1

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

2

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

3

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

4

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

5

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)

0

5

10

Nor

ther

n Ire

land

Gre

at B

ritai

n

Irela

nd

Spa

in

Gre

ece

Italy

Por

tuga

l

Pol

and

Fran

ce

Ger

man

y

Perc

enta

ge o

f her

ds w

ith a

pos

itive

test

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

6

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

7

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

8

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

9

Defra 2008

Is TB self-sustaining in badgers?

Schnews

Bourne et al. 2007 The cattle book 2008: 67,000 animals