[Studies on resistance of to praziquantel XⅥ Biological characteristics of praziquantel-resistant isolates of in snails].

Objective: To investigate the difference of biological characteristics between the praziquantel-resistant and -susceptible isolates of in intermediate host snails.

Methods: Mice were infected with cercariae of praziquantel-resistant and -susceptible isolates of , and the parasite eggs were collected 37 days post-infection to hatch miracidium. Then, the snails were infected with the miracidium of each parasite isolate. The snail infection, survival 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 .

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%; = 3.948, = 0.047) and the number of cercaria released from a single snail (1 460.2 vs. 1 039.3; = 2.507, = 0.02), and there were significant differences between the praziquantel-susceptible and -resistant Hunan isolates in the snail infection (10.00% vs. 21.52%; = 3.980, = 0.046) and the number of cercaria released from a single snail (1 319.4 vs. 1 003.5; = 2.566, = 0.017). However, there were no significant differences between the praziquantel-resistant and -susceptible isolates of in the prepatent period of cercariae and the survival rate of infected snails ( > 0.05).

Conclusions: The praziquantel-resistant isolate of has a higher susceptibility to but less cercaria released from each infected snail than the susceptible isolate.