Graduate School, Faculty of Veterinary Sciences, Universidad Austral de Chile, Chile.
Department of Preventive Veterinary Medicine, Faculty of Veterinary Sciences, Universidad Austral de Chile, Chile.
Prev Vet Med. 2022 Jan;198:105533. doi: 10.1016/j.prevetmed.2021.105533. Epub 2021 Nov 5.
Bovine Viral Diarrhea (BVD) is a ubiquitous endemic disease in most bovine populations that causes a negative economic impact on cattle production systems. However, true herd and individual prevalence in Chile have not been estimated based on statistical and epidemiological considerations and uncertainty regarding the infection's extension at animal and herd levels. In addition, the risk factors that can influence how the infection has spread among the cattle premises have not been assessed yet. Therefore, the study aimed to estimate true herd and animal prevalence of active BVDV infection in pasture-based dairy herds and to evaluate risk factors potentially associated with the status of herds and the within-herd prevalence, using a Bayesian approach. A cross-sectional study was performed over a random stratified (proportional to herd size) sample of one-hundred and fifty dairy herds selected in Chile's two leading dairy regions (Region de Los Ríos and Region de Los Lagos). We obtained 12.311 blood samples from lactating cows, but 4.998 randomly selected samples were processed due to budget constraints. For estimating BVDV Herd Prevalence (HP), a herd was considered infected if at least one positive animal to Ag-ELISA was found. In addition, a survey was completed on each farm, aiming to collect information to assess the influence of some variables over the state of the herds; both estimations were obtained using a Bayesian approach. True herd prevalence and true individual prevalence of BVDV active infection were estimated at 77 % and 3.5 % respectively, no significant differences were found between characteristics like herd size, location, vaccination, etc. Open herds and herds that mix herd categories are more likely to have higher BVDV prevalence.
牛病毒性腹泻（BVD）是一种普遍存在于大多数牛群中的地方病，它给牛群生产系统带来了负面的经济影响。然而，由于统计和流行病学方面的考虑以及对动物和牛群水平感染范围的不确定性，智利尚未根据统计和流行病学方面的考虑以及对感染在动物和牛群水平上的扩展范围的不确定性来估计真正的牛群和个体流行率。此外，尚未评估可能影响感染在牛群中传播的风险因素。因此，本研究旨在使用贝叶斯方法估计牧场奶牛群中活跃的 BVDV 感染的真实牛群和动物流行率，并评估与牛群和牛群内流行率状况相关的潜在风险因素。在智利两个主要的奶牛区域（拉雷纳斯地区和拉戈斯地区）进行了一项横断面研究，对随机分层（按牛群规模比例）选择的 150 个奶牛场进行了抽样。我们从泌乳奶牛中获得了 12311 份血样，但由于预算限制，仅处理了 4998 份随机选择的样本。为了估计 BVDV 牛群流行率（HP），如果至少有一头动物对 Ag-ELISA 呈阳性，则认为该牛群受到感染。此外，还对每个农场进行了调查，旨在收集信息评估一些变量对牛群状况的影响；这两种估计都是使用贝叶斯方法获得的。BVDV 活跃感染的真实牛群流行率和真实个体流行率分别估计为 77%和 3.5%，牛群规模、地理位置、疫苗接种等特征之间没有发现显著差异。开放式牛群和混合牛群类别的牛群更有可能具有更高的 BVDV 流行率。
