INFECTIVTY OF DIFFERENT NUMBERS AND AGES OF SCHISTOSOMA JAPONICUM MIRACIDIA TO ONCOMELANIA HUPENSIS HUPENSIS

Knowledge on the snail-parasite relationships between Schistosom japonicum and Oncomelania hupensis hupensis is important for reference in schistosomiasis control. This paper deals with the infectivity of different numbers and ages of S.japonicum miracidia to O.h.hupensis. Five to six months of laboratory bred F1 adult snails of O. h.hupensis originated from Anhui province have been used to infection with miracidia of Chinese mainland strain of S. japonicum originated from Anhui and had been maintained in laboratory.The infection rate, mortality, prececearial period and cerearial production of snails were observed experimentally by exposing single snail to 1,5,10,20 and 40 miracidia respectively. The infection rate ofsnails was to be increased markedly with multiple number of miracidia, while the mortality of snails infected with 20 or 40 miracidia each was also increased. No significant difference in the mean days of precercarial period was found among these groups of snails exposed individually to different numbers of miracidia. Although there was no significant difference in average number of emerged eercariae from the initial 60 days among these 5 groups of infected snails, the time which the infected snails reach the cercaria-shedding peak was 10 days later in snails infected with 40 miracidia than those infected with 1,5,10and20m miracidia.Both infection rate and precercarial period Of snails exposed individually to 5 miracidia at different ages were performed. The results showed that the infection rate of snails infected with miracidia ages of 8or 12 hours were markedly lower than those at 1 or 4 hours of age. However, there was no significant difference in the precercarial period of snails infected with miracidia between 1-4 and 8-12 hours of age, suggesting the development of the larval stages was not influenced by the ages of miracidia which had penetrated into snail hosts.