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Research shows vaccination benefits during Foot & Mouth outbreak

Research shows that vaccination & prompt culling could achieve a 10 fold reduction in the number of farms loosing livestock in a Foot-and-Mouth outbreak.

New research led by the University of Warwick, sponsored by the Wellcome Trust, has outlined a combined culling and vaccination policy that could achieve a ten fold cut in the number of farms loosing livestock compared to the 2001 UK foot and mouth outbreak; with an optimally targeted vaccination policy providing a four fold increase over prompt and efficient culling.

University of Warwick researchers Matt Keeling and Mike Tildesley and their colleagues used data collected during the 2001 UK's foot and mouth outbreak to develop their model. Their findings (to be published in the journal Nature on 2nd March in a paper entitled 'Optimal reactive vaccination strategies for a foot-and-mouth outbreak in the UK' ) were as follows:

Given current expectations are that DEFRA would be able to vaccinate 35,000 cattle a day the most efficient vaccination zone would be a circle around the infected farms with a radius of between 7 and 8 kilometers. The researchers also detail the most efficient radius if the number of vaccinations a day possible differed up or down from 35,000.

However, the most efficient form of vaccination was to vaccinate first farms based on the shortest distance to infected farm/premises or a potential "Dangerous Contact" and to do so as early as possible. For instance the researchers model shows that if work was progressing to carry out vaccinations in a ring around a particular infected farm and 24 hours later another infected farm was found 20km away then the most efficient action would be to spread vaccination resources to target the nearest farms to both the new and old infected premises, rather than attempting to completely deal with the old outbreak then moving to the new one.

The researchers also looked at the possibility of conserving vaccination resources by deliberately NOT vaccinating cattle in farms within a small inner ring surrounding the infected premises. This idea was based on earlier work that it may be too late to help the cattle within that small ring as these may get infected before vaccination can take affect and they were likely to be culled anyway. However the researchers were surprised to find that their model worked better if all cattle were vaccinated, no matter how close they were to the original infection. If all cattle were vaccinated the model showed the spread of infection was slowed even further as even protecting a small number of additional animals from infection had a significant affect in reducing the spread of infection from one farm to another.

Over 10,000 farms were infected 2001. The researchers' modeling of that outbreak states that the following would have been the likely result if the courses of action below had been followed:

No vaccination but highly efficient culling of infected farms, dangerous contacts & contiguous premises 4,220 farms would have had their livestock removed due to infection or culling.

Culling (of infected farms & dangerous contacts) combined with vaccination of farms in random order 1688 farms lose their livestock

Culling (of infected farms & dangerous contacts) plus vaccination concentrated on largest cattle farms 1535 lose their livestock

Culling (of infected farms & dangerous contacts) plus vaccination concentrated on farms at shortest distance to any infected premises or dangerous contact identified within last 10 days - just 1088 farms lose their livestock.

Interestingly, a policy of shortest-distance vaccination combined with additional culling of contiguous premises actually leads to more farms (1528) losing their livestock to infection or culling.

This research resonates with current concerns over the control of H5N1 in poultry, and emphasizes the advantages of carefully optimized control measures.

Note for Editors: The research was led by Dr. Matt Keeling and Dr Michael J Tildesley at the University of Warwick. Other contributors came from Universities of Cambridge, Edinburgh, Pennsylvania State University, and the National Institutes of Health in Bethesda Marlyland.

For further information please contact:

Dr Matt Keeling
University of Warwick Tel: 024 76 524618
M.J.Keeling@warwick.ac.uk

Dr Mike Tildesley, University of Warwick
Tel: 024 76 518359 M.J.Tildesley@warwick.ac.uk

Peter Dunn, Press and Media Relations Manager, University of Warwick
Tel: 024 76 523708 or 07767 655860 email: p.j.dunn@warwick.ac.uk

PR15 PJD
March 2006