东南地区猪圆环病毒2型检测及分子流行病学分析

Detection and molecular epidemiology analysis of porcine circovirus type 2 in Southeast China

【目的】分析我国东南地区2012-2018年规模化猪场猪圆环病毒2型(PCV2)的流行动态、基因组特性及病毒重组情况,为猪圆环病毒相关疾病(PCVAD)的防控和疫苗开发提供理论依据。【方法】对2012-2018年采自福建、江西、广东、江苏及浙江等省规模化猪场疑似断奶仔猪多系统衰弱综合症(PMWS)猪只的649份组织样本及血清样本采用PCR方法进行检测,对PCV2进行基因分型,并选取54份阳性样品进行PCV2全基因组同源性比对、系统发育分析和重组分析,同时对ORF2基因进行遗传进化分析和衣壳(Cap)蛋白氨基酸序列比对。【结果】东南地区猪场感染PCV2较普遍,PCV2阳性率为41.9%(272/649)。猪场存在PCV2a、PCV2b、PCV2d和PCV2e 4个基因型毒株,其中以PCV2d流行为主。基于PCV2全长核苷酸序列和ORF2基因的系统进化分析表明,54株PCV2毒株均分为4个基因型;PCV2e毒株检出率较低(仅为0.46%),其基因组全长1777 bp,与其他基因型代表毒株的全长核苷酸同源性较低(91.0%~93.0%)。重组分析表明,不同基因型毒株间存在重组现象。Cap蛋白的氨基酸序列分析表明,不同基因型具有特征性的突变位点。【结论】东南地区猪场存在4种基因型PCV2,其中PCV2d为优势基因型,不同基因型毒株间存在重组现象。新基因型PCV2e的检出率较低。

【Objective】This study analyzed the epidemic status,genetic characteristics and virus recombination of PCV2 in Southeast China from 2012 to 2018 to provide basis for prevention and control of PCVAD as well as development of vaccines.【Method】A total of 649 clinical samples and serum samples were collected from large-scale pig farms in Southeast China including Fujian,Jiangxi,Guangdong,Jiangsu and Zhejiang from 2012 to 2018 and PCV2 was detected by the specific PCR detection method.To further study the genetic characteristics of PCV2,54 of 272 PCV2 positive samples were selected for sequenced following amplification by PCR and comprehensive analysis on whole genome of PCV2 was conducted,including genome homology comparison,phylogenetic analysis and recombination analysis.Genetic evolution analysis of ORF2 gene and amino acid sequence comparison of Cap protein were also performed.【Result】Of the 649 samples,PCV2 DNA was identified in 41.9%(272/649)by PCR,indicating PCV2 was distributed widely in swineherds in Southeast China.At least four PCV2 genotypes including PCV2a,PCV2b,PCV2d and PCV2e existed in swineherds,among which PCV2d was the predominant genotype.Phylogenetic analysis based on whole gene and ORF2 gene showed that 54 PCV2 strains were divided into 4 genotypes.A new PCV2 genotype(PCV2e)was detected with very low detection rate(0.46%)in swineherds.Sequencing of whole genomes of PCV2e showed that the genome length was 1777 bp,and it shared a low nucleotide homology with other four representative genotype strains(91.0%-93.0%).Recombination analysis showed that there was recombination among strains of different genotypes.The amino acid sequence analysis of Cap protein showed that different genotypes had characteristic mutation sites.【Conclusion】At least 4 genotypes of PCV2 were present in Southeast China,among which PCV2d was predominant in swineherds.Inter-genotypic recombination events of PCV2 were detected.Although a new genotype PCV2e emerged in swineherds,its detection rate was very low.