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.