Abstract   

    Pathogenicity of avian influenza virus AlChick/Pakistanll/95(H₇N₃) was studied on 30 to 63 days old cockerels. The virus strain was found to be highly pathogenic killing inoculated birds within 2 to 7 days and produced distinct pattern of organ involvement. Extensive proliferation of lining epithelium of larynx and trachea forming tall villi and lymphoid depletion in germinal centers in spleen were the important histological changes in addition to clinical findings and lesions usually attributed to avian influenza infection in chicken.    

Key words: Avian influenza virus, strain H Pathogenicity.