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12/7/2022

Is the badger cull working or not? A closer look at the latest research

Badger (www.lauriecampbell.com)Recently a new study1 was published in Vet Record about badger culling and its relationship with the incidence of bovine tuberculosis (bTB). It was very quickly covered by the news, including BBC News2, The Independent3, Farmers Weekly4 and The Irish News5 and declared a “landmark study”, with the authors concluding that there is no detectable link between badger culling and any decline in incidence of bTB. However, Defra promptly issued a rebuttal and discounted the study as “methodologically flawed”6,7.

Bovine TB is an infectious disease affecting cattle herds across England, able to spread within and between badger and cattle populations. It has a costly and significant impact, resulting in high numbers of compulsory cattle slaughters and devastating impacts on farmers and farming communities. Badger culling has been introduced alongside a number of other measures such as vaccination, bTB testing and surveillance, and herd management8,9. It has mostly been carried out in the High Risk Area for bTB across all or part of 15 counties – extending from Cornwall in the southwest to Derbyshire in the midlands plus East Sussex10. Defra measures bTB incidence by tracking the number of TB-free herds containing at least one confirmed newly infected animal. This is called ‘Officially Tuberculosis Free – withdrawn’, or ‘OTFw’ 10,11.

The latest study published in Vet Record by Langton, Jones, and McGill looked for relationships between badger culling and the rate of OTFw breakdowns using a variety of statistical models. The study used publicly available data published by Defra and studied bTB incidence rates in ten counties in the High Risk Area (Avon, Cornwall, Devon, Dorset, Gloucestershire, Hereford & Worcestershire, Shropshire, Somerset, Staffordshire, and Wiltshire) from 2010 to 2020.

The lack of spatial resolution in the publicly available data led the study to group data by county, rather than by the length of time the cull has been in place as other studies have done. By examining OTFw rates across these ten areas, the study treats large counties, which have high numbers of culling operations, the same as small counties, which have fewer culls. In doing so, it treats different locations the same irrespective of how long culling has been in place, and this is where the crux of the debate lies. Part of the research also compares the peak bTB incidence rate with the start year of culling across these areas and points to the fact that these dates do not line up, claiming this also shows that culling has no impact, or that incidence rates were on the decline before culling began in some places. No statistical testing was done to see if this is significant; the study simply comments on a visual trend. It concludes that there was no detectable link between badger culling and the decline of bTB, stating that there was no statistical evidence that changes in bTB incidence were different in culled and unculled areas. It goes on to suggest that any declines were the result of cattle-based measures including more intensive testing and movement controls, rather than badger culling.

Because the study combines areas within counties that have been undergoing culling for vastly different amounts of time, it is very difficult to interpret the results of the analysis, particularly because it is thought that it takes up to two years for the effects of culling to be seen6,12. Because it uses data grouped by county, the analysis also is unable to take into account that as time has gone on new sites and bTB measures have been introduced, which can mask true data trends. In reality the bTB incidence rate in culling areas has fluctuated as new sites (which have higher bTB rates) have been added6.

Defra has reasserted that the impact of culling on bTB outbreaks in cattle needs time to take effect, usually two years6,12, and where analysis does not account for increases in cull areas, differences in culling duration, and changes in other bTB control measures, it is incredibly difficult to extract meaningful results. Because of how complex bTB data are, the most reasonable way of studying it is by looking at the cull duration (noting that it is not possible to do this using publicly available data). This is what the Chief Veterinary Officer and Defra’s Chief Scientific Adviser did in their statement about the paper6, where over a period of five years between 2015 and 2020, OTFw incidence makes a steady decline across culled areas but fluctuates in unculled areas, starting and ending the 2015-2020 period at 10.9 OTFw incidence per 100 years at risk, going up to 12.8 in 2016/17. In the same period, areas that started culling in 2016 saw a decrease of 8.5, and areas that started culling in 2017 saw a decrease of 6.96.

