The effect of water, sanitation and hygiene conditions on enteric pathogen exposure and related health outcomes in vulnerable children – evidence from two trials

Gastro-intestinal infection by bacteria, viruses, protozoa and soil-transmitted helminths inflict a heavy burden of disease, especially among young children living in settings without safe water, sanitation and hygiene (WASH) services. Historically, it has been the associated diarrhoeal disease burden that has attracted most attention in global health. There is growing evidence of the harmful eIects of asymptomatic enteric pathogen carriage in early life on growth and development. It is unclear whether basic water, sanitation and hygiene interventions are suIicient to prevent exposure to these pathogens and mitigate the adverse health impacts. The aim of this thesis was to assess the eIectiveness of targeted WASH interventions in reducing enteric pathogen exposure and related health consequences in two particularly vulnerable populations.

Evidence is drawn from two randomised controlled trials of WASH interventions implemented in two diIerent settings, urban Kenya and rural Senegal. Both interventions were designed with, and delivered by, the health system with the aim of reducing enteric pathogen exposure among vulnerable children by mitigating the risk posed by environmental hazards, such as contaminated drinking water and food. In Kenya, a food hygiene intervention targeted infants in high-density informal urban neighbourhoods of the city of Kisumu. In northern Senegal, a water treatment and hygiene intervention targeted children undergoing outpatient treatment for severe acute malnutrition (SAM) in predominantly low-density rural areas of the departments ofPodor and Linguère.

There was evidence for both interventions reducing diarrhoea but there was no eIect on enteric pathogen detection in children nor on the other associated outcomes measured, most notably recovery from SAM. The burden of asymptomatic enteric infection in both populations was high and these targeted WASH interventions failed to reduce this. These two trials confirm the importance of reducing enteric pathogen exposure in vulnerable populations but suggest that such limited short-term interventions delivered by the health system are insuIicient to address this. The findings add new evidence to support the ambitious Sustainable Development Goal targets for universal access to safely managed water and sanitation services.