Studies on resistance of Schistosoma to praziquantel (ⅩⅥ)Biological characteris- tics of praziquantel-resistant isolates of Schistomoma japonicum in Oncomelania hupensis snails / 中国血吸虫病防治杂志

ABSTRACT

Objective To investigate the difference of biological characteristics between the praziquantel-resistant and-sus-ceptible isolates of Schistosoma japonicum in intermediate host Oncomelania hupensis snails. Methods Mice were infected with cercariae of praziquantel-resistant and-susceptible isolates of S. japonicum,and the parasite eggs were collected 37 days post-in-fection to hatch miracidium. Then,the snails were infected with the miracidium of each parasite isolate. The snail infection,sur-vival rate of infected snails,prepatent period of cercariae,and the total number of cercariae shed from each infected snail were observed and compared between the praziquantel-resistant and-susceptible isolates of S. japonicum. Results If each snail was exposed to a single miracidium,there were significant differences between the praziquantel-resistant and-susceptible Jiangsu isolates in the snail infection(8.99％vs. 19.74％;χ2=3.948,P=0.047)and the number of cercaria released from a single snail (1460.2 vs. 1039.3;t=2.507,P=0.02),and there were significant differences between the praziquantel-susceptible and-re-sistant Hunan isolates in the snail infection(10.00％vs. 21.52％;χ2=3.980,P=0.046)and the number of cercaria released from a single snail(1319.4 vs. 1003.5;t=2.566,P=0.017). However,there were no significant differences between the pra-ziquantel-resistant and-susceptible isolates of S. japonicum in the prepatent period of cercariae and the survival rate of infected snails(P>0.05). Conclusion The praziquantel-resistant isolate of S. japonicum has a higher susceptibility to O. hupensis but less cercaria released from each infected snail than the susceptible isolate.