Inclusion body hepatitis (IBH)
A disease of chickens characterized by acute mortality, often with severe anemia, is caused by an adenovirus. A number of different serotypes have been isolated from disease outbreaks but they may also be isolated from healthy chickens. This disease was first recorded in 1963 in USA and since then has been reported from many countries including India. Transmission may be vertical or lateral. Infected birds remain carriers for a few weeks. The virus is generally resistant to disinfectants (ether, chloroform, pH) and high temperatures. Since adenoviruses are commonly found in healthy poultry, isolation alone does not confirm that they are the specific cause.
Symptoms and lesions: The virus, mostly as opportunistic behaviour, attacks the host under stress but with low morbidity and low mortality. Immunosuppression, for instance due to early IBD challenge or congenital CIAV infection, may be a perpetuating factor. The birds show depression, jaundice and diarrhea. On PM examination the carcass is anemic and the there is conspicuous enlargement of liver with brown discoloration with hemorrhages, fatty degeneration and necrosis. Nephritic alterations are seen in the kidney, atrophic changes may also be present in the bursa of Fabricius.
Diagnosis: Clinical symptoms and lesions along with intranuclear inclusion bodies demonstrated in hepatocytes is indicative. The inclusions are usually eosinophilic, rarely basophilic, large, and irregular with a clear halo around. Virus isolation from the liver by chick embryo inoculation, detection of viral antigens in affected tissues by fluorescent antibody test and detection of antibodies in recovered chicks by agar gel diffusion or ELISA lead to confirmatory diagnosis.
Prevention and control: Apart from good hygiene and management practices with adequate biosecurity, breeding stock should be checked to reduce the incidence.