Chrysops silacea and C. dimidiata : fly densities and infection rates with Loa loa in the Chaillu mountains, Congo Republic

The densities, infection rates with #Loa loa, and parous rates of #Chrysops silacea and #C. dimidiata were studied in various ecological zones throughout the Chaillu mountains in the People's Republic of the Congo. In the rainy season, #C. dimidiata was the major vector in the forest, whereas #C. silacea was predominant in the cleared forest zones. Fly densities were higher in the forest (natural forest or palm-grove) than in the villages. Parous and infection rates varied according to the ecological zone. The infection rate of parous females was related to the microfilarial rate in the human population, indicating that the #Chrysops populations were extremely stable in the rainy season. (Résumé d'auteur

Trypanosoma cruzi: adaptation to its vectors and its hosts

American trypanosomiasis is a parasitic zoonosis that occurs throughout Latin America. The etiological agent, Trypanosoma cruzi, is able to infect almost all tissues of its mammalian hosts and spreads in the environment in multifarious transmission cycles that may or not be connected. This biological plasticity, which is probably the result of the considerable heterogeneity of the taxon, exemplifies a successful adaptation of a parasite resulting in distinct outcomes of infection and a complex epidemiological pattern. In the 1990s, most endemic countries strengthened national control programs to interrupt the transmission of this parasite to humans. However, many obstacles remain to the effective control of the disease. Current knowledge of the different components involved in elaborate system that is American trypanosomiasis (the protozoan parasite T. cruzi, vectors Triatominae and the many reservoirs of infection), as well as the interactions existing within the system, is still incomplete. The Triatominae probably evolve from predatory reduvids in response to the availability of vertebrate food source. However, the basic mechanisms of adaptation of some of them to artificial ecotopes remain poorly understood. Nevertheless, these adaptations seem to be associated with a behavioral plasticity, a reduction in the genetic repertoire and increasing developmental instability