Genotyping of infectious bronchitis virus in Canada.

From 2014-2023, infectious bronchitis virus (IBV) was detected in 6,589 samples from Canada, and partial nucleotide (nt) sequences of the IBV spike protein () gene were determined for 1,678 samples. Based on their gene nt sequence identities and origin, Canadian IBVs could be classified into 4 groups: 1) 50.3% were variant viruses related to strains described in the United States; 2) 45.6% were vaccine-like viruses; 3) 2.1% were Eurasian viruses; 4) 2.0% were Canadian variants. Outbreaks with IBVs related to strains CAL1734/04, 4/91, and DMV/1639/11 were often associated with more severe disease in all chicken commodity groups. With the emergence of numerous IBV strains, the severity of infection and number of affected flocks increased. Outbreaks with various IBV strains overlapped in their emergence, peaked, and regressed, but the introduction of DMV/1639/11 has resulted in a continuous field challenge since its first detection in 2015.