Data on the badger cull are not born from standardised experiments but from live, varying environments across the country, and not all variables can be measured and accounted for. With complex, long-term data like this, the challenge of bringing together so much information is a big one, and the level of resolution at which it is analysed matters. We urge Defra to commission APHA scientists to carry out a definitive analysis of the data using all available information and maximum available spatial resolution. Doing so will sensibly inform Defra’s plans, which currently involve removing intensive culling licences from 2023, cutting short existing licences without option for renewal (where backed by data), as well as continuing to work on both badger and cattle vaccination programmes16, noting that increased controls on cattle movements, bTB testing, and improved biosecurity have contributed to reductions in bTB6.

Photo credit: Laurie Campbell

References

  1. Langton, T.E.S., Jones, M.W. & McGill, I. (2022). Analysis of the impact of badger culling on bovine tuberculosis in cattle in the high-risk area of England, 2009–2020. Veterinary Record, 190:
  2. BBC News. (2022). Expensive badger cull should be ended, study says. BBC News: Available at: https://www.bbc.co.uk/news/uk-england-gloucestershire-60791793. (Accessed: 28th April 2022)
  3. Dalton, J. (2022). RSPCA calls for badger cull to end as ‘landmark’ research finds it has not cut TB in cattle. The Independent: Available at: https://www.independent.co.uk/news/uk/home-news/badger-cull-tb-bovine-rspca-b2037615.html. (Accessed: 28th April 2022)
  4. Case, P. (2022). Defra dismisses study claims on TB badger cull effectiveness. Farmers Weekly: Available at: https://www.fwi.co.uk/livestock/health-welfare/livestock-diseases/bovine-tb/defra-dismisses-study-claims-on-tb-badger-cull-effectiveness. (Accessed: 28th April 2022)
  5. Simpson, C. (2022). Badger cull ‘unscientific, ineffective, inhumane and unnecessary’. The Irish News: Available at: https://www.irishnews.com/news/northernirelandnews/2022/03/25/news/badger-cull-unscientific-ineffective-inhumane-and-unnecessary--2624070/. (Accessed: 28th April 2022)
  6. Middlemiss, C. (2022). CVO comments on a recent paper on the effectiveness of badger culling. Available at: https://vets.blog.gov.uk/2022/03/21/cvo-comments-on-a-recent-paper-on-the-effectiveness-of-badger-culling/. (Accessed: 7th April 2022)
  7. Defra Press Office. (2022). Rebuttal of claims on TB cull effectiveness. Available at: https://deframedia.blog.gov.uk/2022/03/18/rebuttal-of-claims-on-tb-cull-effectiveness/. (Accessed: 7th April 2022)
  8. Defra. (2021). Bovine tuberculosis: consultation on proposals to help eradicate the disease in England Summary of Responses and Government Response.
  9. Defra. (2011). Bovine TB Eradication Programme for England.
  10. Downs, S.H., Prosser, A., Ashton, A., Ashfield, S., Brunton, L.A., Brouwer, A., Upton, P., Robertson, A., Donnelly, C.A. & Parry, J.E. (2019). Assessing effects from four years of industry-led badger culling in England on the incidence of bovine tuberculosis in cattle, 2013–2017. Scientific Reports, 9:
  11. APHA. (2021). Bovine TB in cattle: badger control areas monitoring report. For the period 2013 to 2020. Addlestone, Surrey.
  12. Jenkins, H.E., Woodroffe, R. & Donnelly, C.A. (2010). The Duration of the Effects of Repeated Widespread Badger Culling on Cattle Tuberculosis Following the Cessation of Culling. Plos One, 5:
  13. Badger Trust. The Badger Cull. Available at: https://www.badgertrust.org.uk/cull. (Accessed: 3rd May 2022)
  14. Badger Trust. (2022). Big Badger Debate goes on without Defra. Available at: https://www.badgertrust.org.uk/post/big-badger-debate-goes-on-without-defra. (Accessed: 3rd May 2022)
  15. APHA. (2020). Bovine TB epidemiology and surveillance in Great Britain, 2020 Bovine tuberculosis in Great Britain. Surveillance data for 2020 and historical trends.
  16. Defra Press Office. (2021). Next phase of bTB eradication strategy confirmed. Available at: https://deframedia.blog.gov.uk/2021/05/28/next-phase-of-btb-eradication-strategy-confirmed/. (Accessed: 4th May 2022)
Topic: Nature , Policy

