Discovery of a novel recombinant avian orthoreovirus in China.

In mid-2020, using next-generation sequencing (NGS) technology, we identified a recombinant cluster 2 avian orthoreovirus (ARV) variant named PHC-2020-0545, isolated from tendons of 33-day-old broilers with leg swelling in China. Complete genomic sequencing and analyses demonstrated that the isolate was genetically significantly distinct from known ARV strains in M1 and M3 genes and its σC coding gene had an extremely high variability, compared with the identified ARV strains grouped into other genotyping cluster. Further analysis showed that many base substitutions were silent and non-silent substitutions are most likely to occur in the first positions of codons. Multiple segmental recombination, intra-segmental recombination and accumulation of point mutations might contribute to the emergence of this isolate. The PHC-2020-0545 strain had a strong replication ability in 1-day-old broilers, and mainly affected the movement, digestion and metabolism of broilers. In addition, the infection route of the isolate is related to its pathogenicity to broilers. Therefore, combined with its unique genetic characteristics and potential origin, we determined that the PHC-2020-0545 field strain is a novel recombinant ARV strain, which has certain reference value for the preparation and evaluation of new vaccines.