Bacterial water pollution and diarrheal diseases in West Africa

In 2017, diarrheal diseases were responsible for 1.57 million deaths, including 606 024 deaths in Sub-Saharan Africa. This situation is due to domestic use of polluted surface waters, deficits in hygiene, access to healthcare and drinking water, and to weak environmental and health monitoring infrastructures. Moreover, climate change is expected to impact water resources by boosting the presence, dissemination and transmission of pathogens. Finally, Sub-Saharan Africa is undergoing major changes in terms of land uses, and demographic growth especially in rural areas.

Escherichia coli (E. coli) is an indicator for the enteric pathogens that cause many diarrheal diseases. This case study, carried out Bagre Reservoir, aims at filling the knowledge gap by analyzing the environmental variables that play a role in the dynamics of E. coli, and cases of diarrhea in West Africa.

Samples of surface water were routinely collected to measure E. coli, enterococci and suspended particulate matter (SPM) at a monitoring point (Kapore) during one year. In addition, satellite data were used to estimate precipitation, water level, Normalized Difference Vegetation Index (NDVI) and SPM. Monthly epidemiological data for cases of diarrhea from three health centers were also collected and compared with microbiological and environmental data.

A positive correlation between E. coli and enterococci in surface waters was found indicating that E. coli is an acceptable indicator of fecal contamination in this region.

E. coli and diarrheal diseases were strongly correlated with monsoonal precipitation, in situ SPM, and Near Infra-Red (NIR) band between March and November. Partial least squares regression showed that E. coli concentration was strongly associated with precipitation, Sentinel-2 reflectance in the NIR and SPM, and that the cases of diarrhea were strongly associated with precipitation, NIR, E. coli, SPM, and to a lesser extent with NDVI.

Moreover, E. coli dynamics were reproduced using satellite data alone, particularly from February to mid-December (R² = 0.60) as were cases of diarrhea throughout the year (R² = 0.76). This implies that tele-epidemiology approach through the use of satellite data could provide an important contribution to water quality monitoring, and thus contribute to the establishment of warning systems.