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"FOOT AND MOUTH DISEASE AND ITS RELATED ISSUES"
A symposium held on Saturday 20th April 2002 at Exeter University
A brief report by Alan Beat
The list of speakers told me what to expect. Most of the day comprised a self-congratulatory and one-sided presentation of the "successful" methods employed to "defeat" the epidemic. Speakers were smug and complacent, had fixed prejudices and said little that was worthy of repeating here. As Nick Green has accurately observed elsewhere "such tripe as there was no effective vaccine, no one would buy vaccinated meat, it doesn t work in sheep and weren t the NFU marvellous routine just bores me now". So I restrict these notes to the few points that deserve it.
Professor Phillip Duffus, University of Bristol, observed that he saw plenty of evidence for the existence of carrier status in livestock, but saw only dubious evidence of transmission from carriers to other livestock.
FMD virus could survive only two weeks in dry faeces but up to six months in slurry.
Professor Joe Brownlie, Royal Veterinary College, confirmed that the Taiwan outbreak of 1997 did not spread from pigs to cattle. He attributed this to subtle differences between strains of the type O virus and said that for this reason, every epidemic was different.
The rest of his presentation was a catalogue of misinformation and misrepresentation, e.g. vaccination against FMD did not prevent disease occurring, it merely masked the symptoms (and this man sat on the Science Group advising on government policy).
Dick Sibley, British Cattle Veterinary Association, described his Devon vet practice and detailed the importance of preserving "precious" dairy cattle during the epidemic, whilst sheep were worthless and best culled to reduce virus load in the region.
He recognised that the crisis had revealed a "new" need to include pet animals in future planning, whose owners had no concern for compensation or export markets.
Highly detailed records for all cattle were now kept (since BSE) on computer but these could not be accessed due to incompatible systems!
He recognised the regional differences between Cumbria (origin of early field data on which computer models were based) and Devon, where "local spread" did not happen and the contiguous cull was unjustified. He argued for local veterinary risk assessment, allowing local delivery of a central policy.
But the slaughter policy had "worked".
The Animal Death Bill was needed, despite "some opposition", to enforce effective control. It was unacceptable for pet owners to resist and "place other livestock at risk".
Vaccination did not work and "experts" he had approached in countries that practise it warned him against using it etc. (this man was also a member of the advisory Science Group)
Alick Simmons, DEFRA, outlined how the slaughter/movement restriction policy had enabled Britain to eliminate Rinderpest and other bovine diseases during the 19th Century, despite the causal organisms not being identified or understood. It was a method that was effective against any disease, anywhere, there was no need to know any more or look any further. Slaughter continued to be effective in recent years against Brucellosis, BSE etc. The contiguous cull was government policy so he was unable to comment or answer questions about it.
Geoff Bateman, Environment Agency, expressed pleasant surprise that so few environmental problems had been encountered during and after the epidemic. He displayed graphs showing, amongst other things, that the Holsworthy pyre did not cause local air pollutants to increase above permitted levels, while admitting that sampling took place upwind of the pyre (unfortunately, I live four miles downwind where air quality was somewhat different).
He stressed the importance of local input to the environmental decision-making process e.g. it had been a wet winter in Devon so ground water levels were too high to permit burial on farm (although he forgot to mention that the Ash Moor mass burial pit was dug on one of the wettest sites possible, with the water table just three feet below the surface).
David Hill, NFU, gave some personal experiences of the crisis. He spoke against the contiguous cull and remained opposed to it; ditto on vaccination, which would have created a two-tier market and caused financial harm to his members. He said the NFU had stopped the proposed use of vaccination, in "eye-ball to eye-ball confrontation" with the Prime Minister. Given this power of veto, he did not explain why the NFU did not also stop the contiguous culling policy, if they opposed this as he now claims.
After all this blatant propaganda, Doctor Marcus Hutber, Epivet, was a breath of fresh air. He had worked on FMD research at Pirbright under Paul Kitching, and lived in Czechoslovakia for three years where FMD is endemic; there, vaccination of only the cattle had reduced outbreaks to zero despite large numbers of pigs being present. The reason was simply that housed pigs do not pick up FMD by aerosol, so housing with effective biosecurity stopped disease.
