Yang D A, Johnson W O, Müller K R, Gates M C, Laven R A
School of Veterinary Science, Massey University, Palmerston North, 4442, New Zealand; EpiCentre, School of Veterinary Science, Massey University, Palmerston North, 4442, New Zealand.
Department of Statistics, University of California, 2232 Bren Hall UC Irvine, Irvine, CA, 92697, USA.
Prev Vet Med. 2019 Apr 1;165:76-84. doi: 10.1016/j.prevetmed.2019.02.014. Epub 2019 Feb 26.
A cross-sectional study of 127 dairy herds distributed across four regions of New Zealand (NZ) was conducted to estimate the regional herd-level prevalence of bovine digital dermatitis (BDD) and the prevalence of cows with BDD lesions within affected herds. Each herd was visited once during the 2016-2017 lactating season and the rear feet of all cows in the milking herd were examined to detect the presence of BDD lesions. Of the 127 herds examined, 63 had at least one cow with a detected BDD lesion. Of the 59 849 cows observed, 646 cows were observed with BDD lesions. All of the herds in which BBD was detected were located in three of the four regions (Waikato, Manawatu and South Canterbury). No convincing lesions were observed on the West Coast. The probability of BDD freedom on the West Coast was predicted to be 99.97% using a Bayesian latent class model. For the three regions where BDD lesions were observed, the true herd level and cow level prevalences were estimated using a Bayesian superpopulation approach which accounted for the imperfect diagnostic method. Based on priors obtained from previous research in another region of NZ (Taranaki), the true herd level prevalences in Waikato, Manawatu and South Canterbury were estimated to be 59.2% (95% probability interval [PI]: 44.3%-73.9%), 43.3% (95%PI: 29%-59%) and 65.9% (95%PI: 49.5%-79.9%), respectively, while the true median within-herd prevalences were estimated as 3.2% (95%PI: 2%-5%), 1.7% (95%PI: 0.9%-3.1%) and 3.7% (95%PI: 2.4%-5.5%), respectively. All of these estimates except for the true herd level prevalence in Manawatu were fairly robust to changes in the priors. For Manawatu region, changing from the prior obtained in Taranaki (the best estimate of the herd level prevalence = 60%, 95% sure > 40%) to one where the mode was 50% (95% sure < 80%) reduced the posterior from 43.3% to 35.2% (95%PI: 20.1%-53.5%). The marked variation in BDD prevalence between regions and between farms highlights the need for further exploration into risk factors for disease.
对分布在新西兰（NZ）四个地区的127个奶牛场进行了一项横断面研究，以估计牛趾间皮炎（BDD）的区域牛群水平患病率以及受影响牛群中患有BDD病变的奶牛患病率。在2016 - 2017泌乳期期间，每个牛场访问一次，检查挤奶牛群中所有奶牛的后蹄，以检测BDD病变的存在。在检查的127个牛群中，63个牛群至少有一头奶牛检测到BDD病变。在观察的59849头奶牛中，有646头奶牛观察到有BDD病变。所有检测到BBD的牛群都位于四个地区中的三个地区（怀卡托、马纳瓦图和南坎特伯雷）。在西海岸未观察到明显病变。使用贝叶斯潜在类别模型预测，西海岸BDD无病概率为99.97%。对于观察到BDD病变的三个地区，使用考虑了不完善诊断方法的贝叶斯超总体方法估计了真实的牛群水平和奶牛水平患病率。根据在新西兰另一个地区（塔拉纳基）先前研究获得的先验信息，怀卡托、马纳瓦图和南坎特伯雷的真实牛群水平患病率估计分别为59.2%（95%概率区间[PI]：44.3% - 73.9%）、43.3%（95%PI：29% - 59%）和65.9%（95%PI：49.5% - 79.9%），而真实的牛群内患病率中位数估计分别为3.2%（95%PI：2% - 5%）、1.7%（95%PI：0.9% - 3.1%）和3.7%（95%PI：2.4% - 5.5%）。除马纳瓦图的真实牛群水平患病率外，所有这些估计对先验信息的变化都相当稳健。对于马纳瓦图地区，如果将先验信息从在塔拉纳基获得的信息（牛群水平患病率的最佳估计值 = 60%，95%确定 > 40%）改为模式为50%（95%确定 < 80%），则后验概率从43.3%降至35.2%（95%PI：20.1% - 53.5%）。地区之间和农场之间BDD患病率的显著差异突出了进一步探索疾病风险因素的必要性。
