Highly Pathogenic Avian Influenza A (H5N1) Infection in Bearded Vultures in Spain

We report mortality in bearded vultures ( Gypaetus barbatus ) associated with highly pathogenic avian influenza HPAI A H5N1 clade 2.3.4.4b, responsible for the current HPAI panzootic. Between April and May 2022, a total of five bearded vultures from Spain, four free-ranging and one captive individual, were found dead in their nest or with acute symptoms of disease. Complete necropsies were performed and histopathological, immunohistochemistry and molecular analyses were carried out. The presence of the HPAI H5N1 virus was confirmed in different organs, oropharyngeal and cloacal swabs and feathers from the affected individuals. The complete viral genome was obtained from three of the affected bearded vultures. Phylogenetic analyses revealed that the sequences obtained from the free-ranging individuals and the captive specimen belonged to the clade 2.3.4.4b and clustered separately. Furthermore, it supports that direct or indirect contact with other sympatric wild birds could be the most likely source of infection. This research highlights the susceptibility of the endangered bearded vulture to HPAI H5N1, thereby contributing to the broader understanding of the virus's host range.