Submission to the Temporary Committee on Foot and Mouth DiseaseR P Kitching National Centre for Foreign Animal Disease
Early February: Probable introduction of FMD virus to Index CaseThe predictions presented by Prof Roy Anderson, in my opinion, heavily influenced the decision to move policy decisions for the management of the outbreak from MAFF to the Science Committee which directly advised COBR. However the calendar of events listed above would indicate that the outbreak was being brought under control before the introduction of the policy recommended by the Science Committee, in particular the 48hr deadline for the contiguous cull. This policy initially required a cull of premises within 3 km of infected premises and was never fully implemented - later it was acknowledged that "the epidemic appeared to be decreasing more quickly in Devon than in areas where the implementation of the contiguous cull had been more effective." (Minutes of the 16th meeting of the FMD official Science Group: 2nd May)
20th Feb: First case identified
23rd Feb: Animal movement ban
21st March: Prof. Roy Anderson in interview with the BBC News night claims that the outbreak is "not under control" and that it would not peak until early May, the date set for the General Election.
27th March: Peak of new reported cases
22nd March: Latest peak for new infections (27th March minus 5 day incubation period)
26th March: First meeting of the Science Committee
27th March: Introduction of Ring Cull
The early predictive models produced were deficient in a number of input parameters, in particular:
1. The PanAsia strain causing the outbreak is not spread significantly as an aerosol. Visits by myself to Sth Korea and Japan where the same strain of virus has caused virgin outbreaks has not been characterised by aerosol spread; and the index case in the UK which had involved 500 adult pigs, infected for at least 3 weeks, had not spread extensively to neighbouring farms, even though initial predictions using aerosol production data derived from pigs infected with another FMD virus strain had indicated virus production sufficient to infect animals on the coast of Denmark. The low aerosol production from animals infected with this strain was later confirmed by experimental data from IAH Pirbright.Following implementation of the policy recommended by the models, all infected premises were required to be slaughtered within 24 hours, and contiguous premises, initially up to a radius of 3 Km from the infected premise, within 48 hours. There was no opportunity for those responsible in the affected areas to use discretion, based on local knowledge or previous experience. Diagnosis was on clinical evidence without laboratory support, and whereas this was acceptable for cattle and pigs, this clinical evidence without laboratory support, and whereas this was acceptable for cattle and pigs, this was not possible for sheep.
2. The models relied on identification of the first clinical case on a farm in order to calculate when the virus first entered the premise. Many of the infections were in sheep in which clinical disease was difficult to identify, and in many cases it was clear the virus had been present a considerable time before being recognized eg the first case in Shropshire was identified on 16th March, but had probably been introduced on 19th or 20th Feb (FMD 2001 outbreak - descriptive epidemiology, HQ Epidemiology Team, 6/4/01).
3. Although the disease was predominantly in the sheep, the models relied on data generated from outbreaks in cattle and pigs, both species in which the virus spread rapidly within the herd and in which clinical disease was easy to recognize. In sheep the disease spread only slowly, affecting only a small percentage of the flock at any one time, this further reduced the potential for aerosol spread, to a level that made it very unlikely that aerosol transmission could occur over more than a few metres. The presence of disease in sheep was many times probably not seen until it spread to cattle, or had been present some time in the sheep flock. However, because so little epidemiological investigation was taking place, this cannot be proven; on the farm that sent sheep to Newcastle through Hexham and Longtown markets, which I did visit (FMD/06), the disease had been recognized in the cattle, but I was able to bleed the sheep on the farm, and we identified a group of sero-positive sheep outside the cattle yard. It was this group of sheep that had been sent to market. No such epidemiological investigations were subsequently carried out on other infected premises, other than the one I visited and sampled in Devon the following week (FMD/07)
4. Because the models did not accommodate the delayed diagnosis of FMD, their predictions of the rate of spread to new premises was inaccurate.
5. "The modellers also agreed that the epidemic was coming under control faster than predicted by the models presented in previous weeks" (Minutes of the 13th Meeting of FMD official Science Group: 19th April).
6. When questioned how the virus was spreading in spite of the movement ban, Prof Anderson explained that this was not a function of the models, and no explanation was required.
On 1st May, I asked for a summary of results generated at Pirbright; of 1876 premises that had been slaughtered, classified as VDR, DCF and SOS, samples from 52.76% were negative on laboratory tests. This was reported to the Science Committee on 2nd May.
On numerous occasions during meetings of the Science Committee, both myself and Dr Alex Donaldson expressed concern about the validity of the policy derived from the models. This was also transmitted in a minute to Minister Spellar by Mr Richard Kornicki on 16th April, for submission to COBR.
The implementation of the rapid cull also prevented any detailed epidemiological investigations, and sometimes even the collection of any samples form and "infected premises" - a concern expresses on the 6th April by the HQ Epidemiology Team.
At no time was the diagnostic capability of IAH overloaded, although we did state that it was not necessary to submit large numbers of samples from each of the suspect farms. Because of the difficulty in making a clinical diagnosis in sheep, and because of the probability than the FMD virus had been present in a suspect flock for sometime, I queried the necessity of using the 24 hour cull policy, as there would be no disadvantage to waiting for laboratory confirmation. A blood sample from a suspect infected sheep would be either virus positive or antibody positive, sometimes both - this advice was ignored. Later the question was raised that the sensitivity of the tests being used at Pirbright was not sufficient to identify al infected animals. In my opinion, samples collected, following recommended procedures, from infected animals in an unvaccinated population , would be close to 100% sensitive.
The consequence of adopting the policy recommended by the models was:
Public perception of control programme both in the UK and abroad was severely damaged
1 Excessive slaughter of healthy animals(during the 1967/8 outbreak in the UK, there were approximately 2500 affected farms, and, 500.000 animals were slaughtered, in the 2001 outbreak, there were 2026 declared infected farms in the UK, and over 4,000,000 animals slaughtered, plus 2,500,000* slaughtered for welfare).
2 Inability to remove carcasses.
3 Necessity to transport carcases through uninfected areas
4 Loss of confidence of local Veterinarians and farmers
Conclusion.In my opinion, MAFF were bringing the 2001 FMD outbreak in the UK under control before any of the policy changes recommended by the Science Committee were implemented and that while predictive models can be a useful tool in helping to formulate an epidemic disease control policy the takeover of the programme from MAFF by the Science committee, which was heavily influenced by the modellers with very limited practical experience of FMD, resulted in the unnecessary slaughter of possibly as many as 2 million animals.
In my opinion, most of the spread of the FMD virus occurred before the imposition of the movement ban on 23rd Feb, but because this was in sheep and clinically not obvious, it was not seen. Therefore, new cases were not added to the daily total, until the virus spread into cattle, often on the same farm, or had cycled a number of times in the sheep flock. This concept was presented to the Science Committee in April as an alternative interpretation to the models being used, one that did account for the observation that apparent new introductions were occurring after the movement ban (Fig 1) My proposal was considered unlikely by the modellers.
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