Molecular Epidemiology and Genetic Evolution Analysis of Porcine Reproductive and Respiratory Syndrome Virus in Southern Xinjiang, China, from 2023 to 2025.

Porcine reproductive and respiratory syndrome virus (PRRSV), a major pathogen causing substantial economic losses in the global swine industry, was studied in southern Xinjiang to characterize its local epidemic features. Based on 632 clinical samples collected from 13 pig farms between 2023 and 2025, quantitative RT-PCR detection showed an overall positivity rate of 18.35% (116/632), with PRRSV-2 single infection accounting for 97.41% (113/116), PRRSV-1 single infection for 1.72% (2/116), and co-infection for 0.86% (1/116). Among 38 ORF5 sequences obtained from positive samples, Sublineage 1.8 (NADC30-like) was dominant, comprising 97.14% of successfully sequenced strains. Molecular analysis revealed that PRRSV-1 isolates carried six amino acid mutations including A129V (consistent with the Chinese strain CN/FJFQ-1/2023), while PRRSV-2 strains exhibited key variations such as the neutralization escape mutation Q13R, virulence-associated site K151R, and an anomalous vaccine marker A137. Furthermore, a recombinant strain (XJLETUQ2025-7) between NADC30 and VR-2332 was identified with breakpoints in NSP2 and NSP10. Serological surveillance of 2043 vaccinated pigs showed an overall antibody positive rate of 83.0% (1696/2043), with increasing annual rates from 72.3% (2023) and 75.4% (2024) to 91.3% (2025). In conclusion, the PRRSV epidemic in southern Xinjiang is primarily driven by NADC30-like strains of PRRSV-2, with recombination events and GP5 epitope variations posing challenges to disease control. These findings enhance the epidemiological understanding of PRRSV in the region and provide valuable insights for vaccine development and prevention strategies.