Punaises aquatiques du Cameroun : Biodiversité, phylogéographie et rôle dans l’écologie de Mycobacterium ulcerans, agent étiologique de l’ulcère de Buruli

Abstract

One of 17 neglected tropical diseases declared by WHO, Buruli ulcer is now a real public health problem in Central and West Africa, where it occurs in nearly 30 countries. This disease mainly affecting people in remote areas remains a myth because we don't know today the exact mode of Mycobacterium ulcerans transmission, the causal agent to humans. A better understanding of the ecology of this bacillus is an important lever to make the information about its transmission as the fight against this scourge. Strongly suspected to playing a role of host or vector of M. ulcerans, some aquatic bugs’ taxa seem to be predisposed by their ecology or behavior to harbor the bacillus or to convey it. The works presented here are intended firstly to identify on anatomical bases complemented by molecular approaches different taxa of aquatic bugs present in Cameroon. Beyond proposing an identification key of taxa and classification of aquatic bugs in Cameroon based on the nucleotide sequences, we discuss the important role of the ecology of some taxa of aquatic bugs in the transmission of M. ulcerans. Different comparative and biostatistics approaches developed in this thesis support the hypothesis that some taxa of water bugs, especially from the Belostomatidae and Naucoridae families acquire the mycobacteria from the environment by sharing habitats (attendance of emerged aquatic vegetation) where the bacilli proliferate, and feeding on prey such as molluscs and small fish themselves contaminated with the bacteria. The flight capacity of aquatic bugs do not appear to facilitate the acquisition of M. ulcerans but seems to be involved in their dissemination by contaminating new the environments. At the end of this thesis, we discuss the ecology of aquatic bugs’ communities and their macroecology in Cameroon, and examine the importance of sampling as an important component of any research work in ecology and evolution of infectious diseases.