Full‐Genome Analysis and Pathogenicity of a Novel Recombinant Field PRRSV‐1 Strain Between Amervac‐Like and NMEU09‐1‐Like Strains in China

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major threat to the global swine industry, causing significant economic losses. In recent years, PRRSV‐1 has become a growing concern in Chinese pig herds, with an increasing number of clinical infections being reported. However, the pathogenic potential of recombinant PRRSV‐1 strains in piglets remains unclear. In this study, a novel recombinant PRRSV‐1 strain, PRRSV1/CN/FJFQ‐1/2023, was isolated in Fujian Province in 2023, and its pathogenicity for piglets was analyzed. The complete genome of PRRSV1/CN/FJFQ‐1/2023 was 15,071 nucleotides (nts) excluding the poly (A) tails, and it had the highest homology (91%) with Amervac PRRS (a live vaccine virus of PRRSV‐1). Compared with LV and Amervac vaccine virus, PRRSV1/CN/FJFQ‐1/2023 showed distinct genetic features, including a continuous 8‐amino acid (aa) deletion in the overlapping region of the ORF3 and ORF4 genes and a unique aa deletion (aa12) in the ORF7 gene. Phylogenetic analysis revealed that PRRSV1/CN/FJFQ‐1/2023 belonged to Amervac‐like isolates of subtype 1 of PRRSV‐1, while recombination analysis showed that it was a recombinant virus from Amervac‐like and NMEU09‐1‐like strains. Animal experiments showed that PRRSV1/CN/FJFQ‐1/2023 could induce 100% morbidity, with obvious clinical symptoms, high viremia, and reduced weight gain, without death. In addition, the PRRSV1/CN/FJFQ‐1/2023 caused moderate lung consolidation and interstitial pneumonia. Our results suggest that PRRSV1/CN/FJFQ‐1/2023 is a moderately pathogenic strain in piglets.