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Efficacy of two licensed H5 vaccines against challenge with a 2015 United States H5N2 clade highly pathogenic avian influenza virus in domestic ducks

Pantin Jackwood, Mary J., DeJesus, Eric, Costa-Hurtado, Mar, Smith, Diane, Chrzastek, Klaudia, Kapczynski, Darrell R., Suarez, David L.
Avian diseases 2019 v.63 no.1 pp. 90-96
Influenza A virus, Pekin, ataxia (disorder), avian influenza, control methods, ducks, genes, hemagglutinins, mortality, reverse genetics, signs and symptoms (animals and humans), vaccination, vaccines, viral shedding, viruses, China, United States
Highly pathogenic avian influenza (HPAI) clade viruses from the H5 Goose/Guangdong lineage caused a major outbreak in poultry in the United States in 2015. Although the outbreak was controlled, vaccines were considered as an alternative control method and new vaccines were approved and purchased by the National Veterinary Stockpile for emergency use. In this study we evaluated the efficacy of two of these vaccines in protecting Pekin ducks against challenge with a H5N2 HPAI poultry isolate. A recombinant alphavirus-based vaccine and an inactivated adjuvanted reverse genetics vaccine, both expressing the hemagglutinin gene of a U.S. H5 clade isolate, were used to immunize the ducks. The vaccines were given either as single vaccination at 2 days of age or in a prime-boost strategy at 2 and 15 days of age. At 32 days of age, all ducks were challenged with A/Turkey/Minnesota/12582/15 H5N2 HPAI virus clade All ducks from the non-vaccinated challenge control group became infected and shed virus; one duck in this group presented mild ataxia and a second duck died. No mortality or clinical signs were observed in vaccinated-challenged ducks, with the exception of one duck presenting mild ataxia. Both vaccines, regardless of the vaccination strategy used, were immunogenic in ducks and reduced or prevented virus shedding after challenge. In conclusion, good protection against H5Nx infection was achieved in ducks vaccinated with the vaccines examined, which were homologous to the challenge virus, with prime-boost strategies conferring the best protection against infection.