Quantification of Mycobacterium bovis transmission in a badger vaccine field trial
Quantification of Mycobacterium bovis transmission in a badger vaccine field trial
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DOI：
10.1016/j.prevetmed.2017.10.010
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发表时间：
2018-01-01
影响因子：
2.6
通讯作者：
de Jong, M. C. M.
中科院分区：
文献类型：
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作者：
Aznar, I.;Frankena, K.;de Jong, M. C. M.
在英国和爱尔兰，为獾接种卡介苗(BCG)已被建议作为控制甚至根除獾中牛分枝杆菌感染的一系列策略之一。在这篇手稿中，我们介绍了在爱尔兰进行的獾野外试验的结果，并讨论了新的试验设计和分析方法如何允许疫苗接种在预防感染方面的效果，更重要的是，对传播的影响被估计。试验区由北向南分为A区、B区和C区，接种覆盖率分别为0、50%和100%。獾被困了4年之久。獾被分配给安慰剂或疫苗治疗，治疗随机分配在B区，每次捕获时采集血液样本，并使用化学发光多重ELISA系统(ENFER测试)对这些样本进行血清学检测。这项分析旨在比较未感染疫苗的獾和未感染疫苗的獾的新感染情况，同时考虑到獾被困的区域和这只獾暴露在其中的感染压力。总共有440份关于未受感染的个体獾随后被捕获的记录可供分析。在研究期间，55例新感染病例发生在未接种疫苗的獾身上(239例占23.0%)，40例发生在接种疫苗的獾身上(201例占19.9%)。使用具有闭合对数链接函数的广义线性模型(GLM)进行分析。统计分析表明，与安慰剂治疗的獾相比，接种疫苗的人对自然暴露牛分枝杆菌的易感性降低：疫苗敏感性VES为59%(95%CI=6.5%-82%)。然而，卡介苗接种对接种獾的传染性完全没有影响，即疫苗传染性效力(VEI)为0%。此外，还估计了作为疫苗接种覆盖率(P)(即R(P))的函数的基本繁殖率。鉴于爱尔兰流行区獾中牛分枝杆菌感染的流行率约为18%，我们估计未接种疫苗人群的繁殖率为R(0)=1.22。因为VES现在是已知的，所以完全接种疫苗的人口的繁殖率估计为R(1)=0.50。这些结果意味着，在獾的疫苗接种率超过30%的情况下，在爱尔兰根除獾中的牛分枝杆菌是可行的，前提是目前的控制措施也保持不变。
In the UK and Ireland, Bacille Calmette-Guerin (BCG) vaccination of badgers has been suggested as one of a number of strategies to control or even eradicate Mycobacterium bovis infection in badgers. In this manuscript, we present the results of a badger field trial conducted in Ireland and discuss how the novel trial design and analytical methods allowed the effects of vaccination on protection against infection and, more importantly, on transmission to be estimated. The trial area was divided into three zones North to South (A, B and C) where vaccination coverages of 0, 50 and 100%, respectively, were applied. Badgers were trapped over a 4 year period. Badgers were assigned to either placebo or vaccine treatment, with treatment allocation occurring randomly in zone B. Blood samples were collected at each capture, and serology was performed in these samples using a chemiluminescent multiplex ELISA system (Enfer test). The analysis aimed to compare new infections occurring in non-infected non-vaccinated badgers to those in non-infected vaccinated ones, while accounting for the zone in which the badger was trapped and the infection pressure to which this individual badger was exposed. In total, 440 records on subsequent trappings of individual non-infected badgers were available for analysis. Over the study period, 55 new infections occurred in non-vaccinated (out of 239 = 23.0%) and 40 in vaccinated (out of 201 = 19.9%) badgers. A Generalized Linear Model (GLM) with a cloglog link function was used for analysis. Statistical analysis showed that susceptibility to natural exposure with M. bovis was reduced in vaccinated compared to placebo treated badgers: vaccine efficacy for susceptibility, VEs, was 59% (95% CI = 6.5%-82%). However, a complete lack of effect from BCG vaccination on the infectivity of vaccinated badgers was observed, i.e. vaccine efficacy for infectiousness (VEI) was 0%. Further, the basic reproduction ratio as a function of vaccination coverage (p) (i.e. R(p)) was estimated. Given that the prevalence of M. bovis infection in badgers in endemic areas in Ireland is approximately 18%, we estimated the reproduction ratio in the unvaccinated population as R(0) = 1.22. Because VEs was now known, the reproduction ratio for a fully vaccinated population was estimated as R(1) = 0.50. These results imply that with vaccination coverage in badgers exceeding 30%, eradication of M. bovis in badgers in Ireland is feasible, provided that the current control measures also remain in place.