Etude de l’introgression des génotypes de Toxoplasma gondii entre la France et l’Afrique de l’Ouest et Centrale, et son impact sur l’épidémiologie de la toxoplasmose dans ces régions

Abstract : Exploring the population structure of Toxoplasma gondii is important to understand its worldwide distribution and the determinants of its evolution. To date, in Europe and North America, most of isolated strains appeared to belong to two main weakly pathogenic clonal lineages: Types II and III. Conversely, studies from South America showed evidence for a substantial genetic diversity in this continent. Other genotypes were described in Africa. Determinants of this spatial structure are still poorly understood. Moreover, globalization of exchanges could drive rapid evolution of T. gondii population spatial structure, with unknown health outcomes. Our aim was to investigate the possible role of maritime trade in T. gondii introgressions between France and Senegal, two countries sharing a long history of trade since the 17th century. In this study, 55 isolates from Senegal were obtained by mouse bioassay from domestic fauna in two ports cities founded by French colons (Dakar and Saint-Louis) and one inland remote region (Kedougou). Genotyping using 15 microsatellite markers revealed the presence of a highly contrasting diversity between port cities and the inland Kedougou. In Saint-Louis, the common lineage Type II and a French Type II variant were predominant (23/26). In Dakar, Type II (10/22) and Type III (6/22) represented together the majority of the isolates, beside a diversity of numerously marginal African lineages and unique strains. Conversely, the highly mouse-virulent African lineage Africa 1 was predominant in Kedougou (4/6). This contrasting population structure between port cities and inland suggests a possible role of maritime trade.