Impact of Home-based Solar Water Disinfection (SODIS) on child diarrhoea in a community-randomized evaluation in Bolivia: Does Drinking up Result in Health up?

Background: Solar drinking water disinfection is a low-cost, point-of-use water purification method disseminated globally. SODIS is highly efficacious in inactivating waterborne pathogens. Previous field studies provided limited evidence for its effectiveness in reducing diarrhoea.

Methods: We conducted a community-randomized trial in 22 rural Bolivian communities to evaluate the effect of SODIS to reduce diarrhoea among children <5. A local NGO conducted a standardised interactive SODIS-promotion campaign in 11 communities targeted at households, communities and primary schools. Mothers completed a daily child health diary for one year.

Results: Within the intervention arm 225 households (376 children) were trained to expose water-filled polyethyleneteraphtalate bottles to sunlight. Eleven communities (200 households, 349 children) served as a control. We recorded 166'971 person-days of observation during the trial representing 80% of the total possible person-days of child observation in intervention and control arms. Mean compliance with SODIS was 32.1%.The reported incidence rate of gastrointestinal illness in children in the intervention arm was 3.6 compared to 4.3 episodes/year-at-risk in the control arm. The relative rate of diarrhoea adjusted for intracluster correlation was 0.81 (95%-CI 0.59-1.12).

Conclusions: Despite an extensive SODIS campaign we found only a moderate compliance with the intervention and detected no significant reduction in child diarrhoea. These results suggest that better evidence is needed of how the well-established laboratory efficacy of this home-based water treatment method translates into field effectiveness under various cultural settings and intervention intensities. Further global promotion of SODIS for general use should be undertaken with care until such evidence is available.