An unusual outbreak of inclusion body hepatitis on a broiler chicken farm: a case report

This study investigated an outbreak of inclusion body hepatitis in ROSS 308 hybrid broiler type chickens between 19 and 25 days of fattening. For this purpose, clinical observation, ELISA fowl adenovirus and chicken anaemia virus antibody detection in serum at 21 and 42 days, mortality evaluation, epidemiological analysis, histology and genetic identification were performed. The six flocks of the farm consisted of 90,000 chickens. Only one flock of 15,000 chickens was affected on this farm. At 19 days of age, ill chickens showed clinical signs of depression, anorexia, somnolence, ruffled feathers, anaemic comb and wattles and occasionally nervous signs. Based on ELISA titres, the antibody response to fowl adenovirus increased greatly from 21 to 42 days. The antibody response to vaccination against infectious bursal disease virus and chicken anaemia virus was at the expected level in all broiler flocks. Necropsy showed diffuse petechial and ecchymotic haemorrhages in skeletal muscles, liver, pancreas, kidney, together with hepatomegaly, splenomegaly and catarrhal enteritis. Histologically, fatty liver degeneration, multifocal liver necrosis and intranuclear inclusions in hepatocytes, as well as focal necrosis in pancreas and spleen parenchyma were seen. The DNA of AAV-1 (avian adenovirus group 1) was detected using the PCR method in paraffin-embedded liver samples. The results revealed no association of inclusion body hepatitis with infectious bursal disease virus or chicken anaemia virus infection, and suggested primary disease. However, the involvement of only one chicken flock on the farm remains unexplained.