PESTIVIRUSES (family Flaviviridae) are single-stranded, positive-sense RNA viruses that are traditionally classified in four species: bovine viral diarrhoea virus type 1 (BVDV-1) and type 2 (BVDV-2), which affect cattle, Border disease virus (BDV), which infects small ruminants and classical swine fever virus, which affects pigs. BVDV and BDV are not strictly host-specific and antibodies to these viruses have been reported in several species of wild ruminants (Vilcek and Nettleton 2006). Pestiviruses can cause a wide range of reproductive clinical manifestations in livestock, and recently, BDV infection has been associated with severe outbreaks of disease in the Pyrenean chamois ( Rupicapra pyrenaica ), leading to severe reductions in its populations (Marco and others 2007, 2009). The Alpine ibex ( Capra ibex ) and Iberian ibex ( Capra pyrenaica ) are mountain ruminants belonging to the subfamily Caprinae (family Bovidae). Although these species are not considered threatened by the International Union for Conservation of Nature, there is concern regarding their genetic diversity, the founder effect and minimum viable populations (Shackleton 1997). Therefore, information about reproductive disorders could be of importance for the conservation and management of these species. The objectives of the present study were to determine the prevalence of antibodies to pestiviruses and to investigate the …