Comprehensive serological analysis of two successive heterologous vaccines against H5N1 avian influenza virus in exotic birds in zoos

Antibody Response of an H9 Subtype Avian Influenza Poultry Vaccine on Three Kinds of Wild Birds in Shanghai Zoo

A semiannual 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 remain 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, including 11 Oriental white storks, 25 peafowl, and 12 silver pheasants, were administered the AI vaccine developed for poultry use. Then, the clinical signs of the immunized birds were observed for 2 weeks, and the antibodies against H9 AI were determined via the hemagglutination inhibition 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 7 log ₂ at 21 days, 30 days, 60 days, 120 days, and 180 days postimmunization. For further study, the H9 AIV titers of 11 peafowls and 6 Oriental storks, which were raised in the nursing ground, were continuously monitored for 15 months. All of their antibody titers were above the national standards of China (5 log ₂; GB/T18936-2003), even at 12 months and 15 months postimmunization. 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.

EVALUATION OF A COMMERCIAL COMPETITIVE ENZYME-LINKED IMMUNOSORBENT ASSAY FOR DETECTION OF AVIAN INFLUENZA VIRUS SUBTYPE H5 ANTIBODIES IN ZOO BIRDS

The hemagglutination inhibition (HI) test is the current gold standard for detecting antibodies to avian influenza virus (AIV). Enzyme-linked immunosorbent assays (ELISAs) have been explored for use in poultry and certain wild bird species because of high efficiency and lower cost. This study compared a commercial ELISA for detection of AIV subtype H5 antibodies with HI test of 572 serum samples from zoo birds. There was no significant difference between the results of the two tests when statistically compared by a McNemar χ² test (P = 0.86) and assessment of κ (κ = 0.87). With a specificity of 94.2% (95% confidence interval [CI], 0.92-0.97), a sensitivity of 93.9% (95% CI, 0.91-0.97), and an excellent correlation between the two tests, this ELISA can be recommended as an alternative to the HI test for preliminary screening of zoo bird sera for antibodies to AIV subtype H5.

Sequential DNA immunization of chickens with bivalent heterologous vaccines induce highly reactive and cross-specific antibodies against influenza hemagglutinin

Vaccines against avian influenza are mostly based on hemagglutinin (HA), which is the main antigen of this virus and a target for neutralizing antibodies. Traditional vaccines are known to be poorly efficient against newly emerging strains, which is an increasing worldwide problem for human health and for the poultry industry. As demonstrated by research and clinical data, sequential exposure to divergent influenza HAs can boost induction of universal antibodies which recognize conserved epitopes. In this work, we have performed sequential immunization of laying hens using monovalent or bivalent compositions of DNA vaccines encoding HAs from distant groups 1 and 2 (H5, H1, and H3 subtypes, respectively). This strategy gave promising results, as it led to induction of polyclonal antibodies against HAs from both groups. These polyclonal antibodies showed cross-reactivity between different HA strains in ELISA, especially when bivalent formulations were used for immunization of birds. However, cross-reactivity of antibodies induced against H3 and H5 HA subtypes was rather limited against each other after homologous immunization. Using a cocktail of HA sequences and/or sequential DNA vaccination with different strains presents a good strategy to overcome the limited effectiveness of vaccines and induce broader immunity against avian influenza. Such a strategy could be adapted for vaccinating laying hens or parental flocks of different groups of poultry.

Heterologous prime-boost vaccination with H3N2 influenza viruses of swine favors cross-clade antibody responses and protection

The emergence of multiple novel lineages of H1 and H3 influenza A viruses in swine has confounded control by inactivated vaccines. Because of substantial genetic and geographic heterogeneity among circulating swine influenza viruses, one vaccine strain per subtype cannot be efficacious against all of the current lineages. We have performed vaccination-challenge studies in pigs to examine whether priming and booster vaccinations with antigenically distinct H3N2 swine influenza viruses could broaden antibody responses and protection. We prepared monovalent whole inactivated, adjuvanted vaccines based on a European and a North American H3N2 swine influenza virus, which showed 81.5% aa homology in the HA1 region of the hemagglutinin and 83.4% in the neuraminidase. Our data show that (i) Priming with European and boosting with North American H3N2 swine influenza virus induces antibodies and protection against both vaccine strains, unlike prime-boost vaccination with a single virus or a single administration of bivalent vaccine. (ii) The heterologous prime-boost vaccination enhances hemagglutination inhibiting, virus neutralizing and neuraminidase inhibiting antibody responses against H3N2 viruses that are antigenically distinct from both vaccine strains. Antibody titers to the most divergent viruses were higher than after two administrations of bivalent vaccine. (iii) However, it does not induce antibodies to the conserved hemagglutinin stalk or to other hemagglutinin subtypes. We conclude that heterologous prime-boost vaccination might broaden protection to H3N2 swine influenza viruses and reduce the total amount of vaccine needed. This strategy holds potential for vaccination against influenza viruses from both humans and swine and for a better control of (reverse) zoonotic transmission of influenza viruses.

