Associations between fecal contamination of the household environment and enteric pathogen detection in children living in Maputo, Mozambique

Abstract

Environmental exposure to enteric pathogens is generally assessed using fecal indicators but relationships between markers of fecal contamination and actual exposure to enteric pathogens remain poorly characterized. We investigated whether Escherichia coli and two human fecal markers (HF183 and Mnif) in urban Mozambican household soil and drinking water were associated with detection in child stool of eight bacteria, three viruses, and three protozoa measured by multiplex reverse-transcription PCR and soil transmitted helminths assessed by microscopy. We used mixed-effects logistic regression with marginal standardization to obtain a pooled estimate of the overall indicator-pathogen relationship while simultaneously estimating pathogen-specific associations that accounted for assessing multiple pathogens per sample. At least one pathogen was detected in 88% (169/192) of child stools. Increasing drinking water E. coli gene concentration was associated with higher Ascaris prevalence, while human HF183 in drinking water was weakly associated with lower prevalence of the most common pathogens but was infrequently detected. No fecal marker in soil was clearly associated with any pathogen. We did not find evidence to support human markers as reliable indicators of enteric pathogen carriage in a high-prevalence domestic setting and recommend targeting enteric pathogens directly.

Keywords: Bayesian g-formula; Water, sanitation, and hygiene (WASH); diarrhea; enteric disease; helminthiasis; marginal standardization; microbial source tracking (MST); molecular pathogen detection.

Figure 1.

Mean and 95% CI marginal prevalence ratio estimates (horizontal axis) of diarrhea and of enteric pathogens in stool (vertical axis) for a ten-fold increase in E. coli concentration (left-two columns) or detection of a human fecal marker (right-two columns) in household stored water (top panel) and domestic soil (bottom panel). Percentages in parentheses correspond to the detection frequency for each fecal marker and outcome, with color indicating the outcome class.