Emergence of a new genotype of avian infectious bronchitis virus in Brazil.

Infectious bronchitis virus (IBV) is the agent of a highly contagious disease that affects domestic fowl (Gallus gallus). Recent reports showed a high prevalence of one main IBV genotype (Brazil or BR-I) with low genetic diversity in commercial poultry flocks from Brazil. This research analyzed IBV positive poultry flocks from different rearing regions to verify the S1 gene variability and geographic distribution of variant IBV strains in recent years (2010 and 2011). Samples of IBV-positive flocks were obtained from 60 different farms. Forty-nine partial S1 gene sequences were determined and aligned for phylogenetic and amino acid similarity analyses. Eleven samples (22.4%) were similar to Massachusetts vaccine strains (Mass genotype) and 34 samples (69.4%) to the previously characterized Brazilian BR-I genotype. Interestingly, the remaining four samples (8.2%) clustered into a new IBV variant genotype (Brazil-II or BR-II), divergent from the BR-I. A unique nucleotide sequence insertion coding for five amino acid residues was observed in all the Brazilian variant viruses (BR-I and BR-II genotypes). These results show a higher genetic diversity in Brazilian IBV variants than previously described.