Vaccination against H5 avian influenza virus induces long-term humoral immune responses in flamingoes (Phoenicopterus spp.)

Avian influenza (AI) can represent a threat to endangered wild birds, as demonstrated with the H5N1 highly pathogenic AI (HPAI) outbreaks. Vaccination against AI using inactivated H5-vaccines has been shown to induce humoral immune response in zoo bird species. In this study, the long-term efficacy of H5-vaccination was evaluated in flamingoes from Barcelona Zoo. Specific H5-antibody titres were maintained at high levels (geometric mean titres ≥32) for over 7 years after vaccination, both against the H5N9 and H5N3 vaccine strains, as well as H5N3 and H5N1 reference strains. In addition the breadth of the immune response was also studied by testing antibody production against H1-, H3-, H4-, H7-, and H10-subtypes. It was observed that most flamingoes presented specific antibodies against H1 virus subtypes, but titres to the other HA-subtypes were rarely detected. We show that AI-vaccines can induce immunity lasting seven years in flamingoes, which suggests that vaccination can provide long term protection from HPAI outbreaks in zoo birds.