Abstract: [Objective] The aim of the present study was to characterize the molecular epidemiology and genetic variation of porcine reproductive and respiratory syndrome virus （PRRSV） in Guangxi Zhuang Autonomous Region. [Method] A real-time fluorescent RT-PCR kit for universal detection of PRRSV was utilized to detect the presence of PRRSV in a lung tissue sample collected from the clinically infected pig on a farm in Guangxi Zhuang Autonomous Region. Subsequently, a dual real-time fluorescent RT-PCR kit specific for the PRRSV American classic strain and NADC30-like PRRSV strain were employed to further identify the sample. The GP5 gene was amplified by PCR, and a homologous comparison was conducted between the obtained nucleotide sequence by sequencing and the GP5 gene sequences of both domestic and international PRRSV reference strains retrieved from the GenBank database. Additionally, a phylogenetic tree was constructed. The amino acid sequences derived from the GP5 gene were analyzed by sequence alignment. [Result] The sample was identified as NADC30-like PRRSV positive and designated as GXYL strain. Homologous analysis of the GP5 gene nucleotide sequences indicated that GXYL strain exhibited 61.9% to 93.2% similarity with both domestic and international PRRSV reference strains, sharing the highest homology with PRRSV NADC30 strain from the United States and the lowest homology with PRRSV LV strain of European type. Furthermore, phylogenetic tree analysis based on GP5 gene sequences placed GXYL strain within a branch alongside NADC30-like strains from China and NADC30 strains from the United States, indicating close relatedness among them within a larger branch containing other American type strains. Amino acid comparison analysis derived from GP5 gene sequences identified 7 mutation sites within GXYL strain, among which 2 sites were located at epitope A, 1 site was located at epitope B, and 4 sites were located at signal peptide region. No amino acid insertions or deletions were found. [Conclusion] GXYL strain is a NADC30-like PRRSV strain, suggesting that the surveillance of prevalence and genetic variation in PRRSV should be strengthened in this region.

Key words: porcine reproductive and respiratory syndrome virus, GP5 gene, genetic variation analysis