Abstract: Objective To investigate and analyze the impact of the devastating flood in Jiangxi Province in 2020 on the spread of Oncomelania snails, so as to provide scientific basis for the monitoring and control of Oncomelania snails in areas following flood disaster. Methods The data on flood disaster were collected from schistosomiasis endemic areas in Jiangxi Province in 2020. Then investigations were conducted on snail spreading in the environments with snails in history, suspected with snails, and snail-free environment bordered in that with snail prevalence after flood disaster. Software Excel 2016 was used to construct the database for the snail spreading after flood disaster, and various indicators for snail status and the nature of snail spreading were summed up and statistically analyzed. Results Snail spreading to a certain extent was found in 95 environments in 63 administrative villages in the 38 towns in 14 endemic counties (cities/districts) after the flood disaster in 2020. The spreading affected an area of 1 411.37 hm², the diffusion area of Oncomelania snails in hill area was 240.82 hm² （17.06%), and that in lake area was 1 170.55 hm² (82.94%). Hilly type Oncomelania snails were found in 80.00% (76/95) of the total environment with snail diffusion, where the average density of live snails was 0.533 8 snails/0.1 m², and significantly higher than that of the marshland and lake type(0.055 8 snails/0.1 m²). The occurrence rate by individual frame with living snails in diffusion environment of hilly type (24.63%) was significantly higher than that in lake type (2.45%). After flooding all 185 single retreated polders in Poyang Lake District, no environments were found to be suspected with snail breeding. Conclusion Catastrophic flood should be the major factor for spread of snails in the hilly environment. Therefore, it is necessary to strengthen the monitoring and control of snails after the disaster to prevent the resurgence of schistosomiasis.

Key words: Schistosomiasis, Flood disaster, Diffusion of snails, Jiangxi Province