Memorandum submitted by British Veterinary
Association (BVA) (BTB 31)
INTRODUCTION
1. The British Veterinary Association (BVA)
is the national representative body for the veterinary profession
in the United Kingdom and represents over 10,000 members. Our
chief interest is to protect and promote the interests of the
veterinary profession in this country and we therefore take a
keen interest in all issues affecting the veterinary profession,
be they animal health, animal welfare, public health or employment
concerns.
2. The BVA welcomes the opportunity to submit
evidence to the EFRACom inquiry into bovine TB: badger
culling, and to examine the Government's proposals for introducing
badger culling as a control measures for bovine tuberculosis,
as set out in the consultation paper issued on 15 December 2005.
BVA has tried to focus on the key questions that Ministers must
address in reaching conclusions on the issues set out in the consultation
paper, and would be willing to provide further information if
requested to do so. However we would like to stress that the consultation
period is still open and therefore the contents of this submission
should be considered as preliminary, and additional comments may
follow.
3. Although much has been learnt about this
complex disease in the last decade a great deal remains to be
discovered. Even known facts are often fiercely disputed by special
interest groups. The need for continuing research, however, is
no excuse for doing nothing to bring a worsening disease situation
under control. We should therefore devise the most effective control
strategy possible using the information currently available. Scientific
research has established that cattle and badgers can be affected
with tuberculosis and that both are reservoirs of infection,
excreting and transmitting the bacteria to susceptible animals.
4. The high incidence areas of bTB
in the UK are well known and many badgers in these areas are infected.
It is scientifically implausible to argue that epidemics of bovine
TB in cattle and badgers in the same area exist independently
and are unconnected, or that either can be effectively controlled
without addressing both. It is now agreed amongst the scientific
community that badgers do play a role in the spread of bTB
in cattle, which is supported by the initial results of the Randomised
Badger Culling Trial (RBCT). The next step is to decide how to
deal with this disease reservoir in the most humane and effective
manner.
5. BVA has objectively assessed the current
control options outlined in the Defra consultation paper from
a veterinary perspective, and our recommendations for action are
outlined below. The response below has been structured in the
same manner as the Defra consultation for ease of reference. A
full submission to Defra will be made before 10 March 2006.
EXECUTIVE SUMMARY
We need to tackle the increasing incidence of
bTB in the UK with the herd incidence of bTB increasing
by 18% a year. The general public supports the need to control
this infectious disease in cattle (92% agreed in a recent survey1).
This disease is prevalent in the UK in two major animal reservoirs—cattle
and badgers. BVA strongly believes that in order to control this
disease, control measures in cattle and badgers are necessary.
We need to improve the current controls in cattle by tightening
controls on cattle movements (which are known to be a significant
factor in the spread of disease from farm to farm), and by introducing
more biosecurity measures on farm with incentives for farmers
to reduce contacts between badgers and cattle. (Please visit the
BVA website for the Association's full policy on bTB control,
which includes detailed recommendations to improve cattle controls
and biosecurity measures, as well as badger controls). We need
to start tackling this disease in badgers now using the scientific
information we have available, and sound veterinary epidemiological
principles where the science is lacking. We need to be realistic
about the options open to us for controlling this disease in badgers:
(a) Vaccination is not currently an option
and won't be in the near future (the next 10 years). However it
is the preferred option should it become available.
(b) Biosecurity is important but will not
work in the absence of any other control.
(c) Culling: scientific evidence has shown
that culling can have a positive effect on reducing the number
of herd breakdowns within a control area, but can have a negative
effect outside of the control area. This suggests that large area
culls would be necessary in order for the positive effects to
outweigh the negative.
In high incidence areas, the BVA believes that,
from a disease control perspective, a large-scale Government co-ordinated
cull of badgers where there is evidence of infection in the species
may well now be necessary to help control this disease. This will
only work if there is significant buy-in from the landowners involved.
Landowners must be provided with adequate scientific data to allow
them to make an informed decision in relation to the culling of
badgers. In the current situation, culling in specific areas linked
to herd incidence using snares and shooting appears to be Government's
most viable short-term option for control in terms of welfare,
cost, and feasibility (with the use of geographical boundaries
where possible). This should be considered for areas where cattle
controls alone are not working. This should be carried out, or
co-ordinated by suitably trained personnel. However it is acknowledged
that this method still has significant practical and welfare issues
which need to be addressed. Gassing using CO has the potential
to be the most efficient, cost-effective, and humane method of
badger control. We recognise that issues surrounding diffusion
into blind tunnels within a sett need to be resolved, but the
technique should be considered as a matter of urgency. The most
important point to remember when assessing the options available
is that we still don't have all the answers. We need, in parallel
with a new policy, to carry out the research, surveillance, and
recording of any culling activity—to enable an assessment
of the effectiveness of the methods to be evaluated properly.
