Centre for Veterinary Epidemiology and Risk Analysis, UCD School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Prev Vet Med. 2010 Dec 1;97(3-4):264-9. doi: 10.1016/j.prevetmed.2010.09.017.
Movement of animals between farms represents a potential risk of bovine tuberculosis (BTB) and other disease transmission. The objectives of this study were to identify and quantify risk factors associated with the first between-herd movement of animals (denoted as risk move). A random sample of 1 percent of Irish calf births registered for 2002 (20,182 animals) was selected. Descriptive and survival analysis on movement over the period 2002-2005 was performed. A total of 12,119 (60%) of animals experienced a risk move over the 4-year study period. Among those that moved, 57% did so within the first 12 months of age. For animals in dairy herds, an early peak in risk move events was observed within the first 12 weeks of age; whereas in animals from suckler herds, a later risk move peak was observed between 21 and 36 weeks of age. The survival models identified a number of risk factors: two that appeared most important in predicting a risk move were gender and enterprise type. Males had a hazard ratio of 2.6 times that of females. The hazards for enterprise type, varied over time, thus a time-varying covariate (ent_type×ln(time)) was included in the Cox model. At 7 days of age, females in suckler herds were at 0.14 times the hazard of females in dairy herds for risk move, and over time, the hazards converged, equalised by day 140, and then diverged, so that by 4 years of age, females in suckler herds were at 4.64 times the hazard of females in dairy herds. Herds with a history of selling animals in previous years maintained that record during the study period with increased hazard of risk move. Enterprise type interacted with gender so that relative to females, males from dairy herds were at greater hazard of risk move than males from suckler herds. Hazard of risk move was also a function of ln (herd area), so that each doubling of farm area was accompanied by a 30.6% decrease in the hazards. The main conclusion was that risk of movement related disease transmission also depends on the purpose of the movement whether for breeding or for beef finishing. While males were at greater hazard of movement than females, they would have a shorter lifespan, thus limiting the opportunity for further transmission post-movement.
动物在农场之间的移动代表了牛结核病（BTB）和其他疾病传播的潜在风险。本研究的目的是确定和量化与动物首次离开畜群（表示为风险移动）相关的风险因素。随机选择了 2002 年登记的爱尔兰小牛出生的 1%作为样本（20182 头动物）。对 2002-2005 年期间的移动进行了描述性和生存分析。在 4 年的研究期间，共有 12119 头（60%）动物发生了风险移动。在那些移动的动物中，57%的动物在 12 个月龄内移动。对于奶牛养殖场的动物，在 12 周龄内观察到风险移动事件的早期高峰；而对于来自哺乳牛群的动物，在 21 至 36 周龄之间观察到了较晚的风险移动高峰。生存模型确定了一些风险因素：两个似乎对预测风险移动最重要的因素是性别和企业类型。雄性的危险比为雌性的 2.6 倍。企业类型的风险随时间而变化，因此在 Cox 模型中包含了一个随时间变化的协变量（ent_type×ln(time)）。在 7 天时，哺乳牛群中的雌性发生风险移动的危险是奶牛群中雌性的 0.14 倍，随着时间的推移，危险会收敛，到第 140 天相等，然后发散，因此到 4 岁时，哺乳牛群中的雌性发生风险移动的危险是奶牛群中雌性的 4.64 倍。在研究期间，有出售动物历史的畜群保持了这一记录，风险移动的危险增加。企业类型与性别相互作用，因此相对于雌性，来自奶牛群的雄性发生风险移动的危险大于来自哺乳牛群的雄性。风险移动的危险也是 ln（畜群面积）的函数，因此农场面积每增加一倍，危险就会降低 30.6%。主要结论是，与移动相关的疾病传播的风险也取决于移动的目的，是用于繁殖还是用于牛肉育肥。虽然雄性比雌性更容易发生移动，但它们的寿命更短，因此在移动后进一步传播的机会有限。
