Benitez Oscar J, LaDronka Rebecca M, Norby Bo, Grooms Daniel L, Bartlett Paul C
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, 736 Wilson Rd, East Lansing 48895.
College of Veterinary Medicine, Iowa State University, 2420 Lincoln Way, Ames 50014.
JDS Commun. 2022 Mar 3;3(3):185-188. doi: 10.3168/jdsc.2021-0187. eCollection 2022 May.
Bovine leukemia virus (BLV) is a retrovirus of cattle that infects approximately 45% of all US dairy cattle, with about 90% of US dairy herds having at least one infected animal. Studies have found BLV infection to be associated with multiple measures of decreased immune function, which may explain the observed economic losses from milk production, decreased cow longevity, and predisposition to lymphoma and other diseases. Our objective was to measure the association between BLV infection and cow longevity in dairy cow operations. Ninety-one dairy herds from 9 US states volunteered to participate in this study. Milking dairy cows (n = 3,611) were tested for BLV antibodies using an ELISA milk test, and their presence in the herd was monitored for an average of 29 mo. The survival analysis controlled for herd and lactation number. Cows sold for dairy purposes were excluded, and individual cow results were not shared with producers so as not to influence culling decisions. Overall, 47.1% (1,701/3,611) of cows were BLV-positive by ELISA. The significant hazard ratio of 1.30 indicated that positive cows were 30% more likely than their negative herdmates to die or be culled during the monitoring period. These results are consistent with other studies in finding a negative effect of BLV infection on cow lifespan.
牛白血病病毒（BLV）是一种牛逆转录病毒，感染了美国约45%的奶牛，美国约90%的奶牛群中至少有一头感染动物。研究发现，BLV感染与免疫功能下降的多种指标相关，这可能解释了观察到的牛奶生产经济损失、奶牛寿命缩短以及易患淋巴瘤和其他疾病的原因。我们的目标是测量奶牛养殖中BLV感染与奶牛寿命之间的关联。来自美国9个州的91个奶牛群自愿参与了这项研究。使用ELISA牛奶检测法对产奶牛（n = 3611头）进行BLV抗体检测，并对它们在牛群中的存在情况进行了平均29个月的监测。生存分析对牛群和泌乳次数进行了控制。排除用于奶牛生产目的而出售的奶牛，并且不向生产者分享个体奶牛的结果，以免影响淘汰决策。总体而言，通过ELISA检测，47.1%（1701/3611）的奶牛为BLV阳性。显著的风险比为1.30，表明阳性奶牛在监测期内死亡或被淘汰的可能性比其阴性同伴高30%。这些结果与其他研究一致，即发现BLV感染对奶牛寿命有负面影响。
