Abstract

Case-patients for a retrospective epidemiological cum microbiological study in Njoro Town, Kenya were selected after self-report of waterborne illness within 7 days of exposure through drinking water. Controls were matched for location, household income and type of drinking water source. Households with piped water in one high-income district reported considerably lower illness rates compared to unconnected households in two low-income districts. Analysis of the ORs identified water from the stream to be associated with the highest risk of illness (OR=3.95, p=0.03) compared to untreated rainwater (OR=2.45, p=0.02), untreated water from boreholes (OR=1.90, p=0.02) or treated water from any source (OR=0.62, p=0.01). Bacteria densities in water obtained from the stream were generally 1–3 log units higher compared to other sources, staying within 3–4 log units for HPC (cfu/ml) and TC (cfu/100 ml), 2–3 log units (cfu/100 ml) for Escherichia coli and intestinal enterococci and within 1 log unit (cfu/100 ml) for Salmonella. Several confounding risk factors other than contaminated water were identified. Their detection for over 50 % of all illness cases was significant. It was concluded that the importance of drinking water quality as the most likely source of endemic waterborne illness in the community may have been previously overestimated. Therefore, interventions on water supply in the town should include strategies that address confounding risk factors, especially, poor hygiene and occupational hazards, as well as piped water distribution to low-income households.