Feeding behaviour of potential vectors of West Nile virus in Senegal

Background: West Nile virus (WNV) is a widespread pathogen maintained in an enzootic cycle between mosquitoes and birds with occasional spill-over into dead-end hosts such as horses and humans. Migratory birds are believed to play an important role in its dissemination from and to the Palaearctic area, as well as its local dispersion between wintering sites. The Djoudj Park, located in Senegal, is a major wintering site for birds migrating from Europe during the study period (Sept. 2008-Jan. 2009). In this work, we studied the seasonal feeding behaviour dynamics of the potential WNV mosquito vectors at the border of the Djoudj Park, using a reference trapping method (CDC light CO(2)-baited traps) and two host-specific methods (horse- and pigeon-baited traps). Blood meals of engorged females were analysed to determine their origin. Results: Results indicated that Culex tritaeniorhynchus and Cx. neavei may play a key role in the WNV transmission dynamics, the latter being the best candidate bridging-vector species between mammals and birds. Moreover, the attractiveness of pigeon-and horse-baited traps for Cx. neavei and Cx. tritaeniorhynchus varied with time. Finally, Cx. tritaeniorhynchus was only active when the night temperature was above 20 degrees C, whereas Cx. neavei was active throughout the observation period. Conclusions: Cx. neavei and Cx. tritaeniorhynchus are the main candidate vectors for the transmission of WNV in the area. The changes in host attractiveness might be related to variable densities of the migratory birds during the trapping period. We discuss the importance of these results on the risk of WNV transmission in horses and humans

Impact des modes de gestion des parcs arborés sur la dynamique des paysages agricoles, un cas d’étude au Sénégal

Au Sénégal, on observe une différenciation remarquable des parcs arborés au sein de mêmes zones pédoclimatiques. Notre contribution s’intéresse à étudier les modes de gestion de ces parcs dans deux sites du département de Bambey situé dans le bassin arachidier du Sénégal. Ces deux sites contrastés, notamment en termes de densité d’arbres, sont pourtant soumis aux mêmes politiques de gestion et de conservation des espaces arborés. Nous faisons ici l’hypothèse que les différences paysagères observées sont dues à des déterminants locaux et des pratiques de gestion différentes. Pour comprendre les facteurs explicatifs de cette hétérogénéité, nous avons enquêté un ensemble d’acteurs intervenant dans la gestion de l’arbre dans les deux sites d’étude. Plus particulièrement, nous nous sommes intéressés aux questions de gouvernance locale, aux usages et utilités de l’arbre, ainsi qu’aux pratiques paysannes vis-à-vis de cette ressource. Les résultats de l’étude indiquent que les modes de gestion paysanne jouent un rôle prédominant dans la structuration du paysage arboré. Les fonctions multiples qu’assure l’arbre font que les paysans opèrent une sélection des arbres qu’ils jugent utiles. Cette sélection paysanne additionnée aux considérations sociales qui diffèrent d’un terroir à un autre fait que les parcs arborés diffèrent d’une parcelle à l’autre et d’un village à l’autre.In Senegal, we observe important discrepancies in forest densities within similar agro-ecological zones. Our work focuses on studying the management methods of two forested areas within a similar agricultural landscape, the groundnut basin of Senegal. These two sites show differences in tree density while being subjected to the same macro-drivers. Here, we make the assumption that local drivers and management practices explain the observed differences. In order to understand the explanatory factors of this heterogeneity, our fieldwork consisted in surveying a range of factors involved in forest management. For instance, we focused on local governance, uses and practices regarding this resource. The results of the study indicate that forest landscapes mainly result from local practices and management methods. Hence, peasant selection, combined with social considerations that differ from one landscape to another, cause forest patches to differ from one plot to another and from one village to another