Kenhoku Livestock Hygiene Service Center, Ibaraki Prefecture, 966-1 Nakagachi, Mito, Ibaraki 310-0002, Japan.
Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan.
J Vet Med Sci. 2020 May 20;82(5):607-614. doi: 10.1292/jvms.19-0634. Epub 2020 Mar 13.
The objective of this study was to provide a screening scheme of persistently infected (PI) cattle on dairy herds by combining reverse-transcription polymerase chain reaction (RT-PCR) to detect bovine viral diarrhea virus (BVDV) in milk tanker samples and commercial enzyme-linked immunosorbent assay to detect BVDV antibodies in bulk tank milk. We conducted a pilot survey and regional survey targeting all dairy farms in Ibaraki Prefecture by using milk tanker and bulk tank milk samples to screen PI cattle. Farms with positive samples underwent a follow-up test to identify PI cattle. In the pilot study, all virus-positive samples in bulk tank milk were included in the positive milk tanker samples. The RT-PCR assay successfully detected BVDV at dilutions of 1:1,600 by using two PI cows' milk. In the regional survey, 5 of 79 milk tanker samples were virus-positive. The virus was detected in three PI lactating cows and one PI calf on three farms. Antibody screening using bulk tank milk samples revealed 15 of 363 samples were positive, and 12 of 348 farms were BVDV antibody-positive. Follow-up tests on one farm identified three PI calves. Thus, eight PI cattle on five farms were identified in this study. In conclusion, combining BVDV detection using milk tanker samples and antibody detection using bulk tank milk is a feasible and economical method to efficiently screen PI cattle and confirm the PI-free status among dairy herds.
本研究的目的是通过结合反转录聚合酶链反应(RT-PCR)检测奶罐样本中的牛病毒性腹泻病毒(BVDV)和商业酶联免疫吸附测定(ELISA)检测批量奶中的 BVDV 抗体,为奶牛群中的持续感染(PI)牛提供一种筛选方案。我们使用奶罐和批量奶样本对茨城县的所有奶牛场进行了试点调查和区域调查,以筛选 PI 牛。阳性样本的农场进行了后续测试以确定 PI 牛。在试点研究中,批量奶中所有病毒阳性样本均包含在阳性奶罐样本中。该 RT-PCR 检测法成功地在稀释度为 1:1,600 时检测到了来自两只 PI 奶牛的牛奶中的 BVDV。在区域调查中,79 份奶罐样本中有 5 份呈病毒阳性。在三个农场的 3 头泌乳 PI 牛和 1 头 PI 小牛中检测到该病毒。使用批量奶样本进行抗体筛选发现 363 份样本中有 15 份呈阳性,348 个农场中有 12 个为 BVDV 抗体阳性。对一个农场的后续测试发现了 3 头 PI 小牛。因此,本研究共在五个农场中发现了八头 PI 牛。总之,结合使用奶罐样本进行 BVDV 检测和使用批量奶进行抗体检测是一种可行且经济的方法,可有效筛选 PI 牛并确认奶牛群中的 PI 无状态。