3 An injectable vaccine for badgers |
38. An injectable BCG vaccine for badgers has been
licensed for use since March 2010. Its availability is the culmination
of 10 years and £11m of government research.
BadgerBCG does not confer complete protection from bovine TB and
has no discernible effect on already infected animals. A study
of infected captive badgers has demonstrated that vaccination
can reduce the progression, severity and excretion of the disease.
Dr Carter, Senior Scientist at FERA, told us that research conducted
in the field supported this conclusion. While the field study
was primarily designed to assess the safety of the vaccine and
gather the data required to license BCG, the results were consistent
with the clinical study.
The study showed vaccinated badgers continued to shed TB bacteria
but to a lesser extent than unvaccinated badgers.
39. Data from the study also demonstrated that the
risk of unvaccinated cubs testing positive for the disease was
reduced by 79% when more than a third of the adults in their social
group had been vaccinated.
This would suggest that not every badger need be vaccinated every
year for a vaccination policy to be effectivethe vaccine
needs to be administered only to enough of the uninfected population
to establish herd immunity.
What is clear is that the longer the vaccination programme was
maintained, the greater would be the benefit realised.
THE BADGER POPULATION
40. The size and spatial variation of the badger
population in the United Kingdom is largely unknown as is the
level of TB infection in that population. The Randomised Badger
Culling Trial (RBCT) demonstrated the degree to which the prevalence
of TB can vary between areas. Within the 10 areas studied in the
RBCT trial TB prevalence ranged from 1.5% to 35%.
Keith Meldrum, a former Chief Veterinary Officer states that 23%
of the more than 13,000 badgers put down under a policy of removal
in the mid-90s showed evidence of TB during post-mortem.
41. A badger sett survey is currently under way,
which will report this summer. The survey will provide an estimate
of the density and abundance of badger social and family groups
by region. A Defra-funded study planned for this winter will look
at the average size of badger groups in different landscapes and
parts of the country.
Neither study will demonstrate the level and distribution of TB
in the badger population.
42. Density of population does not necessarily correlate
with prevalence of disease.
Dr Wilson, Team Leader at FERA, thought that estimating the proportion
of the badger population infected with bovine TB would be difficult
but that 'measures of prevalence on their own are not particularly
useful. What is more useful is looking at how they might vary
either regionally or over time.'
Professor Hewinson admitted there was an 'evidence gap':
We do not know whether TB is in badgers in areas
where there is no cattle TB, and some of the work in Ireland suggests
that there is TB in badgers in both high prevalence and low prevalence
areas; it is just the level of TB in those badgers that is the
EFFICACY OF THE VACCINE
43. The BadgerBCG vaccine has been available only
since March 2010; as Dr Wilson told us 'it is still an embryonic
piece of work'. Clinical
and field trials have demonstrated a beneficial outcome of using
the vaccine but precise efficacy appears difficult to quantify.
For example, three tests used in the 2010 study by Chambers et
al showed that:
· Vaccination was associated with significant
reductions in the incidence of positive Stat-Pak results (73.8%);
· combined Stat-Pak and culture positives
· the incidence of IFNã test-positivity
was not significantly reduced by vaccination.
The study has led many to state that injectable BadgerBCG
reduces positive serological results by 74%.
The Veterinary Association of Wildlife Management (VAWM) contest
that, saying that the study was 'at best a small scale field study,
which only involved 262 animals and which was presumably not designed
to assess efficacy' and that while one test showed results of
nearly 74%, another using the same data showed no significant
difference. In their
written evidence Defra confirm that the study did not produce
'a true efficacy figure'.
44. Since the 2010 study further work has been done
reworking the original data using an additional more complex serological
test. The 2012 work (Carter et al) states that the
used here is the most sensitive and specific measure of M.
bovis infection in a live vaccinated badger and so provides
confidence that these results are biologically meaningful.
The effect of vaccination on the triple testV
outcome was to reduce the risk of a positive result by 54% in
vaccinated individuals. Without post-mortem data it was
not possible to ascertain what proportion of the triple testV-negative,
vaccinated badgers were protected from infection and what proportion
still acquired infection, but were not detected using the triple
It is unsafe to assume that triple testV
negativity equates to the absence of infection. A greater estimate
of vaccine effect (76%) was observed with the dual test. The IGRA
(ESAT-6/CFP-10) was absent from the dual test. As the IGRA is
more sensitive than either the Stat-Pak or culture at detecting
M. bovis infection in live badgers, this result was not
45. As with the 2010 study, the higher figure from
the 2012 work (76%) is widely quoted
despite the more sensitive and specific test showing the effect
of vaccination was to reduce the risk of a positive result to
the lower figure of 54%. In order for vaccination to be considered
part of a strategy to eradicate bovine TB we first need to establish
what level of efficacy can be expected. The research undertaken
by Chambers et al was vital in gathering the data required to
get a badger vaccine licensed and available to use and we congratulate
those involved in achieving this aim. To have another tool to
use against bovine TB is valuable. However, what is also apparent
is that substantial data clearly showing the effect of the vaccine
in the field are lacking. Now that a vaccine is available the
Government should consider addressing this evidence gap by researching
the efficacy of the BadgerBCG vaccine in the field.
