TUESDAY 16 FEBRUARY 1999

PROFESSOR JOHN BOURNE, DR CHRISTL DONNELLY AND DR ROSIE WOODROFFE

  220.  The analogy is with housing conditions particularly in humans.
  (Dr Woodroffe) Certainly the way that badgers sleep together in setts is likely to encourage transmission but they do that regardless of density.

  221.  I want to lure you, Professor Bourne, rather away from your trial itself but this Committee would really appreciate your views.  The first concerns the other causalities.  It is unlikely, is it not, that this is a single causal relationship, it must be multi-factorial?
  (Professor Bourne) Yes.

  222.  Badgers are a pre-eminent cause or a less important cause.
  (Professor Bourne) Yes.

  223.  In your report to Jack Cunningham last year talk about other wildlife species, and you suggest they should be incorporated into a trial.  What is your view on the prevalence and likelihood of causality with other wildlife species, deer, squirrels, foxes, rabbits, ferrets, cats we are told?
  (Professor Bourne) The simple answer is we do not know.  One has to look for an association and this is why we pressed in our report and also subsequently pressed to researchers applying to do this work that one should be looking at the dynamics of infection.  We do not really want an even longer list of animals in the wild which carry M.bovis, M.bovis is ubiquitous.  What we want is some understanding of the dynamics of the possible infection from wildlife either to badgers and maintaining it from the badger population or wildlife direct to cattle.  As I mentioned, these proposals are now coming in for consideration.  I think you have to be sensible about the roles they might play.  For instance, there are some individuals, some ecologists, who think the polecat could be a very important factor.  The fact that the polecat, I believe I am right in saying, is not found south of Gloucester suggests that it is not much of a problem in Cornwall and Devon.  Deer certainly could be, are we talking about farm deer or feral deer? I think it is fairly easy to get material from that species.  Feral cats have been identified as a source of TB in some outbreaks in the south west.  There may be other things like farm rats, etc, which may be present in qualitative numbers which do need to be studied and addressed.  I would expect, I think we would all expect, any wildlife study to embrace a range of wildlife species.  You had probably better respond to this.
  (Dr Woodroffe) Yes.  Our situation at the moment is that the number of other wildlife species that have been sampled is dramatically smaller than the number of badgers which have been sampled.  We have some idea of some species which we believe get TB, some that do not.  Of course, the risk that those species pose to cattle depends upon a variety of factors: how many there are, so even though you had a very low prevalence in rats, there are so many rats that they could maintain a high risk to cattle.  We need to know things like density, we need to know a lot about pathology because some species can become infected but they cannot transmit it any further so effectively they are a dead end and do not matter.  I think the other question we will be able to address in the trial is the extent to which those other wildlife are a dead end or the extent to which they are maintaining infection themselves.  What we will be able to do is by looking in the proactive areas where badgers have been effectively taken away or greatly reduced in number it is possible that the badger is the reservoir of infection that is infecting other species like deer or cats or whatever in addition, conceivably, to cattle.  In that case when badgers are taken out you ought to see the infection disappear from them as you might see it disappear from cattle.  In the course of the trial by monitoring those other wildlife as part of the contracted out research we should be able to look not only at what role those species might play in transmitting to cattle but also the role the badgers might conceivably play in maintaining infection in those other wildlife hosts.

  224.  Do you understand the concern of some badger groups that the badgers have been demonised in all this?
  (Dr Woodroffe) Sure.

  225.  That builds up a sense of resentment to all you are trying to do.
  (Dr Woodroffe) Sure.
  (Professor Bourne) Absolutely.

  226.  If I could run through—you may not want to express a view on these—three other examples of causes, of factors you might want to tell the Committee what you think about: cow to cow transmission, mineral deficiency in the diet of the cattle themselves and spreading cattle slurry in the pasture.  Do you have any views on those three issues?
  (Professor Bourne) All of these have been taken into account in the epidemiological questionnaire of course, all of them.  Certainly with cattle to cattle transmission, you cannot dismiss that, clearly it does play a part in the transmission of the disease.  Again we are not able to quantify that.  That is one of the objectives of the trial, that we can do precisely that.

