Sanitary inspection and microbial health risks associated with enteric bacteria in groundwater sources in Ilara-Mokin and Ibule-Soro, Nigeria

Sanitary inspection and quantitative microbial risk assessment (QMRA) are complementary tools that provide comprehensive risk-based assessment of drinking water quality. This study set out to determine the sanitary risk scores and microbial health risks associated with wells and boreholes in Ilara-Mokin and Ibule-Soro, Nigeria. Water samples were collected over a period of 5 months and sanitary inspection forms were used to determine the sanitary risk scores. The risks of infections were estimated using dose-response models. The sanitary risk scores revealed ‘medium’ and ‘low’ overall risks for the wells and boreholes, respectively. Three risk factors exhibited a highly significant (p < 0.01) association with the presence of Escherichia coli and faecal coliforms in water samples from the wells. E. coli and Salmonella ranged from 1.82 to 2.28 and 2.15 to 2.63 log₁₀ CFU/100 ml, respectively, in water from the wells but were below the detection limit in water from the boreholes. Estimated risks of infection associated with Shigella (2.1 × 10⁻² to 2.3 × 10⁻¹) were higher than Campylobacter (6.7 × 10⁻² to 1.9 × 10⁻¹) and Salmonella (1.9 × 10³ to 5.6 × 10⁻³). Adoption of water safety plans may be advantageous in these settings, since intentional ingestion of water from the wells and boreholes may pose potential risks of diarrhoeal illness to humans.

• Sanitary risks and water samples were collected from wells and boreholes.

• Microbial risk assessment was used to evaluate human dose-response data.

• Sanitary risk scores correlated positively with microbial water quality.

• Risk factors exhibited significant association with the presence of E. coli.

• Estimated risks of infection associated with Shigella were higher than those of Campylobacter and Salmonella.