| Schistosomiasis is an infectious disease that threat people's health severely in the world, especially among the provinces located along and down to the basin of the Yangtze River in the south of China. Chinese government began to put into effect the policy of "breaking dikes or opening sluice for water store" since a disastrous flood appeared in 1998. While the policy reduced the harm of the flood, it changed ecological environment of snails. In China schistosomiasis was mainly caused by schistosoma japonicum (S.Japonicum) and the unique intermediate host of S.Japonicum, oncomelania, was related closely to the environmental factors of snail habitats. The policy of "breaking dikes or opening sluice for water store" changed the distribution of snails and S.Japonicum, so it was significant to clarify the effect of the policy to control schistosomiasis for Chinese department of public health. Traditional epidemiological methods, statistical models and technologies of remote sensing were mainly applied to analyze the effect of the policy preliminarily in this paper."Breaking dikes or opening sluice for water store" brought about three major changesxhanges of schistosomiasis, oncomelania and vegetation. This paper focused on them.1 Application of prevalence research for clarifying the impact of the policy of "breaking dikes or opening sluice for water store"Data of schistosomiasis and snail were collected in the snail habitats by the local schistosomiasis prevention department. Self contrast and concurrent contrast were chosen to analyse the data of schistosomiasis and snail from research regions and contrast regions. We found that prevalence and the density of alive-snails were higher than that before 1998, so a conclusion can be drawn that the policy made epidemic degree of schistosomiasis more serious to some degree than before. Analysis also showed that prevalence of schistosomiasis was statistically related to the density of alive-snails (r=0.764, P=0.045) .Prevalence tendency lines of Jicheng(completely abandoned for water store), Haokou(partially abandoned for water store) and Xiyang(contrast) were compared. Prevalence tendency lines showed that prevalence of three places all decreased before 1998(Xiyang decreased most obviously) and all increased after 1998(Jicheng increased most obviously). It indicated that the policy might cause the change of prevalence.2 Application of statistical model for clarifying the change of prevalence (before 1998 and after 1998)To forecast prevalence of schistosomiasis accurately and quickly can provide the valuable references for the government on how to allocate the limited medical resources. In order to clarify the change of prevalence, Moving average (MA), Exponential smoothing (ES), Autoregressive model (AR) and Autoregressive integrated moving average model (ARIMA model) were applied to analyze the data of research regions. Result showed that sum of square error (SSE) of ARIMA model was smallest in the four methods. The predicted equation of Haokou was y ,=0.6487Yt-1+0.3513Y,.2+0.8671et-1. +0.0223 (yt: predicted value of that year, Yt-1 and Yt-2 real value of last year and the year before last, et-1: predicted error of last year) .The predicted equation of Jicheng was y ,=1.2877Y,.|+0.4246Y,.2-0.7123Yt-3-0.4305et-1+ 0.9981et-2-0.0544(yt: predicted value of that year. Yt-1, Yt-2, Yt-3: real value of last year, the year before last and three years ago.et-1, et-2: predicted error of last year and the year before last). By comparing predicted values, prevalence after 1998 was higher than that before 1998. The conclusion was as same asParti.Same as above, in order to predict prevalence more accurately and test the conclusion, grey model (GM) was applied. The predicted equations ofZhongshan and Jicheng were X(1)(k+1)=-19.373641e-0.081742k+20.677187 andX(1)(k+1)=50.018893e0.130649k-34.478893 respectively. Conclusion was the same, i.e. prevalence after 1998 was higher than that before 1998. Five methods were compared and conclusions could be drawn: different meth...
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