Sanitation Gaps Among Low-Income Urban Populations
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Author(s)
Capone, Drew S.
Advisor(s)
Brown, Joseph
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Abstract
Gaps to achieving safely managed sanitation exist for urban populations in low- middle- and high-income countries. Most of the 2 billion people who still lack access to basic sanitation services live in low- and middle-income countries, but progress is also needed in high-income countries. Here we present the results of studies which investigated access to sanitation services in the urban US and studies in Maputo, Mozambique that evaluated the impact of an urban on-site sanitation intervention. To estimate the number of people without sustained access to flush toilets in the urban US, we combined US Census Data on sub-standard housing with Department of Housing and Urban Development data on homelessness to estimate that at least 930,000 urban Americans lack access to at least basic sanitation. In central Atlanta we systematically surveyed open defecation sites across a predefined 2.4-square-kilometer area. We identified 118 discarded human stools in our search area and 23% (6/26) of the fresh stools tested positive for at least one enteric pathogen. The Maputo Sanitation (MapSan) trial was a controlled trial to evaluate the impact of a shared sanitation intervention on children's health in low-income urban neighborhoods of Maputo, Mozambique. We collected data from participants enrolled in the MapSan cohort and environmental samples taken in the domestic environment to evaluate the intervention's impact on pit-emptying practices, the potential of fecal sludges for pathogen surveillance, the intervention's impact on enteric pathogens in soils, and children's risk of infection from soil ingestion. Twenty-four months following the intervention, we found that intervention compounds were more likely to have hygienically emptied their on-site sanitations system (aRR 3.8, 95% CI: 1.4, 10) compared to control compounds. Using children's stools matched to fecal sludges from septic tanks and pit latrines, we observed that the six most prevalent bacterial pathogens and all three protozoan pathogens were prevalent in the same rank order in both matrices. Furthermore, we collected 179 latrine entrance soils at baseline (e.g. before the intervention) and at the 24-month phase from control (n=91) and intervention (n=88) compounds. We found evidence the intervention reduced the prevalence pathogenic bacteria in latrine entrance soils 24-months following the intervention (aPR = 0.67, 95% CI: 0.45, 0.98), but had no effect on the prevalence of pathogenic viruses, protozoa, and STHs. Despite some positive results, hygienic emptying was not universal at intervention compounds, and we detected at least one enteric pathogen in 86% of intervention soils 24-months after the intervention. In response, we developed a quantitative microbial risk assessment model which indicated that children's annual risk of infection by Shigella spp. and Giardia duodenalis from soil ingestion in low-income Maputo was high. More comprehensive WASH interventions may be needed in similar settings to limit the spread of fecal contamination through site specific pathways. Our analysis of matched stools and fecal sludges indicates that fecal sludge from on-site sanitation systems may be useful for pathogen surveillance. Such an approach may be helpful to characterize the pathogens circulating in a community and inform comprehensive packages of WASH interventions that are tailored to address the local exposure landscape.
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Date
2020-07-28
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Text
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Dissertation