TUESDAY 16 FEBRUARY 1999

PROFESSOR JOHN BOURNE, DR CHRISTL DONNELLY AND DR ROSIE WOODROFFE

  200.  Is it likely to be on the lines you have indicated in answer to my earlier question?
  (Professor Bourne) Yes.

  201.  Can I just ask exactly how you think it would impugn the integrity of your experiment scientifically?
  (Professor Bourne) Two main ways.  Where is outside of the trial? It would have to be in areas of high TB incidence which is exactly where we are working or intend to work.  It could well compromise where we place our trial areas and the randomisation process associated with it.  It would also I think fly in the face of what we are attempting to do, namely to quantitate a contribution of the badger to cattle TB.  This is an assumption that badgers do make a significant contribution and we are totally open minded about that.  There is not strong evidence for this.  This is why we are where we are, and this is why Krebs got to where he got to.  We do not have the evidence.
  (Dr Woodroffe) I think I could perhaps add to that, that the message would go out there that culling badgers was the thing to do and we would find it very difficult to defend our controls.

  202.  Is it in essence jumping to the conclusion? If one goes to that, your purpose is really—
  (Professor Bourne) Absolutely, what is the point of doing what we are doing.  It just prejudges the issue.

  203.  In an aside to an earlier question you dismissed molecular typing as poppycock, I think that was the word you used.  Professor Krebs in his evidence last week suggested that in, say, three years it might be a real runner.
  (Professor Bourne) What I dismissed as poppycock was the suggestion we could put in place now molecular epidemiology which would negate the need of doing the trial.  That is poppycock for two reasons: (a) we do not have the sophisticated molecular epidemiological data that we would like—

  204.  We have had evidence from one academic to say we do.
  (Professor Bourne)—which certainly are available for a whole range of other diseases, both animal and man.  Nor indeed do we have other epidemiological data with the badger which relates to the badger density, prevalence of TB in badgers, other aspects of TB in the badger which you would have from studying other groups, be it man or other farm animals.  We do not have that data, we do not have the techniques so that at the moment it is premature.  If you want to read premature as poppycock—

  205.  You are not prepared to make a guess as to when those techniques might become available either?
  (Professor Bourne) No.  Work is now in place to improve molecular techniques and we will be pressing CSG and MAFF next year to fund more projects on molecular epidemiology with the expectancy that these more refined techniques will become available.  We are optimistic, for instance, that the whole DNA sequence of the tubercle bacillus will be available within the next 12 months, very optimistic about that.  That will need some considerable leaps forward but even so, when we have those techniques, to use them without having further evidence on the epidemiology of TB in badgers or other wildlife is just impossible.  We do need this bulk of evidence.

  Mr George: Can I try another angle on what has been a series of questions which is very much at the nub of where we are.  As I see it, and tell me if I am wrong, the purpose of the study is to prove or disprove the hypothesis of the connection between TB in badgers and that in cattle.  I really wanted to find out to what extent the study is able to adapt if as you are going along in the process, as you progress in the study, you find information/data which, as you say, provides, to use the expression used earlier, surprising answers? For example, to throw out something which is clearly on the fringe of where we are, TB in ferrets or some other animal which also carries TB and you find there may be a stronger connection between that and bovine TB.

  Chairman: Actually, Mr George is running into a series of questions we are taking later.  A brief answer at this stage.

  Mr George: A brief answer but I think it is another point.

  Chairman: I was intending to ask it myself in my next question.

  Mr George: I beg the Chairman's pardon.

  Chairman: Perhaps you could answer it now.

  206.  What I want to know at this stage is how adaptable the study is able to be? I do not necessarily want to know about specific lines of inquiry.  Is it adaptable? Are you into a rigid set of inquiries to prove or disprove the hypothesis?
  (Professor Bourne) No, we are not and I think this is a point I have tried to make clear in the document we presented to you.  We have taken a very broad approach to address a range of scientific questions.  You have highlighted a couple of them, namely what is the quantitative significance of the badger, what is the effect of a culling policy and what will be the cost of that culling policy, there will be two culling policies.  Equally important to that is a whole range of approaches we have put in place to address risk factors with respect to cattle herds, cattle husbandry, factors which relate to the prevalence and maintenance of TB in badger populations and also what is the relevance of that to TB in wildlife populations.  Really it is a completely—what I would like to believe and sincerely believe myself—open minded approach.  It is inevitable that as you go down the track and the results come through these will be assessed, reassessed and other avenues may open up.  Molecular biology and epidemiology is one of them.  We are very optimistic about the power of that particular tool.

  207.  I think that gives the Chairman a very good entrée for a question.  In your document, your report, you suggest that it should be a Government goal to achieve a sustainable policy in the future.  What do you mean by sustainable control policy? Clearly culling badgers is not sustainable and you recognise that this provides only one component of the sustainable strategy you seek.  What other elements do you have in mind in a sustainable control policy?
  (Professor Bourne) The first one you have identified, of course, namely the wholesale elimination of badgers from areas of the UK, will not be socially tolerated.

  208.  No.
  (Professor Bourne) I think we have discussed the welfare issues of the social policy if badger culling in the future plays any part.  Badgers have to be treated with great sensitivity with respect to welfare.  Of course there is the question of economics.  At the end of the day of course it could be that the contribution of the badger is so small as not to warrant any culling.

