Memorandum submitted by the Independent
Scientific Group on Cattle TB (J11)|
1. In our memorandum of February 1999, we
explained that the Independent Scientific Group on Cattle TB (ISG),
established as part of the Government implementation of the Krebs
report on bovine tuberculosis in cattle and badgers , was encouraged
to take a holistic view in the search for a sustainable scientific
base to underpin future control policies while recognising that
the elimination of badgers from large tracts of the countryside
is not an option for future policy. We identified the need to
understand the epidemiology and pathogenesis of TB in cattle and
badgers better and the MAFF programme of research, of which the
field trial is a part, has been designed to achieve this. Implicit
in our approach is that our primary focus is, and shall remain,
on the establishment of the science base, but we accept that any
future control policy will have to take account of social and
economic factors as well as being environmentally sustainable.
2. Past control policies have included the
testing and slaughter of infected cattle (as at present) and various
levels of badger removal (in the past). The effectiveness of these
policies has been criticised to varying degrees by both farmers
3. The evidence to link badgers to bovine
TB in cattle is based, principally, on the observed incidence
of infection of M. bovis in badgers inhabiting affected
areas, coupled with the finding that some early badger removal
strategies appeared to result in a decreased incidence of cattle
TB. Krebs concluded that "the sum of evidence strongly supports
the view that, in Britain, badgers are a significant source of
infection in cattle". However, Krebs also recognised the
lack of unambiguous scientific data to support that view.
4. As is described in detail in our second
report to the Minister of Agriculture, Fisheries and Food 
the Group has developed a wide-ranging epidemiological investigation
into TB in both cattle and wildlife. Our approach has been to
identify the major questions that need to be addressed and how
answers can best be found in order to inform policy development.
Major questions relate to factors influencing the prevalence and
persistence of the disease in cattle and wildlife, risk factors
contributing to the development of the disease in cattle, transmission
routes between and within species, the use of effective diagnostic
techniques and the effectiveness and economic value of potential
5. Currently, a lack of investigative tools
for studying the epidemiology of TB in wildlife means that the
field trial is the only method by which the ISG can collect much
of the essential epidemiological information, and relate the underlying
pattern of TB infection within the badger population to the incidence
of TB in cattle. It is also the only way of quantifying the contribution
of badgers to cattle TB and of determining if culling badgers
is an effective way of controlling TB in cattle. It is essential
to find an effective and acceptable way to control cattle TB in
the long term. Failure to complete our work successfully could
leave the whole issue in limbo for a further extensive period.
6. In our previous memorandum to the Committee
and again in our second report we defined the questions that needed
to be addressed and set out our strategy for obtaining the information
necessary to answer those questions. In summary, there are six
elements to this multi-faceted investigation, ie:
(ii) a questionnaire based epidemiological
(iii) studies into cattle pathogenesis;
(iv) a road traffic accident survey;
(v) evaluation and analysis of existing data;
(vi) other related research.
Progress made on each of these elements from
the Group's perspective is summarised below.
(i) The field trial
7. After a difficult initial period when
delays occurred in the implementation of trial operations, the
Group is broadly content with the subsequent progress that has
been made with the conduct of the trial. All of the 10 triplets
which comprise the trial areas have now been selected and announced.
Five of the 10 triplet areas have now undergone initial, proactive
culling operations and by the end of the calendar year initial
proactive culling should have been carried out in a further two
triplets. This follows the projected timetable presented in our
second report. The remaining three triplets are planned to undergo
initial culling operations in 2001 and work to survey these for
badger activity has been put in hand.
8. We continue to monitor culling effectiveness
in proactive areas and we are confident that, with the exception
of one triplet, operations are achieving an acceptable badger
9. The flow of post mortem examinations
on badgers trapped and culled in trial operations was halted in
1999 when the Health and Safety Executive raised concerns over
the level of protection available to post-mortem staff against
the risk of contracting M bovis infection. Enhanced facilities
had to be installed, resulting in delays to the post mortem programme.
As a result some badgers had to be frozen and kept for later post-mortem.
