Emerging new avian reovirus variants from cases of enteric disorders and arthritis/tenosynovitis in Brazilian poultry flocks

1. The objective of this study was to characterise circulating Brazilian avian reovirus (ARV) strains by genetic analysis of the sigma C protein encoded by segment 1 of the viral genome and compare these with those of viral strains used for immunising commercial poultry. 2. The analysis detected the presence of ARV genomes by quantitative reverse transcriptase PCR (RT-qPCR) in the enteric samples and the joint tissues (JT) of birds with signs of viral arthritis/tenosynovitis. Nucleotide sequencing used 16 strains (three commercial vaccines, 10 from enteric tissues and three from JT). The results indicated high variability in the amino acid sequences of 13 wild strains, showing between 40% and 75% similarity compared with the vaccine strains (S1133 and 2177). 3. The sequences were grouped into three well-defined clusters in a phylogenetic tree, two of these clusters together with previous Brazilian sigma C ARV sequences, and one cluster (VII) that was novel for Brazilian strains. Antigenic analysis showed that there were amino acids within putative epitopes located on the surface of the receptor-binding region of the sigma C protein with a high degree of variability. 4. The study confirmed the presence of ARV genetic variants circulating in commercial birds in Brazil, and according to the antigenic prediction, the possibility of antigenic variants appears to be high.