Birnaviridaeryhmän

Birnaviridae is a family of non-enveloped, double-stranded RNA viruses that infect a range of vertebrate and invertebrate hosts. The virion is isometric, approximately 50-70 nm in diameter, and possesses a T=13 capsid. The genome consists of two segments of double-stranded RNA, designated as segment A and segment B. Segment A encodes proteins involved in viral replication and assembly, including the viral RNA-dependent RNA polymerase. Segment B encodes structural proteins and other accessory proteins.

Replication of birnaviruses occurs in the cytoplasm of host cells. The double-stranded RNA genome is transcribed by the viral RNA-dependent RNA polymerase into single-stranded messenger RNA molecules. These mRNAs are then translated by host ribosomes to produce viral proteins. Viral RNA replication involves the synthesis of new double-stranded RNA genomes from complementary single-stranded RNA templates. Assembly of new virions takes place in the cytoplasm.

Birnaviridae are classified into two genera: Aquabirnavirus and Avibirnavirus. Aquabirnaviruses primarily infect fish, causing diseases such as infectious pancreatic necrosis (IPN) in salmonids. Avibirnaviruses infect birds and are responsible for infectious bursal disease (IBD), a highly contagious and immunosuppressive disease in poultry. The viruses are transmitted horizontally through fecal-oral routes or contaminated environments. Diagnosis typically involves serological tests, virus isolation, and molecular methods. Vaccines are available for some birnaviral diseases, particularly for IBD in poultry.