Departments of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada.
J Vet Diagn Invest. 2021 Mar;33(2):322-330. doi: 10.1177/1040638720985825. Epub 2021 Jan 15.
Porcine reproductive and respiratory syndrome virus (PRRSV) is transmitted vertically, causing fetal death in late gestation. Spatiotemporal distribution of virus at the maternal-fetal interface (MFI) is variable, and accurate assessment of viral concentration and lesions is thus subject to sampling error. Our objectives were: 1) to assess whether viral load and lesion severity in a single sample of endometrium (END) and placenta (PLC), collected near the base of the umbilical cord (the current standard), are representative of the entire organ; and 2) to compare sampling strategies and evaluate if spatial variation in viral load can be overcome by pooling of like-tissues. Spatially distinct pieces of END and PLC of 24 fetuses from PRRSV-2-infected dams were collected. PRRSV RNA quantified by RT-qPCR was compared in 5 individual pieces per fetus and in respective pools of tissue and extracted RNA. Three distinct pieces of MFI were assessed for histologic severity. Concordance correlation and kappa inter-rater agreement were used to characterize agreement among individual samples and pools. The viral load of individual samples and pools of END had greater concordance to a referent standard than did samples of PLC. Larger pool sizes had greater concordance than smaller pool sizes. Average viral load and lesion severity did not differ by location sampled, and no technical advantages of pooling tissues versus RNA extracts were found. We conclude that multiple pieces of MFI tissues must be evaluated to accurately assess lesion severity and viral load. Three pieces per fetus provided a reasonable balance of cost and logistic feasibility.
猪繁殖与呼吸综合征病毒（PRRSV）垂直传播，导致妊娠后期胎儿死亡。病毒在母体-胎儿界面（MFI）的时空分布是可变的，因此准确评估病毒浓度和病变容易受到采样误差的影响。我们的目的是：1）评估在脐带根部（目前的标准）采集的单个子宫内膜（END）和胎盘（PLC）样本中病毒载量和病变严重程度是否代表整个器官；2）比较采样策略，并评估是否可以通过类似组织的汇集来克服病毒载量的空间变化。从 PRRSV-2 感染的母体中收集了 24 个胎儿的 END 和 PLC 的空间上不同的样本。通过 RT-qPCR 定量 PRRSV RNA，并在每个胎儿的 5 个单独样本以及相应的组织和提取 RNA 池中进行比较。对 3 个不同的 MFI 区域进行组织学严重程度评估。使用一致性相关和kappa 组内一致性来描述单个样本和样本池之间的一致性。单个样本和 END 样本池的病毒载量与参考标准的一致性大于 PLC 样本。较大的样本池大小比较小的样本池大小具有更高的一致性。采样位置的平均病毒载量和病变严重程度没有差异，并且未发现组织与 RNA 提取相比具有技术优势。我们得出结论，必须评估 MFI 组织的多个样本，以准确评估病变严重程度和病毒载量。每个胎儿 3 个样本提供了成本和物流可行性之间的合理平衡。
