洞庭湖洲滩坡度与植被对感染性钉螺分布范围的影响

目的查明日本血吸虫感染性钉螺在洞庭湖洲滩的分布环境,着重分析洲滩的离岸距离、地面高程、坡度及优势植被种类等环境因素对感染螺分布的影响,为消除血吸虫病疫源地确定重点目标。方法在洞庭湖上游和下游共选择3类洲滩,分别在1987-1989年及2009年采用系统抽样法进行钉螺与感染性钉螺分布调查,查螺段面从堤岸边最高有螺线往下一直查到最低有螺线止,同时用水准仪测定地面高程（吴淞零点）,并记录植被种类。结果在3类洲滩钉螺孳生地中,有感染性螺分布的面积平均占35.5%。主要分布在大堤边和洲滩上部的坡岸地带。地势高、坡度陡的环境感染性钉螺较多;地势低、坡度小的平坦环境没有查到感染性钉螺。在芦苇地带也没有查获感染性钉螺,而在芦杂、柳林、莎草、藜蒿区均可有感染性钉螺出现。结论洞庭湖区的感染性钉螺有明显的沿堤岸分布趋向,其分布范围与汛期的水位、传染源（终宿主）的活动等有关。

Effect of gradient and vegetation on distribution of schistosome infected Oncomelania snails in Dongting Lake marshland

Objectives To investigate the distribution of Schistosoma japonicum infected Oncomelania snails in the marshland of Dangting Lake region,and explore the effects of gradient and vegetation on the distribution of the infected snails.Methods Three marshland areas in upstream and downstream of Dongting Lake were selected.The snail distribution was investigated and the ground elevation was assessed (Wusong's elevation of zero)and the vegetation types were also recorded from 1987-1989 and 2009.Results In the 3 types of snail habitats of the marshland,the average rate of areas with infected snails was 35.5%,and the snails mainly distributed beside the embankment and slope zone.More infected snails were found in the high altitude and steep slope zone,while no infected snails were found in the low altitude and flat slope zone,and reed areas as well.Conclusion The Schistosoma japonicum infected snails in the marshland of Dongting Lake mainly distribute beside the embankment and slope zoon,and are correlated with the water level in flood seasons and the activities of definitive hosts.