Comments

the disappearance of hedgehogs and too many badgers carrying TB

at 13:29 on 20/07/2022 by Simon Walker

I own approx 53 acres of land mostly woodland near Warminster in Wiltshire.In the last 4 years My wife and I have only seen 2 hedgehogs, both in my yard. Although Badgers are lovely creatures , they are also vicious animals that like wild boar can bite through hard bone decimate caged poultry or game birds,and plough up land like an over excited wild boar. They are very solid and before it was illegal to cull them only No1 shot from a 12 bore shotgun would kill them.You also don't want to hit one with a vehicle as the badger always wins. If one is already dead in the road and you can't avoid the carcase ,it is like driving over a rock. The Badger Trust and it's bunny hugger members should pay millions to eradicate TB , even Brian May finally saw the light and apologised to farmers as he was ignorant of the true facts.

Badgers

at 11:30 on 20/07/2022 by David Randolph

Years ago before there was much talk of Badgers infecting cattle with TB, there were about 200,000 to 250,000 in the UK then came badger baiting up north and public outrage about that caused the Government to ban the killing of badgers. Wrong decision because the problem was the people concerned in baiting NOT anything to do with Badgers. The population of badgers then increased to 600,000 and TB in cattle became rampant. I suggest that we continue to reduce Badger numbers for at least twenty years and take them off the protected list until numbers stabilise at no more than 250,000, We may then find we have less TB in cattle, more hedgehogs, ground nesting birds etc. etc..and, of course we will still have plenty of badgers around but more of their target species.

Badger control.

at 11:19 on 20/07/2022 by Harry Bott

In years past we used to control badger numbers on the farm mainly by gassing. We had 3 badger setts on about 18oo acres and we also had plenty of hedgehogs and ground nesting birds. Due to over protective legislation, I estimate that we now have around 300 badgers. A count with night binoculars has observed at least 30 in one field.. Now, Hedgehogs are extremely scarce, We no longer have Lapwings, Only one nest of Grey Partridges has been successful and very few wild Pheasants have had broods. We would hate to see badgers eliminated from the farm, but please let us quietly control them as we have done in the past.

Evidence for biodiversity benefit of badger cull

at 7:54 on 20/07/2022 by Robert Kenward

It is clear, on an individual observational basis, that hedgehogs benefit from the badger cull, as predicted by work at Oxford in the 70s. However, irrefutable statistical evidence over large areas is needed to convince those inclined to be rational. The tragedy is that the organisations with an interest in management of predators have not got together a suitable survey to show this irrefutably. With modern web-based citizen science (e.g. the Big Farmland Bird Count), it need not be expensive. Liaison with an disinterested partner would give credibility, though this may be harder now for political reasons than when the cull started.

Badger cull

at 18:58 on 19/07/2022 by Paul green

I have lived in north Dorset for 20 years and have never seen hedgehogs cross my lawn but since badger cull they are now regular visitors seems to be working every one

Other wildlife displaced or killed by badgers.

at 18:25 on 19/07/2022 by JEAN WITT

I agree with these comments especially the first 3 where an increase in other wildlife is noticeable in the cull zones.