  209.  What elements are there to a sustainable control policy? There are no other possibilities?
  (Professor Bourne) Social responsibility, cost.  The one we are really forgetting, of course, is scientific credibility.
  (Dr Woodroffe) I think perhaps Professor Bourne is identifying the criteria on which you judge a particular future multi-faceted policy but of course that policy could include a variety of measures in addition or as alternatives to badger culling including a variety of husbandry factors, vaccination.  I am sure Professor Bourne can list them for you.

  210.  It may not be possible to achieve a sustainable control policy if you take into account all those factors so it is socially acceptable therefore we have to accept that TB will run rife in certain areas?
  (Professor Bourne) I think one has to question whether you can control or eliminate and we have talked about control, not elimination.  There is a big difference.

  211.  You are accepting that at the end of this there is a likelihood that TB reactors in cattle will continue to occur at a low level you hope but at a level in the future, it will not be possible to eliminate it?
  (Professor Bourne) I think that is predictable, yes.

  212.  How will the cost benefit analysis you propose be used to inform the development of a sustainable control policy?
  (Professor Bourne) There is a number of factors that have to be taken into consideration there, of course: the cost of field work, the savings to be made by TB control both at local level and national level.

  213.  Right.
  (Professor Bourne) It would be a straight economic appraisal.  The economist on the group, Professor McInerney, constantly reminds us that a cost has to be levelled against the badger and we ask how we can do this and he says: "Well, there are ways in which economists can put a cost against anything" but I am a little less certain about that I must say.  He assures us that there are direct economic costs which can be used to identify all aspects of future control policy.

  214.  Will you regionalise that? Will you recommend spending so much in that region to control the value of the milk?
  (Professor Bourne) I think he would.  I think he would tease out economy at national level and economy at local level, yes.

  215.  At the end of the day, going back to the control policy, will you be able to produce a predictive model for the effect of having combined programming measures under a sustainable control programme? Can you predict what is likely to happen?
  (Professor Bourne) We had not at this stage contemplated modelling our findings.  Can you comment on that?
  (Dr Donnelly) In terms of the percentage reduction you might expect for different components, I would say yes but it depends on the proportion that we are able to explain.  For example, if control of badgers in a particular way leads to a 40 per cent reduction and then certain husbandry measures may add to that.  To the extent there is still a proportion of the incidence that you do not understand the underlying basis for that will add uncertainty.  You can get predictions at least in the short term which will be reliable on the basis of what will come out of these results.

  216.  The margin of error could be quite wide you are saying?
  (Dr Donnelly) Yes, depending on what comes through.  There may be things that with all the research that is being done still do not understand a proportion of the mechanisms.  As the research evolves more research will be suggested by us and by others and will be undertaken.  It will be a rolling and evolving programme.

  217.  Finally, you suggest that alternative strategies might be used to control the incidence of bovine tuberculosis in cattle such as maintaining badger populations below a certain threshold in certain areas.  Can you clarify to us what you mean by that? Would such a cull be targeted at recognised hot spots or be more general in its application?
  (Professor Bourne) There is some suggestion in the literature that maintenance of TB in badger populations is related to their density, and it is a basic tenet of disease control that if you reduce the number of susceptible hosts you reduce the level of infectivity.  As I say, there is some modelling evidence that there is a relationship between badger population, social group size and TB.

  218.  Is it a feature of overcrowding?
  (Professor Bourne) Essentially, yes.  If we find that there is a relationship between badger density, social group size and TB incidence, one way of controlling TB in the badger is to control badger density.  To enable us to do that in the future we need a non invasive technique for measuring badger density and social group size.  Also we need methods of measuring TB's prevalence in badgers.  We have neither at the moment.  We hope through the trial we will develop first a technique for field observation and we hope that laboratory research would also present us ultimately with a live test.  I am doubtful about that and the group is doubtful, which is why we have suggested that the road traffic accident survey is put in place, initially on a limited scale so we can validate a method of estimating TB prevalence in badger populations, initially at a wide level and then ultimately, as we get more data, at the more local level.
  (Dr Woodroffe) Could I perhaps add a little to what Professor Bourne has said.  I must stress that at present the postulated relationship between badger density and TB prevalence in badgers is a modelling result, there is no field data to show that is the case currently.  That is one point and something which will be addressed not only by the trial but also by related research contracted out to independent research.  For the moment, although we can talk about lowering badgering density below a certain threshold, we do not know what that threshold would be.  It might be a small reduction, it might have to be a very large reduction.  There are predictions, again primarily based on modelling rather than field data, which suggest that suppressing badger density leads to increased movement of the population which could exacerbate the problem of TB spread.  We do not know whether that is true, again it is something we will be able to look at in the course of the trial by looking at where proactive culling has occurred over areas where there have been historic culls under previous strategies.  The threshold at which you might conceivably have to maintain badgers below—bad grammar—is something we would be able to at least look at in the course of the trial.  I would also add to Mr Mitchell, I am not sure that it is very helpful to talk about overcrowding.  Badgers are top predators, they do not have predators.  There is not something else which would control their numbers.  Their numbers are determined by—

  219.  The motor vehicle.
  (Dr Woodroffe) Exactly.  The numbers are determined primarily by the availability of food and the weather.  They do not get overcrowded, they get to high density but they like it that way.