الفهرس 
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Abstract
Avian influenza is a contagious disease caused by type A
influenza viruses. In spite of the mild nature of low pathogenic
avian influenza H9N2 virus, the virus was isolated from frequent
disease outbreaks with high mortality in different parts of the
world.
Thirty broiler chicken flocks suspected to be affected with
avian influenza virus of different ages and breeds during 2016-
2017 were examined in Sharkia Govemorate. A total of 75
chickens were submitted for clinical and postmortem
examination.
The examined broiler flocks showed respiratory signs as
Coughing, sneezing, rales, difficult breathing, nasal and ocular
discharges and swelling of periorbital tissues with conjunctivitis.
The postmortem lesions of the examined broiler flocks
shown tracheitis, congestion of lungs, exudation and cast
formation at the tracheal biforcation and lower bronchi as well as
perihepatitis ,pericarditis, peritonitis and air-saculitis .
On analysis of the economic effect of the isolated viruses in
the present study revealed that AI virus subtype H9 infection in
general caused 0.5-12% mortality in broilers. On the other
hand, the presence of concurrent viral or bacterial infections
impair the disease condition which reached to 65% mortality in
infected broiler flock which may be due to concurrent viral or bacterial infections.