Impacts of an Urban Sanitation Intervention on Fecal Indicators and the Prevalence of Human Fecal Contamination in Mozambique

Abstract

Fecal source tracking (FST) may be useful to assess pathways of fecal contamination in domestic environments and to estimate the impacts of water, sanitation, and hygiene (WASH) interventions in low-income settings. We measured two nonspecific and two human-associated fecal indicators in water, soil, and surfaces before and after a shared latrine intervention from low-income households in Maputo, Mozambique, participating in the Maputo Sanitation (MapSan) trial. Up to a quarter of households were impacted by human fecal contamination, but trends were unaffected by improvements to shared sanitation facilities. The intervention reduced Escherichia coli gene concentrations in soil but did not impact culturable E. coli or the prevalence of human FST markers in a difference-in-differences analysis. Using a novel Bayesian hierarchical modeling approach to account for human marker diagnostic sensitivity and specificity, we revealed a high amount of uncertainty associated with human FST measurements and intervention effect estimates. The field of microbial source tracking would benefit from adding measures of diagnostic accuracy to better interpret findings, particularly when FST analyses convey insufficient information for robust inference. With improved measures, FST could help identify dominant pathways of human and animal fecal contamination in communities and guide the implementation of effective interventions to safeguard health.

Urban Onsite Sanitation Upgrades and Synanthropic Flies in Maputo, Mozambique: Effects on Enteric Pathogen Infection Risks

“…However, the results clearly indicated that the shared urban onsite sanitation intervention did not dramatically reduce the QMRA-estimated infection risk from fly-contaminated foods after 1 year, and wide confidence intervals indicated the intervention may have increased the risk of infection. These results corroborate other studies of environmental fecal contamination as part of the MapSan trial during the 12- and 24-month phases, which found the intervention may have had a small protective effect against some enteric pathogens in latrine entrance soils, but levels of fecal contamination remained high post-intervention. While the intervention was associated with a reduction in fly counts at latrine entrances, we observed no difference at food preparation areas, which is where fly contact with food is more likely to occur.…”

Influence of sanitation facilities on diarrhea prevalence among children aged below 5 years in flood-prone areas of Bangladesh: A multilevel analysis

“…This study showed that shared sanitation facilities were positively associated with diarrhea prevalence in both Models I and II, supporting the JMP ladder, which stated that shared sanitation facilities considered limited sanitation services rather than improved services (UNICEF and WHO 2019). Studies examining the Mapsan trial have shown that improving shared sanitation facilities prevents human fecal contamination in target communities (Holcomb et al 2020(Holcomb et al , 2021. The diarrhea prevalence rate among households with children < 5 years of age and shared sanitation facilities was signi cantly higher than that in households with non-shared facilities (Fuller et al 2014).…”

Long-term impacts of an urban sanitation intervention on enteric pathogens in children in Maputo city, Mozambique: study protocol for a cross-sectional follow-up to the Maputo Sanitation (MapSan) trial five years post-intervention

“…We are sampling environmental compartments at a randomly selected subset of 100 intervention and 100 control compounds to represent compound-and household-level exposures [37]. At the entrance to the compound latrine we collect soil, flies, and a large volume air sample, as well as fecal sludge from the latrine or septic tank and any animal feces observed in the shared outdoor space [49,50,56,57]. One household is selected at random among the households in the compound with children enrolled in the child health study, from which we collect swabs of flooring at the household entrance, flies in cooking area, prepared child's food, stored drinking water, and water from the household's primary source [52,58,59].…”

“…Furthermore, overall pathogen prevalence, pathogen counts, E. coli gene copy density, and the individual prevalence of Ascaris and pathogenic E. coli were all significantly reduced in soil at the intervention latrine entrance [50,51], suggesting the intervention effectively contained human excreta. While animals have been implicated as major sources of pathogen exposure in other settings [52], only companion animals were frequently present at study households and a locally validated indicator of poultry fecal contamination (the most commonly observed non-companion animal type) was rarely detected in household environments [53].…”

“…While animals have been implicated as major sources of pathogen exposure in other settings [51], only companion animals were frequently present at study households and a locally validated indicator of poultry fecal contamination (the most commonly observed non-companion animal type) was rarely detected in household environments [52]. Conversely, indicators of human fecal contamination were widespread [50] and the two pathogens most impacted by the intervention-Shigella and Trichuris-are considered anthroponotic [53], suggesting that human excreta was a primary source of enteric pathogens in this dense, urban setting and that humanassociated pathogens were impacted by sustained exposure to the intervention. Enteric pathogen carriage is highly age-dependent [8,12], but we were previously limited by the timing of our follow-up survey (24 months post-intervention) to children under two years of age when assessing impacts on those born into the intervention.…”