Système vectoriel émergent dû aux populations sauvages de triatoma infestans : la maladie de chagas en Bolivie – TIBO

Approximately 10 million people are infected by Trypanosoma cruzi, the pathogen agent of Chagas disease transmitted by hematophagous bugs (Triatominae) in Latin America. The countries of the Southern Cone were the most hit by Chagas disease and the first to implement, in 1991, a control program (INCOSUR) on a regional scale. Quickly, the control strategy based on insecticide spraying directed against the main vector Triatoma infestans was successful and it is considered that, overall, the incidence of the disease has fallen of 70% for 10 years. Nevertheless, the success of control is unequally distributed according to countries and Bolivia remains, with the area of Gran Chaco, the ultimate border for T. infestans elimination. In the Southern Cone countries, the expected success of the elimination program was based on the assumption that T. infestans is an almost exclusive domestic vector. Recent fieldwork revealed that wild populations of the vector are largely widespread throughout Bolivia (Andes and Chaco) and also in neighboring countries. The occurrence of wild T. infestans populations, which could exhibit a synanthropic process, is extremely preoccupant because it could jeopardize the control efforts of the INCOSUR initiative. As a result of the INCOSUR experts recommendations, the wild T. infestans challenge is among the new OPS-OMS research priorities concerning the Chagas disease. The clarification of the epidemiological implication of T. infestans sylvatic populations is a rational approach in order to progress towards the INCOSUR goal, which is the control of the vectorial transmission in the Southern Cone countries. The main objective of the TiBO project is to know the geographical distribution of T. infestans wild populations and to evaluate the risk that they represent for the human health, by the identification of the determinants specific to the vector and the extrinsic ones (environmental, economic and sociocultural), which affect the domestic reinfestation process. The research work will be performed by IRD and Bolivian teams of different Bolivian institutions, that have had a pioneer role in the detection of T. infestans wild foci and have recognized competences on Chagas disease in Bolivia. The project will be based, on the one hand, on data collected on an Andes-Chaco transect. The detection of new wild foci will be carried out in various ecoregions defined on this transect. On the other hand, the determinants of the possible domestication of sylvatic T. infestans will be studied in three areas potentially shared by man and the vector, and representative of three ecosystems already known to shelter wild populations (Andean valley of altitude, Andean Chaco and Chaco lowlands). In all the cases, an interdisciplinary approach (biomedical and social sciences) will be carried out. In the shared areas which extend from the sylvatic environment to the domestic one, the characterization of the environment, the bioecology of the vector and, in particular, its dispersal, the study of the man-vector contact, the parasite stocks circulation and the human behavior will be investigated. The data analysis will assess the risk represented by genetically definite vector populations in a given biophysical and human environment. Recommendations about the surveillance of the wild T. infestans populations will be presented to the health authorities.