Abstract:

Medical geography and spatial epidemiology of schistosomiasis involve plenty of the knowledge and the parameters on the ecological environments of schistosome and its parasites,which provide abundant information for geographical interpretation on classification of the epidemic areas in China that was formulated by practical experiences and field survey in past decades.This paper consulted substantial research publications,systematically summarized and analyzed the ecological characteristics of the schistosome at different life cycle phases (egg,miracidia,cercaria) that has direct relations with ecological environments and its parasites (snails and mammals).Results show that concurrent meeting the ecological needs of both the schistosome and its parasites was the basic conditions for schistosomiasis transmission;most of the life time of the schistosome was spent in the bodies of the terminal parasite (mammals) and the intermediate parasite (snails),the demanding needs of snails for ecological conditions was the key to spatial variation of schistosomiasis transmission,thus the features of snail spatial distribution became the main foundation for classification of the epidemic areas.Finally interrelations among  the geographic factors (vegetation,soil,geomorphology,altitude,hydrology and hydraulics) of snail habitats  were analyzed from geographic point of view.The conclusion was that largescale geomorphology created different hydrological types and different spatial pattern of snail distribution that result in different schistosomiasissusceptible zones,and ultimately determined different schistosomiasis epidemicity types.The result was consistent with the classification scenario made by the Department of Endemic Prevention of State Health Ministry of China.