We understand that the Select Committee will be questioning Professor David King and Professor Roy Anderson today (Wednesday) and request that you give your urgent consideration to these key points:
1) The raw data provided by DEFRA is totally inadequate to provide a sound basis for predictive modelling. Of the 2030 'confirmed cases', many were not tested either for antibodies or live virus, but were slaughtered on clinical signs only. Very few of the contiguous culls, 3km culls or "slaughter on suspicion cases" were actually subject to laboratory testing. The recognised authority on FMD, Dr Paul Kitching, formerly of the Animal Health Institute at Pirbright, has repeatedly said that clinical diagnosis in sheep is impossible and, without laboratory testing, is totally unacceptable. So:
- How many of the infected premises were confirmed by laboratory test?
- How many of the contiguous premises were confirmed by laboratory test?
- How many of the dangerous contact premises were confirmed by laboratory test?
- How many of the slaughter on suspicion premises were confirmed by laboratory test?
- Are the data supplied by DEFRA adequate in scientific terms for accurate predictive work to be undertaken?
2) Professor Anderson's latest published report (Nature, 4th October) states "The median distance of the newly estimated kernel (for disease transmission) is about 4 km, suggesting that most transmission probably occurred through the movement of animals, personnel or vehicles, rather than through animal contact or windborne spread." Note that this completely contradicts previous assumptions of neighbouring farms being most at risk and this admission, that the original data were completely wrong, has entirely destroyed the rationale for contiguous culling. Contiguous premises are now found to be no more at risk than any others within the locality of an infected premises; indeed the average transmission distance of 4 km argues powerfully against slaughter of contiguous premises since this cannot influence disease spread over such long distances, except by the very negative effect of swallowing up valuable resources of time and manpower for no benefit. So:
- What is the average distance between infected premises?
- What evidence exists in the field data to justify the culling of contiguous farms over any others within the 4 km kernel?
3) Again from Anderson's latest report "Farm susceptibility and infectiousness both varied significantly, with smaller farms being substantially less infectious and less susceptible than larger ones. Stratifying farms by the most prevalent species revealed a trend for cattle farms to be more susceptible, and pig farms to be least susceptible." Work by another modelling team (Keeling, Woolhouse et al, Science 4th October) has shown that sheep are fifteen times less susceptible (ie less likely to catch the disease) than cattle. Given these huge differences:
- Does the computer model take any account of the fifteen-fold difference in susceptibility between sheep and cattle?
- Does the computer model take any account of the scale effect, whereby small farms are significantly less likely to catch disease, and to spread it beyond their boundaries, than large farms?
- If the computer model does not take account of the above effects, how do you justify a blanket policy of contiguous culling when the risk of infection to individual farms varies enormously?
4) Anderson's team use the ratio, r, to denote farm infectivity, a measure of the within-farm spread of disease. In Science, 11th May, they state "If r is greater than one, ring culling still accelerates the decline of the epidemic but at the cost of a larger cull than rapid index case slaughter alone". Clearly, a contiguous cull cannot be justified if the net result is a higher slaughter total overall. So, they simply assumed that r wasn't greater than one. They state "We assumed constant infectiousness from 3 days after infection until slaughter, for an average of eight infectious days." This is a gross misrepresentation of within-farm spread, which will mirror the wider epidemic on a miniature scale to give values of r greater than one until all its stock have become infected over time. So:
- What evidence is there to support your assumption that farm infectivity remains constant?
- If your farm infectivity ratio, r, is greater than one, will the contiguous cull result in a higher overall slaughter total than is necessary?
- If your farm infectivity ratio, r, is greater than one, will not the prompt culling of infected premises alone result in the most effective control of disease spread, with fewer animals slaughtered overall?
5) Anderson's October report states "In no week of this epidemic have more than half of contiguous premises been culled within the specified target of 48 hours from report of a new case." In other words, the gruesome experiment has been so incomplete that no conclusions may reasonably be drawn from it. So:
- What evidence is there that the targets of 24 hour cull on infected premises plus 48 hour cull on contiguous premises have ever been achieved in practise?
- Has the 24/48 hour target been achieved over a sufficient period of the epidemic to enable reliable conclusions to be drawn on the efficacy of the policy?
- If these targets have never been achieved, then what other evidence do you have that the culling policy has been effective?
6) A consensus of expert veterinary advice is that contiguous farms should be subject to a rapid site assessment, taking due account of geography, wind direction, separation of stock at boundaries etc. Those farms at genuine risk could then be closely monitored for disease, slaughtering if justifying evidence is found. This is cheaper, faster and more effective at controlling spread of disease by focussing resources where they are most needed. Among many others, the internationally recognised authorities on FMD, Alex Donaldson and Paul Kitching, recommend this approach. So:
- What evidence is there to suggest that isolation, monitoring and laboratory testing of stock on contiguous farms would be any less effective than a blanket contiguous culling policy?
- What is the relative efficiency, in terms of both cost and resources, of blanket contiguous culling compared to veterinary assessment with targeted culling only as above?
7) Finally, and crucially, we dispute the oft-repeated claim that the introduction of the 24/48 hour culling policy brought the epidemic under control. In fact, the peak had already passed, and a marked decline in case numbers noted, before the new policy could possibly have made any impact. The key dates are:
23rd March Contiguous culling introduced
26th March Epidemic peaks with 54 cases in one day
29th March 24/48 hour culling policy introduced
9th April First impact of 24/48 hour culling
At the 23rd March, the delay from report to slaughter on infected premises was up to 7 days, and averaged 3 days. On contiguous premises the delays were longer, since infected premises were given priority for resources. Symptoms of the disease do not appear for an average of 9 days following exposure to infection (Science 4th October). Hence the impact of contiguous culling could not have even begun to take effect on reported new cases of infection until 11 days following the 29th March (48 hours plus 9 days incubation). On that date, 9th April, the daily case numbers had already declined to an average of 32 per day and Professor David King was expressing "cautious optimism" that the new measures were starting to "turn things round" (Veterinary Record, 14th April). So:
- Following the introduction of the new 24/48 hour culling policies, what period of time do you estimate needed to pass before the measures began to make any impact on the daily case numbers?
- Will you explain to the Committee how that time delay is calculated?
- So on what date could it be said that the new culling policy was starting to have an effect?
- How do you explain the already well-established decline in daily case numbers from the peak of 54 on 26th March to the date on which the 24/48 hour cull policy began to take effect on those numbers?
- What evidence do you have that the 24/48 hour culling policy had any impact at all on the progress of the epidemic after the date upon which it finally became effective?
- What evidence is there that 24 hour culling on infected premises alone would not have achieved the same effect as including the 48 cull on contiguous premises?