In 1997, Professor John Krebs, now Baron Krebs, authored a report recommending that MAFF should set up an experiment to "quantify the impact of culling badgers" and suggesting a methodology for this trial. The executive summary of that report is available on the DEFRA website.
His suggestion was accepted and led to what is variously referred to as
the 'Krebs Trial', the 'Randomised Badger Trial' (RBCT), or the
'Krebs/RBCT trial' which started in 1998.
The Randomised Badger Cull Trial was carried out
between 1998 and 2006 by DEFRA, under the guidance of an 'Independant
Scientific Group' of scientists chosen from relevant fields such as
animal behaviour. The work of the ISG was in turn supervised by an
independent statistical auditor, Professor Denis Mollison.
The RBCT tested two culling methods:
Unexpectedly, reactive culling was found to increase
the incidence of Tb by about 27%. This was considered so severe that
this phase of the trial was halted prematurely so as to minimise the
Proactive culling was found to reduce the incidence of BTB inside the area of the cull by 23.2%, but led to an increase in BTB of 24.5% in the areas around the edge of the cull area.
These negative effects were attributed to the so-called 'perturbation effect' of badgers being driven out of the cull area and carrying BTB with them, or of badgers from outside the area exploring the setts of culled badgers once they sensed the absence of badgers in that area.
Interim reports were published, and are available here, and the final report
was published in June 2007. This report is called either the 'ISG Report' or
the 'Bourne Report' after the chairman on the ISG, Professor John
Bourne. The conclusion read as follows:
10.92 Our overall conclusion is that after careful consideration of all the RBCT and other data presented in this report, including an economic assessment, that badger culling cannot meaningfully contribute to the control of cattle TB in Britain.
10.93 We further conclude from the scientific evidence available, that the rigorous application of heightened control measures directly targeting cattle will reverse the year- on-year increase in the incidence of cattle TB and halt the geographical spread of the disease.
This conclusion predictably sparked outrage from the farming and veterinary professions.
In July 2007, the month after the publication of the ISG report,
Sir David King, the UK government's Chief Scientific Advisor, submitted
his own report entitled "Bovine Tuberculosis in Cattle and Badgers."
This report was allegedly an interpretation of the RBCT data "and other
scientific evidence" to aid the understanding of the science by MPs.
His conclusion read:
51. In our view a programme for the removal of badgers could make a significant contribution to the control of cattle TB in those areas of England where there is a high and persistent incidence of TB in cattle, provided removal takes places alongside an effective programme of cattle controls.
This "interpretation" of the ISG report also predictably sparked outrage from the scientific community.
The response of the scientific community to Sir David King's report was scathing.
It should be noted that Sir David King is an expert
in Surface Chemistry, a field unrelated to the bovine TB issue, and
wrote his report based on ten hours of talks with five experts, one
of whom was "present by telephone for part of the discussion." Unlike
the ISG report, the King report was subject to
neither peer review nor an independant statistical auditor. While
submitted to the Secretary of State in July, the report was not
published until October, two days before the House of Commons'
Environment Food and Rural Affairs Select Committee met to discuss this
issue. The ISG were not not consulted, and did not even know of the
existence of this report until the day it was published.
On the 1st of November 2007, the scientific journal Nature published an editorial entitled "In for the Cull" stating that
[...] the mishandling of the issue by David King, the UK government's chief scientific adviser, is an example to governments of how not deal with such advice, once it has been solicited and received.
The Independant Statistical Auditor who had overseen the ISG's work wrote a letter to parliament in which he noted, amongst other remarks, that:
The Final Report of the Independent Scientific
Group (ISG) on the RBCT was painstaking, expert and balanced,
and I commended it to Ministers as an exemplar of how to bring
high quality science into public decision-making. The ISG's main
modelling and statistical analyses have been published in the
highest quality peer-reviewed journals, such as Nature and
the Proceedings of the National Academy of Science.
In stark contrast, the Chief Scientific Adviser's comments published yesterday, as a report Bovine TB in cattle and badgers, would not have passed my audit. It is unbalanced and inexpert.
The ISG themselves responded with a letter and a more detailed point-by-point report, and took part, along with Sir David King,
in a number of discussions with the Parliamentary Select Committee. The
reports of the Select Committee from the sessions of 2007-2008 are
One explanation given by Sir David King for the differences between his conclusions and those of the ISG was that the ISG had been asked to consider the economics and practicality of a culling solution, while he had excluded such issues from his analysis.
A number of studies, such as this one,
have looked at the areas culled during the RBCT to see how the rates of
tuberculosis varied after the trial ended. These studies have shown
that the beneficial effects of the cull persist and are even higher
than observed during the cull, while the increase in BTB in surrounding
areas dies away once the badger population has returned to a stable
level. These results have been used by pro-cull activists to claim that
the ISG's report was too pessimistic and that their conclusions should
However the new evidence has been considered by experts, such as in the recently published report of the Bovine TB Eradication Group for England, and the consensus is still that culling is not justified by the science.
In September 2009 the Farmer's Guardian, in a section devoted to the bovine TB issue, carried a very informative article entitled "TB: The science behind the decisions" based on an interview with Dr Robbie McDonald, the Head of the 'Wildlife and emerging diseases' programme of the UK's Food and Environment Reseatch Agency (FERA) and of FERA Woodchester Park Badger research facility. His conclusion was that he is "adamant culling badgers will make bTB worse and that farmers need to start backing the vaccination programme."
In the same issue another article looked at the alternatives to culling, such as vaccinating badgers and taking measures to exclude them from contact with cattle, concluding that "the work done at Woodchester Park has convinced Mr McDonald that vaccinating badgers for bTB is the right way forward."
A followup study on the aftermath of the RBCT badger culling trials in England was published in February 2010. This study concluded that the cull had yielded no long term benefit to TB rates in cattle, and that "the financial costs of conducting the culling substantially exceed the overall benefits accrued."