Abstract: Objective To understand the epidemic of schistosomiasis in Gaoyou sections of Eastern Route of the South-to-North Water Diversion Project. Methods  The Oncomelania snails were monitored by means of systematic sampling combined with environmental sampling in the Grand Canal, Sanyang River and the adjacent lake areas. Net salvage and rice straw curtains were used to capture the snails for survey of their prevalence in the surveillance sites of the Grand Canal, Sanyang River. Dipstick dye immunoassay( DDIA) and indirect hemagglutination ( IHA) were used to screen residents and livestock in the monitoring area. Both population and livestock with positive findings further underwent pathogen detection using stool hatching or Kato-Katz technique. Results The Oncomelania snails were not found in the Grand Canal and Sanyang River from 2016 to 2019. Investigation of a total area of 11 402. 74 hm² in the adjacent lake area revealed that areas with snails were between 27. 55 hm² and 77. 51 hm². Totally, 125 kg floating debris was refloated and 160 pieces of rice straw curtains were placed in the surveillance sites, in which no snails were detected. Of the 31 311 residents (person-time) underwent detection, positive for DDIA was found in 226, yet infection was free in the 10 736 residents( person-time) received pathogen detection. No infection was seen in the 1 083 livestock detected. Conclusion Although there is no spreading of the Oncomelania hupensis and schistosomiasis prevalence in Gaoyou sections of Eastern Route of the South-to-North Water Diversion Project, yet surveillance over the snails and schistosomiasis remains necessary in those areas.

Key words: Eastern route of the South-to-North Water Diversion Project, Schistosomiasis, Oncomelania hupensis, Surveillance, Gaoyou