[Causes of re-emergence of Oncomelania snails in hardened ditches].

OBJECTIVE: To understand the impact factors of the re-emergence of Oncomelania snails in hardened ditches so as to find out the measures to improve the effect of snail eradication. METHODS: Thirteen infected townships from Jingmen City were randomly selected and investigated with the retrospective method and the field survey. All the data were analyzed for evaluating the effect of the hardened ditches on snail eradication and finding out the causes of the re-emergence of snails in hardened ditches RESULTS: After on-site investigation of 151 hardened ditches, the eradication rate of snail areas was 78.79%, and 71 ditches were founded with snails and the re-emergence rate was 47.02%. The major factors of the snail re-emergence were the spread of the snails from the upstream, the dilapidation of the hardened ditches, no using molluscicides before the hardened ditches, and the snails being brought by the engineering construction. CONCLUSIONS: The only hardened ditches can not eradicate the snails. We should manage an overall plan when processing the ditches hardening project, implementation with molluscicides before the project and strengthen the maintenance of the hardened ditches.