Xiao Chao-Ting, Harmon Karen M, Halbur Patrick G, Opriessnig Tanja
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA; College of Biology, Hunan University, Changsha, China.
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA, USA.
Vet Microbiol. 2016 Dec 25;197:72-77. doi: 10.1016/j.vetmic.2016.11.009. Epub 2016 Nov 11.
Porcine circovirus type 2 (PCV2) vaccination was introduced in the US in 2006 and since has been adopted by most pig producers. While porcine circovirus associated disease (PCVAD) outbreaks are now relatively uncommon in the US, PCV2 remains a concern which is emphasized by increasing numbers of PCR and sequencing requests for PCV2. In the present study, randomly selected lung tissues from 586 pigs submitted in 2015 were tested for presence of PCV2 DNA. Positive samples were further characterized by sequencing and combined with available PCV2 open-reading-frame (ORF) 2 sequences from the client data base of the Iowa State University Veterinary Diagnostic Laboratory. The prevalence of PCV2 in the randomly selected lung tissues was 23% (135/586) with 11.3% PCV2a, 29% PCV2b and 71.8% for PCV2d subgroup PCV2d-2. A total of 455 ORF2 sequences obtained from 2014 through 2016 were analyzed and PCV2d accounted for 66.7% of the 2014 sequences, 71.8% of the 2015 sequences, and 72% of the 2016 sequences. Interestingly, only 1.9% (9/455) of the sequences belonged to the recently identified PCV2e genotype. The present data indicates that despite an almost 100% PCV2 vaccine coverage in the US, PCV2 DNA can still be detected in almost 1 of 4 randomly selected pig tissues. PCV2d-2 is now the predominant genotype in the USA suggesting that PCV2d-2 may have some advantage over PCV2a and PCV2b in its ability to replicate in pigs under vaccination pressure.
2006年猪圆环病毒2型（PCV2）疫苗在美国投入使用，自那以后被大多数养猪生产者采用。虽然在美国猪圆环病毒相关疾病（PCVAD）的爆发现在相对不常见，但PCV2仍然是一个问题，越来越多的PCV2 PCR检测和测序请求就凸显了这一点。在本研究中，对2015年提交的586头猪随机选取的肺组织进行了PCV2 DNA检测。阳性样本通过测序进一步鉴定，并与爱荷华州立大学兽医诊断实验室客户数据库中现有的PCV2开放阅读框（ORF）2序列相结合。随机选取的肺组织中PCV2的流行率为23%（135/586），其中PCV2a为11.3%，PCV2b为29%，PCV2d亚群PCV2d-2为71.8%。对2014年至2016年获得的总共455个ORF2序列进行了分析，PCV2d在2014年的序列中占66.7%，在2015年的序列中占71.8%，在2016年的序列中占72%。有趣的是，只有1.9%（9/455）的序列属于最近鉴定出的PCV2e基因型。目前的数据表明，尽管在美国PCV2疫苗的覆盖率几乎达到100%，但在随机选取的近四分之一猪组织中仍能检测到PCV2 DNA。PCV2d-2现在是美国的主要基因型，这表明在疫苗接种压力下，PCV2d-2在猪体内的复制能力可能比PCV2a和PCV2b具有一些优势。
