Hay K E, Ambrose R C K, Morton J M, Horwood P F, Gravel J L, Waldron S, Commins M A, Fowler E V, Clements A C A, Barnes T S, Mahony T J
The University of Queensland, Queensland Alliance for Agriculture and Food Innovation, St. Lucia 4072, Queensland, Australia.
Department of Primary Industries and Fisheries, Animal Science, St. Lucia 4072, Queensland, Australia.
Prev Vet Med. 2016 Apr 1;126:159-69. doi: 10.1016/j.prevetmed.2016.01.025. Epub 2016 Feb 1.
Viruses play a key role in the complex aetiology of bovine respiratory disease (BRD). Bovine viral diarrhoea virus 1 (BVDV-1) is widespread in Australia and has been shown to contribute to BRD occurrence. As part of a prospective longitudinal study on BRD, effects of exposure to BVDV-1 on risk of BRD in Australian feedlot cattle were investigated. A total of 35,160 animals were enrolled at induction (when animals were identified and characteristics recorded), held in feedlot pens with other cattle (cohorts) and monitored for occurrence of BRD over the first 50days following induction. Biological samples collected from all animals were tested to determine which animals were persistently infected (PI) with BVDV-1. Data obtained from the Australian National Livestock Identification System database were used to determine which groups of animals that were together at the farm of origin and at 28days prior to induction (and were enrolled in the study) contained a PI animal and hence to identify animals that had probably been exposed to a PI animal prior to induction. Multi-level Bayesian logistic regression models were fitted to estimate the effects of exposure to BVDV-1 on the risk of occurrence of BRD. Although only a total of 85 study animals (0.24%) were identified as being PI with BVDV-1, BVDV-1 was detected on quantitative polymerase chain reaction in 59% of cohorts. The PI animals were at moderately increased risk of BRD (OR 1.9; 95% credible interval 1.0-3.2). Exposure to BVDV-1 in the cohort was also associated with a moderately increased risk of BRD (OR 1.7; 95% credible interval 1.1-2.5) regardless of whether or not a PI animal was identified within the cohort. Additional analyses indicated that a single quantitative real-time PCR test is useful for distinguishing PI animals from transiently infected animals. The results of the study suggest that removal of PI animals and/or vaccination, both before feedlot entry, would reduce the impact of BVDV-1 on BRD risk in cattle in Australian feedlots. Economic assessment of these strategies under Australian conditions is required.
病毒在牛呼吸道疾病（BRD）复杂的病因中起着关键作用。牛病毒性腹泻病毒1型（BVDV - 1）在澳大利亚广泛存在，并且已被证明与BRD的发生有关。作为一项关于BRD的前瞻性纵向研究的一部分，研究了澳大利亚饲养场牛接触BVDV - 1对BRD风险的影响。共有35160头动物在入栏时（即动物被识别并记录特征时）被纳入研究，与其他牛一起饲养在饲养场围栏中，并在入栏后的前50天监测BRD的发生情况。对从所有动物采集的生物样本进行检测，以确定哪些动物持续感染了BVDV - 1。从澳大利亚国家牲畜识别系统数据库获得的数据用于确定在原养殖场以及入栏前28天（并已纳入研究）在一起的哪些动物组中包含持续感染动物，从而识别出在入栏前可能接触过持续感染动物的动物。采用多层次贝叶斯逻辑回归模型来估计接触BVDV - 1对BRD发生风险的影响。尽管总共只有85头研究动物（0.24%）被确定为持续感染BVDV - 1，但在59%的牛群中通过定量聚合酶链反应检测到了BVDV - 1。持续感染动物患BRD的风险适度增加（比值比1.9；95%可信区间1.0 - 3.2）。无论牛群中是否识别出持续感染动物，在牛群中接触BVDV - 1也与BRD风险适度增加有关（比值比1.7；95%可信区间1.1 - 2.5）。进一步分析表明，单次定量实时聚合酶链反应检测有助于区分持续感染动物和短暂感染动物。研究结果表明，在进入饲养场之前清除持续感染动物和/或进行疫苗接种，将降低BVDV - 1对澳大利亚饲养场牛BRD风险的影响。需要在澳大利亚的条件下对这些策略进行经济评估。
