Infectious bursal disease in New Brunswick

Area of Science:

• Avian pathology
• Virology
• Immunology

Background:

• Sudden onset disease in four-week-old chickens presented with depression and high mortality.
• Predominant histological finding was lymphocyte necrosis in the bursa of Fabricius.

Purpose of the Study:

• To isolate and identify the causative agent of the disease.
• To characterize the isolated virus and assess its pathogenicity.
• To determine the prevalence of the agent in local poultry flocks.

Main Methods:

• Virus isolation from bursal tissue of affected chickens.
• Serological identification using infectious bursal agent (IBA) assays.
• Characterization of viral properties (chloroform resistance, hemagglutination, cytopathic effect, filtration).
• Pathogenicity studies in four-week-old chicks and chick embryos.
• Serological survey of local poultry flocks.

Main Results:

• A virus, strain Sk-1, was isolated and identified as a strain of IBA.
• Strain Sk-1 was chloroform resistant, non-hemagglutinating, and had an estimated diameter <100nm.
• Inoculation of chicks with Sk-1 caused bursal lymphocyte necrosis.
• Inoculated chick embryos showed characteristic lesions and vascular necrosis.
• Four out of ten local flocks examined showed evidence of IBA infection.

Conclusions:

• Strain Sk-1 is a pathogenic strain of infectious bursal agent.
• The virus can cause significant pathological changes in the bursa of Fabricius in chickens.
• The serological survey suggests circulation of IBA in the local poultry population.