IMPACT OF A PROGRAMME OF BADGER
VACCINATION ON CATTLE
46. There is no direct evidence that a programme
of badger vaccination results in reduced transmission of TB to
cattle. Dr Wilson described the lack of data as 'one of the most
fundamental knowledge gaps that we have'.
Use of the BadgerBCG vaccine is still in its infancy so the lack
of such data is not surprising. It is not clear how or whether
the Government intends to address this problem. In its written
evidence Defra state that to quantify the contribution 'it is
likely we would need to carry out a large-scale field trial (on
a comparable scale to the RBCT) the results of which would take
many years to collect.'
47. The Government currently funds a Badger Vaccine
Deployment Project (BVDP) which covers 120km2 in Gloucestershire.
The project was not set up as a scientific trial but exists to
test the deployment of vaccination and train lay vaccinators.
The BVDP was originally intended to cover six areas but five of
the planned projects were cancelled soon after the current Government
took office. Dr Wilson told us that the area in Gloucestershire
'is not large enough in its own right to look at statistical effects
of TB on cattle herd breakdowns ... there is no doubt, however,
that if all six areas had all been online there would have been
more data for us to work with to start looking and addressing
questions around what effect this work is having on cattle TB
rates ... it is going to be more difficult from the position we
are in now to fill the knowledge gap'.
Although they were not originally planned to test the effectiveness
of the vaccine or the impact of its deployment on the incidence
of TB in cattle, the cancellation of five of the six Badger Vaccine
Deployment Projects represents a missed opportunity to collect
valuable data on the effect of the badger vaccine.
48. The absence of empirical evidence of the impact
of badger vaccination on the incidence of TB in cattle is not
on its own a reason not to pursue a vaccination strategy. A vaccine
that reduces the excretion of M. Bovis bacteria is a powerful
tool. An effective programme of badger vaccination in areas where
badgers are the suspected source of TB in cattle would be expected
to reduce transmission of the disease between the species.
49. The discovery of bovine TB in 'closed herds'
has led to badgers being identified as a source of TB in cattle.
The strength of transmission of M. Bovis between badgers
and cattle is largely unknown as is the route of transmission.
Dr Wilson told us:
In the past, the feeling was that transmission
was more likely on pasture, where cattle come into contact with
contaminated excreta from badgers at latrines. Equally, however,
we now know from research we have carried out in the last few
years that badgers readily enter farm buildings. ... farm buildings
represent a high risk area because we know in some circumstances
badgers and cattle will come into quite close contact with each
50. There is evidence that infected badgers tend
to range further than non-infected individuals and the different
behaviour pattern may increase the likelihood of the infected
badgers encountering cattle.
Not everyone agrees that badgers are a cause of TB in cattle.
In written evidence Martin Hancox made clear his view that:
The widely held belief that cows catch TB from
badger urine with 300,000 bacilli/cc is wildly improbable. Some
99% drains straight into soil; the rest is disinfected by UV in
sunlight within 3 days, so a cow is unlikely to ingest the minimum
dose c1million bacilli, ie 3cc of fresh urine.
51. Although the extent of infection transmitted
between badgers and cattle is subject to debate, we believe there
is merit in gathering information on potential transmission pathways
and we welcome FERA's research project on badger farm visits.
Developing and implementing effective badger exclusion methods
may prove more cost effective than other measures aimed at addressing
the impact of infected badgers on cattle.
52. A specific challenge for a vaccination policy
is to vaccinate animals before they become infected. As Carter
et al (2012) point out:
This is a particular concern for the vaccination
of badgers against TB because they live in close contact with
one another and their young do not generally emerge from their
underground den (sett) for the first two months of their life.
The argument that many badger cubs will become infected during
this period (i.e. before they can be caught and vaccinated), has
been identified as a key potential constraint on the effectiveness
of badger vaccination as a management tool.
