Charge, Kajjansi Research Station, Mr. Digo Tugumisirize, Proprietor of Sunfish farm Ltd and Mr. Paul Ssebinyansi, Proprietor of Ssebinyansi fish farm for permitting me collect fish samples from their farms. Support from their employees is also highly appreciated. I am deeply indebted to Assoc. Prof. JD. Kabasa, the Dean, Assoc. Prof. RT. Muwazi, deputy Dean and Dr. T. Amongi, all of the Faculty of Veterinary medicine, Makerere University Kampala and Prof. HA. Joachim, head of Department, Prof. Heinrich Prosl and Prof. R. Edelhofer of the Institute of Parasitology, University of Veterinary Medicine, Vienna for permitting and providing me with facilities to work. Not forgetting Miss Baerbel Ruttkowski, Mr. Hans Homola and the entire staff of the Institute of Parasitology for their support and kind hospitality during my work. Technical assistance to produce excellent histological slides during the study has been provided by William G. Muyombya, MF. Nakamya, Monica Nambi, Jane Atima, of Department of Anatomy, Faculty of Veterinary Medicine Makerere University and Prof. Peter Böck, head of the institute of Histology and Embryology, University of Veterinary Medicine, Vienna. I am thankful to the people of the Institute of Environment and Natural resources especially Dr. Frank Kansiime, the Director, for allowing me utilise their facilities. Also Dr. FB. Bugenyi, Assoc. Prof. YK. Kizito, Ms. M. Masette and Head of Department, Dr. IG. Basuta, all of Zoology, Makerere University are acknowledged for the assistance they accorded during data collection. Thanks go to Mr. Markus and Denis Fruler of environment Agency Austria for their valuable contribution and not forgetting Franz Jirsa for his valuable discussions on the subject. I am also deeply indebted to my uncles Malika M.Balayo, Lukoye Alex and their wives: Hajarah Malika and Kibone Lukoye respectively for their continuously supported and encouraged during my study. Also thanks to my parents, brothers, sisters, course mates and all other people whose positive and negative criticisms helped me to produce this quality work. Sincere thanks go the Austrian Ministry of Foreign Affairs and the Royal Government of The Netherlands for funding this. iii Table of Contents Abstract.......................................................................................................................... i Acknowledgements ..................................................................................................... iii List of figures .............................................................................................................. vi List of tables ............................................................................................................... vii List of symbols .......................................................................................................... viii 1 INTRODUCTION.................................................................................................... 1 1.1 Background....................................................................................................... 1 1.2 Problem statement ............................................................................................ 3 1.3 Justification....................................................................................................... 3 1.4 Aim of the study ............................................................................................... 4 1.5 Study objectives................................................................................................ 4 1.6 Hypotheses ....................................................................................................... 5 1.7 Limitations........................................................................................................ 5 1.8 Organisation of the thesis ................................................................................. 5 2 LITERATURE REVIEW......................................................................................... 7 2.1 Aquaculture in Africa ....................................................................................... 7 2.2 Aquaculture in Uganda..................................................................................... 7 2.2.1 Potential cultivable fish species in Uganda .............................................. 8 2.3 Fish parasites.................................................................................................. 10 2.3.1 Protozoa.................................................................................................. 10 2.3.2 Phylum: Platyhelminthes........................................................................ 15 3 METHODS AND MATERIALS ..........................................................................