Complete genomic characterization and genetic diversity of four European genotype porcine reproductive and respiratory syndrome virus isolates from China in 2011

Porcine reproductive and respiratory syndrome (PRRS) is an emerging disease that has caused serious economic losses to the swine industry worldwide. In 2011, a nation-wide surveillance program investigated the prevalence of PRRS viruses (PRRSV) in Chinese breeding swine farms, and four European genotype PRRSV (PRRSV-Type 1) were successfully isolated. To explore the genetic diversity of PRRSV-Type 1 in China, these 4 viral strains were subjected to genome sequencing and analysis. The four isolates shared 87.4-90.7 % nucleotide homology with the Lelystad strain (PRRSV-Type 1 stereotype strain). NSP2, ORF3, and ORF4 were the most variable regions and contained discontinuous deletions or insertions when compared to other PRRSV-Type 1 strains. All isolates fell into separate branches of the subtype 1 of PRRSV-Type 1 phylogenetic tree. This analysis of emerging PRRSV-Type 1 strains revealed previously unrecorded genetic diversity. Close attention should be paid to the prevention and control of this evolving virus.