53. Analysis of evidence from the four-year field
study has shown that where a high proportion of group members
were vaccinated, unvaccinated cubs born into those groups were
significantly less likely to test positive for TB. Dr Carter told
us the most plausible explanation for this is herd immunity:
'the cubs were indirectly protected because a higher proportion
of the badgers they were coming into contact with over the course
of the study had been vaccinated and had at least received some
form of protection from the vaccine.'
Results from the field study showed that when more than a third
of the social group had been vaccinated the risk to unvaccinated
cubs was reduced by 79%.
However, Dr Carter explained that owing to a range of factors
including prevalence of infection, population density, and other
environmental factors, 'we cannot say what proportion of the population
you would need to vaccinate to achieve herd immunity'.
54. Herd immunity is a sought after outcome of
any vaccination programme. It means transmission of disease is
reduced and non-vaccinated animals are given a measure of protection
reducing the need for further deployment of the vaccine. The identification
of the indirect effect of badger vaccination on unvaccinated cubs
is an important step forward in research on the effectiveness
of the BadgerBCG vaccine. For herd immunity to occur, a significant
proportion of the uninfected badger population must be trapped
and vaccinated. The precise numbers depend not only on local factors
such as badger population, density and environmental factors but,
as importantly, on the efficacy of the vaccine. While herd immunity
may mean that not every badger has to be vaccinated every year,
we need to be confident, without testing each badger, that herd
immunity has developed. Further research on the indirect effect
of vaccination is therefore necessary and must be included as
part of future evidence-gathering on the efficacy of the vaccine
in the field.
55. Vaccination of badgers is expensive. Defra's
current best estimate of the cost of trapping and vaccinating
badgers is £2,000-£4,000 per km2.
Costs can vary according to factors such as ease of access to
setts, terrain, weather, time of year and experience of personnel.
The cost will also depend on factors such as the size of area
being vaccinated, density of badgers, frequency of vaccination,
and model of deployment. Fixed costs include the vaccine itself,
fridges (as the vaccine needs to be kept in cold conditions at
all times to remain viable), disposables, traps, vehicles and
training. However, as Dr Wilson told us, the largest cost is manpower:
A badger vaccination round on a farm or something
like that would involve a survey, the deployment of the trapsi.e.
putting or digging them into placeand then perhaps several
days of pre-baiting the traps, which involves repeated visits
by staff and operatives going back, with the traps locked open,
putting bait in them and getting the badgers used to going in
them for food rewards. The final step is to set the traps, go
back, check the traps the morning after setting them, vaccinate
the animals and release them, and then remove the traps and clean
up. That can be a two or threeweek programme. Obviously,
if you are talking about manpower for that length of time there
is clearly a significant cost associated with that.
Research by the NFU has indicated that even where
farmers pre-baited traps on their own land, the cost of vaccination
still amounted to £1,736km2.
56. In 2012, work undertaken by FERA, the Welsh Assembly
Government and a number of NGOs led to more than 2,500 badgers
A dozen wildlife organisations now actively deploy the vaccine
in England. Although vaccination is costly, scope exists for
economies of scale but this will need a more coordinated national
approach to badger vaccination to enable equipment and information
to be shared more effectively. There is great enthusiasm among
voluntary organisations for deploying the badger vaccine. The
Government should not miss the opportunity to use them both to
gather evidence and as a resource to carry out vaccination. A
first step should be to set up an advisory service to help NGOs
plan and deploy a programme of vaccination and to advise what
data it would be useful to obtain.
IDENTIFICATION AND SURVEILLANCE
57. Better targeting of resources is key to reducing
the costs of a vaccination programme. Collaborative work undertaken
by the University of Warwick's School of Life Sciences and the
Government (Travers et al 2012) suggests that Polymerase Chain
Reaction (PCR) tests on faeces in badger latrines can determine
whether inhabitants of the related sett are infected with bovine
TB. While the PCR test will not identify which individual badger
has TB, such tests may, when fully developed, prove useful in
identifying which setts harbour infected badgers.
The research concludes that 'field studies are now required to
determine how best to apply the assay for population-level bTB
surveillance in wildlife'.
58. Another option is to test captured badgers for
infection, releasing only those which tested negative. However,
as the BVA made clear, this option could make the problem worse:
the diagnostics for badgerside testing
have a low sensitivity of about 50%. So arguably, in simple terms,
for every two infected badgers that are trapped and tested, one
will be vaccinated and released and one will be culled and removed.
So we still have the disturbance in the badger population from
that proportion that has been culled. That can create perturbation.
