The Impact of Movements and Animal Density on Continental Scale Cattle Disease Outbreaks in the United States

Globalization has increased the potential for the introduction and spread of novel pathogens over large spatial scales necessitating continental-scale disease models to guide emergency preparedness. Livestock disease spread models, such as those for the 2001 foot-and-mouth disease (FMD) epidemic in the United Kingdom, represent some of the best case studies of large-scale disease spread. However, generalization of these models to explore disease outcomes in other systems, such as the United States’s cattle industry, has been hampered by differences in system size and complexity and the absence of suitable livestock movement data. Here, a unique database of US cattle shipments allows estimation of synthetic movement networks that inform a near-continental scale disease model of a potential FMD-like (i.e., rapidly spreading) epidemic in US cattle. The largest epidemics may affect over one-third of the US and 120,000 cattle premises, but cattle movement restrictions from infected counties, as opposed to national movement moratoriums, are found to effectively contain outbreaks. Slow detection or weak compliance may necessitate more severe state-level bans for similar control. Such results highlight the role of large-scale disease models in emergency preparedness, particularly for systems lacking comprehensive movement and outbreak data, and the need to rapidly implement multi-scale contingency plans during a potential US outbreak.全球化提升了新型病原体在大空间尺度范围内传入与扩散的可能性，亟需构建大陆级别的疾病模型以指导应急准备工作。家畜疾病扩散模型，例如用于2001年英国口蹄疫（foot-and-mouth disease, FMD）疫情的相关模型，堪称大规模疾病扩散研究的顶尖案例之一。然而，将这类模型推广应用于其他畜牧体系（如美国养牛业）以探究疾病传播结局的尝试，却因各体系规模与复杂度的差异，以及缺乏适配的家畜移动数据而受阻。本研究依托一套独特的美国肉牛运输数据库，得以构建模拟移动网络，并以此为基础搭建适用于美国肉牛群体潜在口蹄疫类（即快速扩散型）疫情的近乎大陆级别的疾病模型。模拟结果显示，最严重的疫情或波及美国三分之一以上的区域，影响12万家肉牛养殖场所；但相较于全国性的移动禁令，仅对受感染县域实施肉牛移动限制，便可有效遏制疫情扩散。若检测进度缓慢或防控依从性不足，则可能需要实施更为严格的州级移动禁令，才能实现类似的防控效果。上述研究结果凸显了大规模疾病模型在应急准备中的重要作用——尤其针对那些缺乏全面移动与疫情数据的畜牧体系——同时也表明，在美国爆发潜在疫情时，需快速启动多尺度应急防控预案。