Abstract: 　Objective To study the impact of environmental temperature on the development of Schistosoma japonicum larvae within the Oncomelania hupensis. Methods Oncomelania snails, collected from the field and free of S. japonicum infection, were exposed to miracidiae of S. japonicum in a ratio of 1∶20 and raised at 30 ℃, 27 ℃, 24 ℃, 21 ℃ and 18 ℃, respectively. The prepatent period of larvae within the Oncomelania hupensis and the developmental velocity were determined, of which the relationship with the temperature was analysed. Results The average prepatent period of cercariae in snail was (128.89±16.05) d,(95.00±21.03) d,(71.93±12.74) d and (62.74±14.19) d at 21 ℃, 24 ℃, 27 ℃, 30 ℃, respectively. The regression formulation between prepatent period and temperature was y =730.68x -0.8918 (r=0.9976, P<0.01). And the regression formulation between developmental velocity of S. japonicum larvae in snail and temperature was y =0.0235ln(x)- 0.0639(r=0.9973, P<0.01). It was derived that the unitial temperature for the development of S. japonicum within the snails was 15.17 ℃±0.43 ℃. Conclusion The development of S. japonicum larvae within the Oncomelania snails declines with the decrease of temperature.

Key words: Schistosoma japonicum, cercaria, Oncomelania hupensis, developmental velocity, initial temperature, prepatent period