Quantitative Microbial Risk Assessment of Pediatric Infections Attributable to Ingestion of Fecally Contaminated Domestic Soils in Low-Income Urban Maputo, Mozambique.

Rigorous studies of water, sanitation, and hygiene interventions in low- and middle-income countries (LMICs) suggest that children are exposed to enteric pathogens via multiple interacting pathways, including soil ingestion. In 30 compounds (household clusters) in low-income urban Maputo, Mozambique, we cultured and quantified gene targets from soils (: , / (EIEC): , : ) using droplet digital PCR at three compound locations (latrine entrance, solid waste area, dishwashing area). We found that 88% of samples were positive for culturable (mean = 3.2 log CFUs per gram of dry soil), 100% for molecular (mean = 5.9 log gene copies per gram of dry soil), 44% for (mean = 2.5 log), and 41% for (mean = 2.1 log). Performing stochastic quantitative microbial risk assessment using soil ingestion parameters from an LMIC setting for children 12-23 months old, we estimated that the median annual infection risk by was 7100-fold (71% annual infection risk) and by /EIEC was 4000-fold (40% annual infection risk) greater than the EPA's standard for drinking water. Compounds in Maputo, and similar settings, require contact and source control strategies to reduce the ingestion of contaminated soil and achieve acceptable levels of risk.