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The Trouble with the Mathematical modelling in March 2001

From: Use and abuse of mathematical models: an illustration from the 2001 foot and mouth disease epidemic in the United Kingdom
R.P. Kitching , M.V. Thrusfield & N.M. Taylor
Rev. sci. tech. Off. int. Epiz., 2006, 25

  • The mathematical model that drove the contiguous cull was written - not by available experts who were familiar with the Pan Asia 'O' strain - but by epidemiologists and bio-mathematicians who were not
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  • The Pirbright members of the Science Group - Dr Paul Kitching and Dr Alex Donaldson - really knew a great deal about the virus and had studied its spread but were not listened to as they should have been within the Science Group.
  • The Imperial College model's premise was based on a faulty calculation.
  • Much of the data that the Imperial College model used for its predictions and policy were flawed.
  • The Imperial model made assumptions that were inappropriate.
  • There was intense pressure from political sources to show the disease in decline by the time the General Election arrived.
  • Because the data was wrong, the science was wrong and the assumptions about spread were wrong, the contiguous cull itself was wrong, and indeed unnecessary..

  • "Remember that they all start as merely the mathematical expression of the model builder's presumptions and assumptions."



    Ten years on, is the UK as unprepared now for FMD as it ever was?

  • It is time people stopped thinking of FMD as a "deadly" plague. It is not. Literally millions of uninfected animals were killed in 2001 by a control policy based on flawed science - and because FMD is an economic disease for Member States of the European Union. FMD vaccination was banned in the EU 20 years ago because there is a special trading advantage to countries that can show they have no endemic FMD. Lack of vaccination is taken to mean the country has no endemic FMD. Therefore, to be "FMD free without vaccination" confers a huge trading advantage. If there is an outbreak, countries that have this advantage are inclined to kill every animal that might spread disease so that they can get back as quickly as possible to claiming that the disease is not endemic.  The mindset continues that vaccination in a country means that FMD could be endemic - and must put that country at a disadvantage for trade. Vaccination was thought to be able to mask disease by creating "carriers" that looked healthy but could still pass on the virus. This has never been shown to happen in the field. This wrongheadedness means that vaccination has been ignored by such countries as the UK when its use could protect national herds and flocks at the first threat of disease
  • It is very important that the Expert Group driving policy should contain  experts who are adequately qualified in key areas of modern disease control - it is vital, for example, to have a vaccination expert with field experience of implementing vaccination disease control policy so that those who those who have doubts can be properly informed and reassured.

  • Early on-site detection with portable kits such as Smiths Detection BioSeeq can limit the spread of disease by detecting foot and mouth  before clinical signs appear.  This allows for an early stand-still of movements and the possibility of ring vaccination rather than whole country vaccination, and quickly identifies the strain in order to produce the appropriate vaccine. On-site diagnosis gives results about infection within around 90 minutes and makes it unnecessary to kill uninfected animals even if they are within the infected area. Smiths Detection now make an on-site diagnostic kit very similar to that available in 2001 - the one refused by David King (the Chief Scientific Advisor who had no veterinary or FMD experience) because he failed to understand its use. But there is no mention of it in the Contingency Plan - even though such technology can detect FMD infection days before clinical symptoms appear.
  • Emergency or "ring" vaccination, (for which supplies of vaccine for all strains of the virus can be obtained from Merial at Pirbright or other vaccine producers), can be used in a protective ring around any discovered infection - from the outside inwards - to stop the spread of disease. Had it been used early enough in the 2007 outbreak we should not have had the second wave.

  • Given that the decision not to vaccinate in 2007 led to a second wave of spread in Surrey, it is hard to credit that the recent exercise "Silver Birch" in late 2010 decided not to use emergency vaccination AT ALL - for the same discredited claim put forward by the meat industry in 2001 that people wouldn't buy meat of vaccinated animals. Of course they would. All imports of  beef from Argentina or Brazil, for example, come  from vaccinated cattle and were being consumed by British consumers in 2001. UK consumers continue to eat the products from vaccinated animals all the time without realising it. We heard no such arguments when we were all vaccinating against Bluetongue. Meat and products from FMD vaccinated animals do not have to be labelled in the UK,  as both the Consumer Council and the FSA have made clear.

  • In 2001 there were people who said, "They're only meat animals and they'd have died anyway. Farmers are crying crocodile tears." Such a statement shows no understanding of good livestock farmers. The manner of handling animals and of their death matters. There were far too many cases of rushed and cruel practices when officials and slaughterers didn't know how to handle animals in both 2001 and 2007 and had not got the correct equipment or expertise. What's more, so many valuable genetic lines, hefted sheep, rare breeds, breeding stock and pets who were not destined for meat were unnecessarily lost because of the policy of killing healthy animals in a map-drawn circle around infection. (The policy makers had not understood that airborne spread was poor for FMD serotype O, the strain of the virus in the UK in 2001.)

