Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.
US Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services, Strategy and Policy, Center for Epidemiology and Animal Health, Fort Collins, CO, USA.
Prev Vet Med. 2023 Aug;217:105962. doi: 10.1016/j.prevetmed.2023.105962. Epub 2023 Jun 12.
Given the proximity of African swine fever (ASF) to the U.S., there is an urgent need to better understand the possible dissemination pathways of the virus within the U.S. swine industry and to evaluate mitigation strategies. Here, we extended PigSpread, a farm-level spatially-explicit stochastic compartmental transmission model incorporating six transmission routes including between-farm swine movements, vehicle movements, and local spread, to model the dissemination of ASF. We then examined the effectiveness of control actions similar to the ASF national response plan. The average number of secondary infections during the first 60 days of the outbreak was 49 finisher farms, 17 nursery farms, 5 sow farms, and less than one farm in other production types. The between-farm movements of swine were the predominant route of ASF transmission with an average contribution of 71.1%, while local spread and movement of vehicles were less critical with average contributions of 14.6% and 14.4%. We demonstrated that the combination of quarantine, depopulation, movement restrictions, contact tracing, and enhanced surveillance, was the most effective mitigation strategy, resulting in an average reduction of 79.0% of secondary cases by day 140 of the outbreak. Implementing these control actions led to a median of 495,619 depopulated animals, 357,789 diagnostic tests, and 54,522 movement permits. Our results suggest that the successful elimination of an ASF outbreak is likely to require the deployment of all control actions listed in the ASF national response plan for more than 140 days, as well as estimating the resources needed for depopulation, testing, and movement permits under these controls.
鉴于非洲猪瘟（ASF）与美国的临近，迫切需要更好地了解该病毒在美国养猪业中的可能传播途径，并评估减轻策略。在这里，我们扩展了 PigSpread，这是一个基于农场的空间明确的随机隔间传输模型，包含六个传输途径，包括农场之间的猪只流动、车辆流动和本地传播，以模拟 ASF 的传播。然后，我们检查了类似于 ASF 国家应对计划的控制措施的有效性。在疫情爆发的前 60 天内，二次感染的平均数量为 49 个育肥场、17 个保育场、5 个母猪场，以及其他生产类型的不到一个农场。猪只的农场间流动是 ASF 传播的主要途径，平均贡献率为 71.1%，而本地传播和车辆移动的作用则不那么关键，平均贡献率分别为 14.6%和 14.4%。我们证明，检疫、扑杀、限制移动、接触追踪和加强监测的组合是最有效的缓解策略，在疫情爆发的第 140 天，可将二次感染的平均数量减少 79.0%。实施这些控制措施可导致平均有 495619 头动物被扑杀，进行 357789 次诊断测试，发放 54522 个移动许可证。我们的结果表明，成功消除 ASF 疫情可能需要部署 ASF 国家应对计划中列出的所有控制措施超过 140 天，并估计在这些控制措施下扑杀、测试和移动许可证所需的资源。
