Netherlands Food and Consumer Product Safety Authority, The Netherlands.
Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany.
Prev Vet Med. 2016 May 1;127:105-12. doi: 10.1016/j.prevetmed.2016.03.006. Epub 2016 Mar 11.
Although generally considered a rodent virus, pigs sometimes were suggested a potential reservoir host for encephalomyocarditis virus (EMCV), implying pig-to-pig transmission can cause major outbreaks in a pig population (basic reproduction ratio, R0>1). An earlier experimental study on EMCV transmission among pigs was inconclusive in this respect (R0≈1.24; CI 0.4-4.4). In this study we used a simulation model to extrapolate the experimental results to commercial, compartmentalised pig housings and tested to what extend contacts between pigs in different pens needed to be reduced in order to prevent major outbreaks in a compartment following a single introduction. The final size of simulated outbreaks was measured and the probability to observe outbreaks that affected at least 50 or 80% of the pens was calculated. Simulation scenarios compare one homogeneously mixing compartment (no fence) to epidemiological theory and an increasing effect of fencing on the pig-to-pig transmission between pigs in neighbouring pens. For any R0<1.24 the probability to observe outbreaks affecting more than 50% of the pens remained below 10% if compartmentalisation was introduced leaving per capita transmission rate unchanged. If fences also reduced contact transmission the probability to observe major outbreaks was below 50% for any R0<2.7. Only for R0>4, major outbreaks occurred with more than 50% chance even if only minimal contact between adjacent pens was allowed. In conclusion the results suggested that in a compartmentalised pig housing one single EMCV introduction is unlikely to cause a major outbreak by direct pig-to-pig transmission alone. Other mechanisms e.g. multiple introductions from a rodent reservoir may be required for large outbreaks to occur.
虽然普遍认为是一种啮齿动物病毒，但猪有时被认为是脑心肌炎病毒（EMCV）的潜在储存宿主，这意味着猪与猪之间的传播可能导致猪群中发生重大疫情（基本繁殖率，R0>1）。之前关于 EMCV 在猪群中的传播的实验研究在这方面没有定论（R0≈1.24；CI 0.4-4.4）。在这项研究中，我们使用模拟模型将实验结果外推到商业分隔式猪圈，并测试为了防止在一个隔间中发生单一引入后的重大疫情，需要在多大程度上减少不同猪圈之间的猪接触。模拟爆发的最终规模，并计算观察到至少 50%或 80%的猪圈受到影响的爆发的概率。模拟场景将一个均质混合隔间（无围栏）与流行病学理论进行比较，并比较围栏对相邻猪圈中猪之间的猪对猪传播的影响程度。对于任何 R0<1.24，如果引入分区化而不变更人均传播率，则观察到影响超过 50%的猪圈的爆发的概率仍低于 10%。如果围栏还降低了接触传播，则 R0<2.7 时观察到重大疫情的概率低于 50%。只有当 R0>4 时，即使允许相邻猪圈之间的接触最小化，也会有超过 50%的机会发生重大疫情。总之，结果表明，在分隔式猪圈中，单次 EMCV 引入不太可能仅通过猪与猪之间的直接传播导致重大疫情。其他机制，例如来自啮齿动物储存库的多次引入，可能需要发生大规模疫情。