The backlog of frozen badgers was cleared before culling recommenced
in May 2000.We have commissioned research to be carried out to
check that the effects of freezing badgers does not skew the data
obtained from post mortem of frozen carcasses.
10. Strategies for the most effective use
of staff for work in reactive, and follow-up culling in proactive
areas, have been re-considered and refined as necessary to ensure
that badger populations are kept low in proactive cull areas and
that the removal of specific groups in reactive areas is effective.
11. Co-operation from farmers in trial areas
remains high, typically around 80 per cent, despite a high level
of protest activity in places. Ministers and their officials are
working hard to encourage continued high levels of farmer involvement
and to ensure the general public are better informed of the reasons
for the trial, the necessity for killing badgers as part of the
trial design, and the objectivity and balance of the research
programme. This should go some way to counter negative publicity
generated by opponents who focus solely on the trial.
12. We remain aware of the need to demonstrate
our commitment to ensuring that trial operations are conducted
in a way that minimises suffering and maintains high levels of
animal welfare. Standard operating procedures are set to ensure
that captured animals remain in traps for as short a period as
possible, that badgers are killed humanely and that non-target
species are released unharmed where possible.
13. An audit of the procedures for despatching
badgers has been carried out by MAFF internal auditors and by
an independent auditor appointed by MAFF. We welcome the principal
finding of the independent auditor's report that the procedures
adopted by MAFF field staff meet the humane ideal of painlessly
causing instant death or permanent loss of consciousness until
death, and his recognition of the weight that welfare issues are
given in the planning and conduct of trial operations. Members
of the ISG closely observe field activities.
14. Apart from the audit on the humane despatch
of badgers mentioned above, the group has encouraged the setting
in place of audits eg covering aspects of field operations including
sett surveying accuracy, territory delineation and trapping efficiency.
A post hoc check is also carried out by ISG members to assess
the efficiency of badger removal in those trial areas subject
to proactive culling.
15. In addition, MAFF have just put in hand
an audit of the statistical power of the trial's design as recommended
by the Committee. The Group has submitted a report to the Independent
Auditor to assist his assessment. This is attached at Annex A.
16. Work has progressed from planning to
implementation. Procedures to ensure reliable data collection
and comparison across all trial areas have been developed. A large
amount of data is beginning to accrue and will need careful analysis
17. Key to this will be the comparison of
data from the three types of trial area, proactive, reactive and
survey only, and comparison of herd breakdowns (allowing for differences
in numbers of farms, herds and animals); badger activity and TB
prevalence and other factors.
18. The first interim analysis is due to
start in the near future, when 100 breakdowns in triplet areas
have been confirmed. This, and future data analysis work, will
be carried out by Research Assistants working under the direction
of the Group's Vice Chair, Dr Christl Donnelly, with the involvement
of Group members. Further interim analyses will be carried out
thereafter at about six-month intervals.
Additional Work in Trial Areas
19. There are a number of other studies
that are ongoing in trial areas running in parallel with the field
the ecological consequences of removing
badgers from trial areas. This study should reveal valuable data
on the impact of badgers on other species, both birds and mammals,
in an area;
genetic analysis of badgers;
estimation of badger numbers from
field signs in trial areas;
the effect of badger removal on badger
the possible role of other wildlife
on cattle TB;
strain typing of all M. bovis
isolates from trial areas, using a range of typing methods.
(ii) Questionnaire-based epidemiological survey
20. An objective and comprehensive assessment
of the factors which predispose herds to a TB breakdown and their
relative importance is essential. It is our view that this can
best be achieved by surveying a large number of cattle farms using
a structured questionnaire. In designing the questionnaire we
were guided by a number of principles:
(a) the need for objectivity;
(b) the need to be comprehensive;
(c) the need to provide data amenable to
statistical analysis; and
(d) the need for practicability.
21. The TB99 epidemiological questionnaire
has been deployed in the field for more than 18 months. It has
collected invaluable information on a range of risk factors, such
as herd composition, cattle movements, farm management practices,
and the presence of potential wildlife sources of TB infection.
The questionnaire and its implementation has been well received.
