Post on 30-Apr-2020
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Badgers & TB Dave Dawson Defra 2011
Rosie Woodroffe bovinetb.info
Badger ActGassing by MAFF
Cage trapped badgers shot –“clean ring”
KrebsInterim strategy
86-90 91-95 96-00 01-05 06-10
Defra 2011 The cattle book 2008Wilson & Byrnes
Badger licences issued by MAFF 1994 – 1996, not related to bovine TB
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NZ Animal Health Board
Other species infected with bovine TB 1997-2011
Farmed deerPark deer
Wild deer
Domestic catDomestic dog
Domestic pig
Alpaca
Llama
Sheep
Goat
Ferret
Hawkins 2012 Woodroffe
After Defra 2008 Zuckerman archive
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Woodroffe Woodroffe
Woodroffe
The Independent Scientific Group on Cattle TB
An early finding
• Reactive culling increased TB in herds• So reactive culling discontinued in 2003• Four years before the conclusion of the
study
Bourne et al. 2007, confirmed by subsequent work
The effect of “proactive” culling on TB incidence in cattle Culling over 4-7 years compared with no culling
Defra 2011 The Government’s policy on Bovine TB and badger control in England
24% increase
23% decrease
The main findings
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Woodroffe
The “perturbation effect”
• Culling reduced badger numbers • But increased infection of cattle nearby • Implied changed behaviour or susceptibility• The surviving badgers suffered more TB• They also ranged more widely• TB incidence became less “clustered”
Bourne et al. 2007
Bourne et al. 2007:20. odds ratio 1.70
The suspension of cattle surveillance and slaughter during the 2001 foot-and-mouth epidemic was a natural experiment, proving significant transmission of TB from cattle to badgers
Conclusions
Badgers are a source of cattle TB, but Culling can make no meaningful contribution to TB
control. Some policies are likely to make matters worse. A poor cattle testing regime means that cattle contribute
significantly to the persistence and spread of TB, and Cattle are the main source of infection in some areas. The rising incidence can be reversed, and spread
contained, by the rigid application of cattle-based control measures alone.
Bourne et al. Final Report of the Independent Scientific Group on Cattle TB, June 2007
Hilary Benn 2008
• Questioned the recommendations• Misunderstood the evidence for the
perturbation effect• Recommended sustained removal of
badgers preferably in bounded areas.
Ares & Hawkins 2012
David King 2007
• Accepted recommendation not to cull• Aimed by 2015 for injectable vaccines
for cattle and badgers• Meanwhile set up bovine TB
partnership to tackle the disease• Six badger vaccination trials
Jim Paice 2010
• Tory manifesto: “A carefully managed and science-led policy of badger control in areas of high and persistent levels of TB in cattle is necessary to eradicate this disease”
• Cattle controls on their own insufficient• Reservoir in badgers must be controlled• The benefit of the cull persisted well after
the end of the randomised trial• It is a matter of judgement, not science,
whether the farming industry can deliver an effective, coordinated and sustained cull
• Five of the badger vaccine trials cancelled
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International evidence for a wildlife “reservoir”Failure to eradicate despite testing and slaughter
• Northern Ireland• Republic of Ireland• Spain
Control achieved only after work on the reservoir• USA & Canada• Australia• New Zealand is, so far, unsuccessful
Defra 2011 bovinetb.info
Bovine TB incidence in Europe (www.bovinetb.info)
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The effect of widespread culling on TB incidence in cattle. Trends during the cull and the five years after culling ceased.Defra 2011 The Government’s policy on Bovine TB and badger control in England
28% decrease
9% increase
86-90 91-95 96-00 01-05 06-10
Defra 2011 Hawkins 2012
Foot-and-Mouth
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Distress to farmers
Annual testingTesting once every four years
Defra Bovine TB Information Note 04/12
Pre-movement testing of cattle introduced in 2006 and refined more recently
All this partly funded by €23 million p.a. EU funding, c.f. the annual cost to the taxpayer of about £100 million
Current cattle testing regime
Skin test frequency and pre-movement tests depend upon risk zoning
Slaughter-house inspection for infection
Defra 2011b Donelly & Hone 2010
Average
Modelling work using data from the RBCT indicated that, in the absence of transmission from infected badgers, only 3.4% of herds per annum would be expected to have a TB breakdown. This is in contrast to the actual incidence rates of up to 20% seen in high incidence areas. The report of this work concluded that “TB in cattle herds could be substantially reduced, possibly eveneliminated, in the absence of transmission from badgers to cattle.”
