Modeling the impacts of movement restriction in classical swine fever outbreak control in Indiana

Classical swine fever (CSF) has been eradicated from the United States since 1978, its re-introduction could have a huge impact on the US swine industry. Movement restriction, an essential CSF control strategy, could result in animal welfare concerns in pigs due to overcrowding or feed interruption. The study aims were to estimate the magnitude and pattern of a CSF outbreak, to evaluate the effects of various movement restriction zone sizes, and to estimate the extent of animal welfare mitigation strategies in CSF outbreak control in Indiana. Risk metrics were developed to identify the most likely CSF outbreak scenarios in Indiana. The impacts of various movement restriction zone sizes (3 km, 5 km, 9 km, and 11 km) were evaluated and compared to a 7 km zone size. Risk assessment models were developed to estimate the time to animal welfare concerns, the number of swine premises to experience animal welfare concerns, and the extent of animal welfare mitigation strategies (e.g., on-farm euthanasia, movement of pigs to slaughter plants). Nineteen single-site (i.e., with one index premises at the onset of an outbreak) and 15 multiple-site (i.e., with \u3e1 index premises at the onset of an outbreak) CSF outbreak scenarios were selected and simulated. The median (5th, 95th percentiles) epidemic duration (days) was estimated to be 224 (24, 343) in the single-site, and 201 (161, 285) in the multiple-site outbreak scenarios. The movement restriction zone sizes of 3 km, 9 km, and 11 km did not perform well in controlling a CSF outbreak. Overall, a 7 km zone size (and 5 km in some simulations) was more effective than the other investigated zone sizes. The median percent of swine premises (out of 8,631) that would experience animal welfare concerns due to movement restrictions was estimated to be 8.8% and 23.3% in the single-site and multiple-site outbreak scenarios in Indiana, respectively. On-farm euthanasia has to be initiated to alleviate animal welfare concerns on 32% (n=239 in single-site; n=659 in multiple-site) of the swine premises, and 86% to 90% of the on-farm euthanasia has to be carried out within four weeks of movement restrictions. The study findings could assist swine producers in making informed decisions to minimize losses due to a CSF outbreak, and could be used in the preparedness plans for its effective management