Viral Disease and Epidemiology Research Division, National Institute of Animal Health, National Agriculture and Food Research Organization, 3-1-5 Kannondai, Tsukuba, Ibaraki 305-0856, Japan.
Prev Vet Med. 2013 Nov 1;112(3-4):183-93. doi: 10.1016/j.prevetmed.2013.08.010. Epub 2013 Aug 30.
A large-scale foot-and-mouth disease (FMD) epidemic occurred in Japan in 2010. The epidemic arose in an area densely populated with cattle and pigs, continued for 3 months, and was contained by emergency vaccination. In this study, a mathematical simulation model of FMD transmission between farms was developed to generate the disease spread in the affected area. First, a farm-distance-based transmission kernel was estimated using the epidemic data. The estimated transmission kernel was then incorporated into the transmission model to evaluate the effectiveness of several control measures. The baseline model provided a good fit to the observed data during the period from imposition of movement restrictions until the implementation of vaccination. Our simulation results demonstrated that prompt culling on infected farms after detection could contribute to reducing the disease spread. The number of infected farms decreased to 30% of the baseline model by applying the 24-h prompt culling scenario. The early detection scenario resulted in a smaller-sized epidemic. However, the results of this scenario included a 35% chance of large-scale epidemic (more than 500 infected farms), even when the disease was detected 14 days earlier than in the baseline model. As additional options, preemptive culling could halt the epidemic more effectively. However, the preemptive culling scenario required substantial resources for culling operations. The 1-km preemptive scenario involved more than 50 farms remaining to be culled per day. Therefore, preemptive culling scenarios accompanied some difficulties in maintaining a sufficient capacity for culling in the affected area. A 10-km vaccination 7 days after the first detection of the disease demonstrated the potential to contain the epidemic to a small scale, while implementation of a 3-km vaccination on the same day could not effectively reduce epidemic size. In vaccination scenarios, the total number of farms that were either culled or vaccinated exceeded that of the baseline model. Vaccination scenarios therefore posed a problem of appropriate management of many vaccinated animals, whether these vaccinated animals would be culled or not. The present FMD transmission model developed using the 2010 FMD epidemic data in Japan provides useful information for consideration of suitable control strategies against FMD.
2010 年日本发生了一次大规模的口蹄疫（FMD）疫情。疫情发生在一个人口密集的牛和猪养殖区，持续了 3 个月，最终通过紧急疫苗接种得到控制。在这项研究中，我们建立了一个农场间 FMD 传播的数学模拟模型，以生成受影响地区的疾病传播情况。首先，使用疫情数据估计了基于农场距离的传播核。然后，将估计的传播核纳入传播模型中，以评估几种控制措施的效果。在实施移动限制至接种疫苗期间，基准模型对观察数据的拟合效果良好。我们的模拟结果表明，在发现感染农场后立即进行扑杀，可以有助于减少疾病传播。通过应用 24 小时立即扑杀方案，感染农场的数量减少到基准模型的 30%。早期检测方案导致疫情规模较小。然而，这种情况下有 35%的机会出现大规模疫情（超过 500 个感染农场），即使在比基准模型提前 14 天发现疾病的情况下也是如此。作为附加选项，预防性扑杀可以更有效地阻止疫情。然而，预防性扑杀方案需要大量的扑杀作业资源。1 公里的预防性方案每天需要扑杀超过 50 个农场。因此，预防性扑杀方案在维持受影响地区足够的扑杀能力方面存在一些困难。在疾病首次发现后的第 7 天进行 10 公里的疫苗接种可以将疫情控制在较小的范围内，而在同一天进行 3 公里的疫苗接种则无法有效减少疫情规模。在接种方案中，无论是扑杀还是接种的农场总数都超过了基准模型。因此，接种方案面临着对大量接种动物进行适当管理的问题，这些接种动物是否会被扑杀。本研究使用日本 2010 年 FMD 疫情数据建立的 FMD 传播模型，为考虑适合的 FMD 控制策略提供了有用的信息。
