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

IntroductionWe previously assessed the effect of an onsite sanitation intervention in informal neighborhoods of urban Maputo, Mozambique on enteric pathogen detection in children after two years of follow-up (Maputo Sanitation [MapSan] trial, clinicaltrials.gov: NCT02362932). We found significant reductions in Shigella and Trichuris prevalence but only among children born after the intervention was delivered. In this study, we assess the health impacts of the sanitation intervention after five years among children born into study households post-intervention.Methods and analysisWe are conducting a cross-sectional household study of enteric pathogen detection in child stool and the environment in the 16 MapSan study neighborhoods at compounds (household clusters sharing sanitation and outdoor living space) that received the pour-flush toilet and septic tank intervention at least five years prior or meet the original criteria for trial control sites. We are enrolling at least 400 children (ages 29 days-60 months) in each treatment arm. Our primary outcome is the prevalence of 22 bacterial, protozoan, and soil transmitted helminth (STH) enteric pathogens in child stool using the pooled odds ratio across the outcome set to assess the intervention effect. Secondary outcomes include the individual pathogen detection prevalence and gene copy density of 27 enteric pathogens (including viruses); mean height-for-age (HAZ), weight-for-age (WAZ), and weight-for-height (WHZ) z-scores; prevalence of stunting, underweight, and wasting; and the 7-day period-prevalence of caregiver-reported diarrhea. All analyses are adjusted for pre-specified covariates and examined for effect measure modification by age. Environmental samples from study households and the public domain are assessed for pathogens and fecal indicators to explore environmental exposures and monitor disease transmission.Ethics and disseminationStudy protocols have been reviewed and approved by human subjects review boards at the Ministry of Health, Republic of Mozambique and the University of North Carolina at Chapel Hill. De-identified study data will be deposited at https://osf.io/e7pvk/.Trial registration numberISRCTN86084138STRENGTHS AND LIMITATIONS OF THIS STUDYFollow-up to the first controlled health impact trial of an urban on-site sanitation intervention after at least 5 years of intervention conditions. Previous studies have focused on WASH intervention impacts up to 2-3 years after delivery, which may be insufficient time to realize impacts.Primary study endpoint is molecular detection of multiple enteric pathogens in child stool, which unambiguously indicates previous exposure to specific sanitation-related pathogens; enteric pathogens are also assessed across multiple environmental compartments to explore environmental exposures and monitor disease transmission.Primary outcome is the overall impact of the intervention on enteric pathogen exposure using a novel pooled estimate of the treatment effect across a pre-specified set of enteric pathogens.As an observational evaluation of an existing intervention, sample size is constrained by the number of eligible children residing at study sites and selection bias arising from differential enteric pathogen-related mortality may be present, particularly among older age groups.As a cross-sectional study, there is potential for confounding bias in our estimates of the intervention impacts on child health; in particular, the presence of the intervention itself may have influenced the desirability of the intervention sites and thus the socioeconomic status of their residents, which may be associated with increased pathogen exposures.