Risk factors for contracting watery diarrhoea in Kadoma City, Zimbabwe, 2011: a case control study

BACKGROUND: Kadoma City experienced an increase in watery diarrhoea from 27 cases during week beginning 5(th) September, to 107 cases during week beginning 26(th) September 2011. The weekly diarrhoea cases crossed the threshold action line during week beginning 5(th) September at the children’s clinic in Rimuka Township, and the remaining four clinics reported cases crossing threshold action lines between week beginning 12(th) September and week beginning 26(th) September. Eighty-two percent of the cases were children less than 5 years old. We conducted a case controlstudy to determine risk factorsfor contracting watery diarrhoea in children less than 5 years in Kadoma City. METHODS: An unmatched 1:1 case control study was conducted in Ngezi and Rimuka townships in Kadoma City, Zimbabwe. A case was a child less than 5 years old, who developed acute watery diarrhoea between 5(th) September and 1(st) October 2011. A control was a child less than 5 years old who stayed in the same township and did not suffer from diarrhoea. A structured questionnaire was administered to caregivers of cases and controls.Laboratory water quality tests and stool test results were reviewed.Epi Info™ statistical software was used to analyse data. RESULTS: A total of 109 cases and 109 controls were enrolled. Independent protective factors were: having been exclusively breastfed for six months [AOR = 0.44; 95% CI (0.24-0.82)]; using municipal water [AOR = 0.38; 95% CI (0.18-0.80)]; using aqua tablets, [AOR = 0.49; 95% CI (0.26–0.94)] and; storing water in closed containers, [AOR = 0.24; 95% CI (0.07–0.0.83). The only independent risk factor for contracting watery diarrhoea was hand washing in a single bowl, [AOR = 2.89; 95% CI (1.33–6.28)]. Salmonella, Shigella, Rotavirus, and Enteropathogenic Escherichia coli were isolated in the stool specimens. None of the 33 municipal water samples tested showed contamination with Escherichia coli, whilst 23 of 44 (52%) shallow well water samples and 3 of 15(20%) borehole water samples tested were positive for Escherichia coli. CONCLUSIONS: The outbreak resulted from inadequate clean water and use of contaminated water. Evidence from this study was used to guide public health response to the outbreak.