Genomic characteristics and epidemic trends of NADC30-like PRRSV in China.

Background: NADC30-like PRRSV was first identified in China in 2012 and had become the predominant circulating strain since 2016. Currently, the recombination patterns of NADC30-like PRRSV in China exhibit a high degree of complexity, characterized by low whole-genome sequence homology. The genomic features and epidemiological trends of these strains remain to be elucidated.

Results: To evaluate the prevalence of NADC30-like PRRSV in China, this study acquired 30 whole-genome sequences of NADC30-like strains via Next-Generation Sequencing (NGS). These sequences were subsequently integrated with 224 whole-genome sequences from China available in the GenBank database. A comprehensive analysis of the genomic characteristics of contemporary NADC30-like PRRSV strains in China was conducted. Recombinant analysis indicated a yearly increase in the number of NADC30-like strains exhibiting recombination signals, whereas nonrecombinant NADC30-like strains have become nearly extinct. Among the recombination events, those involving L1C and L8E as parental strains are most prevalent. Based on the results of recombination and phylogenetic analyses, this study classified 120 Chinese NADC30-like strains with similar recombination characteristics into groups NADC30-R1 to R12. The intra-group genetic distances of the NADC30-R1 to R12 groups approximately 5.73% (SD ± 1.68), while the inter-group genetic distances between different groups are usually stably greater than 10%. The amino acid alignment of Nsp2 demonstrated that all NADC30-R1 to R12 strains exhibit a discontinuous deletion of 131 amino acids. These classifications do not exhibit consistent pathogenic characteristics within groups, with most NADC30-like PRRSVs showing moderate virulence. Geographical distribution analysis indicated that NADC30 whole-genome sequences in China originated from 19 provinces. Notably, the NADC30-R1 and NADC30-R2 strains are the most widely distributed and abundant, suggesting that these variants have established localized epidemics in specific regions.

Conclusion: In summary, the vast majority of NADC30-like strains in our country have undergone recombination, L1C + L8E is the most common recombination mode. The NADC30-like strains in China can be classified into 12 different recombination patterns, NADC30-R1 and NADC30-R2 strains are already showing pandemic trends. These findings provide a critical foundation for future NADC30-like PRRSV prevention and control strategies.