Molecular Characterization of PRRSV Strains Circulating in North Central Region, Vietnam During 2023-2024

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major pathogen that poses a serious threat to the global pig industry. North Central Vietnam, comprising six provinces, is one of the country’s largest pig-breeding regions; however, the information of molecular characterization of this virus circulating in this area have been limited. To address this gap, 130 samples were collected from these provinces between 2023 and 2024. The results showed a PRRSV-positive rate of 23.07% (30/130). Molecular characterizations of PRRSV were further analyzed based on sequences of the ORF5 and NSP2 hypervariable regions (HVRs), in comparison with reference strains from Vietnam and other countries downloaded from GenBank (NCBI). Phylogenetic analysis revealed that the sequenced strains belonged to PRRSV-2 (lineages 1, 5, and 8). Specifically, 28 PRRSV-2 strains were selected for ORF5 analysis and classified into sublineage 8.7 (HP-PRRSV), sub-lineage 5.1 (classical PRRSV), and the newly identified sub-lineage 1.8 (NADC30-like). The NSP2 HVRs of the identified strains showed amino acid identities ranging from 38.63% to 100%, while ORF5 identities ranged from 80.3% to 100%. Sequence analysis of ORF5 indicated that GP5 mutations were mainly concentrated in HVR1, HVR2, and virulence-associated sites. In summary, the detection of NADC30-like PRRSV for the first time in Vietnam is important, indicating that this HP-PRRSV and classical PRRSV strains reported previously are currently co-circulating among the pig population in North Central Vietnam. Additionally, these findings suggest that PRRSV strains in Vietnam are undergoing substantial genomic divergence.