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

A total of 85 dead 15 farm chickens positive for H9N2 were examined. Fibrinonecrotic, caseated or bloody stained exudate, extended from tracheal bifurcation to involve the primary bronchi. Necrosis or hyperplastic proliferation of bronchial epithelium, pneumonia with fibrinonecrotic exudate entangled with bacterial colonies. Granulomes of variable size seen in the lung. Mycoplasma coinfection was confirmed. Hypercellularity, periglomerular hemorrhage, edema and focal tubulointerstitial nephritis were common. Bursa of Fabricius showed corrugated mucosa, hydropic degeneration or cystic dilatation or ruptured epithilium. Depletion of lymphoid follicle of bursa and spleen and marked lymphocytic necrosis were observed. Necrotic enteritis with pancreatitis, while necrobiotic changes intensely infiltrated by mononuclear cells in the liver. Organized pericarditis was accompanied with myocarditis. Coinfection plays an essential role in increasing the severity of lesions and rate of mortality in H9N2 infected broilers under natural condition. IBV, Mycoplasma as well as E coli are common coinfecting organisms. The main cause of death in LPAIV H9N2 infection is a combination between respiratory failure, asphyxia and renal failure in addition to immunosuppression that enhance secondary infection

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