Environmental determinants ofE. coli, link with the diarrheal diseases, and indication of vulnerability criteria in tropical area (Kapore, Burkina Faso)
Authors: Robert Elodie , Grippa Manuela , Nikiema Dayangnéwendé Edwige , Kergoat Laurent , Koudougou Hamidou , Auda Yves , Rochelle-Newall Emma 
Published: April 2021

In 2017, diarrheal diseases were responsible for 606 024 deaths in Sub-Saharan Africa. This situation is due to domestic and recreational use of polluted surface waters, deficits in hygiene, access to healthcare and drinking water, and to weak environmental and health monitoring infrastructures.

Escherichia coli(E. coli) is an indicator for the enteric pathogens that cause many diarrheal diseases. The links betweenE. coli, diarrheal diseases and environmental parameters have not received much attention in West Africa, and few studies have assessed health risks by taking into account hazards and socio-health vulnerabilities. This case study, carried out in Burkina Faso (Bagre Reservoir), aims at filling this knowledge gap by analyzing the environmental variables that play a role in the dynamics ofE. coli, cases of diarrhea, and by identifying initial criteria of vulnerabilities. A particular focus is given to satellite-derived parameters to assess whether remote sensing can provide a useful tool to assess health hazard.

Samples of surface water were routinely collected to measureE. 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. Finally, semi-structured interviews were carried out to document the use of water resources, contacts with elements of the hydrographic network, health behaviors and conditions, and water and health policy and prevention in order to identify the initial vulnerability criteria.

A positive correlation betweenE. coliand enterococci in surface waters was found indicating thatE. coliis an acceptable indicator of fecal contamination in this region.

E. coliand 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 thatE. coliconcentration 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, the use of satellite data alone allowed to reproduce the dynamics ofE. coli, particularly from February to mid-December (R²= 0.60) and those of cases of diarrhea throughout the year (R²= 0.76). This implies that satellite data could provide an important contribution to water quality monitoring.

Finally, the vulnerability of the population is found to increase during the rainy season due to reduced accessibility to healthcare and drinking water sources and increased use of water of poor quality. At this period, surface water is used because it is close to habitations, free and easy to use irrespective of monetary or political constraints. This vulnerability particularly impacts the Fulani, whose concessions are often close to surface water (river, lake) and far from health centers, a situation aggravated by marginality.

Author summary

In 2017, diarrheal diseases were responsible for 1.57 million deaths, principally in Sub-Saharan Africa. Many diarrheal diseases are caused by the presence of enteric pathogens in surface water includingEscherichia coli (E. coli), a frequently used indicator of the presence of these pathogens. Yet, few studies have been carried out in West Africa to verify this link or to study the relationship between diarrheal diseases,E. coliand environmental parameters. These diarrheal diseases also depend on socio-health vulnerabilities. This case study addresses the dynamics ofE. colialong with another fecal indicator bacteria, enterococci, as well as diarrheal diseases (from three health centers) and socio-health vulnerability (from three villages and Fulani settlements) and their relationship with hydro-meteorological parameters derivable by satellite. The study site is located in the Bagre reservoir in Burkina Faso where Suspended Particulate Matter (SPM) andE. coliwere monitored over one year. Water was generally polluted by bacteria of fecal origin throughout the year and more so during the rainy season. We observed a significant relationship betweenE. coliand enterococci.E. coliconcentrations were strongly correlated to, and predicted by, precipitation, satellite reflectance in the NIR band by Sentinel-2, and SPM measured in-situ. Diarrheal diseases were also strongly correlated with these variables as well asE. coli. Vulnerability of the population to diarrhea increases during the rainy season. The microbiological health risk is more important during the rainy season, from June to September, and especially concerns the Fulani settlements.