Abstract: Objective To evaluate the transmission risk of schistosomiasis in Yunnan Province in 2020 for evidence to formulate prevention and control measures against this infection. Methods Four counties (cities),including Weishan,Midu, Dali and Ninglang of Yunnan Province,were included to undergo risk assessment in 2020. The evaluation was performed in one administrative village selected from each township. The data on schistosomiasis prevalence and control were obtained from 2018 to 2020 in the counties involved in assessment. Field survey was conducted on the snail prevalence and infection in the wild feces in sampled villages. Then the results were comprehensively evaluated for the risks of schistosomiasis transmission. Results The epidemiological data showed that no patients,infected animals or infected snails were detected in the 7 villages assessed between 2018 and 2020. In the field survey site,only 10 living snails were captured by systematic sampling in areas with snail prevalence in history. The occurrence rate of snail was 6. 52% (3 / 46) for individual frame,and the average density of living snails was 0. 22 snails / 0. 11 m2,2 living snails were captured in 3 248 frames by environmental sampling. Totally,1 082 living snails were captured by systematic sampling in the environment with snails. The total occurrence rate of frames with living snails was 4. 01%(297 / 7 413),and the average snail density was 0. 15 / 0. 11 m2,31 living snails were captured in 2 627 frames by environmental sampling. LAMP detection showed negative results in all snails obtained. No positive infection was detected by miracidium hatching test in a total of 261 aliquots of wild feces,including 54 aliquots of cow feces (20. 69%),129 dog feces (49. 43%),33 equine feces ( donkey and mule) (12. 64%),7 pig feces (2. 68%),21 sheep feces (8. 05%) and 17 human feces (6. 51%). The risk level of each assessment county is level Ⅲ. Conclusion The risk of schistosomiasis transmission was concluded at lower level in Yunnan Province in current study,yet certain unfavorable aspects still exist,including large number of livestock in stock,free ranged livestock,complex and large
quantity of wild feces as well as reemergence of Oncomelania hupensisin historical snail environment. These findings suggest
that it is essential to further strengthen the prevention and control measures and develop perfect risk assessment and monitoring mechanisms in order to consolidate the previous efforts.

Key words: Schistosomiasis, Oncomelania hupensis, Wild manure, Risk assessment, Yunnan Province