Ausvet Pty Ltd., Canberra 2617, Australia.
UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin D04 W6F6, Ireland.
J Dairy Sci. 2019 Mar;102(3):2525-2538. doi: 10.3168/jds.2018-15696. Epub 2019 Jan 26.
The aim of this study was to evaluate the utility and cost-effectiveness of a range of national surveillance methods for paratuberculosis in Irish dairy herds. We simulated alternative surveillance strategies applied to dairy cattle herds for the detection of Mycobacterium avium ssp. paratuberculosis (MAP)-infected herds (case-detection) or for estimation of confidence of herd freedom from infection (assurance testing). Strategies simulated included whole-herd milk or serum serology, serology on cull cows at slaughter, bulk milk tank serology, environmental testing, and pooled fecal testing. None of the strategies evaluated were ideal for widespread national case-detection surveillance. Herd testing with milk or serum ELISA or pooled fecal testing were the most effective methods currently available for detection of MAP-infected herds, with median herd sensitivity >60% and 100% herd specificity, although they are relatively expensive for widespread use. Environmental sampling shows promise as an alternative, with median herd sensitivity of 69%, but is also expensive unless samples can be pooled and requires further validation under Irish conditions. Bulk tank milk testing is the lowest cost option and may be useful for detecting high-prevalence herds but had median herd sensitivity <10% and positive predictive value of 85%. Cull cow sampling strategies were also lower cost but had median herd sensitivity <40% and herd positive predictive values of <50%, resulting in an increased number of test-positive herds, each of which requires follow-up herd testing to clarify status. Possible false-positive herd testing results associated with prior tuberculosis testing also presented logistical issues for both cull cow and bulk milk testing. Whole-herd milk or serum ELISA testing are currently the preferred testing strategies to estimate confidence of herd freedom from MAP in dairy herds due to the good technical performance and moderate cost of these strategies for individual herd testing. Cull cow serology and bulk tank milk sampling provide only minimal assurance value, with confidence of herd freedom increasing only minimally above the prior estimate. Different testing strategies should be considered when deciding on cost-effective approaches for case-detection compared with those used for building confidence of herd freedom (assurance testing) as part of a national program.
本研究旨在评估一系列用于爱尔兰奶牛场副结核病国家监测方法的实用性和成本效益。我们模拟了替代的监测策略，应用于奶牛场，用于检测感染了禽分枝杆菌副结核亚种（MAP）的牛群（病例检测）或用于估计牛群无感染的置信度（保证测试）。模拟的策略包括全群牛奶或血清血清学、屠宰场淘汰牛的血清学、批量奶罐血清学、环境测试和粪便混合测试。评估的策略都不是广泛用于国家病例检测监测的理想选择。用牛奶或血清 ELISA 或粪便混合测试进行牛群检测是目前检测 MAP 感染牛群最有效的方法，中位牛群敏感性>60%，100%的牛群特异性，尽管它们的广泛使用成本相对较高。环境采样作为替代方法显示出一定的前景，中位牛群敏感性为 69%，但除非可以对样本进行混合且需要在爱尔兰条件下进一步验证，否则成本较高。批量奶罐奶测试是成本最低的选择，可能对检测高流行率的牛群有用，但中位牛群敏感性<10%，阳性预测值为 85%。淘汰牛采样策略的成本也较低，但中位牛群敏感性<40%，牛群阳性预测值<50%，导致更多的测试阳性牛群，每个牛群都需要进行后续的牛群检测以明确状态。与先前的结核病检测相关的可能假阳性牛群检测结果也给淘汰牛和批量奶测试带来了后勤问题。由于这些策略对单个牛群检测的技术性能良好且成本适中，因此全群牛奶或血清 ELISA 检测是目前估计奶牛场 MAP 无感染牛群置信度的首选检测策略。淘汰牛血清学和批量奶罐奶采样仅提供最小的保证价值，牛群无感染的置信度仅略有增加，高于先前的估计。在决定具有成本效益的病例检测方法时，应考虑不同的检测策略，而与建立牛群无感染的置信度（保证测试）作为国家计划的一部分相比。
