Modelling the spread of foot-and-mouth disease in the USA
by
Dr. Mike Tildesley
University of Warwick
Coauthors: Prof. Matt Keeling

Since 2001, models of foot-and-mouth disease (FMD) spread, supported by data from the UK epidemic, have been expounded as some of the best examples of problem-driven epidemic models (1,2,3). Detailed data is available on size and locations of all farms in the UK as well as infection and culling dates of those specifically affected by disease during 2001. It is unclear how the models and parameters from the UK can be translated to other scenarios where data is not quite so comprehensive (4). Here we consider how the model framework used to capture the UK epidemic can be applied to a hypothetical FMD outbreak in the USA.

In the USA, precise size and location of livestock farms in unknown, with data only available at the county scale. Models of the spread of FMD in the USA have been developed assuming random locations of farms within counties. We consider two scenarios: the first allocates random locations to farms within counties whilst the second locates farms non-randomly within clusters. We then investigate the robustness of the modelling approach, and the effect on both epidemic size and the optimal strategy to control disease spread to precise knowledge of farm location within counties. The model predicts that epidemic size is highly dependent upon farm location. However, the level of clustering within a county has little effect on the preferred strategies for disease control. This result highlights an important premise – county-scale data can be used to develop a sophisticated national control strategy to prevent spread of disease in the event of any future FMD epidemic in the USA.

1. Keeling, M.J., Woolhouse, M.E.J., Shaw, D.J., Matthews, L., Chase-Topping, M., Haydon, D.T., Cornell, S.J., Kappey, J., Wilsmith, J. and Grenfell, B.T. (2001) Dynamics of the 2001 UK Foot and Mouth Epidemic: Stochastic Dispersal in a Heterogeneous Landscape. Science, 294, 813-817.

2. Tildesley, M.J., Savill, N.J., Shaw, D.J., Deardon, R., Brooks, S.P., Woolhouse, M.E.J., Grenfell, B.T. & Keeling, M.J. (2006) Optimal reactive vaccination strategies for an outbreak of foot-and-mouth disease in Great Britain, Nature 440, 83-86.

3. Tildesley, M.J., Deardon, R., Savill, N.J., Bessell, P.R., Brooks, S.P., Woolhouse, M.E.J., Grenfell B.T. & Keeling, M.J. (2008) Accuracy of Models for the 2001 UK Foot-and-Mouth Epidemic. Proc. R. Soc. B, in press.

4. Tildesley, M.J. & Keeling, M.J. (2008) Foot-and-Mouth Disease - A Modelling Comparison between the UK and Denmark. PREVET, 85 (1-2), 107-124.

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Date received: April 28, 2008