Epidemiology and Genetic Characteristics of Porcine Reproductive and Respiratory Syndrome Virus in the Hunan and Hebei Provinces of China

SIMPLE SUMMARY: Porcine reproductive and respiratory syndrome virus (PRRSV) is the major cause of huge economic losses to the pig industry in China. The present study was performed to investigate the epidemiological characteristics of PRRSV in two provinces (Hunan and Hebei) in China in 2021. The results revealed the high prevalence of PRRSV in the healthy and diseased pigs in Hunan and Hebei province. The PRRSV lineages prevalent in Hunan and Hebei province were diverse, while the NADC30-like (sublineage 1.8) and HP-PRRSV (sublineage 8.7) strains predominated. Moreover, four PRRSV strains were isolated in this study, and a novel sublineage 1.8 strain recombinant from the NADC30-like strain and JXA1 (or MLV)-like strain was confirmed via investigating its complete genomic characteristics. In summary, this study has offered the latest information on the epidemiology and genetic characteristics of PRRSV in Hunan and Hebei province, which would be beneficial for PRRS control in the future. ABSTRACT: Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant threat to the pig industry in China. However, the epidemiological characteristics of PRRSV after the outbreak of African swine fever in China were not thoroughly investigated. In the present study, the serological and epidemiological investigations of PRRSV in pigs from the Hunan and Hebei provinces of China were assessed. The results showed that 73.12% (95% CI 71.74–74.49) of pigs were positive for PRRSV-special antibody by enzyme-linked immunosorbent assay. Out of 5799 samples, 482 (8.31%, 95% CI 7.60–9.02) samples were positive for PRRSV nucleic acids. The positive rates of PRRSV in healthy pigs from farms and slaughterhouses were 2.27% (47/2072) and 7.70% (217/2818), which were lower than that in diseased pigs (23.98%, 218/909). Furthermore, the full-length OFR5 gene sequences of 43 PRRSV strains were sequenced and analysed. Phylogenetic analysis revealed that 43 isolates were classified into three lineages, namely lineage 1 (n = 24), lineage 8 (n = 15), and lineage 3 (n = 4). Lineage 1 could be further divided into sublineage 1.5 (n = 2) and sublineage 1.8 (n = 22), and lineage 8 was classified into sublineage 8.1 (n = 3) and sublineage 8.7 (n = 12). Collectively, our findings revealed the severe prevalence of PRRSV in the Hunan and Hebei provinces, where sublineage 1.8 and sublineage 8.7 predominated. The present study provides the update information of the epidemiological and genetic characteristics of PRRSV in the investigated regions, which will be beneficial for PRRS control.