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Exploring Relationship Between Fecal Exposure Pathways and Enteric Infections in Children in Vellore

UNC Water and Health Conference

Presenter: Sydney Hubbard

Rapid urbanization has led to a sanitation crisis in many low- and middle-income countries (LMIC). Studies of exposure to fecal contamination through different pathways have been conducted in LMICs. However, it is not clear whether exposure to fecal indicators (e.g. E. coli) from these pathways is associated with health outcomes (e.g. infection/illness). In March 2014, SaniPath in collaboration with the Christian Medical College (CMC) of Vellore, India conducted a cross-sectional exposure assessment in Old Town, a dense, urban unplanned settlement in Vellore. A total of 191 samples were collected from open drains, drinking water, public latrines, soil, raw produce, bathing water, child handrinse, and toy feeding spoon rinse and analyzed for E. coli using membrane filtration method. Spatial coordinates were also collected for each sample. From March 2010 - February 2012, the MAL-ED study, a multi-site project examining enteric infections, enteric dysfunction, and growth outcomes, enrolled a birth cohort of 190 children in Old Town, Vellore. At least 16 stool samples were collected from each child over two years of follow up and were tested for multiple bacterial and viral pathogens. Symptomatic illness was recorded. Geospatial data for Old Town, including open drains, water pipe network, open defecation areas, were extracted from shape files provided by CMC. Under the assumption that the urban environment and the exposure behaviors did not change dramatically between the close of the cohort in 2014 and the SaniPath assessment the same year, each child in the MALED study was linked with the closest environmental samples for each sample type from the SaniPath study. Spatial variables like the distance to the closest open defecation site, cumulative open drain/street/waterpipe lengths within a 100-meter radius, and the number of children also enrolled in the cohort within a 100-meter radius were generated. Generalized linear models were used with the bacterial infection rate, viral infection rate, and symptomatic illness rate as outcomes and environmental fecal contamination from different pathways and spatial variables as covariates. E. coli concentration from the closest public latrine and the distance to the closest open defecation site were significant predictors of bacterial infections in children. The sum of the open drain lengths within a 100-meter radius of the child, as well as the sum of street lengths within a 100-meter radius of the child, were significant predictors of viral infections in children. The E. coli concentration of the closest piped water was the only significant predictor of symptomatic illness in children. These preliminary findings that connect health outcomes to environmental exposure pathways and spatial information indicate differential risk factors for bacterial infections, viral infections, and symptomatic enteric illness in children under 2. These results highlight the need for safe excreta management in dense, urban settings to prevent bacterial infections, while contaminated drinking water seems to be a major driver of symptomatic illness in this population. Human congestion, as proxied by summative surrounding street lengths and open drains, is a key risk factor for viral infection.

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