Increasing Bovine leukemia virus (BLV) proviral load is a risk factor for progression of Enzootic bovine leucosis: A prospective study in Japan
Increasing Bovine leukemia virus (BLV) proviral load is a risk factor for progression of Enzootic bovine leucosis: A prospective study in Japan
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DOI：
10.1016/j.prevetmed.2019.04.009
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发表时间：
2020-05-01
影响因子：
2.6
通讯作者：
Imakawa, Kazuhiko
中科院分区：
文献类型：
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作者：
Kobayashi, Tomoko;Inagaki, Yasuko;Imakawa, Kazuhiko
牛白血病病毒(BLV)属于逆转录病毒科DeltaRT病毒属，在病原学上与牛传染性白血病(EBL)有关。大多数感染BLV的牛在整个生产过程中都没有症状，而大约5%-10%的感染牛发展为EBL。最近积累的数据表明，感染BLV的牛的全血前病毒载量(PVL)水平可以作为田间疾病进展的指标。然而，也有一些横断面研究的报道。在这里，我们前瞻性地评估了在2015年8月至2015年12月期间登记的866头牛，并跟踪到2018年11月，确定了407头无症状的BLV感染牛。在群体血清阳性类别(p=0.57)、群体规模(p=0.19)以及在群体中既往EBL病史类别(p=0.31)之间，PVL水平的中位数没有显著差异。在研究期间，12头牛发生了EBL。登记时EBL牛的PVL水平显著高于未进展到EBL的牛(中位数，90,695比39,139拷贝/10(5)细胞，p=0.0005)。此外，根据Cox比例风险脆弱模型估计，PVL增加的调整危险比为2.61(95%可信区间为1.51-4.53)。这些结果表明，高PVL水平是进展到EBL的一个重要危险因素，并可能被用作识别在EBL进展之前很久就从牛群中淘汰的牛的一个指标。这些知识可能有助于设计一种战略，以减少EBL造成的经济损失，甚至将其从羊群中根除。
Bovine leukemia virus (BLV) belongs to the genus Deltaretrovirus in the family Retroviridae, and is etiologically associated with Enzootic Bovine Leukosis (EBL). The majority of BLV-infected cattle remain asymptomatic throughout their productive lives, whereas approximately 5%-10% of infected cattle develop EBL. Data accumulated recently indicate that whole blood proviral load (PVL) levels of BLV-infected cattle could be an indicator of disease progression in the field. However, a few cross-sectional studies have been reported. Here, we prospectively evaluated 866 cattle enrolled between August 2015 and December 2015, and followed until November 2018, identifying 407 asymptomatic BLV-infected cattle. There were no significant differences in the median PVL level among the category of herd seroprevalence (p = 0.57), herd size (p = 0.19), nor among the category of past EBL history in the herd (p = 0.31). During the study period, 12 cattle developed EBL. The PVL levels of EBL cattle at the time of enrollment were significantly higher than that of cattle that did not progress to EBL (median, 90,695 vs 39,139 copies/10(5) cells, p = 0.0005). Moreover, the adjusted hazard ratio for the increase in PVL was 2.61 (95% CI, 1.51-4.53) as estimated by the Cox proportional hazards frailty model. These results indicate that a high PVL level is a significant risk factor for progression to EBL, and could potentially be used as an indicator for the identification of cattle to be culled from the herd long before the progression of EBL. This knowledge might be useful to design a strategy for decreasing economic loss from EBL or even eradicating it from herds.