| Schistosomiasis is a serious parasitic zoonosis. Nowdays its epidemic situasions stay critical in China. To a great extent, it remains endemic in lake and marshland regions in Hunan, Hubei, Anhui, Jiangxi, Jiangsu Provinces and mountainous areas in Yunan and Sichuan Provinces. Qianliang Lake district is on the Northwest of Dongting Lake. And it had been densely covered with snails in the past. This article is aimed at studying the natual growth and decline and analyzing the influence of that on endemic situation of Schistosomiasis in Qianliang Lake area, so as to explore the causes of extinction and to provide the evidence for formulating Schistosomiasis control strategy. The whole study was divided into 3 parts:Part 1 Analysis of the natural growth and decline of oncomelania snails in the marshland of Qian Liang Lake district in Eastern Dongting Lake areaObjective To understand the change trend of snails in the bottomland areas of Qian Liang Lake district in Eastern Dongting Lake so as to provide the evidence for formulating schistosomiasis control strategy. Methods The monitoring data of snails of Qian Liang Lake district from 1988-2011 was collected retrospectively and analyzed using the method of trend chi-square test. The correlations between the snail density indicators was analyzed. Results During 1988-2011, the area of snails surveyed didn’t change and was 433.2hm2. The monitoring data showed that the change trend of the density of alive snails and the infection rates of snails were not obvious (P>0.05), but the mortality of snails showed falling trends(P<0.05);There were positive correlations between the average density of infected snails and the mortality of snails(R=0.640, P<0.05), the positive rate of snails (R=0.639, P<0.05), and the average density of living snails(R=0.646,P<0.05). There was no correlation between other snail indicators. In 1999, only 7 snails were found, of these, only one snail was alive. Alive snails were not found after 2000. Conclusion The change trend of the density of alive snails were not obvious from 1988-1998 in the bottomland areas of Qian Liang Lake district, but the number of snails underwent a sharp drop in 1999 and snails were not found till now.Part 2 Distribution of univalvia molluscs in area with natural decline of Oncomelania hupensis snails in Eastern Dongting Lake areaObjective To understand the distribution of univalvia molluscs in Eastern Dongting lake area where the Oncomelania hupensis is extinct, so as to explore the causes of extinction and to provide the evidence for formulating schistosomiasis control strategy. Methods The univalvia molluscs of the Qianliang Lake district, Jianxin District and Junshan Park were investigated in August of 2013. All the collected snails were classified and identified. The data were analyzed by using the method of Shapiro-Wilk normality test and non-parametric test. The ecological biodiversity differences from each district were compared by the biodiversity indexes. Results The univalvia molluscs collected were from 6 species in 3 families in Gastropoda class, namely Oncomelania hupensis Gredler in Pomatiopsidae family, Parafossarulus striatulus, Alocinma longicornis, Parafossarulus sinensis, Bithynia fuchsisana in Bithyniidae family, and one genus provisionally named Radix in Lymaneidae family. In Junshan Park, a total of 4 553 snails were collected, among which 1 264 were Oncomelania snails. In Jianxin District,336 univalvia molluscs were collected, and no Oncomelania snails were found. In Qianliang Lake district, there were only 7 Alocinma longicornis snails,2 Parafossarulus sinensis snails and 1 Parafossarulus striatulus snail collected. There were significant differences among the distributions of the samples from the three districts (χ2=166.225, P<0.01).The Simpson’s diversity indexes in Qianliang Lake area, Jianxin District and Junshan Park were 0.402 8,0.718 6 and 0.678 8, respectively, and the Shannon-Wiener indexes of the 3 areas were 0.721 5,1.431 3 and 1.1999, respectively. Conclusion With the extinction of Oncomelania snails, the species and quantities of other snails become rare in Qianliang Lake area. Whether their causes are relevant is worth further studying.Part 3 Analysis the influence of natural decline of Oncomelania hupensis snails on endemic situation of Schistosomiasis in area in Eastern Dongting Lake areaObjective To understand the change trend of endemic situation of Schistosomiasis in the bottomland areas of Qian Liang Lake district in Eastern Dongting Lake so as to provide the evidence for formulating schistosomiasis control strategy. Methods To choose the Qian Liang Lake district to be the experimental field and the Liulin Zhou district distributes with snail as control site. The monitoring data of positive rate of people and cattle of Qian Liang Lake district from 1998-2010 was collected retrospectively and analyzed using the method of trend chi-square test. Results The monitoring data of the infection rates of people and cattle showed falling trends from 1998-2010 (P<0.05). The data showed that the difference between the two districts’ infection rates of people was not obvious in 1998 (P>0.05). Yet the situation went contrarily that the infection rates of people and cattle in Qianliang Lake area were significantly lower than that in Liulin Zhou area from 2004-2010 (P<0.05).The infection rate of cattle between the two districts were also obvious from 2004-2010 (P<0.05). In 1998, the average density of living snails in Qianliang Lake district was 0.434 No./0.1m2. Yet that last 0 til now. The average density of living snails in Liulin Zhou district went around 0.3 No./0.1m2 from 1998 to 2003. And that increased up to 1 No./0.1m2 from 2004 to 2010, the maximum was 2.384 No./0.1m2. Conclusion The natural decline of oncomelania snails decreased the positive rates of people and cattle of Schistosomiasis in Qianliang Lake district. |
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