Studies on Fascioliasis with special reference to Fasciola Gigantica in East Africa

Following a general introduction, the extensive literature on fascioliasis is reviewed. The distribution, importance, pathogenesis and pathology of the disease are considered, with special emphasis on Fasciola gigantica infections.Field studies are reported on the epidemiology and control of F. ßiganti.ca in East Africa and a survey described of infections with Fasciola spp. in African wild mammals. This survey was undertaken in order to assess the importance of wild mammals in the epidemiology of this disease, in view of the increasing development of game parks and ranching schemes.The techniques used in the experimental studies are outlined with emphasis on those modified during this work. The techniques described include the cultural methods by which the infective agents were obtained, with special reference to the large scale production of metacercariae of F. gigantica and a detailed discussion of the problems which had to be overcome before this was possible. Other techniques described include those used in haematological examinations, faecal egg counts, liver function tests, serum enzyme assays and other biochemical studies.The difficulties which had to be overcome to obtain and maintain experimental cattle and sheep free of intercurrent diseases in Kenya are discussed.Observations are described which were made in the course of several experiments using a total of 35 sheep and 46 cattle in Edinburgh and in Kenya.In Edinburgh the experiments comprised studies on the pathogenesis of acute and chronic fascioliasis (Fasciola hepatica) in sheep.In Kenya chronic fascioliasis (F. gigantica) was studied in sheep with special emphasis on the economic importance of this condition. It was found that the infected animals gained weight more slowly than the uninfected controls and that this arose mainly from differences in the amount of body fat.Several experiments were carried out in Kenya on cattle infected with single doses of 500, 1000 or 2000 metacercariae of F. gigantica or with two doses of 500 metacercariae ten weeks apart. The pathogenesis of the disease and the parasitological findings in these animals are described in detail. Other studies described include observations on long term chronic fascioliasis in cattle.The gross pathology of P. giçantica infections in cattle from 2 -51 weeks after infection is also described.The main finding from these studies is that F. gigantica appeared to be less pathogenic for cattle than reported by earlier workers.There was no evidence of an "acquired self- cure" under the conditions of these experiments, which would support the suggestion that resistance to F. sigantica infections in cattle may be merely related to the fibrosity of the liver parenchyma. Further support was found for this suggestion from the study of the leucocyte levels and other observations.Evidence was found that F. gigantica has a relatively short life in cattle.The dissertation ends with a discussion of the results from the experimental infections