Benitez Oscar J, Roberts Jennifer N, Norby Bo, Bartlett Paul C, Maeroff Jacqueline E, Grooms Daniel L
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, 736 Wilson Rd, East Lansing, MI, 48895, USA.
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, 736 Wilson Rd, East Lansing, MI, 48895, USA.
Theriogenology. 2019 Mar 1;126:187-190. doi: 10.1016/j.theriogenology.2018.12.005. Epub 2018 Dec 3.
Bovine leukosis is a chronic lymphoproliferative disorder that leads to significant economic losses in the beef and dairy industries. The major route of virus transmission is believed to be iatrogenic through the transfer of blood containing infected lymphocytes. In addition, BLV proviral DNA has been identified in nasal secretions, saliva, milk, colostrum, semen and smegma; however, natural transmission of BLV through these secretions has not been clearly demonstrated. The use of bulls for natural breeding has been identified as a risk factor in BLV infected dairy herds. However, the risk of BLV-infected bulls transmitting the virus is unknown. The objective of this study was to evaluate the potential for BLV transmission during natural breeding between a BLV-infected bull and uninfected heifers. Forty healthy, BLV seronegative, and proviral-negative beef heifers were randomly assigned to one of two groups: control heifers (n = 20) exposed to a BLV seronegative and proviral negative bull and challenged heifers (n = 20) exposed to a BLV seropositive and proviral-positive bull. Each group was housed with the bull for a period of 38 days in a 5-acre pasture to replicate the housing of commercial beef cattle during the breeding season. Blood samples were collected from heifers at -60, -30 and 0 days prior to breeding and day 30, 60 and 90 after the breeding period ended. Blood samples were tested for BLV antibodies by ELISA and BLV proviral DNA by CoCoMo-qPCR. New infection was not detected by ELISA or CoCoMo-qPCR in any of the challenge or control heifers at any time point during the study. Based on these results, BLV infected bulls that are healthy and aleukemic may not be a significant risk of BLV transmission during a defined breeding season.
牛白血病是一种慢性淋巴细胞增殖性疾病，会给肉牛和奶牛产业造成重大经济损失。病毒传播的主要途径被认为是通过含有感染淋巴细胞的血液进行医源性传播。此外，在鼻分泌物、唾液、牛奶、初乳、精液和包皮垢中已鉴定出牛白血病病毒前病毒DNA；然而，尚未明确证明牛白血病病毒通过这些分泌物进行自然传播。在感染牛白血病病毒的奶牛群中，使用公牛进行自然配种已被确定为一个风险因素。然而，感染牛白血病病毒的公牛传播该病毒的风险尚不清楚。本研究的目的是评估感染牛白血病病毒的公牛与未感染的小母牛自然配种期间传播牛白血病病毒的可能性。将40头健康、牛白血病病毒血清阴性且前病毒阴性的肉牛小母牛随机分为两组：对照组小母牛（n = 20），接触牛白血病病毒血清阴性且前病毒阴性的公牛；受挑战小母牛（n = 20），接触牛白血病病毒血清阳性且前病毒阳性的公牛。每组小母牛与公牛一起在一个5英亩的牧场中饲养38天，以模拟繁殖季节商业肉牛的饲养环境。在配种前60天、30天和0天以及配种期结束后第30天、60天和90天从小母牛采集血样。通过酶联免疫吸附测定法检测血样中的牛白血病病毒抗体，并通过CoCoMo-qPCR检测牛白血病病毒前病毒DNA。在研究期间的任何时间点，在任何受挑战或对照小母牛中，酶联免疫吸附测定法或CoCoMo-qPCR均未检测到新的感染。基于这些结果，健康且无白血病的感染牛白血病病毒的公牛在规定的繁殖季节可能不是传播牛白血病病毒的重大风险因素。