The Badger Cull

at 17:40 on 19/07/2022 by Neil Bennett

As long as the current system of testing cattle continues to leave an average of 20% false negatives in the heard bTB will remain in the herd. It’s called bTB for a reason. A better testing regime, improved control over cattle movements and farm biosecurity is the answer. For those with anecdotal evidence re: hedgehogs, we have plenty, we also have lots of Badgers, to two species have coexisted for millennia without issue. The biggest cause of decline in Hedgehogs is habitat loss. Jeees, I can’t believe I’m having to write this… it’s common knowledge. And, maybe if Gamekeepers like Alan Wilson stopped killing them (35 recorded), and no doubt he’s not alone in this, then maybe our Hedgehogs would fare better.

Badger cull

at 17:28 on 19/07/2022 by Philip Gray

Unrelated to bovine TB, but to the national increase in badgers. They are now well established in the fens, where they have been pushed by over population. Apart from their usual quarry they are now eating wader chicks and eggs on fenland washes including black tailed godwits. Making setts in river banks causing flood risk and in agricultural land causing damage to farm implements. Yet everyone seems to be scared to propose a cull here for fear of a backlash from a noisy minority of ecowarriors.

Badger Cull

at 16:09 on 19/07/2022 by John Lea

If you want to know if the Badger Cull is working ask a Hedgehog or Lapwing. To give the Badger full protection is about as stupid as it gets when other more vulnerable species are seriously under threat.

Badger Cull

at 16:03 on 19/07/2022 by Matthew Dobbs

I would also echo the previous comment. Many more hedgehogs around our area since they cull. This seems to me to feed into the general debate we seem unable to have sensibly about controlling top predators to allow greater balance in bio-diversity

Badgers and other wildlife

at 12:59 on 19/07/2022 by Ben Williams

The cull zones has seen an increase in other wildlife such as skylark and other ground nesting birds. As well as an increase in hedgehogs and brown hares. Is it not time to put the badger back on to a closed season and do away with it protected status like most of Europe.

The Langton, Jones McGill report ….

at 12:51 on 19/07/2022 by Alec Swan

If the managed badger cull isn't having any material effect, then the answer to that is to increase the cull. Shooting individual badgers is disruptive and so, harmful to the balance of local herd populations. The only truly effective system of badger reduction, would be to take a map of individual badger setts and then target a percentage and gas them. Removing family units in their entirety, would be far more beneficial and in the long term, far less damaging to a local population. I accept that since WWII 'gassing' is unlikely to gather much public support but from the aspect of both efficacy and the well being of a local badger population, it is and without question, the better way.

Badger cull

at 11:28 on 19/07/2022 by Patrick McCanlis

To the non tech among us the scientific data is almost impossible to follow! I don`t think you have any firm conclusion either. What cannot be in dispute is that if there are less badgers there will be less to transmit TB! QED! No one wants to eradicate Tommy Brock completely BUT numbers must be controlled as the effects of TB, & the numbers of cattle killed & farms ruined, is destructive to the livestock industry.

Is it working

at 11:00 on 19/07/2022 by H R Oliver-Bellasis

Thank goodness for an informed review of the paper Langton, T.E.S., Jones, M.W. & McGill, I. (2022). The issues raised by GWCT clearly challenges the authors interpretation of available data and they seem to have erred by consistently ignoring the length of time the cull has been in place a crucial issue highlighted by Defra as important. Logic suggests that one would not aggregate sites of different cull lengths and size of area anyway, unless one wanted to obfuscate? Well done GWCT for highlighting the error.

Badger cull

at 10:58 on 19/07/2022 by IAN PRATT

Whilst not in any way empirical and very much based on observation we have seen a marked increase in the numbers of hedgehogs in our area, which is in the cull zone, over the last year or so and would be very interested to hear any evidence based work to show that there is a causal link. When I say a marked increase I mean having gone from a position in the 1970's where hedgehogs were regular sightings to a position in the last 10+ years where they might as well have become extinct to them being regularly seen again and unfortunately on one stretch of main road of half a mile there being circa 11 roadkill deaths in the last year alone.

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