Modelling the dynamics and spatial distribution of Culicoides (Diptera: Ceratopogonidae) biting midges, potential vectors of African horse sickness and bluetongue viruses in Senegal. M. Diarra1, 2, M. Fall1, A.G. Fall1, A. Diop2, R. Lancelot3, 4, M. T. Seck1, I. Mall1, A.M. Dusom1, M. Ndao1, C. Garros3, 4, X. Allène3, 4, I. Rakotoarivony3, 4, J. Bouyer 1,3,4 and H. Guis3,4. 1 Institut Sénégalais de Recherches Agricoles, Laboratoire National de l’Elevage et de Recherches Vétérinaires, Dakar, Sénégal, 2 Université Gaston Berger, Laboratoire d’Etudes et de Recherches en Statistiques et Développement, Saint-Louis, Sénégal, 3 Cirad, UMR15 CMAEE, F-34398 Montpellier, France, 4 INRA, UMR1309 CMAEE, F-34398 Montpellier, France Background In Senegal, the 2007 epidemic of African horse sickness (AHS) caused the death of 1,169 horses and considerable economic loss (Akakpo et al. 2011). The vectors responsible for biological transmission of the virus belong to the genus Culicoides (Diptera: Ceratopogonidae). In Senegal, studies on Culicoides are rare, out of date and did not specifically target the species in the vicinity of horses. Thus we initiated two studies in 2011 to better understand the dynamics and distribution of the Culicoides of Senegal and their involvement in the transmission of AHS virus (AHSV). Dynamics of Culicoides in the Niayes region Methods A one-year monthly trapping campaign using two light traps for three consecutive nights in five sites of the Niayes region (Figure 1) was carried out in 2011-2012. Rainy season = Peak of abundance Results  224,665 specimens of the Culicoides genus (in 354 collections) belonging to at least 24 different species.  The most abundant species (Figure 2) were C. oxystoma, C. kingi, C. imicola, C. enderleini and C. nivosus C. enderleini 4% C. imicola 13% C. nivosus 2% C. oxystoma 45% C. kingi 36% Figure 2: Proportion of total catch for the dominant Culicoides species in the Niayes of Senegal Figure 1: Locations of Culicoides trapping sites in the Niayes of Senegal Figure 3: Seasonal variations of dominant Culicoides species in the Niayes of Senegal. See complete results in Diarra et al. Parasites & Vectors 2014, 7:147.  Peaks of abundance coincide with the rainy season in September and October (Figure 3). Nation-wide distribution of Culicoides In 2012, a nation-wide Culicoides trapping campaign was set up to better describe spatial distribution of Culicoides in Senegal. Methods  Two successive collection nights were carried out in 98 sites in 12 (out of 14) regions of Senegal Results More than 1,367,000 Culicoides belonging to at least 35 species were collected in this spatial survey (Figure 4 and 5).  Period: End of the rainy season (September - October).  Climatic and environmental variables: land surface temperatures (LST) of the day and night, normalized difference vegetation index (NDVI), rainfall, livestock density, land cover. Figure 5: Diversity of Culicoides species in 2012 Species with proportion of total catch > 0.1%  MaxEnt (Maximum entropy) model (Phillips et al., 2006) to characterise suitable habitats of 4 proven or potential vectors of AHSV and bluetongue virus (BTV) in Senegal (C. oxystoma, C.imicola, C. miombo and C. bolitinos)  GLM (Generalized linear models) model (McCullagh and Nelder, 1989) for mapping the abundance of C. oxystoma, C. imicola, C. miombo and C. bolitinos Important species for AHSV and BTV transmission: C. oxystoma: Suspected BTV vector & very abundant C. imicola: Proven BTV and AHSV vector & abundant C. miombo: Suspected BTV vector & abundant C. bolitinos: Proven vector BTV & not abundant Figure 4: Spatial distribution of Culicoides in Senegal Figure 6: Probability of presence for C. imicola, C. bolitinos (2 proven vectors of BTV and/or AHSV), C. oxystoma, C. miombo (2 suspected vectors of BTV) in Senegal Conclusion: Overall, this work allowed updating the list of Culicoides species of Senegal, describing their dynamics, characterising suitable habitats and mapping abundance of the potential vectors of AHS and bluetongue viruses in Senegal. Figure 7: Abundance model (GLM) for C. imicola, C. bolitinos (2 proven vectors of of BTV and/or AHSV), C. oxystoma, C. miombo (2 suspected vectors of BTV) in Senegal References: Akakpo, A. J., Wombou, T. C. M., Mankor, A. & Ly, C. 2011 Impact économique de l'épizootie de la peste équine de 2007 au Sénégal. Bulletin of Animal Health and Production of Africa 59, 1-16. McCullagh P. and Nelder J. Generalized linear models. 1989. Phillips, S.J., R.P. Anderson, R.E. Schapire, 2006. Maximum entropy modeling of species geographic distributions. Ecological Modelling 190: 231-259.