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Simulation Modeling of Food-and-Mouth Disease Spread and Control


<OL> <LI> Modify existing simulation model to enable simulation of complex (real world) vaccination control strategies to be simulated. <LI>Evaluate the impact of vaccination as a control strategy in two states with similar numbers of livestock facilities by type. <LI>Make results available to state and US regulatory veterinary decision makers and industry.

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NON-TECHNICAL SUMMARY: The introduction of foot-and-mouth disease (FMD) into the US could have tremendous negative economic consequences.1 Given the controversy surrounding massive slaughter (10 million head) during the UK FMD epidemic in 2001 and the success of vaccination in the control of the disease in The Netherlands the same year, the US must rethink its strategy of mass depopulation, movement controls, surveillance and vaccination if FMD were to enter this the US. Currently, if FMD were introduced into the US, ring depopulation could be implemented along with ring vaccination, if shown to be cost-effective or if the disease persisted for more than 6 months. However, due to many factors including climate, transportation needs, and availability of resources, the predominant forms and distributions of livestock production differ across the country, and therefore, optimal control strategies may vary depending on the location of the outbreak. Simulation models have been developed to consider alternative FMD controls. Given the availability of improved diagnostic techniques, modified regulations, public pressure to avoid mass slaughter of infected, as well as non-infected animals, and potential costs associated with additional herd outbreaks ($8,000 per head in California7), benefits of alternative FMD controls strategies should be reconsidered. The purpose of the proposed research is to assess whether the impact of FMD vaccination strategies on livestock as well as direct cost and economic differences is affected by the geographic location of the outbreak. Results of FMD outbreak simulations in two US states in different geographic regions; Indiana and California will be used. Accurate premises location data are available for both. Indiana has more swine facilities than California, fewer livestock facilities overall and a greater number of smaller facilities. The total numbers of dairies, beef and sheep operations in the two states are, however, similar. Documented importance to CA - Although FMD has not been present in California since 1929, recent outbreaks in Taiwan, Argentina, Brazil, the UK, Ireland, France, and The Netherlands reaffirm the possibility that FMD may return to the US. One study recently estimated the economic impact of FMD in California could exceed $8 billion dollars. The proposed research may impact future decisions regarding how FMD control strategies in the US are selected, with the ultimate impact being savings of animal lives as well as reducing the impact on the livestock industry and US economy.


APPROACH: Design - Locations of CA livestock premises have been obtained from the California Department of Food and Agriculture (CDFA), the Indiana Board of Animal Health (IBAH), and the National Agriculture Statistics Service (NASS) and information about direct and indirect livestock facility contacts have been obtained from producer surveys. A spatial, epidemic simulation model written in R programming language, will be run to simulate FMD epidemics in California and Indiana. 1,000 iterations will be run for each scenario to compare the results of with and without vaccination. Vaccination constraints, such as number of doses delivered by time and herd type, e.g. dairy- and feedlot-specific vaccination strategies, will be evaluated. Movement, surveillance and depopulation controls will be implemented, using current USDA recommended guidelines and vaccination will be added as a comparison. Outcomes to be compared are: IPs, epidemic duration, direct costs, and economics.
<P>Anticipated results - The data expected are distributions of epidemic size, duration and cost, numbers and types of herds infected, and numbers and types of animals. Distribution means, 95% probability intervals, and statistical significance will be reported. Comparisons of with and without vaccination will be made for each state. Data analysis - Cost information pertaining to the financial impact of FMD per herd and animal affected has been obtained from a recent evaluation of the economic impact of FMD in California8 and will be updated to reflect new USDA guidelines regarding the personnel and supplies required to control an FMD epidemic. Differences in number of IPs or duration will be further evaluated by calculating the cost for each alternative and combined with an economic equilibrium model (Agriculture Sector Model, ASM) to evaluate the economic impact of the alternatives examined. The simulated differences will be quantified and compared by different geographic location. Outcomes will be tested using a Kruskal-Wallis, 1-way ANOVA by ranks with a two-sided test of significance adjusted for multiple comparisons. Communication - Findings will be shared with CDFA and the IBAH through progress reports, and industry and scientific publications and meetings. Our findings have been presented in industry news letters as well as agriculture radio and TV shows. We have presented findings to CDFA, USDA, DHS, a US Congressman from CA, and a US House Oversight Committee with potential spread and control information at their request. We have a well-documented record of disseminating our results. We maintain a collaboration with Martin Smith (Vet Extension) on a 4H biosecurity survey in California, information from which will be used in the FMD simulation model.

Carpenter, Tim
University of California - Davis
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