He stressed there was much that any farmer could do to protect his stock against infection, simply by housing them, using stock-free barrier fields, moving to furthest fields from the source of infection, away from roads etc.
Experiments at Pirbright had shown that passage of FMD through sheep was poor, with transmission from animal to animal breaking down and disease petering out with no intervention necessary. So it followed that the spread of FMD in the 2001 epidemic (as distinct from the "seeding") must have been via cattle, while pigs were hardly involved.
He said that 50% of the animals killed were tested as healthy.
He dismissed existing FMD computer models as worthless in the UK epidemic.
He had made a close study of "breakdowns" among vaccinated, intensively-farmed cattle in Saudi Arabia, and found that intra-farm epidemics (i.e. within a single herd or flock) precisely mirror the larger-scale epidemic across a region or country. Therefore, data gathered from the first week of an outbreak enables accurate prediction to be made of the subsequent epidemic, informing the choice of best control policies early on.
Antibody levels in blood vary with the time elapsed since vaccination, and susceptibility of cattle to FMD varies significantly with the age of the individual. Given this data for a farm, the initial number of cases determines the response for best control. Low herd antibodies and large number of early cases - slaughter fast. High herd antibodies and few initial cases - vaccinate fast.
The intermediate case - low herd antibodies, few initial cases - he likened to the 2001 UK outbreak, mainly seeded among sheep flocks that respond to FMD rather like cattle with low antibody levels. Here the initial data enables modelling of the epidemic to predict outcomes with good levels of accuracy. If slaughter takes eleven months to eliminate the epidemic, as in the UK, the much faster elimination and lower cost of vaccination outweighs the twelve-month trading penalty. If slaughter provides a much faster route to elimination, then the benefits and costs of vaccination versus slaughter can be weighed, and a decision taken, at the very beginning of an epidemic.
He described a computer model, developed to make these predictions, from basic input data of farms and their livestock in any given situation.
The question-and-answer session that followed was restricted to pre-submitted written questions, enabling the previous speakers to repeat themselves ad nauseam without challenge. However, I could remain silent no longer when Professor Brownlie misrepresented the Dutch outbreak of 2001 with false statements about more animals killed per case because of vaccinate-to-kill requirements. I interrupted and challenged him to give an honest account instead, and outlined the facts i.e. Dutch permission was for vaccinate-to-live, Dutch farmers had agreed on that basis, the area vaccinated was generous on that basis, and only after the disease had been eliminated did the Dutch government go back on its word and slaughter instead, for solely economic reasons.
Both he and Dick Sibley admitted that these facts were correct and hastily re-drew their description of the Dutch epidemic.
Janet Bayley also spoke out from the audience, to outline that the Dutch delegation at the Brussels FMD conference last December had stated that they would never again allow vaccinates to be slaughtered under such circumstances, and that the EU must change existing rules that place unfair trading penalties against vaccination-to-live. She said that the EU was now considering a revision of policy in this area to allow resumption of trade after six months instead of twelve following vaccination-to-live, via the use of tests to distinguish between vaccinated and infected animals.
This was the only opportunity to challenge the speakers throughout a long day.
Afterwards I spoke with Dr Hutber and he demonstrated the computer model on his laptop. I pointed out that his stance on intra-farm epidemics mirrored my own criticism of the Anderson and Woolhouse computer models used in the UK epidemic, since these models were based on the flawed assumption that no intra-farm epidemic existed (they both assume that farm infectivity remains constant over time). He agreed that these models were worthless for this reason alone; they bore no relationship to reality. He also elaborated on the variance of cattle susceptibility with age, saying that young stock were far less likely to pick up infection than post-breeding animals. His computer model required the age of cattle to be entered as basic input data.
I have since written to Dr Hutber and hope to learn more of his innovative approach in due course.
Alan Beat 21st April (2002)