I heard most of this item and it was clear that Prof King's
scientific credibility was left in tatters.
One statement he made (more than once, and forcefully)
blatantly ignored the most basic scientific principles.
If you remember, back in March MAFF engaged three lots of
consultants to model the epidemic. They
each produced predictions from three scenarios:
- continue as up to then
- cull infected farms inside 24 hours
- do this as well as contiguous cull within 48 hours.
We were told then that the models showed that only the last
scenario would work. As we know, since
then the third scenario has been followed with puritanical zeal - and the
course of the disease has indeed followed the curve predicted.
King was challenged this morning on whether the contiguous
cull was necessary. He said that the
fact that the epidemic had followed the predicted course was proof that the
contiguous cull was indeed necessary. However, this is NOT what
the data shows - nor could it possibly show that.
Essentially the question he was being asked was: was
contiguous culling necessary, or would culling of infected farms within 24
hours have worked on its own? If the
data is to distinguish between these situations, they must each have been tried
separately. However, they were both
done at the same time! Therefore the
most you can say is that it APPEARS that doing both together worked (you can
never, of course, be certain that the "successful" curve was not
produced by weather, luck, the movement ban or something else altogether). Anyone with any scientific integrity at all
(even one as out of date as me) would never make the statement he made on the
evidence available. (The national
curriculum as covered by my ten-year-old daughter includes the concept of the
"fair test". This was not
one!)
There are two more fundamental flaws in the case King was
trying to make.
One
is that the "three scenarios" did not include vaccination. There is no scientific justification I can
think of for this. I believe the
consultant experts were unprofessional in not insisting that all realistic
scenarios were included. I suspect that
the curve from a vaccination scenario just showed too vertical a drop to be
allowed to appear on the same graph!
The second flaw is, as I understand it, that the three sets of
consultants were using versions of the same model. This is very poor practice. Models of this kind are often very sensitive to which
mathematical basis they use, and the weight given to the many different data
items (in fact the criticism in the instance above was exactly such a one -
that the models gave undue weight to the efficiency of airborne
infection). This is why it is good
practice to use several independent teams (which was done), to make sure that
they are using independent models (which does not seem to have been done), and
to make sure that the models are run with a wide range of values (which as far
as I can see was not done).
It seems to me that the models were not properly tested to
see whether they were unduly sensitive to inaccurate estimates of data such as
the efficiencies of the various viral transmission methods. I should be delighted to be proved wrong.
Personally (speaking as a mere ecologist, and admittedly
without the benefit of much data) I am very doubtful that air-borne transmission is a
significant factor compared with mechanical dispersal (vehicles etc) and
animal-to-animal contact. It is
noticeable that after the first 20 days almost no single case occurred more
than a mile or two from another (see Andrew Heggie's animated map on
www.hjones-sons.co.uk/fmdani.htm).
It's curious that the contiguous cull is justified by
exactly the same arguments which are ignored when it comes to deciding whether
GM maize (a wind-pollinated plant) can contaminate other maize crops!
You can find the "three scenarios" graphs on:
www.maff.gov.uk/animalh/diseases/fmd/news/king.asp (linked to
www.maff.gov.uk/animalh/diseases/fmd/news/king.pdf) This is from the Imperial
College report - I remember at least one of the other versions being on the
MAFF site at one time, but can't now find it.