Department of Disease Control and Epidemiology, National Veterinary Institute, SE-751 89 Uppsala, Sweden.
Prev Vet Med. 2013 Jan 1;108(1):47-62. doi: 10.1016/j.prevetmed.2012.07.010. Epub 2012 Aug 15.
Previous investigations suggest that the prevalence of Mycobacterium avium subsp. paratuberculosis (MAP) in Swedish cattle is low and all recent cases have been linked to imported animals. The aim of this study was to evaluate the surveillance system for MAP infection in Swedish cattle and to estimate the probability that the Swedish cattle population is free from this infection. Calculations of surveillance sensitivities and probability of freedom were made using stochastic scenario-tree modelling, which allows inclusion of information from several different sources, of complex surveillance data including results from non-representative sampling, as well as of documentations of differences in risk of being infected. The surveillance components included in the model were: (1) clinical surveillance, (2) fallen stock investigations, (3) the national surveillance programme (mainly beef herds), (4) a survey involving dairy herds and (5) a risk-based survey targeting herds with imported cattle. Previous or current presence of imported animals and participation in the on-going control programme was specified for each tested herd, in order to adjust for differences in risk. Calculations were made for each year from the start of 2005 to the end of 2008, and this formed the basis for a final estimate covering the whole study period and predictions of future probabilities of freedom from MAP. Results show that when applying a design prevalence of one animal in 0.1% of the herds, the probability of freedom at the end of 2008 was 0.63. At the design prevalence of one animal in 0.5% of herds, the estimated probability is >95% and it is demonstrated that the prevalence of MAP in Swedish cattle is below this level or absent. In order to increase the annual surveillance sensitivity in the future and thereby improve the probability of freedom, new surveillance activities or an intensification of current ones are needed.
先前的研究表明，分枝杆菌副结核亚种（MAP）在瑞典牛群中的流行率较低，且所有近期病例都与进口动物有关。本研究旨在评估瑞典牛群中 MAP 感染的监测系统，并估计瑞典牛群免受该感染的可能性。使用随机情景树模型进行监测敏感性和自由概率的计算，该模型允许纳入来自不同来源的信息，包括复杂监测数据，包括非代表性抽样的结果，以及记录感染风险的差异。纳入模型的监测组成部分包括：（1）临床监测；（2）病畜调查；（3）国家监测计划（主要是牛肉牛群）；（4）涉及奶牛群的调查；（5）针对进口牛群的基于风险的调查。为了调整风险差异，为每个测试牛群指定了以前或当前存在进口动物和参与正在进行的控制计划的情况。从 2005 年开始到 2008 年底，每年进行计算，这为涵盖整个研究期间的最终估计和未来 MAP 自由概率的预测提供了基础。结果表明，当应用设计流行率为 0.1%的牛群中每 1 头动物时，2008 年底的自由概率为 0.63。当设计流行率为 0.5%的牛群中每 1 头动物时，估计的概率>95%，并且证明了 MAP 在瑞典牛群中的流行率低于这一水平或不存在。为了提高未来的年度监测敏感性，从而提高自由概率，需要开展新的监测活动或加强当前的监测活动。
