Avian infectious bronchitis (IB) is an acute and highly contagious respiratory disease of chickens.
The disease is caused by avian infectious bronchitis virus (IBV), a coronavirus (Coronaviridae, Orthocoronavirinae, genus Gammacoronavirus, subgenus Igacovirus),[1] and characterized by respiratory signs including gasping, coughing, sneezing, tracheal rales, and nasal discharge.
[2][3] Coughing and rattling are common, most severe in young, such as broilers, and rapidly spreading in chickens confined or at proximity.
Many laid eggs have a thin or soft shell and poor albumen (watery), and are not marketable or proper for incubation.
The most updated classification of IBV places the virus in Coronaviridae, Orthocoronavirinae, genus Gammacoronavirus, subgenus Igacovirus.
The virions are enveloped and characterized by large surface projections (spikes or S) partially embedded in the double lipid layer.
Attenuated vaccines will revert to virulence by consecutive passage in chickens in densely populated areas, and may reassort with field strains, generating potentially important variants.
For virus characterization, the methodology using genomic amplification (PCR), firstly by the reverse transcription of viral RNA into cDNA, the cyclic amplification of cDNA and sequencing of products, will enable very precise description of strains, according to the oligonucleotide primers designed and target gene.
Biosecurity protocols, including adequate distancing of flocks, isolation and disinfection are important in controlling the spread of the infection and disease.