  • The Contingency Plan is almost impossible to make head or tail of because of its dense bureaucratic language - but what is very clear is that there is no indication that vaccination (even though produced by Merial at Pirbright in Surrey) would be rolled out immediately - or used at all. Emergency vaccination is most effective if it is deployed early on.  The plan should be a real set of actions that everyone understands - and ought to be clear and sensible enough for any vet and farmer to agree with. This is not the case. There is no longer even a separate plan for FMD. The plan simply includes it together with other diseases in a very long document.  The Northumberland Report produced after the 1967-1968 epidemic is scientific, simple and succinct; in many respects it is everything that is required of a Contingency Plan. The Northumberland Report recommended the use the diagnostic tests - available even in 1968  - to detect incubating disease in contact animals.  Present policy   following the Animal Health Act of 2002 makes it possible that diagnositics can be used only for epidemiological purposes, not to prevent killing. This is a regressive move and ignores the benefits of  effective, humane technology now available in the twenty-first century.

  • For DEFRA to make such a fuss about "biosecurity"   gives the government an opportunity to blame farmers if the worst happens, but this is a red herring - or red tape. No sane farmer or smallholder is going to want disease anywhere near their farm and they know it is in their own interests to take no  risks at all  whereas the lack of a good clear and modern contingency plan is the responsibility of the Government..  There is a high risk of the virus being introduced and, once here, it is the responsibility of everyone, including farmers, to  take every possible measure to reduce spread.  It is very unfortunate that as soon as FMD was confirmed in 2001 there was no immediate targeting of animal dealers and halting of animal movements. 

  •  Where does the virus come from? Bushmeat, illegal imports and so on - but also research and development within establishments thought to be proof against virus escape. Farmers themselves can do nothing about this at all. There is a dangerous complacency in the UK about unsafe imports.  

  • By its reluctance to have vaccination as its first line of defence, to make no mention of portable rapid diagnosis and to make no proper preparations  for the use of either,  DEFRA makes an outbreak of FMD in the UK a very dangerous risk. The Government has never carried out a proper risk assessment analysis, looking carefully and with independent, informed input at a variety of possible policies. That is real risk taking. Even if vaccination were agreed by a more enlightened Ministry, it would take vital days or even weeks to get it going.

  • That correctly administered FMD vaccination works is not in doubt by any informed scientist anywhere. In 2001, Uruguay had a very similar outbreak to the UK's but their farmers vaccinated their own cattle. The virus was soon stopped in its tracks - whereas in the UK it dragged on for almost the whole year with disastrous consequences for farmers, smallholders and owners of pet animals of susceptible species.

  • At least 10 million animals died (evidence on in 2001 and the trauma suffered and social consequences have never been forgotten (See Lancaster University Research study).  The waste in terms of money and resources was quite out of proportion to any supposed political or economic gain.  In the present global financial situation, such a waste should be thought unthinkable.  

  • Research showed that the epidemic in 2001 had peaked before the 3km contiguous cull policy began. Our mass cull policy was as unnecessary as it was cruel.  It was also illegal  in 2001 to kill animals that had not been exposed to the virus.  The Animal Health Act of 2002 sought to legitimise retrospectively the mass killing that had been done and make legal what could be done in future.  The thought that it could all happen again is sickening.  

  • There are now  DIVA vaccines and tests proven to differentiate vaccinated from infected animals - and vaccinated animals are not a risk as carriers even when, as is rare, some vaccinates might be sub-clinically infected. We are STILL waiting for validation for these DIVA vaccines so that post outbreak testing can be carried out swiftly.

  • The political assumption is that the "FMD free without vaccination" trading status is too valuable to lose because if one uses vaccination it takes longer for that trading status to be returned. There is no scientific reason for this trading disparity. If it is assumed that 6 months is the time for a country that has used vaccination to resume trade, it is just as valid that it should be 6 months for a country that has not (where the disease could be lurking anywhere and testing should be just as stringent, if not more stringent, before trading is resumed.)

  • When  mistaken policy is decided on by people taking charge over things that they do not understand, that policy can disastrously affect the lives of others. The political centre always wants to keep control - but this results in the sidelining of the real FMD experts and also of people on the ground with local knowledge and veterinary and farming expertise. It was a tragedy that informed vets and scientists were not listened to - and are still trying to make their voices heard.

  • The tragedy of FMD is being played out still. In 2010 the Japanese farmers of Miyazaki were given the same reasons and suffered the same distress when thousands of animals were killed - simply because Japan clung to its economic trading status. In South Korea now the disease has raged out of control and vaccination is being used - but too late for the thousands of farmers who have had their animals snatched away or for those animals already infected. In Bulgaria the authorities are blaming Turkey, rebuilding border fences - and refusing to vaccinate. In all cases this reluctance is because of the trading status of "FMD free without vaccination". The trading status gives an advantage to big business. We and our animals are the ones who pay for this and the price is too high. 

  • Rinderpest has been defeated globally by the correct use of science. There is no reason why FMD should not be eradicated globally too
  • UPDATE Sunday 6th February 2011

    (Please contact the website for more information on any of the statements made above.)