Comparative Studies for Development of Three Different Geographic Strains of Schistosoma japonicum Cercariae in Five Subspecies of Oncomelania hupensis.

Cercarial maturation time, duration of cercarial emergence and number of cercariae released were studied in five subspecies of laboratory-reared Oncomelania hupensis (Oncomelania hupensis nosophora, O. h. hupensis, O. h. formosana, O. h. chiui and O. h. quadrasi) infected with three different geographic strains of Schistosoma japonicum. O. h. nosophora, O. h. hupensis and O. h. formosana were the most suitable host snails for the Japanese, Chinese and Taiwanese strains of S. japonicum, respectively. The cercarial maturation time in the most suitable host snails were 8 weeks for the Taiwanese strain of S. japonicum and 10 weeks for the Japanese and Chinese strains after exposure to 5 miracidia. The duration of cercarial emergence were 9 weeks for the Taiwanese strain, 17 weeks for the Chinese strain and 16 weeks for the Japanese strain. The duration of cercarial emergence was similar in the remaining subspecies, but the maturation time of cercariae was longer. For numbers of cercariae emergenced from snails, the most suitable host snails had a tendency to released more cercariae than the remaining snails.