Inclusion-Body Hepatitis in Broiler Chickens

Abstract

SUMMARY Eighty-six outbreaks of inclusion-body hepatitis were identified in broiler chickens in Ontario. The disease occurred mainly in birds 5 weeks old, and mortality (ranging from 0.1 to 7%) was most common in the spring. Grossly, the common lesions were stellate or punctiform hemorrhagic areas in extremely fatty livers, enlarged pale kidneys, hemorrhagic lesions in the visceral fat and muscles, pale bone marrow, and an extremely small firm bursa of Fabricius. Histological examination of tissues revealed intranuclear inclusion bodies in the hepatocytes with massive necrosis of liver parenchyma, regression of the follicles and proliferation of interstitial connective tissue in the bursa, aplastic bone marrow with little hemopoietic tissue functioning, and a moderate to severe nephrosis involving the proximal and distal convoluted tubules. Bacteriological examination was negative. Electron-microscope examination of the livers revealed abnormal intranuclear structures; however, no distinct virus particles were seen. A virus was isolated and produced cytopathic changes in chick and'duck embryo cell cultures.