Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 12/4/2015
Publication Date: N/A
Technical Abstract: In the field, poultry are exposed to a variety of infectious agents, many of which are immunosuppressive. Co-infections between these agents are common, and these co-infections have effects on disease, immune response, and vaccine efficacy. The effect of co-infections in poultry between immunosuppressive agents and avian influenza virus (AIV) on AIV vaccine efficacy has yet to be fully evaluated. To study vaccine efficacy in immunosuppressed birds, immunosuppression was induced using infectious bursal disease virus (IBDV), and mortality, viral shed, and vaccine antibody titers were examined. Specific pathogen free white rock chickens were exposed to variant E IBDV at one week of age and were subsequently vaccinated with an inactivated H7 AIV vaccine one week later. Prior to vaccination, bursas of Fabricius were taken from IBDV infected and non-infected birds to confirm IBDV infection. Three weeks post-vaccination antibody titers were determined pre-challenge. The chickens were then challenged with six different doses (1 log10-6 log10) of highly pathogenic H7 AIV. Vaccinated birds exposed to IBDV had an almost two-fold decrease in geometric mean antibody titers compared to non-exposed vaccinated birds, indicating immunosuppression. Exposure to IBDV prior to vaccination eliminated the protective effect of the vaccine. The mortality in vaccinated birds exposed to IBDV was the same as non-vaccinated controls. This is in contrast to vaccinated birds that were not exposed to IBDV, which were protected from mortality when compared to non-vaccinated controls. Prior exposure to IBDV also decreased the mean death time (2.3-3.7 days) compared to vaccinated birds not exposed to IBDV (4-7 days). Differences in percent shedding and amount of viral shedding were observed among the higher challenge dose groups (5 log10-6 log10). These results indicate that vaccination prevents mortality by limiting systemic disease, not localized replication, and immunosuppression by IBDV eliminates this preventive effect.