The contribution of comparative genomics to health geography research: A case study on the identification of sites at which M. ulcerans contamination occurs in Benin.

We report here a significant advance in research into Buruli ulcer, a skin disease caused by an environmental bacterium (Mycobacterium ulcerans). We demonstrate the utility of crossed analyses of comparative genomics and geographic data to improve our understanding of the spatial dynamics of this disease and to identify potential sites of contamination with greater precision. An analysis of patient isolates from the endemic region Ouémé-Plateau (Benin) led to the detection, of a spatial clustering of three specific genotypes. It suggests the existence of different ecological reservoirs or particular environmental conditions favoring the restriction of the bacterium to particular areas with very tight geographic boundaries. A health geography survey was performed on patients infected with these genotypes, based on a method developed by our team: a detailed interview concerning the patient's place of residence, followed by a commented tour on foot of the sites mentioned, with the patient. All the sites visited were geolocalized by GPS. A cross-analysis of spatial and comparative genomics data led to identify zones frequented by multiple patients potentially linked to exposure to the bacterium. This mixed dynamic research approach, pave the way for a better understanding of M. ulcerans transmission and for improving preventive strategies.