School of Veterinary Science, Massey University, Palmerston North, New Zealand.
N Z Vet J. 2020 Jul;68(4):238-241. doi: 10.1080/00480169.2019.1705932. Epub 2020 Jan 29.
To determine whether sheep that co-grazed with cattle that were suspected to be positive for bovine viral diarrhoea (BVD) virus had serological evidence of exposure to the virus. Eighteen commercial farms that routinely co-grazed cattle and sheep in the same paddocks were recruited through purposive sampling. The recruiting veterinarians identified nine farms with cattle herds that were known or highly suspected to be positive for BVD and nine farms that were considered to be free of BVD. Blood samples were taken from 15 ewes aged 1 year on each farm and samples were submitted to a commercial diagnostic laboratory to test for antibodies against pestiviruses using an ELISA. All samples that were positive were then tested using a virus neutralisation test (VNT)for antibodies against BVD virus. Of the 270 blood samples, 17 were positive for pestivirus antibodies by ELISA and these originated from two farms that were known or suspected to have BVD virus-positive cattle. None of the samples from the nine flocks co-grazed with cattle herds that were known or suspected to be BVD virus-negative were positive for pestivirus antibodies. Within the two positive farms, 2/15 samples from the first farm and 15/15 samples from the second farm were antibody-positive. When the 17 positive blood samples were submitted for VNT, all 15 samples from the second farm tested positive for BVD virus antibodies with the highest titre being 1:512. In this small sample of New Zealand sheep and beef farms with suspected BVD infection in cattle, there was evidence of pestivirus exposure in co-grazed sheep. Although we were unable to confirm the origin of the exposure in these sheep, these findings highlight that farmers who are trying to eradicate BVD from their cattle should be mindful that the infection may also be circulating in sheep, and both populations should be considered a possible risk to each other for generating transient and persistent infections. Further work is needed to estimate the true prevalence of New Zealand sheep flocks that are affected by BVD and the associated economic impacts.
为了确定是否与疑似感染牛病毒性腹泻病毒（BVD）的牛共同放牧的绵羊具有接触该病毒的血清学证据。通过有针对性的抽样，从 18 家常规在同一围场中共同放牧牛和羊的商业农场中招募了研究对象。招募的兽医确定了 9 家已知或高度怀疑牛群感染 BVD 的农场和 9 家认为没有 BVD 的农场。从每个农场的 15 只 1 岁的母羊身上采集血液样本，并将样本提交给一家商业诊断实验室，使用 ELISA 检测抗瘟病毒的抗体。所有 ELISA 检测呈阳性的样本随后使用病毒中和试验（VNT）检测抗 BVD 病毒的抗体。在 270 份血液样本中，有 17 份通过 ELISA 检测出抗瘟病毒抗体，这些样本来自两家已知或怀疑有 BVD 病毒阳性牛的农场。从与已知或怀疑为 BVD 病毒阴性的牛群共同放牧的 9 个羊群中采集的样本均未检测出抗瘟病毒抗体。在这两个阳性农场中，第一个农场的 15 个样本中有 2 个和第二个农场的 15 个样本中有 15 个样本为抗体阳性。当这 17 份阳性血液样本提交进行 VNT 时，第二个农场的 15 个样本全部对 BVD 病毒抗体呈阳性，最高滴度为 1:512。在新西兰具有疑似 BVD 感染的绵羊和肉牛养殖场的这一小样本中，共同放牧的绵羊有接触瘟病毒的证据。尽管我们无法确定这些绵羊感染的来源，但这些发现表明，正在努力从牛群中根除 BVD 的农民应注意到感染也可能在绵羊中传播，并且两个群体都应被视为彼此之间产生短暂和持续感染的潜在风险。需要进一步开展工作来估计受 BVD 影响的新西兰绵羊群体的真实流行率及其相关经济影响。
