Abstract
Porcine reproductive and respiratory syndrome virus (PRRSV) is characterized by its extensive genetic diversity. Here we analyzed 101 sequences of NSP2 hypervariable region, 123 ORF3 sequences, and 118 ORF5 sequences from 128 PRRSV-positive clinical samples collected in different areas of China during 2008–early 2012. The results indicated that the amino acid identities of the three genes among these sequences were 87.6%–100%, 92.5%–100%, and 77%–100%, respectively. Meanwhile, 4 novel patterns of deletion and insertion in NSP2 region or GP5 were first found. The phylogenetic analysis on these 3 genes revealed that the Chinese PRRSV strains could be divided into three subgroups; majority of genes analyzed here were clustered in subgroup 3 with multiple branches; the strains with 30-aa deletion in NSP2-coding region were still the dominant virus in the field. Further phylogenetic analysis on four obtained complete genomic sequences showed that they were clustered into different branches with the Chinese corresponding representative strains. Our analyses suggest that the genetic diversity of genotype 2 PRRSV in the field displays a tendency of increasing in recent years in China, and the 30-aa deletion in NSP2-coding region should be no longer defined as the molecular marker of the Chinese HP-PRRSV.
Highlights
Porcine reproductive and respiratory syndrome (PRRS) characterized as reproductive failure in sow and respiratory disorder in all-age pigs [1] is regarded as one of the major concerns for disease controlling in pig farms [2,3,4,5]
The results showed that totally 101 NSP2, 123 ORF3, and 118
ORF5 sequences were successfully obtained from 128 PRRSVpositive samples collected during the period from 2008 to early 2012 (Table 2)
Summary
Porcine reproductive and respiratory syndrome (PRRS) characterized as reproductive failure in sow and respiratory disorder in all-age pigs [1] is regarded as one of the major concerns for disease controlling in pig farms [2,3,4,5]. Since the first outbreak of PRRS in China was documented at the end of 1995 [27], this disease has been accompanying the Chinese swine industry [28]. Considering China has the largest number of pig farms with diversity of size and different levels of biosecurity control and management, the economical cost caused by PRRS in China should be higher than that in the United States, which was estimated to be $664 million per year [4, 29]. The phylogenetic analyses have indicated that the causative pathogen HP-PRRSV was evolved by a gradual variation and accumulation progress of genome changes from the early Chinese domestic strain [25, 26]. A phylogenetic tree based on the fulllength genomic sequence is conducted in order to analyze the evolutionary relationship of these strains
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