Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada, T2N 4N1.
Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada, N1G 2W1.
J Dairy Sci. 2018 Dec;101(12):11218-11228. doi: 10.3168/jds.2018-14854. Epub 2018 Oct 11.
Johne's disease is a progressive, chronic disease with inflammation of the small intestine of ruminants caused by Mycobacterium avium ssp. paratuberculosis (MAP). Accurately estimating prevalence of MAP infections is important when controlling spread of infection or monitoring effectiveness of control programs. In the absence of a consistent test method used in prevalence studies across Canada, prevalence estimates among regions and programs cannot be compared. The aim of the current study was to estimate and compare prevalence of MAP infection in Western Canada, Ontario, Québec, and the Atlantic provinces, as well as among varying herd sizes and housing types. On 362 dairy farms located in all 10 provinces of Canada, environmental samples were collected and cultured for detection of MAP. For each herd, 1 sample was collected from the lactating cow area and manure storage. An additional environmental sample was collected from the area where breeding-age heifers were housed. Using prior distributions from previous research, diagnostic sensitivity and specificity were calculated to assess the ability of only 2 environmental samples (manure storage and lactating cow area) to identify MAP-positive farms, resulting in a sensitivity and specificity of 38 and 100%, respectively. We found no difference in sensitivity and specificity when including breeding-age heifers environmental samples. Test characteristics were applied to environmental culture results from the 362 participating farms in all 4 regions, resulting in true prevalence estimates of 66% for farms in Western Canada, 54% in Ontario, 24% in Québec, and 47% in Atlantic Canada. Herds housed in tiestalls had lower prevalence than freestall-housed herds, and herds with 101-150 and >151 cows had higher prevalence than herds with ≤100 cows. This was the first time MAP prevalence was determined using 1 detection method, performed in 1 laboratory, and within a single year across Canada, enabling direct comparisons of prevalence among regions, housing types, and herd sizes.
约翰氏病是一种由牛分枝杆菌副结核亚种（MAP）引起的反刍动物小肠慢性进行性炎症疾病。准确估计 MAP 感染的流行率对于控制感染的传播或监测控制计划的效果非常重要。在加拿大，没有在流行率研究中使用一致的测试方法，因此无法比较各个地区和计划之间的流行率估计值。本研究的目的是估计和比较加拿大西部、安大略省、魁北克省和大西洋省份以及不同畜群规模和畜舍类型中 MAP 感染的流行率。在加拿大所有 10 个省的 362 个奶牛场采集环境样本并进行培养，以检测 MAP。对于每个畜群，从泌乳牛区和粪便储存区采集 1 个样本。还从育成母牛畜舍区采集了另一个环境样本。使用先前研究的先验分布，计算了诊断敏感性和特异性，以评估仅 2 个环境样本（粪便储存区和泌乳牛区）识别 MAP 阳性农场的能力，结果敏感性和特异性分别为 38%和 100%。当包括育成母牛的环境样本时，敏感性和特异性没有差异。将测试特征应用于来自所有 4 个地区的 362 个参与农场的环境培养结果，结果表明加拿大西部的农场真阳性流行率为 66%，安大略省为 54%，魁北克省为 24%，大西洋省份为 47%。牛舍为牛蹄厩的畜群比牛舍为散栏的畜群的流行率低，牛群规模为 101-150 头和>151 头的畜群比牛群规模为 100 头及以下的畜群的流行率高。这是第一次在加拿大使用 1 种检测方法、在 1 个实验室和在 1 年内确定 MAP 流行率，从而能够在地区、畜舍类型和畜群规模之间直接比较流行率。