Defra 2011, citing Donnelly & Hone 2010
“TB in cattle herds could be substantially reduced, possibly even eliminated, in the absence of transmission from badgers to cattle. The results are based on observational data and a small data set so provide weaker inference than from a large experimental study.”
Donnelly & Hone 2010, who estimated 95% confidence limits of 0 – 6.7%
The current government policy*• Consultations, 2010 and 2011, policy in Dec 2011• Culling organised by farmers• Combination of trapping and free shooting• Estimated under half the cost of alternative culling methods• Up to ten areas of at least 150km2 begin each year• Bounded by features restricting badger movement• Culled over a six week period repeated at least four years • To reduce badger numbers below 30%• Any vaccination of badgers ancillary• Licenced by English Nature• Two pilot areas first where effectiveness, humaneness and safety
of badger control assessed by an Independent Expert Panel• Eradication policy also includes cattle surveillance, biosecurity
and work on TB in other farmed species
*England. Different arrangements exist in Wales and Scotland, Defra website
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Why not vaccinate cattle?• It’s illegal under EU legislation:• Incompatible with international standards for animal
health (OIE)• Vaccine not proved fully effective and• Vaccinated animals can test positive• Much to resolve: food safety, human health, trade• Projected timetable for vaccine approval takes 10 years
Letter from EU Health Commissioner January 2013
Vaccination of wild badgers
BCG gave a 75% reduction of infection in badgers.
An injectable badger TB vaccine was licensed in March 2010.
The contribution of this to reducing TB in cattle is unknown.
To quantify this needs a large-scale field trial over many years.
Vaccination of badgers, on its own, is insufficient to address bovine TB in cattle.
However, there is potential to use vaccination in combination with culling
Defra 2011
Why not vaccinate badgers? Smith et al. 2012
Simulation of the cattle-badger-TB system, with badger options
150km2
150km2 Smith et al. 2012
Simulation of the cattle-badger-TB system, with badger options
CoreplusRing
Core Ring Nocontrol
Cull only
Cull+Ring vaccinationVaccination
-40
-35
-30
-25
-20
-15
-10
-5
0
TB incidence in cattle (% effect)
Zone
Action
Simulation of the cattle-badger-TB system, with badger control options
Cull only Cull+Ring vaccination Vaccination
Smith et al. 2012
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Simple practical measures can substantially reduce the likelihood of badger visits to buildings and reduce some of the potential for contact and disease transmission between badgers and cattle.
Judge et al. 2011
Biosecurity measures
• Keeping badgers away from stored cattle feed• Making farmyards less attractive to badgers• Having an awareness of high risk areas at
pasture
However, on-farm biosecurity controls are likely only to reduce, not eliminate, TB transmission risks from infectious badgers. Eliminating transmission risks through biosecurity controls can only be achieved in secure cattle containment conditions that are associated with experimental settings – conditions that are very difficult to achieve and impracticable on most working cattle farms. It is possible to protect housed animals but it is much more difficult to stop badger-to-cattle contact at pasture, and therefore there will be a residual risk of disease transmission despite on-farmbiosecurity measures being implemented.
Defra 2011
Ares & Hawkins 2012
West Gloucestershire
West Somerset
Pilot cull areas
• Licences to NFU late 2012• Shooting guidance late 2012• Postponement to 2013
While this can contribute to our understanding of the benefits, the results vary depending on the assumptions used and cannot be considered conclusive and there is no guarantee that these results wi ll be realised. The precise contribution it could make to reducing TB incidence in cattle is therefore unknown. To be able to quantify this contribution precisely would require a large-scale field trial (on a comparable scale to the Randomised Badger Culling Trial), and it would be many years before the results of any such trial were available.
Defra 2011
Changes in the incidence of TB in cattle will be reported, relative to historical incidence within the culled area, and relative to an un-culled comparison area.
Defra 2011
It’s become rather heated
• Cull in Tory manifesto in 2010 but Labour stuck to their earlier position
• Farmers not happy with tight surveillance of cattle• New Welsh Labour administration, 2011, reversed
previous culling policy to in favour of vaccination• Seven different English Wildlife Trusts plan badger
vaccination• e-Petition with 170,000 signatories sparked a
Commons debate• Over 30 prominent scientists described the
proposed cull as a costly distraction