In this experiment, pathogenesis of H9N2 avian influenza virus (AIV), experimentally infected with infectious bursal disease virus (IBDV) in broiler chicks was examined. Three groups of twenty were randomly selected. Day old chickens in group 1, were infected by 103 CID50 of IBDV intrabursaly, and in thirty days of age groups 1 and 2 were challenged with 106 EID50 H9N2, intranasaly-intraoculary. Chickens in group 3 remained as control (uninfected with neither IBDV or AIV). Tracheal and cloacal swabs, and tissue samples, were collected at 3, 7, and 11 days postinoculation (PI). Serum samples examined for antibodies against avian influenza virus (AIV) by hemagglutination inhibition test (HI). IBD caused lower H9N2 antibody level. IBDV infected chickens (g1) shed AI virus for a longer period than AIV infected birds (g2), from both trachea and cloac. IBDV was related with AIV in brain and liver. Isolation of AIV from trachea, conjunctiva, bursa and lung in IBDV infected group (1), prolonged till 11 days PI. Our study provides evidence that a previous history of IBDV infection in chickens may cause them to be more susceptible to H9N2 low pathogenic avian influenza (LPAI) virus infection and may alter its tissue tropism.
Key words: Infectious bursal disease, avian influenza, virus shedding, broiler chicks.
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