Examination of Witnesses (Questions 100
- 107)
MONDAY 18 JUNE 2007
PROFESSOR JOHN
BOURNE CBE, PROFESSOR
CHRISTL DONNELLY,
PROFESSOR JOHN
MCINERNEY
OBE AND PROFESSOR
ROSIE WOODROFFE
Q100 Mr Drew: I am interested because
it is my area that has a trial under way. As you will know, where
we have run into arguments both with yourself and Defra is that
we always call for plan B. We never specified what plan B was
going to be. I am pretty sure I know what plan B is going to be.
It is going to be vaccination. The problem is we are always ten
years away and we are always debating: should it be cattle or
badgers that are vaccinated. If I was to have more than a hunch—I
have spent my life arguing this—we have to get that vaccine
in place. Everybody, including the Irish, would agree that vaccination
long term is the only sustainable policy. Why do we not try much
harder to get a vaccine? My argument would be a vaccine to be
used in badgers rather than cattle because of the problems with
vaccination of cattle and TB free status and so on. Why do we
not just go for that and move it forward more quickly? Forget
the rest of this because to cull or not to cull is not any longer
a question. Let us go for vaccination and try and persuade Defra
to put some serious resources into this and hope that it does
pay dividends. It did with human beings, after all.
Professor Bourne: It has not yet.
Defra are doing exactly that. We carried out a review of vaccination,
as you know, which we published in 2003 with the expectancy that
that work would continue over a long time frame before it led
to any extension into the field. We produced a full report with
the expectancy that another group other than us would pick it
up and take it forward way beyond the life of the ISG. That has
happened. Defra have a group in place to extend this work. We
have only briefly commented on vaccination in our report to emphasise
the main findings of the document that we published in 2003 and
to emphasise the problems of getting a badger vaccine into the
field and particularly in collating data and evidence that the
vaccine was achieving what we hoped it would achieve in respect
to reducing cattle breakdowns. It is a very long haul. I think
it is unfair to suggest that not enough scientific effort is being
directed into this area. Internationally, there is a massive global
programme. The scientists at VLA of a very high calibre are closely
linked into that programme as indeed are the guys who are sitting
on that Vaccine Committee at the moment. Success demands a number
of things. With respect to developing a badger vaccine, it does
require developing a way of getting this to badgers in the field.
We know there are serious limitations for BCG but no one suggests
it does not have a role. Measuring the contribution it makes is
difficult. With respect to getting improved vaccines, you are
waiting for scientific breakthroughs and you cannot predict those.
Even when one has a cattle vaccine, there has to be a clear strategy
for how you are going to use that in cattle. I am not persuaded
that Defra have given this any thought at all. They have not given
it any thought at all yet.
Q101 Mr Williams: The Chairman and
I met with the president of the Royal College of Veterinary Surgeons
the other day and we asked her about this and whether there was
a technical problem in getting a breakthrough. The Chairman will
correct me if I am wrong but the response was that the real problem
is the cost between taking it from the laboratory to getting it
to market and all the regulatory processes that have to take place
then. We asked her, "What do you think the cost would be?"
She said, "Perhaps £20 million." If you look at
that in relation to what it is costing this country in terms of
TB at the moment, it would seem to me that that would be a very
little contribution to solving a big problem.
Professor Bourne: I am sure she
is right about the market. It would be extremely limited because
no other European country—
Q102 Mr Williams: The process of
taking it from—
Professor Bourne: In fairness,
you really should talk to the committee that is now in place driving
the vaccine programme. I would certainly give that our total support,
as we have. I would also highlight that again there is no quick
fix here. It is going to be a long haul.
Q103 Chairman: One of the points
that the president did make to us was that the requirements of
the vaccine as defined by Defra in their judgment—I hope
they do not mind us quoting around lunch table conversation, because
the information may not have been given with the rigour that would
have been the case had they been giving evidence to us—and
the impression I gained was that what this vaccine was supposed
to be doing, if you like, the performance criteria, had been set
at such a high level that going back to using BCG, for example,
would not score. In other words, it was not good enough to achieve
the kinds of results that they would say were effective. The vets
were saying, "It is better than anything and it has worked
in human beings."
Professor Bourne: I do not think
that is true. That is not the approach that Defra are taking.
My understanding is that they are developing the possibility of
a BCG vaccine to use in badgers. The situation in cattle is very
different.
Q104 Chairman: It is currently costing
Defra £90 million a year to deal with the consequences of
this disease against a current background where all the ways to
mitigate it do not seem to be having any serious effect. You might
say, "If the Government wanted in the long term to save themselves
a shed load of cash, they would bung a great deal more money at
it to try and crack it now."