Although recent scientific evidence has brought many issues to
light, there are still many issues that remain unresolved.
RESPONSE TO
THE SPECIFIC
CONSULTATION QUESTIONS
Question 1. In light of the evidence presented
as part of this consultation, on balance, do you think a policy
to cull badgers should be part of the approach to help control
the disease in cattle in high incidence areas?
6. Yes. Control measures in cattle must
be accompanied by simultaneous and appropriate measures in wildlife.
BVA supports a targeted humane culling policy aimed at eradicating
bTB where sufficient evidence exists to classify a badger
population as infected. Although significant new scientific results
and postulates have come to light from the initial results of
the RBCT, which makes a policy decision on whether to cull more
difficult to make, it does not change the fact that we still need
to tackle this disease in the UK. It is in the interests of public
and animal health that the spread of bTB from infected
badgers be contained. The current controls which attempt to control
the disease in cattle only, are not working and are not sufficient.
7. It is recommended that a long-term strategy
for control should include both culling and vaccination, when
the latter becomes available, which is expected to take about
10 years. It is conceivable that vaccination of badgers may eventually
supersede the need for badger culling, but that remains no more
than a possibility at present. In a situation where the control
of an animal-based disease is critical, yet absolute science is
absent, the application of first principles of disease control
by the veterinary profession is essential ie wherever the disease
is identified it should be removed to reduce the possibility of
further infection. The eradication of Rinderpest at the turn of
the 1900s and of rabies in 1903, and the identification and implementation
of control measures for BSE in the 1990s were both undertaken
with success by the application of such principles without a pre-emptive
diagnostic test and without a clear understanding of the pathogenesis
and epidemiology of the disease.
8. There is sufficient scientific evidence
to conclude that the presence of M. bovis in the badger
population is presenting a wildlife reservoir of infection that
inevitably increases the risk of cross infection to other susceptible
species, particularly cattle2, 3, 4, 5, which is supported by
the initial results of the RBCT6. Results from the RBCT showed
badger infection levels to be as high as 40%. In order to reduce
the incidence of bTB in cattle we need to increase cattle
controls, particularly to reduce the risk of transmission posed
by cattle movements from one herd to another, which are known
to be a significant factor in the spread of disease7. But we also
need to decrease the number of infected badgers in areas where
cattle are kept, or decrease the time that infected badgers are
infectious, or find ways to separate cattle form badgers and their
excretions—in order to deal with both reservoirs of infection.
The Wilsmore review commissioned to inform Defra on the evidence
relating to culling badger, concluded that international evidence
clearly shows that bovine tuberculosis in cattle
cannot be eradicated by cattle controls alone when there is a
secondary reservoir of infection from wildlife8.
9. There has been a number of trials undertaken
that suggest positive benefits from the removal of badgers in
infected areas on the incidence of bTB in cattle including
the Thornbury Trial, the Steeple Leeze Trial, the Hartland Trial,
the Offaly Trial and the Irish Four Areas Trial4,5,9, 10. Critics
damn much of this work as being scientifically unsound by virtue
of deviations from standard scientific protocol. The reality is
that scientific study inevitably leads to the generation of further
questions and further scientific study rather than the provision
of absolute answers. The RBCT6, although conducted in a scientifically
correct manner, was set up to answer specific policy questions
and therefore also contained a number of variables within the
data which make interpretation of the results more difficult.
RESULTS FOR
THE RBCT
10. Initial data from the RBCT shows that
badgerculling can reduce the incidence of bTB in cattle6.
It also shows that it can increase the incidence of bTB
in cattle in neighbouring control areas. The latter effect has
been attributed to social perturbation, where culling disrupts
the social patterns of the badgers in the area, leading to an
increase in movement and therefore transmission of the disease.
Although it is scientifically accepted that social perturbation
can occur as a result of badger culling, the studies were unable
to confirm that the increased incidence at the "edges"
were a direct result of the increased badger perturbation. We
must guard against a "postulate" becoming accepted as
a scientific fact. It is felt that there is tendency to over-conclude
the results of the RBCT and it is important to remember that they
only apply to the conditions set within the trial. The RBCT was
a trial of two potential policy options—and it was clearly
demonstrated that they didn't work under the conditions set in
the trial.
11. The results of the RBCT could have been
due to a number of factors, including variations in compliance,
coverage and culling success within the trial areas. Although
the overall average culling rate was estimated to be between 60-80%,
in some areas within the trial areas it was as low as 20%, therefore
social perturbation would have been occurring throughout the culled
areas, as well as in neighbouring areas. The initial results of
the trial also don't tell us what level of clearance would be
necessary to result in the disappearance of infection, or what
level of population decrease would result in a sustainable level
of bTB infection within the badger population that would
result in a minimal impact on the level of bTB in cattle.
