Birnaviridae is a family of viruses. Salmonid fish, young sexually immature chickens, and insects serve as natural hosts. There are currently six species in this family, divided among 4 genera. Diseases associated with this family include: IPNV: infectious pancreatic necrosis in salmonid fish, causes significant losses to the aquaculture industry. chronic infection in adult, and acute viral disease in young salmonid fish.
The large RNA segment, segment A, of birnaviruses codes for a polyprotein (N-VP2-VP4-VP3-C)  that is processed into the major structural proteins of the virion: VP2, VP3 (a minor structural component of the virus), and into the putative protease VP4.
VP4 protein is involved in generating VP2 and VP3.recombinant VP3 is more immunogenic than recombinant VP2.
Non structuralprotein VP5 is found in RNA segment A. The function of this small viral protein is unknown.
It is believed to be involved in influencing apoptosis, but studies are not completely concurring. The protein can not be found in the virion.
Viruses in Birnaviridae are non-enveloped, with icosahedral and Single-shelled geometries, and T=13 symmetry. The diameter is around 70 nm. Genomes are linear and segmented, around 15.2.3-3kb in length. The genome codes for 5 to 6 proteins.
Viral replication is cytoplasmic. Entry into the host cell is achieved by penetration into the host cell. Replication follows the double-stranded RNA virus replication model. Double-stranded RNA virus transcription is the method of transcription. Salmonid fish, young sexually immature chickens, and insects serve as the natural host. Transmission routes are contact.
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