A semi-annual immunization with a commercial inactivated H9 subtype avian influenza virus (AIV) vaccine developed for poultry has been used to prevent and control the avian influenza (AI) infections among captured wild birds in Shanghai Zoo. However, the overall safety and effectiveness of the poultry vaccine for housed birds in the zoo remains unclear. To verify the safety and efficacy of the commercial inactivated H9 AI vaccine on zoo birds, and to explore a more reasonable and effective immunization procedure, 48 zoo birds, including11 Oriental white storks, 25 peafowl, and12 silver pheasants were administered the AI vaccine developed for poultry use. Then, the clinical signs of the immunized birds were observed for two weeks, and the antibodies against H9 AI were determined via the hemagglutination inhibition (HI) test. Results showed that no harmful effects related to the vaccination were observed, and the antibody titers of the Oriental white stork, peafowl, and silver pheasants were all higher than 7log2 at 21 days, 30 days, 60 days, 120 days and 180 days post-immunization. For further study, the H9 AIV titers of eleven peafowls and six Oriental storks, which were raised in the nursing ground, were continuously monitored for 15months. All of their antibody titers were above the national standards of China (5log2, GB/T18936-2003), even at 12 months and 15 months post-immunization. We concluded that the commercial inactivated H9 AI vaccine used at the present time in Shanghai Zoo can induce high and prolonged immune responses in vaccinated birds.

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