Effects of local handwashing agents on microbial contamination of the hands in a rural setting in Northwest Ethiopia: a cluster randomised controlled trial

OBJECTIVE: To evaluate the effectiveness of handwashing with water and wood ash in reducing faecal contamination of the hands. DESIGN: A cluster randomised controlled trial was employed with two arms: handwashing with water and wood ash versus handwashing with water alone. SETTING: Rural households of East Dembiya District, Central Gondar Zone, Amhara National Regional State, Ethiopia. PARTICIPANTS: 440 mothers and caregivers of children younger than 5 years assigned (1:1, 220 in each group) in clusters, with buffer zones between each cluster. INTERVENTION: Health education on effective handwashing was given to the intervention and control groups. Participants in the intervention group used wood ash of the same quantity (ie, one closed palm). OUTCOME MEASURES: The primary outcome was microbial contamination of the hands, measured by means of Escherichia coli counts before and after handwashing. RESULTS: At baseline, 75.9% and 67.7% of the participants in the intervention and control groups, respectively, had dirt on their fingernails, and the hands of all participants in both groups were contaminated with E. coli. The mean E. coli counts recovered at baseline were 3.07 log10 colony forming unit (CFU)/swab in the intervention group and 3.03 log10 CFU/swab in the control group, while at endline it was 1.4 log10 CFU/swab in the intervention group and 3.02 log10 CFU/swab in the control group. The mean E.coli counts was reduced by 1.65 log10 due to the intervention (difference-in-differences: β= −1.65, 95% CI= −1.84 to –1.46). CONCLUSION: Two-thirds of the swab samples tested positive for E. coli after handwashing with water and wood ash, which indicates wood ash is not very effective in terms of completely removing micro-organisms on the hands. However, wood ash was significantly better than water alone in reducing the concentration of faecal coliform organisms on the hands. Local health authorities should primarily promote handwashing with soap. However, in the absence of soap, use of wood ash over water alone might be appropriate. TRIAL REGISTRATION NUMBER: PACTR202011855730652.