الفهرس 
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Abstract
The study was performed to declare the pathogenicity of H9N2 AI virus in SPF chickens
and in immunosupressed ones. The experiment was carried on 100 unvaccinated one day
old broiler SPF chicks. They were divided into four groups of 25 birds each. Group I kept
as non treated control group, group II intranasally infected with H9N2 AI virus, group III
fed on diet containing 0.75 ppm aflatoxins from one day old and group IV fed on diet
containing 0.75 ppm aflatoxins and infected with H9N2 AI virus. Five chicks were kept
as contact control to group Il and group IV. The experiment extended for 27 days from
the infection day. Serum was collected from the experimental groups for HI and ELISA.
Samples were collected from the nasal chonchae, trachea, lung, liver, kidney, brain, bursa
of Fabricious, thymus, spleen and the pancreas for histopathology and for
immunohistochemistry by immunoperoxidase technique. no deaths were recorded during
the experimental period. The histopathological lesions were more severe and persist till the end of experiment in group IV. The main pathological lesions recorded in the groups
infected with H9N2 AI virus were rhinitis, tracheitis and interstitial pneumonia. Apart
from the respiratory system the kidneys and brain was affected in addition to depletion of
the lymphoid organs. Pancreatitis was recorded in the aflatoxin virus group which
indicates the dissemination of the virus. the liver showed limited changes in group II.The
histopathological lesions were confirmed by the presence of viral antigen by
immunoperoxidase technique. The antibodies titer by HI recorded low values in the
aflatoxin - virus group than the virus group indicating the immunosuppressive effect of
aflatoxins.