Taylor L F, Janzen E D, Van Donkersgoed J
Department of Herd Medicine and Theriogenology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon.
Can Vet J. 1997 Jan;38(1):23-8. doi: 10.4141/cjas58-003.
In 1992, significant calf losses occurred between birth and weaning in a 650-cow Saskatchewan beef herd. These losses occurred subsequent to ill-thrift and disease, and every calf necropsied was found to be persistently infected with bovine viral diarrhea virus (BVDV). The objectives of this study were to describe the losses associated with fetal infection with BVDV in this herd and to determine why they occurred. For investigative purposes, blood samples were collected from the entire cow herd and the surviving calves at pregnancy testing in 1992, and tested by virus isolation for BVDV. Between 51 and 71 persistently infected calves were born in 1992. Bovine viral diarrhea virus was only isolated from calves. The only confirmed fetal infections with BVDV were recorded as the birth of persistently infected calves. However, abortions, reduced pregnancy rates, and delayed calvings were also recorded in the cow herd and may have been the result of fetal infections. The herd was monitored again in 1993. Fetal infections with BVDV were recorded as the birth of stunted, deformed, and persistently infected calves. The greatest losses due to fetal infection with BVDV in the 2 years of this study occurred in cows that were 3-years-old at calving (second calves). Bovine viral diarrhea virus appears to have remained endemic in this herd by transmission from persistently infected calves on young 3- and 4-year-old cows to naive calved 2-year-old cows that were mingled with them annually for rebreeding. Significant numbers of the 2-year-old cows remained naive to BVDV, because they were segregated from persistently infected calves at weaning, preventing cross-infection with BVDV.
1992年，萨斯喀彻温省一个拥有650头牛的肉牛群在出生至断奶期间出现了大量犊牛死亡。这些损失发生在生长不良和疾病之后，每头进行尸检的犊牛都被发现持续感染牛病毒性腹泻病毒（BVDV）。本研究的目的是描述该牛群中与BVDV胎儿感染相关的损失，并确定损失发生的原因。为了进行调查，1992年在妊娠检测时从整个牛群和存活的犊牛中采集了血样，并通过病毒分离法检测BVDV。1992年出生了51至71头持续感染的犊牛。牛病毒性腹泻病毒仅从犊牛中分离出来。唯一确诊的BVDV胎儿感染记录为持续感染犊牛的出生。然而，牛群中也记录到了流产、妊娠率降低和产犊延迟，这些可能是胎儿感染的结果。1993年对该牛群再次进行了监测。BVDV胎儿感染记录为发育迟缓、畸形和持续感染犊牛的出生。在本研究中的两年里，由于BVDV胎儿感染造成的最大损失发生在产犊时3岁的母牛（二胎母牛）身上。牛病毒性腹泻病毒似乎通过从3岁和4岁年轻母牛身上持续感染的犊牛传播给每年与之混群进行再次繁殖的未感染过的2岁产犊母牛，从而在该牛群中保持地方流行性。大量2岁母牛对BVDV仍未感染，因为它们在断奶时与持续感染的犊牛隔离，防止了BVDV的交叉感染。
