Family: Birnaviridae

Genus: Avibirnavirus

Distinguishing features

Viruses in the genus infect only birds. 

Virion

See discussion under family description. 

Genome organization and replication

See discussion under family description. 

Biology

Infectious bursal disease virus (IBDV) causes an immunosuppressive disease in chickens by destruction of B lymphocytes in the bursa of Fabricius. Apoptosis has also been observed in this and other lymphoid organs. VP5 inhibits apoptosis at the early stage of viral infection in chicken embryonic fibroblast cells, whereas VP2 induces apoptosis in transfected mammalian cells. The latter finding correlates with evidence of apoptosis and B cell death in chickens infected with IBDV. The rapid depletion of B cells in the bursa of Fabricius leads to immunosuppression and increased susceptibility to other infections and diseases. The virus is highly contagious and is of major importance to the poultry industry worldwide. Two serotypes (1 and 2) of IBDV have been identified by cross-neutralization assays. Serotype 1 strains are pathogenic in chickens, whereas serotype 2 strains are nonpathogenic. 

Species demarcation criteria

Not applicable.