RESUMEN
Objective To understand the variation in response of Oncomelania hupensis to niclosamide. Methods Snails were collected from 37 sampling areas distributed in 10 provinces (municipalities) using random environmental sampling methods in accordance with the different types and categories of snail habitats. In laboratory the snails were immersed in solutions of niclosamide for 24 and 48 hours at 25℃. Results 1.0 mg/L niclosamide showed 100% killing effect on snails in 24 hours. The LC 50 concentrations for snails immersed for 24 hours ranged from 0.0320 to 0.1689 mg/L with a mean value of 0.0920 mg/L. 0.5 mg/L niclosamide showed 100% killing effect on snails in 48 hours. The LC 50 values for snails immersed for 48 hours ranged between 0.0299 and 0.1114 mg/L with a mean of 0.0627 mg/L. There is a significant difference in snail sensitivity to niclosamide between sampling areas. Conclusion The sensitivity to niclosamide varied in snails from different sampling fields, but the chemical in a concentration of 1.0 mg/L showed 100% effect of killing snails, which is consistent to the manual of schistosomiasis control.