Professor Bourne: I do not think
that is the answer. You should speak to the group driving this
programme. From my perspective, I am quite assured of the competence
of the scientists and the group. Throwing more money at the problem
is not going to provide the answer. They are effectively linked
into an international network that is massively funded. You just
have to wait for science to deliver. Defra meanwhile, from my
knowledge, are pursuing the option of using a BCG vaccine in badgers
and developing appropriate delivery systems. At the moment they
are looking at aspects of safety control for purposes of registration.
I do urge you to speak to the group that has now taken on responsibility
for this work.
Professor Woodroffe: To add a
note of caution on vaccination, it would be marvellous if you
could vaccinate badgers effectively. In New Zealand, they have
something called a possum puffer, used for remotely delivering
the vaccine to possums. One issue you have to confront is that,
if you are putting vaccine out in the environment for badgers
to consume, there is a strong risk of cattle encountering it and
therefore becoming sensitive to the test. It is not all roses.
Mr Williams: Professor Bourne this morning
said that with improved testing there could be a reduction in
TB incidence without badger culling. What is the scientific evidence
for that? Is that an extrapolation or does that have real substance?
Chairman: Mr Rogerson wanted to add to
that with a point about the gamma interferon testing.
Q105 Dan Rogerson: There is quite
a lot in here about what could be done to speed things up to be
far more accurate by a combination of testing.
Professor Bourne: It is based
upon cattle pathogenesis findings which are documented in the
report in one of the appendices, work that is being carried out
primarily in laboratories of VLA in Weybridge, Stormont and IAH.
It is also extrapolation, taking information from a simple model
that Sir David Cox has developed and using that model to predict
how the application of these techniques would influence the curve
with respect to the reproduction rate of the disease. He determined
a reproduction rate of 1.1. That relates to between herd transfer,
not within herd amplification of the disease. That figure has
also been arrived at by an independent approach, developed by
the workers at the University of Warwick, which does suggest that
an effort to improve diagnosis would tip the balance and bring
the reproduction rate below one and bring a downward trend to
the incidence of the cattle disease. He also postulates from the
model that improving diagnostic sensitivity would have a speedier
effect on reducing the incidence of disease. As one is talking
about herd to herd transmission, animal movement controls as well
as diagnosis are important components of that.
Professor Donnelly: In terms of
the way the model works, essentially what you are looking at is
trying to shorten the time between a herd becoming infected and
it being cleared. Improving test sensitivity is one way of doing
that so you are sure you are not missing anything. You can talk
about it as a herd test but if there is only one animal in a herd
that is infected it is the per animal accuracy that matters. Either
improving the sensitivity—that is, the proportion of infected
animals that are correctly detected—or testing more frequently,
so shortening test intervals. Those two things, especially if
they are combined together, reduce the time that a herd spends
potentially infectious to other herds and in circulation. Obviously
since that work was done pre-movement testing has been brought
in and we have discussed the possibility of doing that with more
sensitive tests and even the possibility of adding in post-movement
testing, which would add another level of security. From that
modelling work, it showed 1.1 as the figure that characterises
the rate of increase of the disease. Estimating the reproduction
number has been used in many other human and animal diseases but
it allows you to say that one is the threshold of where you just
have continuing disease at a level. If you could do things so
that the model predicts it goes below one, that suggests not that
you would get instant eradication but that you would start on
a decline. Both faster testing and improved testing through greater
sensitivity are predicted to do that.
Q106 Mr Cox: Perhaps somebody could
deal with the question of the edge effect and the 25% incidence
outside the culling areas. There was a question by a number of
epidemiologists that the findings of that 25% did not seem to
have sufficient of a time lag in order to produce the effects
that were observed. I am sure that is easily dealt with by you
because you will have heard it before and therefore you will have
devised some thinking.
Professor Woodroffe: We know that
to cause that effect badgers have to start ranging more widely,
contacting one another more often and contacting cattle more often.
That happens within the course of a few days in response to culling.
What has to happen next is that cattle have to be tested. They
have to become exposed and develop sensitivity to the test. That
takes about three weeks. We have published the sequence of events
and it has gone through peer review.
Q107 Mr Cox: You would argue that
the period is relatively short?
Professor Woodroffe: Yes.
Professor Bourne: Our remit throughout
our study has not been badger protection. It has been control
of cattle TB. That has been our driving force throughout the work
we have done. How can one best control cattle TB? Our whole report
is directed to cattle TB control.
Chairman: Can I thank you very much indeed
for your final appearance before us as the Independent Scientific
Group? As individuals and experts it may not be your final appearance
before the Committee. Thank you very much indeed, as always, for
your contribution and your patience in dealing with our questions.
We appreciate it very much.
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