Department of Veterinary and Biomedical Sciences, University of Minnesota, 1971 Commonwealth Avenue, St. Paul, MN 55108, USA.
Vet Microbiol. 2013 Oct 25;166(3-4):365-74. doi: 10.1016/j.vetmic.2013.06.011. Epub 2013 Jun 21.
Porcine circovirus 2 (PCV2), the cause of porcine circovirus-associated disease (PCVAD), is widespread in swine farms throughout the United States with vaccine controlling disease, but not eliminating infection. We examined the PCV2 virological and immunological status of sows, pre-suckling piglets, and the farrowing environment of sow farms to determine PCV2 exposure risks, transmission dynamics, and immunological impacts at the time of farrowing. PCV2 was widely distributed in animals and the farrowing environment of 6 midwestern US sow farms irrespective of sow vaccination status. High levels of PCV2 capsid-specific antibodies were observed in sow serum and colostrum and had no apparent effect on PCV2 transmission to and infection in piglets. In 281 pre-suckling piglets from 59 sows, PCV2 DNA was detected in 63% of serum samples and on 93% of axillary skin swabs. PCV2 was present in one or more samples from 58 of 59 sows and in the farrowing environment. Isolated infectious virus samples from sows, presuckling piglets, and the environment were shown by sequencing to be genetically similar from all farms. In conclusion, piglets are readily infected with PCV2 in utero and are under constant challenge by PCV2 through contact with infected sows and a contaminated farrowing environment. However, maternal immunity did not affect PCV2 transmission to piglets or the viral load in sows. These findings illustrate the importance of maternal infection, despite robust anti-PCV2 immunity, in early infection of newborn piglets, and the need to develop appropriate infection models for elucidation of mechanisms of protective immunity.
猪圆环病毒 2 型（PCV2）是引起猪圆环病毒相关疾病（PCVAD）的病原体，在美国各地的养猪场广泛存在。疫苗可以控制疾病，但不能消除感染。我们检查了母猪、初生仔猪和母猪养殖场分娩环境中的 PCV2 病毒学和免疫学状况，以确定 PCV2 的暴露风险、传播动态以及分娩时的免疫影响。无论母猪是否接种疫苗，6 个美国中西部母猪场的动物和分娩环境中都广泛存在 PCV2。母猪血清和初乳中观察到高水平的 PCV2 衣壳特异性抗体，但对 PCV2 向仔猪的传播和感染没有明显影响。在来自 59 头母猪的 281 头初生仔猪中，63%的血清样本和 93%的腋窝皮肤拭子中检测到 PCV2 DNA。59 头母猪中的 58 头母猪及其分娩环境中均存在 1 个或多个样本中存在 PCV2。从所有农场分离的母猪、初生仔猪和环境中的感染性病毒样本的测序结果表明，它们在遗传上是相似的。总之，仔猪在子宫内很容易感染 PCV2，并通过与感染母猪和受污染的分娩环境接触而不断受到 PCV2 的挑战。然而，母源免疫并不影响 PCV2 向仔猪的传播或母猪的病毒载量。这些发现表明，尽管存在强大的抗 PCV2 免疫，但母体感染在新生仔猪的早期感染中非常重要，需要开发适当的感染模型来阐明保护性免疫的机制。
