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. 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. Four hypotheses were tested to understand the impact of different biosecurity strategies: (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 measures improves FMD outbreak control; (H4) the combination of regional zoning and earlier detection provides synergistic reduction in FMD impact beyond either strategy alone. The four hypotheses were tested using three geographically distinct infection seed sets; 100 iterations of each scenario were simulated over 210 days and compared to the baseline. Key impact metrics included the daily number of infected premises, the outbreak duration, and the total number of infected premises across the outbreak scenarios. Results suggest shorter outbreak durations and reduced total infected premises under the hypothesized scenarios, compared to the baseline scenario. 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 in terms of total infected premises. Post hoc Dunn's tests indicated that enhanced biosecurity outperformed other control strategies tested. 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.