Pathogenicity of avian influenza virus subtype H9N2 in Turkeys and protection efficacy evaluation under experimental condition of an inactivated H9N2 vaccinePathogenesis of avian influenza virus subtype H9N2 in turkeys and evaluation of inactivated vaccine efficacy

AAvian influenza H9N2 viruses circulate in all types of poultry species including turkeys and cause significant losses for the poultry industry in many parts of the word. The aim of this study was to assess the pathogenesis of the Moroccan avian influenza virus (AIV) H9N2 under experimental conditions in turkeys, and the protection efficacy of an inactivated commercial vaccine against AIV H9N2. Unvaccinated turkeys showed marked depression sinusitis, respiratory distress characterized by bronchiolar and tracheal rales of moderate severity and a mortality rate of 50%. Post mortem examinations of dead and euthanatized birds revealed the presence of fibrinous tracheitis, and airsacculitis lesions. Vaccination reduced the mortality rate to 30%. Vaccinated birds recovered at day 10 post challenge quickly and only 12.5% (1/8) and 37.5% of them still displayed fibrinous and non-fibrinous airsacculitis lesions respectively at day 15 post-inoculation. Viral shedding in cloacal and tracheal swabs was lower in vaccinated than in control birds. While viral RNA was detected in the cloacal swabs of all unvaccinated turkeys at day 3 post-inoculation, only 50% of the vaccinated turkeys were positive for virus detection. At day 11 post-inoculation, no viral RNA was detected in oropharyngeal swabs of vaccinated turkeys, while 40% of the unvaccinated turkeys were still shedding virus.