Avibirnaviruses

Avibirnaviruses are a genus of single-stranded RNA viruses belonging to the *Birnaviridae* family, primarily known for infecting birds. These viruses are classified under the species *Avibirnavirus A*, with *Avian birnavirus 1* (ABV-1) being the most well-studied serotype. They are enveloped viruses with a segmented genome consisting of two linear RNA molecules, designated as segments A and B. Segment A encodes the viral polymerase and the viral protein (VP) 2, which is the major capsid protein, while segment B encodes the VP3 and VP4 proteins, which are involved in viral replication.

Avibirnaviruses are associated with a range of diseases in poultry, most notably infectious bursal disease (IBD), also known as Gumboro disease. This highly contagious viral infection primarily affects young chickens, particularly those between 3 and 6 weeks of age, causing severe immunosuppression, high mortality, and significant economic losses in the poultry industry. The virus spreads through the fecal-oral route, with contaminated feed, water, and equipment serving as common transmission vectors.

The clinical signs of IBD include lethargy, pale combs, diarrhea, and dehydration. In severe cases, the infection can lead to bursal atrophy, a key diagnostic feature. Diagnosis is typically confirmed through serological tests, such as enzyme-linked immunosorbent assays (ELISAs), or molecular techniques like reverse transcription-polymerase chain reaction (RT-PCR). Prevention and control measures include vaccination, biosecurity practices, and culling infected flocks to prevent widespread outbreaks.

Avibirnaviruses are not known to infect humans, and their host range is largely restricted to birds. However, they serve as important models for studying viral replication and pathogenesis in avian species. Research continues to explore the genetic diversity of these viruses, their evolution, and the development of more effective vaccines and control strategies to mitigate their impact on global poultry production.