Current Schistosoma mansoni exposure and infection have distinct determinants: a data-driven population-based study in rural Uganda

Exposure to parasitic flatworms causing schistosomiasis is a complex set of human-environment interactions. Yet, exposure often is equated to current infection. Here we studied risk factors and population patterns of exposure (water contact) within the SchistoTrack Cohort for 2867 individuals aged 5-90 years in Eastern and Western Uganda. Households within 0.34 km of waterbodies accounted for 80% of all water contact. We found a 15-year gap between population-level peak in water contact (age 30) and infection (age 15) with practically no correlation (ρ=0.03) of individual-level water contact and current infection. Bayesian selection for 30 biosocial variables was used to separately predict water contact and current infection. Water contact was positively associated with older age, female gender, fishing occupation, lack of site contamination, unsafe village drinking water, number of sites and type (beach/pond), lower village-level infection prevalence, and fewer village roads. Among these variables, only older age and fishing were positively, though inconsistently associated with infection status/intensity. Water, sanitation, and hygiene influenced water contact but not infection. Our findings highlight that exposure was highly focal and at-risk groups for exposure and infection were different. Precision mapping and targeted treatment/interventions directly focused on exposure are needed to save medicines and reduce transmission.