Wiseman J, Cassidy J P, Gormley E
Veterinary Sciences Centre, UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland; Department of Agriculture, Food and the Marine, Central Veterinary Research Laboratory - Backweston Campus, Young's Cross, Celbridge, Co. Kildare, Ireland.
Veterinary Sciences Centre, UCD School of Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland.
Vet J. 2024 Dec;308:106266. doi: 10.1016/j.tvjl.2024.106266. Epub 2024 Nov 9.
The dynamics of Mycobacterium bovis infection in cattle can influence the proportion of infected animals that are diagnosed by ante-mortem tests in routine bovine tuberculosis (bTB) surveillance and monitoring programmes. Although the current diagnostic tests based on cell-mediated or serological responses are imperfect, they are effective in diagnosing the majority of infected animals. However, the lack of perfect sensitivity and specificity also leads to failure to diagnose all infected animals leading to persistence of infection in herds. The terms residual, subclinical, latent and anergy have been used interchangeably to denote the presence of continued undiagnosed M. bovis infection within cattle herds, which ultimately hinders the eradication of bTB and imposes substantial financial burdens on farming communities and national economies. Epidemiological data suggests the existence of M. bovis-infected, but often undetected, cattle within herds that contribute to eradication failure. This has similarities with human tuberculosis, caused by Mycobacterium tuberculosis, where latent infection is defined as the persistence of viable but quiescent bacilli for extended periods in patients without clinical symptoms but with a detectable immune response to M. tuberculosis antigens. If a similar infection state exists in cattle infected with M. bovis, the persistence of such animals in disease-managed herds is unlikely to be common given that those found to have positive immune responses to M. bovis antigens are routinely culled to minimise future risk of transmission. Apart from contributing to the burden of herd infection, such residual infection without detection may also 'seed' recipient herds following animal movements, and potentially play an important role in the overall epidemiology of bTB as the prevalence of disease decreases and the attendant altered predictive value of the diagnostic tests result in a greater proportion of infected animals remaining undetected. This review examines how the different stages of M. bovis infection in cattle may contribute to the failure to diagnose infected animals using conventional testing methodologies and the attendant risk this poses in creating prolonged or recurrent herd breakdowns.
牛群中牛分枝杆菌感染的动态变化会影响在常规牛结核病（bTB）监测和监控计划中通过生前检测确诊的感染动物比例。尽管目前基于细胞介导反应或血清学反应的诊断测试并不完美，但它们在诊断大多数感染动物方面是有效的。然而，缺乏完美的敏感性和特异性也导致无法诊断出所有感染动物，从而使感染在牛群中持续存在。残留、亚临床、潜伏和无反应等术语已被交替使用，以表示牛群中持续存在未被诊断出的牛分枝杆菌感染，这最终阻碍了bTB的根除，并给养殖社区和国家经济带来了巨大的经济负担。流行病学数据表明，牛群中存在感染牛分枝杆菌但往往未被检测到的牛，这导致根除失败。这与由结核分枝杆菌引起的人类结核病有相似之处，在人类结核病中，潜伏感染被定义为在没有临床症状但对结核分枝杆菌抗原有可检测免疫反应的患者中，存活但静止的杆菌长期持续存在。如果感染牛分枝杆菌的牛中存在类似的感染状态，那么在疾病管理的牛群中，这些动物的持续存在不太可能常见，因为那些对牛分枝杆菌抗原有阳性免疫反应的动物通常会被扑杀，以尽量减少未来的传播风险。除了增加牛群感染负担外，这种未被检测到的残留感染在动物移动后也可能“播种”到接收牛群中，并可能在bTB的总体流行病学中发挥重要作用，因为疾病患病率下降，随之而来的诊断测试预测价值改变导致更大比例的感染动物未被检测到。本综述探讨了牛分枝杆菌感染的不同阶段如何导致使用传统检测方法无法诊断感染动物，以及这随之带来的造成牛群长期或反复疫情爆发的风险。
