Epidemiology of urinary schistosomiasis in Coastal Kenya: Spatial and social patterns.

Schistosomiasis is one of the most prevalent parasitic diseases worldwide. Yet its public health significance is often underappreciated because severe infection and morbidity occurs in only a subset of the infected population. Control efforts are centered on morbidity reduction through targeted treatment of school-aged children, the population at greatest risk for this disease. Reducing infectious water-contacts of individuals is also being attempted. However, in high prevalence communities, risk for infection may also be determined by more distal group- or community-level factors such as household proximity to transmission sources or socioeconomic resources. Accordingly, we examined the spatial and social patterning of urinary schistosomiasis using cross-sectional data that was collected in Coastal Kenya. Spatial analysis of the patterning of infection within a community could indicate hot spots of infection that may need additional focal transmission control beyond chemotherapy treatment for infection. We used geographic information systems (GIS) and spatial analyses to detect patterning of schistosomiasis and determined that the clustering of household infection following mass treatment changed with time. The spatial patterning of infection also changed when individuals and households with no reported history of treatment were included in the analyses. Since spatial analysis did not consistently implicate particular environmental sources, we also examined infection in relation to age, sex, exposure, and schistosomiasis knowledge, as well as household socioeconomic status. Individual-level factors were assessed using regression models, and these models were then compared to marginal models that incorporated correlation of individuals within households. Age and knowledge were significantly associated with infection, but sex and self-reported exposure were not associated. Household resources may determine the extent to which an individual is exposed to S. haematobium in the course of performing regular household water access and use needs. Socioeconomic status was associated with decreased odds of infection, even though risk for exposure in contaminated sources increased with higher socioeconomic status. Risk for exposure and disease was associated with household factors, and analysis of the spatial and social patterns of infection illustrated the need to also consider household-level factors in the development of local schistosomiasis control efforts.Ph.D.EpidemiologyHealth and Environmental SciencesPublic healthUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/125915/2/3224775.pd