Water, sanitation and hygiene interventions to combat childhood diarrhoea in developing countries

Water, sanitation and hygiene interventions to combat childhood diarrhoea in developing countries

Hugh Waddington, Birte Snilstveit, Howard White, and Lorna Fewtrell
Corresponding author email: hwaddington [at] 3ieimpact.org
August 2009
Synthetic review 001
International Initiative for Impact Evaluation (3ie).

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Summary

This report is a synthetic review of impact evaluations examining effectiveness of water, sanitation and hygiene (WSH) interventions in reducing childhood diarrhoea.

The review has been conducted to Campbell/Cochrane Collabo ration standards of systematic review, as well as employing mixed methods of data analysis to assess not only which interventions are effective, or not, but why and under what circumstances. The review provides an update of previous reviews conducted in this area, notably Fewtrell and Colford (2004).

A comprehensive search was conducted of published and unpublished materials. Studies were identified for inclusion which employed rigorous impact evaluation techniques, using experimental (randomised assignme nt) and quasi-experimental methods, and which evaluated the impact of water, sanitation and/or hygiene interventions on diarrhoea morbidity among children in low- and middle-income countries. 65 rigorous impact evaluations were identified for quantitative synthesis, covering 71 distinct interventions assessed across 130,000 children in 35 developing countries during the past three decades. Each study was coded for a range of variables relating to type of intervention, effect size and precision, internal validity (relating to evaluation quality) and external validity (relating to context and behavioural mechanisms). Interventions were grouped into five categories: water supply improvements, water quality, sanitation, hygiene and multiple interventions involving a combination of water and sanitation and/or hygiene. Data were collected and synthesised on both quantitative and qualitative information presented in the evaluations.

The results challenge the notion that water quality treatment in the household (at point -of-use) and sanitation ‘software’ (hygiene) interventions are necessarily the most efficacious and sustainable interventions for promoting reduction of diarrhoea.

While point-of-use water quality interventions appear to be highly effective – and indeed, more effective than water supply or source treatment in reducing diarrhoea – much of the evidence is from trials conducted over small populations and short time periods. More evidence is needed on sustainability, as water quality interventions conducted over longer periods tend to show smaller effectiveness, while compliance rates, and therefore impact, appear to fall markedly over time.

Hygiene interventions, particularly provision of soap for hand-washing, are effective in reducing diarrhoea morb idity, and there does not appear to be evidence that compliance falls over time. The analysis suggests that sanitation ‘hardware’ interventions are also highly effective. However, relatively few studies have been conducted in this area to-date and studies are particularly needed that quantify the possible environmental spillovers from sanitation provision.

Evidence on the combined impact of multiple interventions is mixed. Further primary studies employing factorial design – that is, comparing different interventions using multiple treatment arms – are needed for more conclusiveness on whether water and sanitation/hygiene interventions are substitutes or complements in the health production function.

The study highlights the importance of behavioural factors in determining up-take and sustainable adoption of WSH technologies. Insights from diffusion theory suggest that preventive interventions tend to be adopted more slowly as benefits are difficult to observe and users presumably discontinue treatment as they perceive that the costs of using the intervention outweigh the benefits. These problems are more relevant for interventions aiming to reduce disease prevalence which do not have additional benefits, for example time savings. Unfortunately, few impact evaluations addressing sustainability collect data on the reasons for the levels of compliance and acceptance found among beneficiaries. This information is an essential guide to fostering long-term impact.