[Study on snails infected with miracidia under different conditions in snail-existent non-endemic areas of schistosomiasis in Nantong City].

Objective: To understand the forming cause of the snail-existent non-endemic areas of schistosomiasis (SENEAS), and to verify the conclusion of previous studies, so as to provide the evidence for schistosomiasis monitoring in such areas in Nantong City, Jiangsu Province.

Methods: The controlled field tests were carried out to observe the snails artificially infected by schistosome miracidia in SENEAS. The influence of the soil from SENEAS and the endemic areas on snails artificially infected by miracidia were observed.

Results: All the experimental snails could be infected by schistosome miracidia except the smooth-shell snails from Tangyuan Village in the controlled field test environment of SENEAS or the endemic areas. The infection rates of the smooth-shell snails were lower than those of the ribbed-shell snails, but there were no statistically significant differences. The mortality rates of the smooth-shell snails were higher than those of the ribbed - shell snails, which were statistically significant ( = 135.118, = 122.836, =154.436, = 138.288, = 151.923, all < 0.01). There were no significant differences in the infection rates of snails between each test group of the soil from SENEAS and the endemic areas ( = 0.071, = 0.216, both > 0.05). Also there was no significant difference between each test group and the control group without soil ( = 7.148, > 0.05).

Conclusions: It is likely to form the spread of schistosomiasis in SENEAS in Nantong City with sufficient amount of infection source of schistosomiasis imported. It is still necessary to implement the surveillance of schistosomiasis and snails in Nantong City.