The variants are more immunosuppressive than the classic strains. Avibirnaviruses are immunosuppressive and predispose flocks to intercurrent viral pathogens and secondary bacterial infection. Infectious Bursal Disease is a major restraint to productivity and profitability in the poultry industries of both industrialized and developing nations. Indirect infection with IBDV occurs as the agent can survive in the environment for up to 3 months. Contaminated equipment, houses, and clothing of personnel is frequently a source of infection.
Affected birds are depressed and show recumbency, ruffled plumage and white diarrhea.
9.5 Pathology Dehydration and muscular hemorrhages are evident in dead birds. In acute cases the characteristic lesion comprises enlargement of the bursa of Fabricius which is often surrounded by gelatinous exudate. Sectioning the organ may show hemorrhages. Recovered birds show bursal atrophy. Airsacculitis and E. coli septicemia are frequent complications following exposure to respiratory viruses and in the presence of climatic or environmental stress.