12. We can conclude that culling will not
be successful or justified, if compliance and coverage is patchy
as the edge effect will be increased throughout the culled area
and will outweigh any positive effect on the rate of bTB
in cattle from culling. However it is important to note that even
with social perturbation occurring throughout the proactive areas,
a 19% decrease of bTB incidences in cattle was still achieved.
The overall impact on the total area influenced by the culling
is close to zero when roughly 100 km2 is culled (according to
John Bourne in a letter sent to Ben Bradshaw on 7 October 2005).
In order for a culling policy to be successful the area would
have to be sufficiently large to outweigh edge effects. It is
estimated that an area of 300 km2 would have to be covered to
achieve a 25% reduction in the incidence of bTB among cattle.
It would also be necessary to ensure that edge effects did not
occur within the culling areas.
13. The cause of the increase in herd breakdowns
on farms close to culled areas is not certain, but the evidence
to support social perturbation is compelling2, 11. bTB
in badgers is a complex disease and TB incidence has not been
found to correlate directly to the density of the population.
The level of disease in cattle does not correlate with the size
of the badger population, or the incidence of bTB in badgers
(which also do not correlate with the size of the population12.
These findings support the social perturbation theory, and suggest
that culling disrupts the social patterns of the badgers in the
area, leading to an increase in movement and therefore transmission
of the disease, regardless of the number of badgers in a population.
This figure is however dependent on the number of infected badgers
within a population, and the chances of them interacting with
cattle. A culling policy should therefore aim to reduce the level
of infection in a population, and should take into account wherever
possible, ecological knowledge of the badger population in an
area.
14. The results from the proactive areas
do support the perturbation effect but they do not inform the
policy maker about what would happen if one increased the efficiency
of culling. Would this decrease the perturbation effect seen?
From the initial results of the RBCT it would suggest that each
time the population is reduced further the positive effects of
culling increase, and the negative effects (social perturbation)
decrease. In a letter to the Minister Ben Bradshaw, dated 29 November
John Bourne noted that analysis of the initial results of the
RBCT did suggest that the effect of culling in reducing breakdowns
within trial areas increased, amounting to an estimated 5.2% greater
reduction in TB incidence for each year since the initial cull,
(95% CI: 16.1% greater to 7% less, p=0.39 for confirmed TB breakdowns
in whole trial areas based on VETNET location data). By contrast,
the analysis also suggested that the effect of culling in increasing
breakdowns in the neighbouring areas declined by an estimated
3.7% for each year since the initial cull, (95% CI: 17.3% smaller
to 12.1% greater, p=0.63 for confirmed Tb breakdowns in whole
trial areas based on VETNET location data). Therefore it could
be suggested that if repeated culling continued the negative effect
would decrease and the positive effect would increase significantly.
IMPORTANT FINDINGS
FROM OTHER
TRIALS
15. The "Four Areas" Badger Culling
Trial (FABCT) is considered to provide the strongest evidence
that badgers play some role in bTB in cattle5 and supports
the need for a large-area consistent cull. Although many have
reservations about the statistical design and analysis of the
FABCT, in the opinion of the CSA the trial shows strong evidence
of lower incidence of bTB in removal compared to reference
areas (the trial areas in the FABCT were also larger than in the
RBCT). In removal sites badgers were intensively culled, in the
reference sites, low level "reactive" culling occurred.
The difference between the two sites is not thought to be due
to social perturbation, as the incidence of bTB did not
increase in the reference areas over the study period. However,
the incidence of bTB in the removal areas decreased significantly.
The trial areas were also well isolated from surrounding cattle
and badger populations by geographical features, which may reduce
the edge effects.
16. The level of landowner co-operation
was also extremely high. Although there are significant differences
between the UK and Ireland in terms of badger densities, bTB
prevalence, stocking density, herd testing regimes and cattle
movements for example, there are also significant correlations
which need to be looked into in more detail. It has been noted
that edge effects were also not seen in the Thornbury or East
Offaly trials10 which is thought to be due to the fact that they
were geographically isolated with boundaries relatively impermeable
to badgers. This demonstrates that badger impermeable boundaries
are effective in preventing the edge effect and should be used
whenever possible.
THE BADGER
POPULATION IN
THE UK
17. Badgers are a protected species and
the BVA supports the continued protection of the badger from those
elements of society that might wish harm on the species in the
name of sport or recreation. However, badgers are not an endangered
species and in the right conditions will breed prolifically. The
current population is estimated to be around 300,000 and there
is no immediate risk to the overall numbers of badgers should
culling in particular areas of high bTB incidence be an integral
part of any control policy. There is still a shortage of truly
accurate information as to the level of infection in the badger
population with bTB both in the risk areas and outside
and further research in this area should be encouraged. The BVA
would urge Government to consider a census of badger numbers as
a matter of urgency.
February 2006
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