Detection, virus isolation, and phylogenetic analysis of PRRSV2 in China from 2022 to 2025.

BACKGROUND

Porcine reproductive and respiratory syndrome (PRRS) is one of the most important diseases threatening the global pig industry. It has been reported that PRRSV predominantly circulating in clinical practice in China belongs to the genotype 2 (PRRSV2), comprising four lineages: lineages 1, 3, 5, and 8. Among these, lineage 1 strains are further divided into sublineage 1.5 (NADC34-like strains) and sublineage 1.8 (NADC30-like strains).To further understand the prevalence and variation characteristics of PRRSV2 in China, this study conducted detection, virus isolation, and genetic evolution analysis of PRRSV2 from 2022 to 2025.

RESULTS

This study employed qRT-PCR to detect PRRSV2 in 23,962 samples collected nationwide from 2022 to 2025, with an average positive detection rate of 33.29%. Phylogenetic analysis based on the ORF5 gene revealed that sublineage 1.8 PRRSV was predominant in China, followed by sublineage 1.5 and lineage 8. A total of 389 PRRSV2 strains were isolated using porcine alveolar macrophage (PAM) cells, of which 59 strains could proliferate in Marc-145 cells. Different amino acid variations, insertions, and deletions were identified in the ORF5 and Nsp2 genes of the 389 PRRSV2 strains. Whole genome sequencing was performed on 79 PRRSV strains, and 93.67% (74 strains) exhibited inter-lineage recombination.

CONCLUSION

This study demonstrates the positive detection rate and predominant strain types of PRRSV2 in China. Sequencing results of isolated PRRSV strains reveals amino acid variations and recombination in the ORF5, Nsp2, and whole genomes. Overall, this study provides data support for the molecular epidemiology of PRRSV2 in China.