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

OBJECTIVE

To describe the exposure patterns related to schistosomiasis transmission in 10 villages in rural Xichang County, Sichuan, China.

METHODS

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.

RESULTS

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.

CONCLUSION

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.