With LPAI outbreaks in poultry there is mild to moderate inflammation of the trachea, sinuses, air sacs and conjunctiva. In laying birds there often is ovarian atresia and involution of the oviduct. Various degrees of congestive, hemorrhagic, transudative, and necrotic lesions have been described.
In HPAI infection, gross lesions in chickens are the most extensive and severe. Fibrinous exudates may be found in the air sacs, oviduct, pericardial sac, or on the peritoneum. Small foci of necrosis may be apparent in the skin, comb, and wattles or in the liver, kidney, spleen, or lungs. Indications of vascular damage often include congestion, edema, and hemorrhages at many sites.
Classical lesions of HPAI in chickens include cyanosis and edema of the head, vesicles and ulceration on the combs, edema of the feet, blotchy red discoloration of the shanks, petechiae in the abdominal fat and various mucosal and serosal surfaces, and necrosis or hemorrhage in the mucosa of the ventriculus and proventriculus.
Lesions of HPAI in turkeys are not well described, but encephalitis and pancreatitis have been reported.
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