Effects of water, sanitation, and hygiene interventions on detection of enteropathogens and host-specific faecal markers in the environment: a systematic review and individual participant data meta-analysis

• Authors: Andrew Mertens, University of California Berkeley; Benjamin F Arnold, University of California San Francisco; Jade Benjamin-Chung, Stanford University; Alexandria B Boehm, Stanford University; Joe Brown, University of North Carolina; Drew Capone, Indiana University Bloomington; Thomas Clasen, Emory University; Erica Fuhrmeister, University of Washington; Jessica A Grembi, Stanford University; David Holcomb, University of North Carolina; Jackie Knee, London School of Tropical Medicine & Hygiene, London, UK; Laura H Kwong, University of California Berkeley; Audrie Lin, Pennsylvania State University; Stephen P Luby, Stanford University; Rassul Nala, Instituto Nacional de Saúde Maputo; Kara Nelson, University of California Berkeley; Sammy M Njenga, Kenya Medical Research Institute; Clair Null, Mathematica, Princeton; Amy J Pickering, University of California Berkeley; Mahbubur Rahman, Infectious Diseases Division; Heather E Reese, Emory University; Lauren Steinbaum, University of Georgia; Jill Stewart, University of North Carolina; Ruwan Thilakaratne, University of California Berkeley; Oliver Cumming, London Sch Trop Med & Hyg; John M Colford, University of California Berkeley; Ayse Ercumen, North Carolina State University
• Journal Title: LANCET PLANETARY HEALTH
• Volume: Volume 7, Number 3
• Publisher: ELSEVIER SCI LTD | 2023-03-01, Pages E197-E208
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1016/S2542-5196(23)00028-1
• Subjects: Health Sciences, Public Health; Health Sciences, Epidemiology; Environmental Sciences
• Keywords: Science & Technology; Life Sciences & Biomedicine; Environmental Sciences; Public, Environmental & Occupational Health; Environmental Sciences & Ecology; NUTRITIONAL INTERVENTIONS; ESCHERICHIA-COLI; DRINKING-WATER; CHILD GROWTH; QUALITY; DIARRHEA; SOIL; CONTAMINATION; TRANSMISSION; VARIABILITY

Abstract

Background: Water, sanitation, and hygiene (WASH) improvements are promoted to reduce diarrhoea in low-income countries. However, trials from the past 5 years have found mixed effects of household-level and community-level WASH interventions on child health. Measuring pathogens and host-specific faecal markers in the environment can help investigate causal pathways between WASH and health by quantifying whether and by how much interventions reduce environmental exposure to enteric pathogens and faecal contamination from human and different animal sources. We aimed to assess the effects of WASH interventions on enteropathogens and microbial source tracking (MST) markers in environmental samples. Methods: We did a systematic review and individual participant data meta-analysis, which included searches from Jan 1, 2000, to Jan 5, 2023, from PubMed, Embase, CAB Direct Global Health, Agricultural and Environmental Science Database, Web of Science, and Scopus, of prospective studies with water, sanitation, or hygiene interventions and concurrent control group that measured pathogens or MST markers in environmental samples and measured child anthropometry, diarrhoea, or pathogen-specific infections. We used covariate-adjusted regression models with robust standard errors to estimate study-specific intervention effects and pooled effect estimates across studies using random-effects models. Findings: Few trials have measured the effect of sanitation interventions on pathogens and MST markers in the environment and they mostly focused on onsite sanitation. We extracted individual participant data on nine environmental assessments from five eligible trials. Environmental sampling included drinking water, hand rinses, soil, and flies. Interventions were consistently associated with reduced pathogen detection in the environment but effect estimates in most individual studies could not be distinguished from chance. Pooled across studies, we found a small reduction in the prevalence of any pathogen in any sample type (pooled prevalence ratio [PR] 0·94 [95% CI 0·90–0·99]). Interventions had no effect on the prevalence of MST markers from humans (pooled PR 1·00 [95% CI 0·88–1·13]) or animals (pooled PR 1·00 [95% CI 0·97–1·03]). Interpretation: The small effect of these sanitation interventions on pathogen detection and absence of effects on human or animal faecal markers are consistent with the small or null health effects previously reported in these trials. Our findings suggest that the basic sanitation interventions implemented in these studies did not contain human waste and did not adequately reduce exposure to enteropathogens in the environment. Funding: Bill and Melinda Gates Foundation and the UK Foreign and Commonwealth Development Office.