[Retrospective investigation on endemic situation of schistosomiasis in Hubei Province].

OBJECTIVE: To explore the changing rules of schistosomiasis infection and Oncomelania hupensis snail situation in areas where schistosomiasis transmission was controlled or interrupted or transmission rebounded after the interruption. METHODS: Daye City, Wuxue City and Jingshan County were selected and investigated retrospectively to collect the schistosomiasis epidemiological information 10 years before they reached the criteria of transmission controlled and the subsequent years until 2008. The database of retrospective investigation was established for analyzing the trends and rules of the changes of snail status and human infection status. RESULTS: In Daye City, there was no snail areas and schistosomiasis patients and cattle after reaching the criteria of transmission interrupted in 1987. The infection rate of residents were positively correlative with the infection rate of cattle and snail areas (r = 0.865, 0.843, P < 0.01). In Wuxue City, the proportion of snail areas occupying the historic snail areas kept a steady from the transmission controlled to transmission interrupted, but it began to rebound to the highest level in the history (8.93%) after the transmission interrupted for 3 years. In Jingshan County, the infection rates of residents and cattle were all stable from 1% to 2% after the transmission controlled. The proportion of snail areas occupying the historic snail areas was rebounded from 1.63% in 1985 to 21.50% in 2008, and the densities of living snails rebounded from 2005. CONCLUSIONS: The infected snails could be the sensitive indicator of the rebound of snail situation and human infection. The elimination of schistosomiasis still depends on the control of snail areas, including strengthening the infected snail control.

[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.