L'émergence de la dengue dans des environnements en mutation – ANR-05-SEST-0010

Dengue fever, transmitted primarily by Aedes aegypti and Ae. albopictus mosquitoes, is the most widespread arbovirus in the world. Its incidence is approximately 80 million cases recorded annually, concerning more than 100 countries. It is currently expanding to different ecological settings. The French nationals living in the DOM-TOM, the French troops on military intervention abroad and tourists are largely exposed. The important socio-economic repercussions associated with dengue fever constitute one of the major drawbacks for the development. The distribution and intensity of dengue disease transmission is overwhelmingly dictated by physical, climatic and socio-economical conditions. Vectors populations that are involved in the transmission live mainly in and around human settlements. Demographic and social changes influence the emergence of the disease while environmental conditions associated with characteristics of human activities, ecological and climatic factors are the many underlying determinants of dengue transmission. Our project will mainly aim at modelling the risks of dengue emergence, transmission and epidemic out breaking, based on retrospective and prospective field-data collected specifically from two different eco-geographical situations namely are Bolivia and Cameroon. At each site, data will be obtained jointly on the same human populations by a multi-disciplinary approach in terms of epidemiological relationships with viral, entomological, geographical, ethnological, demographic determinants. The multi-focus models will be used to assess the risk of dengue fever across both spatial and temporal scales. Macro-geographical transects through different ecological environments both in Bolivia and Cameroon will allow investigating the circulation of the virus according to human behaviour and migration, and vector biology. We will assess the geographical distribution, biology, the genetics and competence of disease vectors. Such analytical approach will allow quantifying the underlying determinants of dengue transmission both within and between the two countries. A detailed microgeographical approach will mainly focus on 3 cities: Douala and Garoua in Cameroon and the city of Santa Cruz (divided in 3 zones) in Bolivia. Sero-epidemiological studies will be caaried out regularly in sentinel houses selected for the entomological and social investigations (ethnological, geographical and demographic investigations). The constitution of a mappable dataset with field data entries (biological and medical sciences), local environmental and sociological data will be built upon the geographical information systems and link with the epidemiological and environmental models. The scope of this proposed programme is that the objectives are related to eight scientific disciplines, for which four French Institutes (IMTSSA, CPC from Institut Pasteur network, IRD, CEA) were called upon. The partners of the South are represented by six Institutes or Universities. The team constituted is therefore unique first because of its competence in field and laboratory-based research and secondly because it is represented simultaneously on the two continents chosen. We anticipate that the methodologies that will be rigorously developed, the collaborative networks that will be established, and the expected results should make it possible to durably set the French teams and their partners in the international competition on these topics.