TUESDAY 16 FEBRUARY 1999

PROFESSOR JOHN BOURNE, DR CHRISTL DONNELLY AND DR ROSIE WOODROFFE

  132.  Professor Bourne, welcome to this session of the Agriculture Committee.  We are grateful to you and your very distinguished colleagues for coming to see us this morning.  May I begin by asking you to put on the record your name and those of your colleagues.
  (Professor Bourne) I am Chairman of the Independent Scientific Group, advising Ministers with respect to cattle and bovine TB, as you know.  I have held professorships, on various aspects, in veterinary medicine for a number of years.  My career has been devoted to practical issues of animal disease control.  On my right is Dr Rosie Woodroffe, who is an ecologist.  She has worked on the ecology of badgers.  She has recently moved from the University of Cambridge to the University of Warwick.  Dr Christl Donnelly is a statistician of the University of Oxford.  You will probably know of her work because of her involvement with Professor Roy Anderson on BSE, doing statistical analysis in that area.  It is a baptism of fire, I think, for Dr Donnelly.

  133.  We have three of the six members of your team with us today, is that correct?

  (Professor Bourne) Correct.

  134.  Thank you for that.  I think you will understand that we are going to focus very much on the design and the implementation of the culling experiment today, by Professor Krebs, whom we saw last week; although there may be other issues we will wish to come to as well in the questions, of sustainable policy for bovine tuberculosis and its control.  We may have misinterpreted you, or perhaps not.  In your reply you seem to imply that there is a kind of trade-off between retaining the scientific rigour of Krebs' approach, and establishing cost-effective and practical methodology which could be implemented on the ground.  Is that a fair reading of your assessment?
  (Professor Bourne) I think it is an over-statement.  Clearly we accept that doing a field trial is quite different to carrying out a controlled experiment where the edges are not blurred.  We have imposed some additional blurrings ourselves, by restricting ourselves to cage trapping, rather than the suggestion that we used other methods of trapping, which could conceivably increase the efficiency of trapping above the 80 per cent one would expect with cages.  But we accept that it is a field experiment; it has been designed as such; and the power of the experiment takes that into account.

  135.  May I ask particularly about the question of trapping.  That has been quite a controversial issue, and the use of snares.  The original intention was to use snares but that is now not happening.  I do not know what a leg cuff looks like, I have to be honest.  Can you make a distinction between snares and leg cuffs?
  (Professor Bourne) The original intention was to use snares.  We were asked to consider that, which we did, and rejected it on the grounds primarily of public perception and the influence it could have on the integrity of the trial.

  136.  Was any political pressure put to bear on you at that specific point, or was that a decision which you reached freely as experts?
  (Professor Bourne) It is a decision which we reached freely as experts.  As you know, the Krebs' report was exposed to wide consultation.  We took that on board.  We also carried out our own consultation.  It was on the basis of that, that we reached the decision we did.  With respect to leg cuffs: of course, that is nothing to do with the trial.  We suggested work might be done to investigate the possibility of their use at some future date but that is not part of the trial.  Although I understand that work is going on, I am not familiar with progress in that area.

  137.  So you are satisfied that the experiment is not compromised by the decision not to use snares?
  (Professor Bourne) That is correct.

  138.  Can you tell us why you went for circles rather than squares.
  (Professor Bourne) This is a pragmatic thing in the sense that it does reduce boundary effects.  Also, within the circle we were able to retain strict criteria that perhaps the squares did not offer.  I think it is important to state that when Krebs proposed schemes, he did so with a view that he was not going to be dogmatic about that.  He did say that there would be some variation on this, some further thinking on this, as the field trial was put in place.  Dr Donnelly, would you like to comment on this from a statistical point of view.
  (Dr Donnelly) The squares that were used in the Krebs report were merely for illustration: to say, for example, if you took these areas.  It was always envisioned that at a later date further thought would be given to the design of the trial.  By using circles rather than squares it also eliminates the issue of: if a square was turned 45 degrees, you would then be excluding some areas, and including some areas you had not included before.  It also meant that if you used a square, as opposed to a circle, then some areas were being included that were further away from other areas which had been excluded, but realising that the circles then are guideline.  When that is actually put into place on the ground, it is no longer a circle because of farm boundaries; and also trying to use natural boundaries that badgers would not freely cross.

  139.  Fine.  Another issue is the closed period for lactating sows, which has been a subject of comment, both by those who welcome it, those who think it is not adequate to cover the period, and those who think it might compromise the integrity of the trial and that there should not be a closed period at all.  Perhaps you could tell us your thinking on that.
  (Professor Bourne) If I could introduce that topic and then Dr Woodroffe can pick it up.  You appreciate that we were aware from the outset that we had to work towards scientifically underpinning the future policy for cattle TB disease control, which was sustainable, and which would take account of welfare as well as other interests.  In doing so we considered the cage trapping issue and the snaring issue which we have already discussed.  The other issue, which we were made aware of through the wide consultation process that had been put in place, was concern about cubs dying underground.  Now the evidence we had for the timing of birth of cubs was and is very incomplete.  The most compelling evidence was the timing of nidation, that is, the time at which gestation starts in a badger to gestation being fixed.  That evidence suggested to us that the majority of births would occur during the latter part of January to early February.  We were able to adjust the culling period, so that we had a no-cull period in the months of February, March and April, to avoid, what we believed, were the majority of cubs which were likely to die underground.  That was indeed a compromise but we nonetheless believe that in making that compromise between badger deaths, and also the practicalities and the logistics of carrying out field activity, we were able to reduce the proportion of cub deaths.
  (Dr Woodroffe) Perhaps I would add a couple of other things.  What has happened in the past has been that badger lactating females have been released, which has also been criticised as it compromised culling of past badger removals, so we did not consider that an option and we thought that the closed season was a good way of getting round the problem.  As Professor Bourne says, our designation of that three-month period was based upon the best available data from known or projected birth dates of badgers, which we considered to avoid, wherever possible, the leaving of cubs to starve underground.  I should add, of course, that this is a welfare issue, not an objection to killing cubs.  The idea is that cubs would still be killed but it would be with cage traps when they were old enough to go into cage traps, come 1 May.