What you have actually done is release infected badgers back into
that perturbed population. Potentially you could make the perturbation
effect worse than removing badgers on a pure culling exercise
59. PCR testing of badger faeces has the potential
to identify those setts which harbour infected badgers. Doing
so will not only enable a vaccination programme to be better targeted
and therefore more cost-effective but may also be able to show
whether the vaccination has been successful in creating herd immunity
in particular social groups. We recommend that the Government
provide funding to explore how this research might be applied
practically in the field.
60. Vaccination can be undertaken only by trained
vaccinators. The Government has made up to £250,000 a year
available over three years to support and encourage badger vaccination.
The scheme is aimed at supporting vaccination in the cull pilot
areas and to subsidise lay vaccinator training and certification
costs for voluntary and community organisations only.
Brock Vaccination and the NFU considered that the allocation of
funding resources might be better targeted if farmers who wished
to undertake the vaccinator training were also eligible for support.
We agree. Farmers are not entitled to funding to complete the
lay vaccinator training course despite it being their land on
which access is required to undertake the vaccination. This is
perverse. The Government should amend eligibility for the course
to include farmers.
61. Gloucestershire Wildlife Trust report that training
capacity for lay vaccinators and subsequent certification and
licensing is a limiting factor for any significant increase in
voluntary deployment: 'in 2013 there are only 50 places on the
FERA training course, with 10 places available per course.'
The Government should increase the number of places on its
lay vaccinator training course. It would be disappointing if a
lack of qualified vaccinators became the limiting factor in a
programme aimed at reducing TB in badgers.
62. If cost-effective, a programme of badger vaccination
will undoubtedly meet greater support and public approval than
culling. It would be unlikely to be subject to public protest
and disruption and, while trapping brings with it welfare concerns,
a programme of vaccination is more likely than other options to
result in a healthy badger population. There is also no evidence
of the perturbation effect that is attributed to culling. The
efforts of wildlife NGOs, the Welsh Assembly Government and FERA
have demonstrated that deploying an injectable vaccine, while
expensive, is feasible in limited areas. However, it remains the
case that vaccination does not remove and has no effect on already-infected
badgers. Indeed, mitigating the effect of the disease through
vaccination may increase the survival time of carriers and secretors.
63. Benefits from vaccination would be expected to
accrue incrementally over several years as the number of badgers
vaccinated increased and infected badgers died off. Although,
according to Defra, most individual badgers already infected with
bovine TB will die off within five years, it is likely that annual
vaccination would need to last many years more to be successful.
For vaccination to produce herd immunity, a significant proportion
of badgers need to be captured. The Carter et al research suggested
that vaccination reduced the risk of a positive test result by
54% in vaccinated individuals. However, if only 50% of badgers
were trapped and vaccinated with a vaccine that is 54% effective
then just a quarter of the badger population would have a reduced
risk of infection - and that is assuming that those vaccinated
were not already infected. The more endemic the disease the more
difficult it will be and the longer it will take for vaccination
to be effective.
The Government needs to undertake further research in order
to have confidence in the level of efficacy to be expected from
the vaccine when deployed in the field.
64. The development of a vaccine that reduced
the level of infection in badgers would be a valuable tool in
the battle against bovine TB but, despite 10 years of research
and £11million spent in development, it is one that Defra
lack a strategy for using. A number of voluntary organisations
are deploying the vaccine and, while we commend their actions,
in the absence of a clear nationally coordinated strategy this
work can only have a limited impact on the wider problem of bovine
TB. We are particularly concerned that Defra may miss the opportunity
to make use of the enthusiasm that exists in the voluntary sector
for badger vaccination.
65. Badger vaccination is expensive and no magic
bullet. We agree with the Wildlife Trusts that if it is going
to make a difference, it needs to be deployed strategically in
areas where it is likely to have the biggest impact. The vaccine
has been available for use for more than three years. Having developed
the vaccine, Defra must now produce a clear strategy for its use.
57 Ev w2 [RSPCA] Back
Q 15; Chambers et al, Bacillus Calmette-Guérin vaccination
reduces the severity and progression of tuberculosis in badgers,
Proceedings of the Royal Society: B, 22 June 2011, vol.
278 no. 1713 1913-1920, available at http://rspb.royalsocietypublishing.org/content/278/1713/1913.full Back
Ev w29 [VAWM], Q 15 and Carter SP, Chambers MA, Rushton SP, Shirley
MDF, Schuchert P, et al, BCG Vaccination Reduces Risk of Tuberculosis
Infection in Vaccinated Badgers and Unvaccinated Badger Cubs.
