Safety and Immunogenicity of Poultry Vaccine for Protecting Critically Endangered Avian Species against Highly Pathogenic Avian Influenza Virus, United States

Authors: KATZNER, TODD - Us Geological Survey; BLACKFORD, ASHLEIGH - Us Fish And Wildlife Service; DONAHUE, MARY - Animal And Plant Health Inspection Service (APHIS); GIBBS, SAMANTHA - Us Fish And Wildlife Service; LENOCH, JULIANNA - Animal And Plant Health Inspection Service (APHIS); MARTIN, MICHAEL - North Carolina Department Of Agriculture & Consumer Services; ROCKE, TONIE - Us Geological Survey; ROOT, JEFFREY - Animal And Plant Health Inspection Service (APHIS); STYLES, DARREL - Animal And Plant Health Inspection Service (APHIS); COOPER, SUNNY - Carolina Raptor Center; DEAN, KRISTIN - Carolina Raptor Center; DVORNICKY-RAYMOND, ZACHARY - San Diego Zoo; KELLER, DOMINIQUE - Los Angeles Zoo And Botanical Garden; SANCHEZ, CARLOS - Oregon Zoo; DUNLAP, BRETT - Animal And Plant Health Inspection Service (APHIS); GRIER, THOMAS - Purdue University; JONES, MICHAEL - American Eagle Foundation; NITZEL, GREGORY - Zoetis; PATRICK, ERIN - Animal And Plant Health Inspection Service (APHIS); PURCELL, MAUREEN - Us Geological Survey; SPECHT, AARON - Purdue University; Suarez, David

Submitted to: Emerging Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2025
Publication Date: 4/15/2025
Citation: Katzner, T., Blackford, A.V., Donahue, M., Gibbs, S.E., Lenoch, J., Martin, M., Rocke, T., Root, J.J., Styles, D., Cooper, S., Dean, K., Dvornicky-Raymond, Z., Keller, D., Sanchez, C., Dunlap, B., Grier, T., Jones, M.P., Nitzel, G., Patrick, E., Purcell, M., Specht, A.J., Suarez, D.L. 2025. Safety and Immunogenicity of Poultry Vaccine for Protecting Critically Endangered Avian Species against Highly Pathogenic Avian Influenza Virus, United States. Emerging Infectious Diseases. 31:(6). https://doi.org/10.3201/eid3106.241558.
DOI: https://doi.org/10.3201/eid3106.241558

Interpretive Summary: Highly pathogenic avian influenza) virus can infect and cause disease in a wide variety of wild bird and poultry species. In 2023 an outbreak of HPAI was reported in California condors, a highly endangered species, that resulted in the death of over 20 birds. Because there are less than 600 birds in the entire population, great concern was raised about HPAI causing the extinction of all condors. In an effort to save the condors, vaccination of these birds using a poultry vaccine was considered and approved. As a safety test, black vultures, a closely related species were vaccinated first to assure no the birds would have no adverse affects to the vaccine and would respond with an antibody response. The black vultures were vaccinated and did immunologically respond where it was likely a protective response. Based on this data California condors in captivity were also vaccinated. Although the antibody titers were lower in condors than in vultures, the program was thought to be successful and provide at least some protection to birds in the field.

Technical Abstract: Highly pathogenic avian influenza (HPAI) virus has caused widespread disease and mortality of poultry and wildlife worldwide. In 2023, one subpopulation of critically endangered California condors experienced an HPAI outbreak during which = 21 individuals died (~18% of the subpopulation). We evaluated safety, immunogenicity, vaccination strategies, and correlates of antibody response of a conditionally licensed influenza vaccine for poultry in a surrogate, black vultures, and for California condors. We detected no adverse effects and differences in antibody titers between vaccinated and unvaccinated animals (vultures: p = = 0.004; condors: p = 0.020). All vaccinated vultures, 80% of vaccinated condors, and no control birds, showed maximum an antibody response in the range of that associated with survival of vaccinated chickens previously virallyexperimentally challenged (i.e., HI titers = 16). Antibody responses trended higher, but were not statistically different, for vultures and condors given two standard vaccinations (0.5 mL) vs one double vaccination (1 mL) of vaccine. We did not detect variation in antibody titers related to sex of vultures or condors, or to bone lead levels of vultures. These results were sufficiently promising that a vaccination program was initiated for California condors, illustrating a model pathway for disease mitigation for a critically endangered species.