Abstract: Objective To investigate on snail spread in schistosomiasis endemic areas of Hunan Province after flood disaster in 2020 for proposals in planning the prevention and control measures throughout the province. Methods The Oncomelania snails were investigated in the schistosomiasis endemic areas affected by flood disaster in the province by environmental sampling and systematic sampling. All snail samples collected were crushed to undergo microscopic examination for determining whether they were alive or dead and status of schistosomiasis infection. In addition, the area with snail spreading, occurrence of frame with snails and density of live snails were statistically analyzed. Results Snail spread occurred in 96 environments in 11 of the 41 schistosomiasis endemic counties (cities and districts) in Hunan Province of the snail survey in 2021. The area with snail spreading, a frame with snails and density of live snails were 1 084.09 hm², 7.41%, and 0.183 4 snails/0.1m², respectively. No infected snails were found. Snail spread was seen in the basins of Xiangjiang River, Zishui River, Lishui River and Dongting Lake, and most serious in the basins along Lishui River, with a total of 81 environments that accounted for 970.44 hm² (89.52%).The diffusion nature is dominated by the newly developed environment, with the newly developed snail area of 754.54 hm² (69.60%).The diffusion environments were primarily associated with beach (968.74 hm², 89.36%), and the vegetation with snail diffusion was dominated by weeds (883.76 hm², 81.52%). Conclusion Flood disasters can increase the risk of Oncomelania snails spreading in endemic areas. In order to consolidate the achievements of schistosomiasis control in the whole province, efforts should be made to check and control snails, improve the environment and monitor the diffusion status of snails.

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