Molecular reconstruction of Newcastle disease history in Nigeria. Poster 71

Since its first records in the 1950s in West Africa, Newcastle disease virus (NDV) has been submitted to several surveillance campaigns that have provided large datasets of samples. In this study, we analysed 137 complete fusion gene sequences of NDV obtained from poultry sampled between 2006 and 2011 from nine West African countries: Nigeria (n=94), Cameroon (n=6), Ivory Coast (n=7), Mali (n=7), Burkina Faso (n=2), Mauritania (n=1), Niger (n=6), Benin (n=2), and Togo (n=2). In order to understand the transmission dynamics of NDV in Nigeria and the neighbouring countries, we conducted phylogenetic analyses by considering the temporal and the spatial evolution of the virus: (i) phylodynamic analyses at a regional scale to highlight the evolution of virus mutations over time that may reflect viral adaptations; and (ii) phylogeographic methods to infer the geographical history of NDV genotypes as well as to estimate the rate of virus transmission and spatial spread in the region. By combining spatial and genetic analyses and using Bayesian stochastic search variable selection (BSSVS) procedure, we identified frequently invoked rates to explain the diffusion process. We revealed the pathways of introduction and transmission of NDV from neighboring countries to Nigeria. We also analysed the Nigerian diffusion pathways in relation to national commercial poultry networks. By implementing molecular clocking, we estimated the date of virus diffusion and showed longstanding presence of NDV in West Africa, revealing how virus diffusion may enable endemic maintenance. (Texte integral)