Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic condition of dairy cattle, and is endemic in the UK. Lack of understanding of the relative importance of different transmission routes reduces the impact of control scheme recommendations. The long incubation period for Johne's disease makes evaluation of control schemes difficult, and so this long-term cohort study offers a rare and valuable insight into the disease epidemiology. A longitudinal study was carried out following a cohort of 440 UK dairy cows in 6 herds recruited in 2012-2013. Individuals entering the milking herd were routinely monitored for the presence of MAP using quarterly milk ELISA testing. Using a Cox proportional-hazards regression model the relationship between time until first detection of infection and dam MAP status was investigated. We then compared the magnitude of the effect of dam status with that of other risk factors in order to understand its relative importance. Dam status was found to be the only observed factor that was significantly associated with time to an individual testing MAP-positive (p = 0.012). When compared to negative dams, we found a marginally significant effect of having a positive dam at time of calving, that increased the hazard of an individual testing positive by a factor of 2.6 (95% confidence interval: 0.89-7.79, p = 0.081). Further positive associations were found with dams becoming positive after the birth of the subject; a dam seroconverting within 12 months post parturition being associated with a 3.6 fold increase in hazard (95% confidence interval: 1.32-9.77, p = 0.013), and dams seroconverting more than a year after calving increased the hazard by a factor of 2.8 (95% confidence interval: 1.39-5.76, p = 0.004). These results suggest that cows may be transmitting MAP to their offspring at an earlier stage than had previously been thought, and so raise important questions about how this transmission may be occurring. The results of the study may have important practical implications for the management on-farm of the offspring of MAP-positive animals, with the potential to vastly reduce the time required to eliminate this chronic disease.

中文翻译：

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小牛鸟分枝杆菌副结核感染-大坝感染状况的影响。

由鸟分枝杆菌亚种引起的约翰病。副结核病（MAP）是奶牛的一种慢性病，在英国很流行。缺乏对不同传输路径的相对重要性的了解会降低控制方案建议的影响。约翰病的潜伏期长，难以评估控制方案，因此，这项长期的队列研究为疾病流行病学提供了罕见且有价值的见解。在2012-2013年招募了6头牛群中的440头英国奶牛之后，进行了一项纵向研究。使用季度牛奶ELISA测试，常规监测进入挤奶群的个体是否存在MAP。使用Cox比例风险回归模型研究了直到首次检测到感染为止的时间与大坝MAP状态之间的关系。然后，我们将水坝状况的影响程度与其他风险因素的影响程度进行了比较，以了解其相对重要性。发现水坝状态是唯一与单独测试MAP阳性时间显着相关的观察因素（p = 0.012）。与负水坝相比，我们在产犊时发现正水坝具有显着的显着效果，这使单个测试阳性的危险增加了2.6倍（95％置信区间：0.89-7.79，p = 0.081） 。发现进一步的正相关，受试者出生后水坝变为正。分娩后12个月内进行大坝血清转换，危害增加3.6倍（95％置信区间：1.32-9.77，p = 0.013），产犊后一年以上进行大坝血清转换使危害增加2.8倍（ 95％置信区间：1.39-5.76，p = 0.004）。这些结果表明，母牛可能比先前所认为的更早地向其后代传播MAP，因此引发了有关这种传播如何发生的重要问题。研究结果可能对MAP阳性动物后代的农场管理具有重要的实际意义，并有可能极大地减少消除这种慢性疾病所需的时间。产犊后一年多来进行大坝和血清转换的危险增加了2.8倍（95％置信区间：1.39-5.76，p = 0.004）。这些结果表明，母牛可能比先前所认为的更早地向其后代传播MAP，因此引发了有关这种传播如何发生的重要问题。研究结果可能对MAP阳性动物后代的农场管理具有重要的实际意义，并有可能极大地减少消除这种慢性疾病所需的时间。产犊后一年多来进行水坝和血清转换的危险增加了2.8倍（95％置信区间：1.39-5.76，p = 0.004）。这些结果表明，母牛可能比先前所认为的更早地向其后代传播MAP，因此引发了有关这种传播如何发生的重要问题。研究结果可能对MAP阳性动物后代的农场管理具有重要的实际意义，并有可能极大地减少消除这种慢性疾病所需的时间。因此提出了有关这种传播如何发生的重要问题。研究结果可能对MAP阳性动物后代的农场管理具有重要的实际意义，并有可能极大地减少消除这种慢性疾病所需的时间。因此提出了有关这种传播如何发生的重要问题。研究结果可能对MAP阳性动物后代的农场管理具有重要的实际意义，并有可能极大地减少消除这种慢性疾病所需的时间。