Foot and mouth disease (FMD) is a viral infection of cloven-hoofed animals, including livestock species such as cattle. Outbreaks of FMD are expensive because of trade restrictions and costly control measures, and therefore, there is interest in understanding potential outbreaks and identifying ways to reduce losses. In the U.S., the agricultural industry differs from countries that have experienced recent FMD outbreaks, and this could greatly impact potential outbreaks; understanding these differences could assist in preparedness plans. The United States Disease Outbreak Simulation (USDOS), which was developed in an international collaborative effort between the Colorado State, Linköping and Warwick Universities, and the U.S. Department of Agriculture, with support of from the U.S. Department of Homeland Security, is a simulation model that allows for exploration of national-scale infection patterns and control of FMD outbreaks in cattle. USDOS is a premises-level model, incorporating information on both local spread and long-distance transmission events. Using USDOS, we explore the impacts of premises demographics, county characteristics, and shipments on predicted outbreaks, and the influence these factors have on control effectiveness. To explore control, we selected and parameterized scenarios that include combinations of culling, vaccination and movement bans, with input from experts to capture realistic resource constraints and the types of control that may be considered in the event of a U.S. FMD outbreak.
Results/Conclusions
We find identifiable factors, such as high degrees of premises clustering, that contribute to risk of outbreaks of FMD and to its further spread. Outbreak patterns are also influenced by the incidence of shipments, which are important for infecting new areas. Our results indicate that the importance of local spread versus shipment spread of FMD differs among areas in the U.S. Our results also indicate that control actions, such as movement bans, culling and vaccination, are most effective when applied rapidly and with the maximum possible resources. Additionally, we find that in large outbreaks, the time and resource constraints on controls can impede the effectiveness, and potentially allow the outbreak to outpace the mitigation efforts. Using a combination of the demographic information, shipment patterns, and control results, we identified the most effective control in different areas in the U.S. Together these results provide a detailed picture of potential FMD outbreaks for the contiguous U.S. and the first exploration of control scenarios on this scale. These results can be used to inform policy makers on potential FMD outbreaks and to identify effective control actions.