Thesis (M.Sc.) - Cairo University - Faculty of Veterinary Medicine - Department of Virology

Low pathogenic H9N2 avian influenza virus (AIV) causes great economic losses in broiler chickens. In the present study, two experiments were carried out for studying the pathogenicity of H9N2 AIV in broiler chickens after vaccination with different live respiratory viral vaccines. One-day- old specific pathogen free (SPF) chicks were divided into four groups in each experiment. In experiment 1; groups 1 and 2 were inoculated with H9N2 AIV via nasal route at 1st day old, groups 1 and 3 were vaccinated with live IBV vaccine at 5th days old and group 4 was left as a negative control. In experiment 2; groups 5and 6were inoculated with AIV subtype H9N2 via nasal route at 1st day old, group 5 was vaccinated with live IBV vaccine and live NDV vaccine at 5th days and 18th days old; respectively, groups 6 and 7 were vaccinated with live NDV vaccine at 18th days old and group 8 was left as a negative control. Chicks were kept in isolators for 18 days in first experiment and 35 days in the second experiment. Tracheal and Cloacal swabs were collected at 3rd, 5th, 7th, 10th, 12th and 15th days old from all groups in experiment 1; 21th, 23th, 25th and 28th days old from all groups in experiment 2. Quantitative Real time (rRT-PCR) was applied on the collected tracheal swabs for detecting RNA copies of H9N2 AIV and revealed a significant increase in H9N2 AIV titer with extension in the period of viral shedding in groups 1 and 5

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