Modeling foot-and-mouth disease dissemination in Brazil and evaluating the effectiveness of control measures

Foot-and-mouth disease (FMD) infects multiple food-animal species and thus is capable of disseminating among ungulate species with distinct transmission rates. Here, we present a multilevel compartmental stochastic model, that takes into account population dynamics, births, and deaths, and explicit representation of species-specific transmission dynamics. The model considered two major modes of transmission, within-farm and between-farm Susceptible-Exposed-Infected-Recovered (SEIR) transmission with species-specific transmission dynamics. Our model outcomes are the number of secondarily infected animals and farms, spatial dissemination distances, the role of major transmission pathways, and the effectiveness of different scenarios to control outbreaks. We demonstrated that after 20 days of FMD dissemination, the median number of infected farms when considered all species was 8 (IQR: 3-22), and 7 (IQR: 3-22) when considered only bovine, 3 (IQR: 1-6) for swine farms, and 1 (IQR: 1-1) for small ruminants. We demonstrated that animal movement was the primary route for dissemination in the first days of epidemics, while at ten days, spatial transmission was the predominant cause of bovine infections and between-farm animal movements led to the most swine infections. Furthermore, we have also shown that the median distance between seeded and secondary infections was 5.77 km (IQR: 1-10.29 km), with some long-range dissemination at 695.40 km. The depopulating of 12 and vaccinating of 15,000 farms per day after 20 days of FMD silent dissemination, faded 93.4% of the epidemics with a median of 9 (IQR: 3-23, max: 221) infected farms within 54 days of the deployment of control actions. In conclusion, the developed transmission model allows for cross-species transmission to be considered in FMD policymaking, and the software implementation facilitates the adaption of scientific-based support to FMD planning.