Surveillance of schistosomiasis japonica in potential endemic areas in China, 2011

Abstract

Objective To explore the potential risk factors of schistosomiasis transmission in potential endemic areas so as to provide scientific basis for setting up the prediction and surveillance systems to respond the emergence of schistosomiasis.Methods In 2011,fixed and floating surveillance sites in potential endemic areas of 11 counties in Anhui,Jiangsu,Chongqing,Hubei and Shandong were selected.Immunological assays and/or stool examinations were carried out to investigate the infection situation of floating population and livestock.The distribution of Oncomelania snails was investigated in risk areas and suspicious areas,and spreading patterns of snails were observed in the rivers that directly connected with the river.Results In Anhui,Jiangsu,Chongqing and Hubei,a total of 5 600 of floating population were screened by indirect hemagglutination assay (IHA),and the positive rate of antibody was 1.39％(78/5 600).All antibody positives were examined by stool tests and there were two positives and the positive rate was 2.56％(2/78).The two patients came from the Chaohu Lake area.There were 480.01 ha (1 ha=10 000 m2) investigated for Oncomelania snail detection at the fixed surveillance sites.Only at the Jinhu County Shijian sands and Gaoyou County Xinmin sands,the Oncomelania snails were found,the areas were 29 940 m2 and 12 000 m2 separately.The 125 Oncomelania snails were captured and dissected,but no one was positive.There were 45 circumstances,about 234.27 ha investigated for Oncomelania snail and 8 530 frames surveyed at the floating surveillance sites,with no Oncomelania snails found.A total of 9 018.4 kg flotage were refloated and 814 other snails found but no Oncomelania snails found.The rice straw curtains attracted 8 047 aquatic snails,with no Oncomelania found.Conclusions The imported patients of schistosomiasis had been found among the population in potential endemic areas.At present,Oncomelania snails exist in the historic epidemic areas passed by water conservancy projects,and it is the potential risk of imported Oncomelania snails spreading to the potential endemic areas.Therefore,the surveillance of the potential risk factors of schistosomiasis transmission must be effectively reinforced over a long-term. Key words: Schistosomiasis; Potential endemic areas; Prevalent factors; Surveillance