A review of its design, based on field experience, currently taking
place suggests only minor modifications. The Group was concerned
to learn that use of the TB99 form had been halted temporarily
as a result of the demands currently being made on the resources
of the State Veterinary Service by the Classical Swine Fever (CSF)
outbreak. We have strongly advised MAFF that the use of the questionnaire
in trial areas is critical and should be resumed immediately,
even if it cannot be used elsewhere in the country at the moment.
An initial analysis of TB99 data will be made after 100 breakdowns
in trial areas.
(iii) Cattle pathogenesis studies
22. The successful control of bovine TB
in most of Great Britain based on the slaughter of infected cattle
identified by regular tuberculin testing, coupled with movement
restrictions when reactors are found in a herd, has been interpreted
as evidence for the existence of a wildlife reservoir of infection
in areas where TB control using these measures has not been achieved.
This may or may not be true, but we believe that there is a need
to question, in these high risk areas, whether control of the
disease is constrained by limitations in current testing procedures
and whether cattle-to-cattle transmission is contributing to disease
transmission and persistence in herds.
23. The Group attaches a high priority to
answering these questions and to knowing more about the dynamics
of the disease in cattle and its temporal relationship to diagnosis,
transmission routes and the effectiveness of early diagnosis.
We are pleased that MAFF has funded a major pathogenesis study
involving laboratory-based investigations on experimentally-infected
animals linked to a field study of naturally TB-infected cattle.
(iv) The Road Traffic Accident Survey
24. We recommended that valuable data on
the prevalence on TB in badgers could be obtained from a road
traffic accident (RTA) survey. We proposed a survey of badgers
found dead at roadside, to be carried out in seven counties: Cornwall,
Devon, Gloucestershire, Herefordshire, Worcestershire, Shropshire
and Dorset, plus badgers found dead on farms in trial areas. We
are concerned that, while plans for the survey have been in development
for some time, the start of the survey has been further delayed.
We have urged MAFF to take steps to minimise the delay in implementing
this part of the programme.
(v) Analysis of historical TB data
25. Analysis has begun of data held by MAFF
on past TB breakdowns and badger removal operations. This should
contribute to our understanding of the dynamics of the disease
in cattle and badgers.
(vi) Other related research
26. The Group advise MAFF on the content
of its wider research programme on TB. There are major programmes
in place on improved diagnostic tests, improved tools for molecular
epidemiological studies and on TB vaccine development. The joint
MAFF/Wellcome Trust Foundation-funded project sequencing the M.
bovis genome, which is in progress at various centres of excellence
in the UK and abroad, is expected to be completed soon and should
pave the way for further advances in understanding the epidemiology
and pathogenesis of tuberculosis.
27. In our second report to the Minister
we recommended that MAFF should commission studies on the economic
impact of the disease, both at farm level and in the wider agriculture
industry, and on the economic evaluation of policy options for
the control of TB. This recommendation was implemented by MAFF
in its Research Requirements Document for 2000 and the Group is
assisting the Ministry in its assessment and selection of suitable
projects in this area from the proposals submitted.
28. The ISG and the National Farmers Union
recommended that consideration be given to the establishment of
a forum of interested parties to meet, discuss and plan what could
be done in the short term to control cattle TB by focusing on
"cattle" options. We are pleased that MAFF established
the TB Forum in December 1999 and we are happy to play an appropriate
part in it.
29. Considerable progress has been made,
notably on the field trial, on the epidemiological survey and
on the TB-related research programme, since the Committee last
reviewed the Government's strategy for the control of cattle TB.
The Group is indebted to MAFF and its agencies, in particular
staff at the Wildlife Unit and the Veterinary Laboratories Agency,
for their work in support of the Group's objectives. We are also
very appreciative of the consistent support shown by MAFF Ministers
for our work.
27 October 2000
1. Bovine Tuberculosis in Cattle and Badgers.
Report by the Independent Scientific Review Group (Chairman: Professor
J Krebs FRS). MAFF Publications, 1997.
2. An Epidemiological Investigation into
Bovine Tuberculosis. Second report of the Independent Scientific
Group on Cattle TB (Chairman: Professor F J Bourne MRCVS). MAFF