Spatial and temporal phylogeny of border disease virus in Pyrenean chamois

Border disease virus (BDV) (Genus Pestivirus, Family Flaviviridae) affects a wide range of ruminants worldwide, mainly domestic sheep and goat. Since 2001 several outbreaks of disease associated to BDV infection have been described in Pyrenean chamois (Rupicapra pyrenaica pyrenaica) in Spain, France and Andorra. These outbreaks have decimated several Pyrenean chamois populations, with mortalities ranging from 40% to 85%. The infection has become endemic in the Central and Eastern Pyrenees. After the severe BDV outbreaks, different epidemiological scenarios have appeared in the Pyrenees, some of which are having a negative impact on host population dynamics. The aim of this study was to clarify the origin and dispersion of the Pyrenean chamois BDV genetic variant by reconstructing the spatial and temporal dynamics of BDV 5’ UTR sequences of Pyrenean chamois, 10 novel sequences and 41 retrieved from public databases. Sheep BDV sequences (n=43) from Spain and France were also retrieved. A phylogenetic analysis was performed using a Bayesian Markov chain Monte Carlo (MCMC) method implemented in the BEAST v.1.74 package. The maximum clade credibility tree summarizing all of the trees obtained during the MCMC search showed a main clade supported by posterior probabilities of 1, corresponding to the Pyrenean chamois phylogenetic group. The chamois clade originated from sheep BDV and the time of the most recent common ancestor estimates for the chamois clade was 19 years ago, thus indicating its relatively recent emergence (mean estimate 1992). There were also some highly significant subclades among chamois sequences clustering three geographical areas in Pyrenees: Eastern area (Freser); Central area (Cadì, Cerdanya-Alt Urgell, Orlu) and Western area (Val d’Aran, Pallars Sobira, Aragon and Andorra). Our data suggest that Pyrenean chamois phylogenetic group originated from sheep BDV genotype 4, generating a founder effect due to intra-species spread and spatial dispersion, still going on such as Western direction.