Research On The Cultivation Of Fasciola Metacercariae And Kinetics Of Specific Antibodies In Rabbits Experimentally Infected With Fasciola

Fascioliasis is a world-widely significant disease of ruminants caused by infection with the digenetic trematodes, Fasciola hepatica and Fasciola gigantica which live in the bile ducts of final host and cause liver cirrhosis, hepatic fibrosis, anaemia and the reduction of growth, draught performance, fertility, lactation and cause great economic losses. Though similar form of live cycle between these two species, Fasciola hepatica and Fasciola gigantica are epidemiologically separate entities. The mechanism of specific immunity against Fasciola gigantica has not been elucidated compared to the enormous researches on Fasciola hepatica. Research on the immune mechanism of Fasciolaisis is being done on our laboratory to find out the interaction mechanism between host and Fasciola in the level of cell and molecule and then to devise highly effective vaccines. The experiment is the prophasic work which aims to devise a method that cultivate Fasciola gigantica metacercariae in laboratory and set up a way of detecting immune response and to find out the immune mechanism of host and escaping mechanism of Fasciola then to give a comparison of Fasciola gigantica and Fasciola hepatica and make a foundation for the further work.Metacercaria, an intermediate phage of Fasciola gigantica, were cultivated before the experiment of infection. 500 intermediate host of snails were infected with miracidium and the survival rate was 46%. The production of metacercariae was 16000 and the average production was 70.Temperature, density, the infection proportion of miracidium to snails and oxidation were the preferably considered factors. Time for the hatch of eggs to miracidium couldbe shortened with the rise of temperature and vice versa. The whole development was in high related to temperature.Eggs could hatch into miracidium after 15-17d and cercariae could release after infection of 35-40d provided on the temperature of 25-28 癈 regulated by air-conditioning and heating machine.The best density was 20cm2 per snail.The infection proportion of miracidium to snails was 1-2:10 Vitality of metacercariae could last for halfa year on the condition of moist and low temperature of 4-10 癈. Snails were fed by lettuce subsided with milk powder and poplar leafs. The key of cultivation was to maintain the snails live and infection success. The experiment confirmed the conclusion of the intermediate host of Fasciola gigantica in GuangXi is Galba pervia.Enzyme-linked immunosorbent assay was used to detect the kinetic development of specific antibodies in rabbits experimentally infected with Fasciola hepatica and Fasciola gigantica. Excretory-secretory antigen(EsAg) was 0.25 n g per pool. Sera and Peroxidase anti-rabbit IgG were diluted 400 and 4000 folds respectively. The results showed that rabbits infected Fasciola hepatica and Fasciola gigantica both developed antibodies to FgEs after 2 or 3 weeks of infection and immunoglubin G increased. The difference was that the antibodies of rabbits infected with Fasciola gigantica rised gradually compared to the rabbits infected with Fasciola hepatica whose antibodies rised rapidly and remained high until experiment finished. Differences of immune mechanisms were manifested by the comparison of number of flukes recovered, percent take of metacercariae and pathologic changes. The experiments detected the kinetics of antibodies and also provided a method of diagnosing Fascioliasis by ELISA.