Quantitative microbial risk assessment related to urban wastewater and lagoon water reuse in Abidjan, Côte d'Ivoire

We assessed the infection risks related to the use of wastewater in Abidjan, Côte d'Ivoire, by using quantitative microbial risk assessment (QMRA). Giardia lamblia and Escherichia coli were isolated and identified in wastewater samples from the canal and lagoon. The exposure assessment was conducted using a cross-sectional survey by questionnaire with 150 individuals who were in contact with the wastewater during their daily activities of swimming, fishing, washing, and collecting materials for reuse. Risk was characterised using the Monte Carlo simulation with 10,000 iterations. Results showed high contamination of water by G. lamblia and E. coli (12.8 CFU/100 mL to 2.97 × 10(4)CFU/100 mL and from 0 cyst/L to 18.5 cysts/L, respectively). Estimates of yearly average infection risks for E. coli (90.07-99.90%, assuming that 8% of E. coli were E. coli O157:H7) and G. lamblia (9.4-34.78%) were much higher than the acceptable risk (10(-4)). These results suggest the need for wastewater treatment plants, raising awareness in the population in contact with urban wastewater and lagoon water. Our study also showed that QMRA is appropriate to study health risks in settings with limited data and budget resources.