PLoS ONE 7(12): available at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049833 Back
Ev w20 [Humane Society] and Carter et al study Back
Ev w22 [RSPB] Back
Q 14 Back
Ev w19 [Keith Meldrum] Back
Q 13 Back
See written evidence from Martin Hancox, Ev w8, for further discussion
on this subject and Bovine Tuberculosis in Cattle and Badgers:
Report to the Rt Hon Dr Jack Cunningham MP by Professor J
Krebs and the Independent Scientific Review Group, p46 Back
Q 14 Back
Q 313 Back
Q 52 Back
Chambers et al, Bacillus Calmette-Guérin vaccination reduces
the severity and progression of tuberculosis in badgers, Proceedings
of the Royal Society: B, 22 June 2011, vol. 278 no. 1713 1913-1920
For example, Ev w27 [Network for Animals], Ev w42 [British Veterinary
Zoological Society], Ev w50 [Secret World Wildlife Rescue] Back
Ev w29 [VAWM] Back
Ev 70 [Defra] Back
Carter SP, Chambers MA, Rushton SP, Shirley MDF, Schuchert P,
et al, BCG Vaccination Reduces Risk of Tuberculosis Infection
in Vaccinated Badgers and Unvaccinated Badger Cubs. PLoS ONE
7(12): available at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0049833 Back
For example, Ev w20 [Humane Society], Badger Trust press notice
18 December 2012 http://www.badger.org.uk/_Attachments/Resources/776_S4.pdf Back
Q 38 Back
Ev 70 [Defra] Back
Q 23 Back
In this context a closed herd is one without contact with cattle
from outside the herd. Back
Q 42 Back
Qq 43-4; FERA told the NIA Agriculture and Rural Development Committee
that 'Of the 32 farms [studied], 19 had visits from badgers. Some
of those had only one or two visits recorded over the whole year,
but at the other end of the scale, about 10% of the farms had
visits on 70% to 80% of nights. Badgers came on five or six nights
a week. It was not just one badger, it was not just one incursion
a night, and they were not just travelling through the farmyards;
they were going into the farm buildings'. See Northern Ireland
Assembly Agriculture and Rural Development Committee Report, Review
into Bovine Tuberculosis, paras 105-109 for further discussion
of badger visits to farm buildings. Back
Ev w31 [Society of Biology] and Qq 44-5 Back
Ev w8 [Martin Hancox] Back
Carter et al study, 2012, see earlier footnote for full citation Back
Herd immunity occurs when the vaccination of a significant proportion
of a population provides a measure of protection for individuals
that have no immunity. It arises when a sufficiently high percentage
of the population is protected through vaccination to disrupt
chains of infection and therefore stop the spread of disease.
Establishing herd immunity is therefore a sought after outcome
of vaccination policy. Back
Q 20 Back
Ev 70 [Defra] Back
Q 20 Back
Ev 70 [Defra]; Gloucestershire Wildlife Trust published a cost
range of £41-51 per hectare for their work in 2011 and provide
a detailed breakdown of costs in their report Nature Reserves
Badger Vaccination Deployment Programme 2011, while the Welsh
Assembly Government's project cost £3912 per km2
in its first year. Back
Q 31 Back
Ev w51 [NFU] Back
Ev w22 [RSPB]; In the first year of the Welsh Assembly Government's
five year vaccination programme a total of 1,424 badgers were
vaccinated over an area of 288km2 at a cost of £943,000. Back
Ev 46 [IFAW]; Travis ER, Gaze WH, Pontiroli A, Sweeney FP, Porter
D, et al. (2011) An Inter-Laboratory Validation of a Real Time
PCR Assay to Measure Host Excretion of Bacterial Pathogens, Particularly
of Mycobacterium bovis. PLoS ONE 6(11). Similar work, funded
by Defra, is also being undertaken by Queens University Belfast. Back
Q 252 Back
Defra website, https://www.gov.uk/government/news/update-on-measures-to-tackle-bovine-tb
and Ev 70 [Defra] Back
Defra are providing funds to cover 50% of the cost of becoming
an accredited and certified lay vaccinator. Farmers are not eligible
to apply for funding from this scheme to train as vaccinators.
To date, Fera have trained 137 lay vaccinators on the Cage Trapping
and Vaccination of Badgers course. Back
Gloucestershire Wildlife Trust Nature Reserves Badger Vaccine
Deployment 2012 available at www.gloucestershirewildlifetrust.co.uk Back
Ev w17 [Ian Kett] Back
The British Cattle Veterinary Association has referred to a timescale
of 12 years and Paul Livingstone, Technical Manager of the Animal
Health Board in New Zealand,has referred to a timescale of 20
years - see www.bovinetb.info for further discussion. Back
Options for the use of badger vaccines for the control of bovine
TB, Defra Back