Infectious Diseases

The chapter describes bacerial, viral, parasitic and fungal infections commonly detected in pet birds. The chapter includes history, etiology, susceptible hosts, transmission, pathogenesis, clinical symptoms, lesion, diagnosis, zoonosis, Treatment and control strategy of Tuberculosis, Salmonellosis, Chlamydiosis, Campylobacteriosis, Lyme disease, other bacterial infection, Newcastle disease, Avian Influenza infection, West Nile Virus infection, Usutu virus infection, Avian Borna Virus infection, Beak and feather disease, other viral infection, Toxoplasmosis, Giardiasis, Cryptosporidiosis, other parasitic infection, Cryptococcosis, Aspergillosis, Other fungal infections.

The response of mute swans (Cygnus olor, Gm. 1789) to vaccination against avian influenza with an inactivated H5N2 vaccine

Background

Recent epidemics of highly pathogenic avian influenza (HPAI) produced an unprecedented number of cases in mute swans (Cygnus olor) in European countries, which indicates that these birds are very sensitive to the H5N1 virus. The HPAI outbreaks stirred a debate on the controversial stamping-out policy in populations of protected bird species. After preventive vaccination had been approved in the European Union, several countries have introduced vaccination schemes to protect poultry, captive wild birds or exotic birds in zoos against HPAI. The aim of this study was to investigate the immune response of wild mute swans to immunization with an inactivated AI H5N2 vaccine approved for use in poultry. The serological responses of mute swans were assessed by comparison with racing pigeons (Columba livia), a species which is characterized by different susceptibility to infection with the H5N1 HPAI virus and plays a questionable role in the ecology of influenza (H5N1) viruses.

Results

Swans were vaccinated once or twice at an interval of 4 weeks. The humoral immune response was evaluated by hemagglutination inhibition (HI) and NP-ELISA. The lymphocyte blast transformation test was used to determine the cell-mediated immune response. Higher values of the geometric mean titer (GMT) and 100 % seroconversion (HI ≥32) were noted in double vaccinated swans (1448.2) than in single vaccinated swans (128.0) or in double vaccinated pigeons (215.3). Significant differences in HI titers were observed between swans and pigeons, but no variations in ELISA scores were noted after the booster dose. Immunization of swans had no effect on the proliferative activity of lymphocytes.

Conclusions

The inactivated H5N2 vaccine was safe and immunogenic for mute swans and pigeons. Vaccination may have practical implications for swans kept in zoos, wildlife parks or rehabilitation centers. However, challenge studies are needed to prove the efficacy of the H5N2 AI vaccine.

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.

Low pathogenic influenza A virus activity at avian interfaces in Ohio zoos, 2006-2009

This investigation to examine influenza A virus activity in avian species at four Ohio zoos was initiated to better understand the ecology of avian-origin influenza A (AIV) virus in wild aquatic birds and the possibility of spill-over of such viruses into captive zoo birds, both native and foreign species. Virus isolation efforts resulted in the recovery of three low pathogenic (LP) AIV isolates (one H7N3 and two H3N6) from oral-pharyngeal or cloacal swabs collected from over 1000 zoo birds representing 94 species. In addition, 21 LPAIV isolates possessing H3N6, H4N6, or H7N3 subtype combinations were recovered from 627 (3.3%) environmental fecal samples collected from outdoor habitats accessible to zoo and wild birds. Analysis of oral-pharyngeal and cloacal swabs collected from free-ranging mallards (Anas platyrhynchos) live-trapped at one zoo in 2007 resulted in the recovery of 164 LPAIV isolates (48% of samples) representing five HA and six NA subtypes and at least nine HA-NA combinations. The high frequency of isolate recovery is undoubtedly due to the capture and holding of wild ducks in a common pen before relocation. Serologic analyses using an agar gel immune diffusion assay detected antibodies to the influenza A virus type-specific antigen in 147 of 1237 (11.9%) zoo bird sera and in 14 of 154 (9%) wild mallard sera. Additional analyses of a limited number of zoo bird sera demonstrated HA- and NA-inhibition activity to 15 HA and nine NA subtypes. The spectrum of HA antibodies indicate antibody diversity of AIV infecting zoo birds; however, the contribution of heterologous cross-reactions and steric interference was not ruled out. This proactive investigation documented that antigenically diverse LPAIVs were active in all three components of the avian zoologic-wild bird interfaces at Ohio zoos (zoo birds, the environment, and wild birds). The resulting baseline data provides insight and justification for preventive medicine strategies for zoo birds.