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We report the results of a randomized controlled intervention study (September 2007 to March 2009) investigating the effect of solar disinfection (SODIS) of drinking water on the incidence of dysentery, nondysentery diarrhea, and anthropometric measurements of height and weight among children of age 6 months to 5 years living in peri-urban and rural communities in Nakuru, Kenya. We compared 555 children in 404 households using SODIS with 534 children in 361 households with no intervention. Dysentery was recorded using a pictorial diary. Incidence rate ratios (IRR) for both number of days and episodes of dysentery and nondysentery diarrhea were significantly (P0.001) reduced by use of solar disinfection: dysentery days IRR = 0.56 (95% CI 0.40 to 0.79); dysentery episodes IRR = 0.55 (95% CI 0.42 to 0.73); nondysentery days IRR = 0.70 (95% CI 0.59 to 0.84); nondysentery episodes IRR = 0.73 (95% CI 0.63 to 0.84). Anthropometry measurements of weight and height showed median height-for-age was significantly increased in those on SODIS, corresponding to an average of 0.8 cm over a 1-year period over the group as a whole (95% CI 0.7 to 1.6 cm, P = 0.031). Median weight-for-age was higher in those on SODIS, corresponding to a 0.23 kg difference in weight over the same period; however, the confidence interval spanned zero and the effect fell short of statistical significance (95% CI -0.02 to 0.47 kg, P = 0.068). SODIS and control households did not differ in the microbial quality of their untreated household water over the follow-up period (P = 0.119), but E. coli concentrations in SODIS bottles were significantly lower than those in storage containers over all follow-up visits (P0.001). This is the first trial to show evidence of the effect of SODIS on childhood anthropometry, compared with children in the control group and should alleviate concerns expressed by some commentators that the lower rates of dysentery associated with SODIS are the product of biased reporting rather than reflective of genuinely decreased incidence.

Solar disinfection (SODIS) effectively improves the microbial quality of drinking water for preventing diarrhea; however, the effect of participant motivation has not been studied. This 1-year randomized controlled trial investigated the effect of SODIS of drinking water and motivation on the incidence of dysentery and nondysentery diarrhea among children of age 6 months to 5 years living in periurban communities in South Africa.We compared 383 children in 297 households using SODIS with 335 children in 267 households with no intervention. At baseline 62.4% of the study households had stored water which met World Health Organization guidelines for zero thermotolerant coliforms per 100 mL. Dysentery was recorded using a pictorial diary. Incidence of dysentery was significantly associated with higher motivation, defined as 75% or better completion of diarrhea data. Incidence rates were lower in those drinking solar disinfected water (incidence rate ratio 0.64, 95% CI 0.39 - 1.0, P = 0.071) but not statistically significant. Compared with the control, participants with higher motivation achieved a significant reduction in dysentery (incidence rate ratio 0.36, 95% CI 0.16 - 0.81, P = 0.014). However, there was no significant reduction in risk at lower levels of motivation. Solar disinfection was not significantly associated with nondysentery diarrhea risk overall (P = 0.419). A statistically significant reduction in dysentery was achieved only in households with higher motivation, showing that motivation is a significant determinant for measurable health gains. Failure of three-quarters of participants to achieve a significant reduction in dysentery suggests that research into effective implementation is required.