Jacobs R M, Pollari F L, McNab W B, Jefferson B
Department of Pathology, University of Guelph, Ontario.
Can J Vet Res. 1995 Oct;59(4):271-8.
Of the 920 cows tested, 56.7% showed antiretroviral serological reactivity. Prevalence rates (95% confidence interval) of antiretroviral antibodies among individual dairy cows in Ontario were: BIV 5.5% (4.0-7.0), BLV 25.7% (22.9-28.6), and BSV 39.6% (36.4-42.8). The following percentages of cows showed serological reactivity against the specified retroviruses: BIV 2.3%, BLV 14.0%, BSV 27.5%, BIV and BSV 1.3%, BIV and BLV 0.9%, BLV and BSV 9.9%, BIV and BLV and BSV 0.9%. These rates of sero-positivity are similar to those found in other countries. Serological test results were not adjusted for sensitivity and specificity. The prevalence rates of antibodies to the three retroviruses (BIV, BLV, and BSV) were significantly different, but no associations were observed between specific retroviral serological test results among individual cows. The prevalence rates of BIV and BSV seropositivity were constant across Ontario, whereas, there was a significant trend for the prevalence rate of BLV seropositivity to decrease going from southwestern to eastern Ontario; cows in eastern Ontario had approximately half the prevalence rate of those in southwestern Ontario. Cows that were seropositive for BSV were significantly older than BSV seronegative cows. There was no association between culling rate and BSV serology. Significant negative associations were found with winter or summer housing of calves separate from adults and summer outdoor exercise for dry cows. The use of calf hutches in the summer had a significant positive association with BSV seropositivity. Regression analyses were done to assess the association of retroviral (BIV, BLV, and BSV) seropositivity on calving interval, milk somatic cell count, and milk production. Serological test results for BIV, BLV, and BSV were entered into all models and all models were adjusted for intra-cluster (intraherd) correlation. Herd size and age were found to be important confounding variables. BIV seropositivity was not associated with any changes in production using this approach, however when considered in isolation BIV seropositivity remained associated with decreased milk production. BLV seropositivity was significantly associated with longer calving intervals and higher somatic cell counts in older cows. As well, in older cows, BSV seropositivity was significantly associated with higher milk production.
在接受检测的920头奶牛中，56.7%表现出抗逆转录病毒血清学反应性。安大略省个体奶牛中抗逆转录病毒抗体的流行率（95%置信区间）为：牛免疫缺陷病毒（BIV）5.5%（4.0 - 7.0），牛白血病病毒（BLV）25.7%（22.9 - 28.6），牛病毒性腹泻病毒（BSV）39.6%（36.4 - 42.8）。以下百分比的奶牛表现出针对特定逆转录病毒的血清学反应性：BIV 2.3%，BLV 14.0%，BSV 27.5%，BIV和BSV 1.3%，BIV和BLV 0.9%，BLV和BSV 9.9%，BIV、BLV和BSV 0.9%。这些血清阳性率与其他国家的情况相似。血清学检测结果未针对敏感性和特异性进行调整。三种逆转录病毒（BIV、BLV和BSV）抗体的流行率存在显著差异，但在个体奶牛的特定逆转录病毒血清学检测结果之间未观察到关联。BIV和BSV血清阳性率在安大略省各地保持恒定，而BLV血清阳性率从安大略省西南部到东部呈显著下降趋势；安大略省东部的奶牛流行率约为西南部奶牛的一半。BSV血清阳性的奶牛比BSV血清阴性的奶牛年龄显著更大。淘汰率与BSV血清学之间没有关联。发现与犊牛冬季或夏季与成年牛分开饲养以及干奶牛夏季户外锻炼存在显著负相关。夏季使用犊牛栏与BSV血清阳性呈显著正相关。进行了回归分析以评估逆转录病毒（BIV、BLV和BSV）血清阳性与产犊间隔、牛奶体细胞计数和产奶量之间的关联。将BIV、BLV和BSV的血清学检测结果纳入所有模型，所有模型均针对集群内（ herd内）相关性进行了调整。发现牛群规模和年龄是重要的混杂变量。使用这种方法，BIV血清阳性与任何生产变化均无关联，然而单独考虑时，BIV血清阳性仍与产奶量下降有关。BLV血清阳性与年长奶牛较长的产犊间隔和较高的体细胞计数显著相关。此外，在年长奶牛中，BSV血清阳性与较高的产奶量显著相关。
