Comparison of SaniPath exposure assessments in low-income urban areas in eight countries

American Society of Tropical Medicine and Hygiene 2019

November 20-24, 2019

Wolfgang Mairinger, Yuke Wang, Suraja Raj, Habib Yakubu, Casey Siesel, Jamie Green, Sarah Durry, Christine Moe

Emory University, Atlanta, GA, United States

The SaniPath exposure assessment tool compares risks of exposure to fecal contamination in urban environments across multiple exposure pathways. The tool has been deployed in 39 neighborhoods in 8 cities: Accra, Ghana, Vellore, India; Maputo, Mozambique; Siem Reap, Cambodia; Dhaka, Bangladesh; Atlanta, United States; Lusaka, Zambia; and Kampala, Uganda. Ten exposure pathways were investigated (open drains, ocean water, surface water, floodwater, public latrines, soil, bathing water, raw produce, drinking water, and street food) through behavior surveys and environmental sample analyses. Exposure was expressed as monthly dose (average amount of fecal contamination ingested as measured by E. coli colony-forming units [CFU]) and the percent of population exposed to fecal contamination for each pathway. Magnitude of fecal contamination, frequency of exposure behavior, and estimated fecal exposures were compared across pathways, neighborhoods and cities. The most common dominant exposure pathways for adults were raw produce, open drains, and street food and for children were open drains, produce, and floodwater. For produce, the dose was usually very high (>106 CFU/ month), and a large percent of the population was exposed (>80%). For street food, average E. coli concentration ranged from 101.3 CFU/serving in one neighborhood in Lusaka, Zambia to 105.5 CFU/serving in one neighborhood in Dhaka, Bangladesh. Exposure to open drains resulted in high doses (>104 CFU/month), but the population exposed varied (5%-92%) even within the same city. Exposure to fecal contamination via floodwater, usually affected a high percent of population (>80%) but had variable doses (102.5-1010 CFU/month). Both dose and percent of population exposed varied for public latrines and municipal piped water. This information can help city governments choose effective interventions to reduce the risk of exposure to fecal contamination. Widespread risks from contaminated produce and street food within and across cities underscore the link between excreta management and food safety and need for global action.

WHO and UNICEF Position Paper makes reference to SaniPath Exposure Assessment Tool

The WHO and UNICEF position paper Implications of recent WASH and nutrition studies for WASH policy and practice summarized three high-quality studies in the WASH sector that resulted in little or no impact on reducing childhood diarrhea and stunting. The paper aimed to contextualize the findings and distill the implications for future WASH investments.

The report highlighted that oftentimes fecal contamination of produce is not considered when designing and implementing interventions despite prior evidence that this is a dominant exposure pathway in many settings. The paper cites SaniPath as the source of this important piece of evidence.

The evidence generated through SaniPath's work is increasing awareness about this major exposure pathway and contributing to influential position papers such as this one. The data generated from deployments is encouraging policies and practices to address food safety issues that arise from fecal contamination along the value chain.

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.