Dynamiques de peuplements, modifications environnementales et variation du risque trypanosomien dans le sud-ouest du Burkina Faso de 2005 à 2014

L’augmentation générale des densités de population, dans un contexte de forte variabilité climatique, a provoqué des changements environnementaux majeurs en Afrique de l’Ouest. Si la population a tendance à s’urbaniser, elle reste toujours majoritairement rurale. C’est particulièrement vrai au Burkina-Faso où les modes de vie, les activités de subsistance et les conditions d’accès à l’eau exposent souvent les populations rurales et urbaines aux piqûres d’insectes susceptibles de transmettre des pathogènes responsables de maladies graves et/ou mortelles (paludisme, trypanosomiase, dengue, onchocercose etc.). Nos travaux s’intéressent aux fortes dynamiques de peuplements et de paysages survenues sur les rives du fleuve Comoé (terroirs de Folonzo et de Logogniégué) dans le Sud-ouest du Burkina-Faso entre 2005 et 2014, et au risque encouru par les populations humaines et animales à l’origine de ces dynamiques, de contracter les trypanosomoses transmises par les glossines (ou mouche tsé-tsé). Nos résultats mettent en évidence une multiplication par deux des densités de population humaine, la mise en place d’un élevage sédentaire et une augmentation de l’emprise rurale entre 2005 et 2014, ainsi qu’un rapprochement significatif des populations aux berges de la Comoé infestées de glossines. Ils montrent aussi l’intensification de pratiques spatiales humaines associables au risque trypanosomien, et confirment l’existence de la Trypanosomose Animale Africaine dans le cheptel bovin sédentaire récemment installé dans la zone. Cette étude illustre l’impact que des modifications environnementales engendrées par une dynamique de peuplement peuvent avoir sur les conditions de transmission des trypanosomoses humaines et animales. The general increase of population densities in Subsaharian Africa, in an effective climate change context, caused major population movement and environmental changes. While urbanization is expanding, the population is still mostly rural. Ways of life, subsistence farming and limited access to water sources expose these rural and urban populations to insect bites that could pass on the pathogen responsible for serious or deadly pathological conditions (malaria, trypanosomiasis, dengue fever, onchocerciasis, etc.). In the research conducted in South-West of Burkina Faso, our interest focused on current patterns of settlements and landscapes along river Comoe’s banks and on the exposure risks taken to human and animal trypanosomosis, both transmitted by tsetse flies which live in forest gallery of rivers. To achieve this, human and animal (bovine) populations were counted and mapped, and the rural encroachment on the Comoe’s banks mapped, to make a diachronic comparison between 2005 and 2014. The aim was also to understand the behaviors of people and animals associated with trypanosomosis risks. Simultaneously, tsetse flies were captured to ascertain their density in the studied area. Previously inventoried, bovine blood samples were analyzed in order to determine trypanosomosis infection level. From 2005 to 2014, our results have shown a high rise of the human population located in the area studied (multiplied by two), but also a change in its gender and ethnic structure. Furthermore we noticed a rise of the farmland surface, detrimental to the wooded savannah and gallery forest, and a decrease of tsetse flies densities due to this landscape degradation. Moreover, we observed the beginning of a bovine breeding and a reconciliation of people to the banks of Comoe, still infested by tsetse flies. Our results shown that 10% of the bovines sampled were infected by trypanosomes. This study shows settlements dynamics, mainly due to population growth, and their environmental impact on a savannah ecosystem in Burkina Faso. It aims to describe the consequences of such phenomenon on population health, with the specific example of human and animal trypanosomoses, both transmitted by tsetse flies.