Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada.
CentralStar Cooperative, Inc., Lansing, Michigan, USA.
J Vet Intern Med. 2022 Sep;36(5):1827-1836. doi: 10.1111/jvim.16506. Epub 2022 Aug 11.
There is currently no commercially available method in Canada to identify bovine leukemia virus (BLV)-positive cows with high proviral load (PVL).
First, develop a model to predict PVL using common, commercially available, cost-effective diagnostic tests. Second, investigate the relationship between lymphocyte count and PVL in BLV-positive cows.
A total of 339 BLV-positive and 62 BLV-seronegative cows on 15 dairy farms.
Cross-sectional study. Blood and milk samples were collected from all lactating BLV-positive cows on each farm and 5 to 10 BLV-seronegative cows depending on herd size. Blood and milk samples were tested for anti-BLV antibodies using enzyme-linked immunosorbent assay (ELISA). Complete blood counts were performed on blood samples, and standard components analyses were obtained for milk samples. Proviral load was determined by quantitative polymerase chain reaction for each cow.
The inverse of lymphocyte count, the square of the inverse of lymphocyte count, and milk ELISA percent positivity were positively associated with increasing PVL in BLV-positive cows. For BLV-positive cows, lymphocyte count >5.2 × 10 /L predicted a high PVL (BLV:Bovine DNA of >1 in blood) with a sensitivity of 92.4% and a specificity of 79.8%. For BLV-positive cows, white blood cell count >10.8 × 10 /L predicted a high PVL, with a sensitivity of 85.5% and a specificity of 83.6%.
Based on these results, producers can implement commonly available diagnostic tests to identify cows with high probability of having high PVL, which may help in designing effective disease control strategies for BLV-positive herds.
加拿大目前尚无商业方法可用于鉴定高前病毒载量（PVL）的牛白血病病毒（BLV）阳性牛。
首先，使用常见的、商业上可用的、具有成本效益的诊断检测方法，建立一种预测 PVL 的模型。其次，研究 BLV 阳性牛的淋巴细胞计数与 PVL 之间的关系。
15 个奶牛场的 339 头 BLV 阳性牛和 62 头 BLV 血清阴性牛。
横断面研究。从每个牛场的所有泌乳 BLV 阳性牛以及根据牛群规模的 5 至 10 头 BLV 血清阴性牛采集血液和牛奶样本。使用酶联免疫吸附试验（ELISA）检测血液和牛奶样本中的抗 BLV 抗体。对血液样本进行全血细胞计数，对牛奶样本进行标准成分分析。对每头牛进行定量聚合酶链反应以确定前病毒载量。
BLV 阳性牛的淋巴细胞计数倒数、淋巴细胞计数倒数的平方和牛奶 ELISA 阳性百分比与 PVL 增加呈正相关。对于 BLV 阳性牛，淋巴细胞计数>5.2×10 /L 可预测高 PVL（BLV：血液中>1 的牛 DNA），其灵敏度为 92.4%，特异性为 79.8%。对于 BLV 阳性牛，白细胞计数>10.8×10 /L 可预测高 PVL，其灵敏度为 85.5%，特异性为 83.6%。
根据这些结果，生产者可以实施常用的诊断检测方法来鉴定高概率具有高 PVL 的牛，这可能有助于设计针对 BLV 阳性牛群的有效疾病控制策略。
