Individual and village‐level study of water contact patterns and Schistosoma japonicum infection in mountainous rural China

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Abstract
To describe the exposure patterns related to schistosomiasis transmission in 10 villages in rural Xichang County, Sichuan, China. Individual and village-level study of water contact exposure and Schistosoma japonicum reinfection; after initial infection survey and treatment, reinfection was determined 2 years later for 1604 individuals, of whom 578 also participated in a cross-sectional survey to assess their water contact behaviours. The highest intensity of reinfection was observed in farmers aged 20-29 years, with no difference between sexes. While water contact measured as m(2)-minutes of contact was not associated with reinfection, an exposure metric computed by spatially weighting water contact by cercarial risk was correlated with both infection status and intensity. Village-level indicators based on snail density, number of infected snails, mouse bioassay data, and averaged individual-level exposures were associated with village reinfection rates. Age-acquired immunity may be present in this population, but the study lacked sufficient power to discern differences in the exposure infection relationship with age.