Prevalence and Molecular Characteristics of Bovine Respiratory Syncytial Virus in Beef Cattle in China

SIMPLE SUMMARY: Bovine respiratory syncytial virus (BRSV) is an important pathogen causing cattle respiratory disease; however, the prevalence and molecular characteristics of BRSV in China remain largely unknown. The purpose of this study was to investigate the prevalence and molecular characteristics of BRSV in beef cattle with BRDC in China, and the results showed that BRSV had a wide geographical distribution, and subgroup III strains were the dominant strains in China. The Chinese strains in this study showed a unique evolutionary trend based on phylogenetic analysis of the G and F genes and genomic sequences, which contributed to a better understanding of the prevalence and genetic evolution of BRSV. ABSTRACT: Bovine respiratory syncytial virus (BRSV) is an important pathogen of the bovine respiratory disease complex (BRDC); however, its prevalence and molecular characteristics in China remain largely unknown. In this study, 788 nasal swabs from 51 beef cattle farms with BRDC outbreaks in 16 provinces and one municipality were collected from October 2020 to July 2022, and 18.65% (147/788) of samples from 23 farms across 11 provinces were detected as BRSV-positive by reverse transcription-insulated isothermal PCR (RT-iiPCR) assay. Further, 18 complete G gene sequences were classified into BRSV subgroup III, and 25 complete F gene sequences were obtained from 8 and 10 provinces. Compared to the known BRSV strains in GenBank, the G proteins and F proteins in this study shared several identical amino acid (aa) mutations. Moreover, five nearly complete genome sequences were obtained and clustered into a large branch with two America BRSV subgroup III strains (KU159366 and OM328114) rather than the sole Chinese strain (MT861050) but were located in an independent small branch. In conclusion, this study reveals that BRSV has a wide geographical distribution in China, and subgroup III strains, which have unique evolution characteristics, are the dominant strains. The results contribute to a better understanding of the prevalence and genetic evolution of BRSV.