This paper presents the classifications of the infection source areas for schistosomiasis japonica in the lake beach and embankment regions, systematically demonstrates the geo-graphical and endemic characteristics of different types of infection source areas. The results provide the basis for making control strategies of the disease.

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.