McClurkin A W, Coria M F, Cutlip R C
J Am Vet Med Assoc. 1979 May 15;174(10):1116-9.
A Holstein-Friesian bull and three Holstein-Friesian cows were seronegative for bovine viral diarrhea (BVD) virus but were persistently infected with the virus. Virus was isolated from buffy coat cells and nasal and lacrimal secretions during their lifetime, and they remained free of clinical signs of BVD. The three cows were pregnant when purchased, and they gave birth to full-term calves. One calf lived only a few hours, one calf became ill and died within a few days, and one calf became ill and was euthanatized within a few weeks. One cow was then bred and became pregnant but aborted a 7-month fetus. A second cow was bred approximately 5 months after parturition but did not conceive. The third cow was necropsied 6 weeks after calving, because of loss of weight. Although the bull's semen contained BVD virus when seropositive cows were bred, normal calves were born. When seronegative heifers were bred, they became seropositive to BVD virus within two weeks, with higher titers in six weeks. On heifer conceived after one service but aborted a 6-month fetus. Three others continued to have estrous cycles until their titers rose to 1:128, then they conceived and gave birth to normal calves. Another heifer conceived on the first service, had a titer of 1:128 two weeks after breeding, and gave birth to a normal calf.
一头荷斯坦 - 弗里生公牛和三头荷斯坦 - 弗里生奶牛对牛病毒性腹泻（BVD）病毒血清学检测呈阴性，但却持续感染该病毒。在它们的一生中，从血沉棕黄层细胞以及鼻和泪分泌物中分离出了病毒，并且它们没有出现BVD的临床症状。这三头奶牛购买时已怀孕，并产下了足月犊牛。一头犊牛仅存活了几个小时，一头犊牛生病并在几天内死亡，还有一头犊牛生病并在几周内被实施安乐死。然后，其中一头奶牛再次配种并怀孕，但流产了一个7个月大的胎儿。第二头奶牛在分娩后约5个月配种，但未受孕。第三头奶牛在产犊6周后因体重减轻而进行了剖检。虽然当用这头公牛的精液给血清学阳性的奶牛配种时精液中含有BVD病毒，但仍产下了正常犊牛。当用这头公牛的精液给血清学阴性的小母牛配种时，它们在两周内对BVD病毒血清学检测呈阳性，六周时滴度更高。一头小母牛配种一次后怀孕，但流产了一个6个月大的胎儿。另外三头小母牛在其滴度升至1:128之前一直有发情周期，之后它们受孕并产下了正常犊牛。另一头小母牛在首次配种时受孕，配种两周后滴度为1:128，并产下了一头正常犊牛。
