Susceptibility to this virus and the possible role as vectors or reservoirs vary greatly between different wild bird and poultry species ( 1, 2). In particular, HPAI (H5N1) of Asian lineage is known for its potential to be transmitted to mammals, including humans. Highly pathogenic avian influenza A (HPAI) virus poses a major threat to poultry but is also of great concern for other avian species and humans. Vaccination could protect these valuable birds and, through reduced virus shedding, reduce risk for transmission to other avian species and humans. Vaccinated birds showed no influenza virus antigen in tissues and shed virus at lower titers from the oropharynx only. For the nonvaccinated birds, histopathologic examination showed tissue degeneration and necrosis, immunohistochemical techniques showed influenza virus antigen in affected tissues, and these birds shed high levels of infectious virus from the oropharynx and cloaca. All vaccinated birds survived all unvaccinated birds died within 5 days.
We then challenged 5 vaccinated and 5 nonvaccinated falcons with HPAI (H5N1). Ten falcons vaccinated with an inactivated influenza virus (H5N2) vaccine seroconverted. Because fatal infections with highly pathogenic avian influenza A (HPAI) virus subtype H5N1 have been reported in birds of prey, we sought to determine detailed information about the birds’ susceptibility and protection after vaccination.