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ARS Home » Midwest Area » West Lafayette, Indiana » Livestock Behavior Research » Research » Publications at this Location » Publication #329981
Title: Evaluation of movement restriction zone sizes in controlling classical swine fever outbreaks

Author
item YADAV, SHANKAR - Purdue University
item WIDMAR, NICOLE - Purdue University
item Lay Jr, Donald
item CRONEY, CANDACE - Purdue University
item WENG, HSIN-YI - Purdue University

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2016
Publication Date: 12/23/2016
Citation: Yadav, S., Widmar, N.O., Lay Jr., D.C., Croney, C., Weng, H. 2016. Evaluation of movement restriction zone sizes in controlling classical swine fever outbreaks. Frontiers in Veterinary Science. 3:124. doi: 10.3389/fvets.2016.00124.

Interpretive Summary: If Classical Swine Fever were to enter the United States it is imperative that a strategy is identified to limit its impact on the swine industry and swine welfare. Therefore, this study evaluated the comparative impacts of selected movement restriction zone sizes and their associated compliance levels on the outbreak-related outcomes (e.g., epidemic duration, number of infected, pre-emptively culled premises, number of affected premises due to adverse animal-welfare outcomes, and total depopulated premises). The objective of this study was to compare the movement restriction zone sizes of 3-kilometers (km), 5-km, 9-km, and 11-km with that of 7-km in controlling a classical swine fever outbreak. Four single-site and four multiple-site outbreak scenarios in Indiana were simulated incorporating various zone sizes and compliance assumptions using a stochastic between-premises disease spread model to estimate epidemic duration, number of infected, and pre-emptively culled swine premises. Furthermore, a risk assessment model was developed to estimate the number of swine premises under movement restrictions that would experience overcrowding or feed interruption during an outbreak. Compared with the 7-km zone size, 3-km zone size increased the epidemic duration by 6% to 20% and total number of depopulated premises (premises with adverse animal welfare outcomes, infected, and pre-emptive culled) by 10% to 35%. Assumption of a lower compliance level for the 9-km and 11-km zone sizes increased the epidemic duration by 5% to 33%, total number of depopulated premises by 7% to 44%, and swine premises to experience adverse animal welfare outcomes by 26% to 70% compared with the 7-km zone size. The magnitude of impact due to a zone size varied across the outbreak types. Compared with the 7-km zone size, the 5-km zone size was comparable or better in some circumstances. Overall, the 7-km zone size was found to be the most effective in the simulated Classical Swine Fever outbreak scenarios. This study provides regulatory authorities with information to best manage an outbreak should Classical Swine Fever enter the United States.

Technical Abstract: The objective of this study was to compare the movement restriction zone sizes of 3-km, 5-km, 9-km, and 11-km with that of 7-km in controlling a classical swine fever (CSF) outbreak. Three assumptions of compliance level were considered: baseline, baseline ±10%, and baseline ±15%. The compliance level was held constant across all zone sizes in the baseline simulation. In the baseline ±10% and baseline ±15% simulations, the compliance level was increased for 3-km and 5-km and decreased for 9-km and 11-km from the baseline by the indicated percentages. Four single-site (i.e., with one index premises at the onset of an outbreak) and four multiple-site (i.e., with more than one index premises at the onset of an outbreak) CSF outbreak scenarios in Indiana were simulated incorporating various zone sizes and compliance assumptions using a stochastic between-premises disease spread model to estimate epidemic duration, number of infected, and pre-emptively culled swine premises. Furthermore, a risk assessment model was developed to estimate the number of swine premises under movement restrictions that would experience overcrowding or feed interruption during a CSF outbreak. Each outcome of a zone size was compared with that of the7-km zone size, expressed as the percent change. Compared with the 7-km zone size, 3-km zone size increased the epidemic duration by 6% to 20% and total number of depopulated premises (premises with adverse animal welfare outcomes, infected, and pre-emptive culled) by 10% to 35%. Assumption of a lower compliance level for the 9-km and 11-km zone sizes increased the epidemic duration by 5% to 33%, total number of depopulated premises by 7% to 44%, and swine premises to experience adverse animal welfare outcomes by 26% to 70% compared with the 7-km zone size. The magnitude of impact due to a zone size was varied across the outbreak types. Compared with the 7-km zone size, the 5-km zone size was comparable or better in some circumstances. Overall, the 7-km zone size was found to be the most effective in the simulated CSF outbreak scenarios.