Nelsen April, Lin Chun-Ming, Hause Ben M
Department of Veterinary and Biomedical Sciences, South Dakota State University, Brookings, SD, United States.
Animal Disease Research and Diagnostic Laboratory, South Dakota State University, Brookings, SD, United States.
Front Vet Sci. 2021 Aug 13;8:726884. doi: 10.3389/fvets.2021.726884. eCollection 2021.
Porcine respiratory disease complex (PRDC) is a significant source of morbidity and mortality, manifested by pneumonia of multiple etiologies, where a variety of pathogens and environment and management practices play a role in the disease. Porcine reproductive and respiratory syndrome virus (PRRSV), influenza A virus (IAV), and porcine circovirus 2 (PCV2) are well-established pathogens in PRDC. Porcine parvovirus 2 (PPV2) has been identified in both healthy and clinically diseased pigs at a high prevalence worldwide. Despite widespread circulation, the significance of PPV2 infection in PRDC and its association with other co-infections are unclear. Here, PPV2 was detected in the lung tissue in 39 of 100 (39%) PRDC-affected pigs by quantitative polymerase chain reaction (qPCR). Using hybridization (ISH) in conjunction with tissue microarrays (TMA), PPV2 infection was localized in alveolar macrophages and other cells in the lungs with interstitial pneumonia in 28 of 99 (28.2%) samples. Viral load tended to correlate with the number of macrophages in the lungs. Assessment of the frequency, viral titers, and tissue distributions showed no association between infection of PPV2 and other major viral respiratory pathogens. In one-third of the PPV2-positive samples by qPCR, no other known viruses were identified by metagenomic sequencing. The genome sequences of PPV2 were 99.7% identical to the reference genomes. Although intensive intranuclear and intracytoplasmic signals of PPV2 were mainly detected in alveolar macrophages by ISH, no obvious virus replication was noted in cell culture. Together, these results suggest that PPV2 is associated, but may not be the sole causative agent, with PRDC, warranting the control and prevention of this underdiagnosed virus.
猪呼吸道疾病综合征（PRDC）是发病率和死亡率的重要来源，表现为多种病因引起的肺炎，多种病原体以及环境和管理因素在该病中起作用。猪繁殖与呼吸综合征病毒（PRRSV）、甲型流感病毒（IAV）和猪圆环病毒2型（PCV2）是PRDC中公认的病原体。猪细小病毒2型（PPV2）在全球范围内健康猪和临床患病猪中均有高流行率的报道。尽管PPV2广泛传播，但其在PRDC中的感染意义及其与其他合并感染的关联尚不清楚。在此，通过定量聚合酶链反应（qPCR）在100头受PRDC影响的猪中的39头（39%）的肺组织中检测到PPV2。使用原位杂交（ISH）结合组织微阵列（TMA），在99个样本中的28个（28.2%）间质性肺炎肺组织中，PPV2感染定位于肺泡巨噬细胞和其他细胞。病毒载量倾向于与肺中巨噬细胞数量相关。对感染频率、病毒滴度和组织分布的评估表明，PPV2感染与其他主要病毒性呼吸道病原体之间无关联。在qPCR检测为PPV2阳性的样本中，三分之一通过宏基因组测序未鉴定出其他已知病毒。PPV2的基因组序列与参考基因组的同源性为99.7%。尽管ISH主要在肺泡巨噬细胞中检测到PPV2强烈的核内和胞浆内信号，但在细胞培养中未观察到明显的病毒复制。总之，这些结果表明PPV2与PRDC有关联，但可能不是唯一的病原体，需要对这种诊断不足的病毒进行控制和预防。
