Toward an integrated genetic epidemiology of parasitic protozoa and other pathogens.

Due to the increase of human migrations, the appearance of emerging and reemerging endemies, growing antibiotic resistance, and climatic changes, infectious diseases most probably constitute the major challenge for medicine in the next century. The advent of molecular methods of pathogen characterization has considerably improved our knowledge of the epidemiology of these diseases. However, the use of concepts of evolutionary genetics for interpreting "molecular epidemiology" data remains limited, although the application of such methods would broaden considerably the scope of this field of research, and allow epidemiologic and taxonomic approaches to be ascertained on a much firmer basis. In turn, pathogens, hosts, and vectors provide fascinating models for basic research. The artificial character of the border between "basic" and "applied" research is especially apparent with regard to the "integrated genetic epidemiology of infectious diseases" concept. The goal of this chapter is to evaluate the respective impact, on the transmission and pathogenicity of infectious diseases, of the host's, the pathogen's, and the vector's (for vector-borne diseases) genetic diversity, and the interactions between these three parameters (coevolution phenomena).