Inclusion Body Hepatitis

Inclusion body hepatitis (IBH) is an acute disease of young chickens associated with anemia and hemorrhagic disorders. A similar disease has been reported in quail with quail bronchitis ( Quail Bronchitis: Introduction) caused by an avian adenovirus. Once considered common, IBH is now rarely diagnosed, but it has been seen in many areas of the world.

Etiology, Transmission, and Pathogenesis:
Adenoviruses have been considered to be the cause. A birnavirus (the cause of infectious bursal disease [IBD], Infectious Bursal Disease: Introduction ) and a circovirus (the chick anemia virus [CAV], Chicken Anemia Virus Infection: Introduction ) have been associated wit. adenovirus infections; both of these cause immunosuppression and contribute greatly to the severity of disease caused by adenoviruses.

Adenoviruses are ubiquitous and are transmitted horizontally and vertically. Infections are common and widespread in chickens. Chicks and young chickens are affected most commonly. Infection by adenovirus usually results in minimal hepatic disease; however, if birds infected with the IBD virus or CAV are infected with adenoviruses, clinical disease becomes evident.

Clinical Findings, Lesions:
Sudden mortality usually is seen in chickens <6 wk old. Mortality is seldom >7%. Signs associated with diseases caused by other pathogens (eg, bacteria, fungi, or viruses) commonly occur if birds are immunosuppressed. In these cases, mortality rates may be >30%. Hemorrhage may occur in any organ. The bursa of Fabricius usually is small. Bone marrow, livers, and other organs usually are pale. Congestion and multifocal areas of light or dark discoloration are seen in. livers. Microscopically, solitary prominent basophilic inclusion bodies are seen in hepatocyte nuclei. Inclusion body hepatitis, chicken

A tentative diagnosis is based on typical microscopical findings and confirmed by isolating adenoviruses from portions of liver. Immunosuppression resulting from infection with the IBD virus or CAV usually is the. predisposing event that culminates in clinical IBH.

Treatment, Control, and Prevention:
Treatment consists of nursing care. Antibiotics may help prevent secondary bacterial infections. Sulfonamides are contraindicated if evidence of hematologic disease or immunosuppression is seen.

Broiler-breeder flocks should have high levels of IBD antibody before they begin to lay fertile eggs. Vaccines against IBH or CAV are not commercially available in the USA. In Australia, a peracute form of IBH has occurred in broiler chickens in the absence of infections with either the IBD virus or CAV. A live IBH vaccine is effective in preventing IBH in progeny when administered P. or in drinking water to breeder chickens several weeks before the onset of lay. In Pakistan, IBH is an essential part of the hydropericardium syndrome of broiler chickens in which an excessive amount of clear, watery or jelly-like fluid accumulates in the pericardial sac of chickens 3-6 wk old. A formalized vaccine prepared from the homogenated livers of experimentally infected chickens is 80-90% effective in preventing the hydropericardium syndrome when administered SC to chicks 10-12 days old.

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