Badgers & TB Dave Dawson Defra 2011

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1 Badgers & TB Dave Dawson Badger Act Gassing by MAFF Cage trapped badgers shot clean ring Interim strategy Krebs Rosie Woodroffe bovinetb.info Badger licences issued by MAFF , not related to bovine TB The cattle book 2008 Wilson & Byrnes 1

2 NZ Animal Health Board Other species infected with bovine TB Ferret Llama Sheep Goat Farmed deer Park deer Alpaca Wild deer Domestic pig Domestic dog Domestic cat Hawkins 2012 Woodroffe After Defra 2008 Zuckerman archive 2

3 Woodroffe Woodroffe The Independent Scientific Group on Cattle TB Woodroffe The main findings An early finding Reactive culling increased TB in herds So reactive culling discontinued in 2003 Four years before the conclusion of the study 24% increase 23% decrease The effect of proactive culling on TB incidence in cattle Culling over 4-7 years compared with no culling Bourne et al. 2007, confirmed by subsequent work The Government s policy on Bovine TB and badger control in England 3

4 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 Woodroffe Bourne et al Conclusions 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 Bourne et al. 2007:20. odds ratio 1.70 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 David King 2007 Questioned the recommendations Misunderstood the evidence for the perturbation effect Recommended sustained removal of badgers preferably in bounded areas. Hilary Benn 2008 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 Ares & Hawkins

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 bovinetb.info Percentage of herds with a positive test Northern Ireland Bovine TB incidence in Europe ( Great Britain Ireland Spain Greece Italy Portugal Poland France Germany The effect of widespread culling on TB incidence in cattle. Trends during the cull and the five years after culling ceased. 9% increase 28% decrease The Government s policy on Bovine TB and badger control in England Foot-and-Mouth Hawkins

6 Annual testing Testing once every four years Pre-movement testing of cattle introduced in 2006 and refined more recently Distress to farmers All this partly funded by 23 million p.a. EU funding, c.f. the annual cost to the taxpayer of about 100 million Defra Bovine TB Information Note 04/12 Current cattle testing regime Skin test frequency and pre-movement tests depend upon risk zoning Average Slaughter-house inspection for infection b Donelly & Hone 2010 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 even eliminated, in the absence of transmission from badgers to cattle., 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 150km 2 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 6

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 Vaccination of wild badgers BCG gave a 75% reduction of infection in badgers. An injectable badger TB vaccine was licensed in March 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 Letter from EU Health Commissioner January 2013 Why not vaccinate badgers? 150km 2 Smith et al Simulation of the cattle-badger-tb system, with badger options 150km2 Smith et al Simulation of the cattle-badger-tb system, with badger control options Smith et al TB incidence in cattle (% effect) Vaccination Cull+Ring vaccination Core plus Ring Core Zone Ring No control Cull only Action Simulation of the cattle-badger-tb system, with badger options Cull only Cull+Ring vaccination Vaccination 7

8 Biosecurity measures Keeping badgers away from stored cattle feed Making farmyards less attractive to badgers Having an awareness of high risk areas at pasture 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 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-tocattle contact at pasture, and therefore there will be a residual risk of disease transmission despite on-farm biosecurity measures being implemented. Licences to NFU late 2012 Shooting guidance late 2012 Postponement to 2013 Pilot cull areas 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 will 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. West Gloucestershire West Somerset Ares & Hawkins 2012 It s become rather heated 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. 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 8

9 Is TB self-sustaining in badgers? Defra 2008 Schnews Bourne et al The cattle book 2008: 67,000 animals 9