  227.  Do you have a view on mineral deficiency, as a vet?
  (Professor Bourne) As a vet I have had a view on mineral deficiency since I graduated in the 1960s.  There is no doubt that minerals and their deficiency are intimately linked to cattle health.  Some with respect to production diseases, others with local deficiencies that lead to genuine health problems: copper, cobalt, etc..  Whether mineral deficiency is widespread—certainly it is not widespread in the cattle population at the moment.  Whether it has an effect at individual herd level, I do not know.  If it does I think it would be in situations where the general husbandry of the herd was poor I would suggest, but I do repeat it is one of the issues we are looking at with respect to the questionnaire that we would be doing a risk analysis on.  Personally I do not expect much to come out of it but who knows.

  228.  We have a trial that is really testing exposure rather than susceptibility?
  (Professor Bourne) Sorry?

  229.  We have a trial that is testing exposure and not susceptibility?
  (Professor Bourne) Exposure to?

  230.  To TB? Should we be doing more to test for susceptibility of cattle?
  (Professor Bourne) How do you do that?

  231.  I do not know.
  (Professor Bourne) Why would they be more susceptible to TB than some other pathogen? I come back to my statement.  There is no way to get a clear handle on this.  I think the indirect way we are adopting through the epidemiological analysis is the only way you will get anything that is sensible.

  232.  Dr Woodroffe?
  (Dr Woodroffe) Yes, I can perhaps add to what Professor Bourne has said.  This is yet another piece of interesting information which will come out of the proactive areas.  One of the very powerful things we shall be able to do by having such excellent background data on the badger population is that we will be able to compare farms with a history of TB with farms which do not have a history of TB in the same area.  Because they have all been culled and we will have all the badger data we will know if there are farms where they have badgers heaving with TB and yet they have never gone down with tuberculosis.  I think analysing that sort of situation is something which could potentially be very powerful in getting at that question about susceptibility versus exposure.

  233.  Following the Chairman's line of questioning about other factors which may be in the system which we have touched on quite a bit this morning, one of those may well be husbandry practices on the farms and changes that may make a difference.  Do you have a view about that?
  (Professor Bourne) Yes.  Again much score has been given to the potential risks associated with certain husbandry practices, as you well know.  The difficulty is that not all risks have been identified and the ones that have have not been quantitative.  You will not have seen the final questionnaire yet because we have not signed this off and we hope to do this this week.

  234.  We have been promised it by the end of the week so I hope you will sign it off.
  (Professor Bourne) That means we have to sign it off tomorrow.  You will see the focus there is on the herd, both the herd and then on the individual reactor cow.  Many of the questions are repeated.  I do not think we can really over-emphasise the importance of this risk analysis to the work we are doing.  It does focus very clearly on these risks which are mainly associated with husbandry.  Of course, badger aspects come into that risk as well, as indeed do other wildlife, but the main focus is on cattle husbandry and management systems as well as climate, local geography, etc.  So we can quantitate what these risks are and give farmers some guidance on how we can avoid or reduce these risks.  At the moment it is very much a guessing game and I have great sympathy for farmers saying: "Well, okay I will do it but is it really going to provide any benefit to me" and the answer is we do not know.

  235.  Those facts are dealt with within the questionnaire.
  (Professor Bourne) Yes.

  236.  Going back to the husbandry question, it does seem to be common throughout the questions and answers today that the badger is up there as the larger than life villain and all these other factors which people might mention, which could affect results, seem to have less emphasis—if I can put it that way—than the study upon the badger.  In other words, husbandry may be a strong factor, it may not be.
  (Professor Bourne) That is right but that is a misconception of our approach and what we are trying to do.

  237.  Husbandry is something that the farmer or MAFF in conjunction with the farmer can do something about straight away.  The badger is a longer term hit and miss programme at this stage until we know the results which come through.
  (Professor Bourne) It is true the farmer can do something straight away.  There is no evidence that what he is doing is meaningful.

  238.  At this moment the evidence is fairly scattered in all of the areas, is it not? That is the whole purpose of your experimental trial to move this forward.
  (Professor Bourne) Yes.

  239.  At the moment it is all leaps in the dark, is it not?
  (Professor Bourne) Absolutely.  MAFF, as you know, had a pamphlet available for some years identifying what are conceived to be high risk factors.  The NFBG I believe now are working on producing a similar document but the problem is we do not know what those high risk factors are, we can only guess at them.