Abstract
BackgroundPorcine reproductive and respiratory syndrome virus (PRRSV) exhibits extensive genetic variation. The outbreak of a highly pathogenic PRRS in 2006 led us to investigate the extent of PRRSV genetic diversity in China. To this end, we analyzed the Nsp2 and ORF7 gene sequences of 98 Chinese PRRSV isolates.ResultsPreliminary analysis indicated that highly pathogenic PRRSV strains with a 30-amino acid deletion in the Nsp2 protein are the dominant viruses circulating in China. Further analysis based on ORF7 sequences revealed that all Chinese isolates were divided into 5 subgroups, and that the highly pathogenic PRRSVs were distantly related to the MLV or CH-1R vaccine, raising doubts about the efficacy of these vaccines. The ORF7 sequence data also showed no apparent associations between geographic or temporal origin and heterogeneity of PRRSV in China.ConclusionThese findings enhance our knowledge of the genetic characteristics of Chinese PRRSV isolates, and may facilitate the development of effective strategies for monitoring and controlling PRRSV in China.
Highlights
Porcine reproductive and respiratory syndrome virus (PRRSV) exhibits extensive genetic variation
Previous studies have focused mainly on the ORF5 or Nsp2 genes, while the genetics of the Chinese PRRSVs based on the ORF7 gene are not well characterized
The highly pathogenic PRRS viruses with a discontinuous 30 amino acid deletion have been the dominant strains circulating in China
Summary
Porcine reproductive and respiratory syndrome virus (PRRSV) exhibits extensive genetic variation. The outbreak of a highly pathogenic PRRS in 2006 led us to investigate the extent of PRRSV genetic diversity in China. To this end, we analyzed the Nsp and ORF7 gene sequences of 98 Chinese PRRSV isolates. Porcine reproductive and respiratory syndrome (PRRS) is a severe disease characterized by reproductive disorders in gilts and sows, especially during late gestation, and by respiratory distress in pigs. Since the first report of PRRSV in China in 1996 [10], the North American type PRRSV, with considerable genetic variation, has spread throughout the country [11,12,13]. The N protein has been extensively used for determining the genetic variation and the phylogenetic relationships among PRRSVs [23,24,25], suggesting a significant role for ORF7 in PRRSV evolutional surveillance
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