Testing Control Strategies for Foot-and-Mouth Disease in New England Using the InterSpread Plus Model: Impacts of Regional Zoning, Early Detection, and Enhanced Biosecurity

Foot-and-mouth disease (FMD) poses a significant threat to the United States dairy industry, potentially causing substantial economic losses through trade disruptions and control measure costs. This study evaluates the effectiveness of regional zoning, enhanced detection, and biosecurity in controlling FMD spread, focusing on the New England milkshed, using the InterSpread Plus (ISP+) model. We adapted a baseline ISP+ configuration incorporating United States dairy farm data, movement networks, cattle dealers, markets, and slaughterhouses, with milk processing plants as a model addition. By implementing regional movement management, increasing passive surveillance, and reducing indirect disease transmission, four hypotheses were tested across three geographically distinct infection seed sets (mixed proximity to New England, close to New England, and distant southwestern): (H1) Regional zoning limits the interregional spread of FMD post-detection; (H2) Earlier detection in New England via increased passive surveillance reduces the overall outbreak impact; (H3) Reduced indirect transmission through enhanced biosecurity states improves FMD outbreak control; (H4) The combination of regional zoning and earlier detection provides synergistic reduction in FMD impact beyond either strategy alone. Through 100 iterations of each scenario simulated over 210 days, scenarios were compared to the baseline. Key metrics included the daily number of infected premises, the outbreak duration, and the total number of infected premises across the outbreak scenarios. Results suggest a shorter outbreak duration following the hypothesized scenarios, compared to the baseline scenario. Results also indicate that regional zoning, early detection, enhanced biosecurity, and the combination of heightened passive surveillance with regional zoning, all reduced the total infected premises. Kruskal-Wallis H tests confirmed significant differences across the baseline, regional zoning, early detection, enhanced biosecurity, and the combination of heightened passive surveillance with regional zoning scenarios, for total infected premises. Post-hoc Dunn's tests indicated that enhanced biosecurity outperformed other control strategies tested. Limitations include model assumptions on the location of disease introduction and its spatial spread patterns, as well as the proportion of dairy premises with heightened local spread. These findings demonstrate that layered interventions may substantially curtail both the national amplification and local spread of FMD, and thus, protect the consumer milk supply and reduce cascading economic shocks from an outbreak.