Longitudinal Effects of a Sanitation Intervention on Environmental Fecal Contamination in a Cluster-Randomized Controlled Trial in Rural Bangladesh

Abstract

Household latrine access generally is not associated with reduced fecal contamination in the environment, but its long-term effectiveness has not been measured. We conducted an environmental assessment nested within the WASH Benefits Bangladesh randomized controlled trial (NCT01590095). We quantified E. coli and fecal coliforms in samples of stored drinking water, child hands, mother hands, soil, and food among a random sample of households from the sanitation and control arms of the trial. Samples were collected during eight quarterly visits approximately 1–3.5 years after intervention initiation. Overall, there were no substantial differences in environmental fecal contamination between households enrolled in the sanitation and control arms. Statistically significant reductions were found in stored water and child hands after pooling across sampling rounds, but the effects were small and not consistent across rounds. In addition, we assessed potential effect modification of intervention effects by follow-up time, season, wealth, community-level latrine density and coverage, population density, and domestic animal ownership. While the intervention had statistically significant effects within some subgroups, there were no consistent patterns of effect modification. Our findings support a growing consensus that on-site latrines are insufficient to prevent fecal contamination in the rural household environment.

Effectiveness of interventions to improve drinking water, sanitation, and handwashing with soap on risk of diarrhoeal disease in children in low-income and middle-income settings: a systematic review and meta-analysis

“…Interventions providing basic sanitation services might not be able to sufficiently reduce faecal environmental contamination. 96 , 97 , 98 , 99 When considering basic sanitation, there was no evidence that risk of diarrhoea was associated with the level of community coverage ( appendix 2 p 13 ). This finding could be due to how basic sanitation interventions often fail to adequately isolate excreta from the environment and due to human exposures at different stages along the sanitation chain, from containment to emptying, conveyance, treatment, and disposal or reuse.…”

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

“…71 A cluster-randomized trial in rural Bangladesh likewise found scant evidence of reductions in culturable E. coli concentrations from sanitation improvements. 72,73 Latrine provision also did not reduce the prevalence of pathogenic E. coli genes in soil, meaning neither culture-nor molecular-based measurements of soil E. coli were affected. 39 Other recent trials have not assessed intervention impacts on fecal contamination of soil, but several have evaluated contamination of drinking water, with some also testing child hands, food, or fomites.…”

“…A cluster-randomized trial in rural Bangladesh likewise found scant evidence of reductions in culturable E. coli concentrations from sanitation improvements. , Latrine provision also did not reduce the prevalence of pathogenic E. coli genes in soil, meaning neither culture- nor molecular-based measurements of soil E.…”

“…coli concentrations in rural Bangladesh, collected at eight timepoints over 2.5 years from 720 households, demonstrates the advantages of maximizing the number of basic measurements across time. Although pooled estimates from certain sample types achieved statistical significance, the sheer quantity of information available convincingly demonstrated the lack of physically meaningful sanitation intervention impacts on ambient fecal contamination …”

Impacts of an urban sanitation intervention on fecal indicators and the prevalence of human fecal contamination in Mozambique

“…Although pooled estimates from certain sample types achieved statistical significance, the sheer quantity of information available convincingly demonstrated the lack of a physically meaningful sanitation intervention impacts on ambient fecal contamination. 73 Many have speculated that sanitation's apparent lack of effect may be due in part to animal fecal contamination. 12,22 Animal feces often contain pathogens capable of infecting humans and animal fecal biomass in domestic environments is estimated to far exceed that from humans.…”