Badger culling controls TB: is everything really so black and white?

This article is part of theGIST Science for Society 2014 Article Competition. The top three articles will present their work at the conference. Vote for your favourite article here. Voting closes on Friday 31st October 2014.

Coming from a veterinary family and a farming area, I could not fail to see the toll that bovine tuberculosis (bTB) had on livelihoods and families throughout my childhood. This particular tuberculosis, which mainly infects cows and other wildlife, has a massive economic impact in the UK. In the past ten years alone, it is estimated to have cost the UK taxpayer £500 million in terms of cattle loss and control. In the 1980s, wild badgers were pinpointed as the reservoir for this infection, thought to be maintaining transmission to cows on farmland. After much deliberation, the government implemented official badger culls last year, sparking uproar with animal welfare groups, conservationists and the public alike. Much scientific research has been published on the subject, but I have found it extremely difficult as a scientist (albeit an inexperienced student one) to tease out the facts; both from those that underpin the nation’s policy, and those that undermine it.

Badger culling is therefore a hugely controversial issue that has had the nation debating for the past ten years. The bumbling badger with his characteristic black and white stripes has been an officially protected animal since 1993, and is widely regarded as a part of our local wildlife that many don’t wish to see destroyed. It’s never quite as cut and dried as it seems though. Many other species are controlled through culling to prevent the spread of potentially fatal diseases, or to control damaging invasive species. It is an unpleasant and unfortunate task to have to undertake, but in some cases necessary.

Badger culling was (and still is) an enticing principle, because effectively you are removing the threat that lurks nearby to farms. However, the science behind this isn’t quite so simple. Way back in 1998, the government requested that research on badger culling take place. The Randomised Badger Culling Trial (RBCT) was born, and sought to understand what impact removing badgers had on TB transmission to cows. Although it was found to decrease the number of herds coming down with the disease by 12-16% over their 10 year trial, culling had an unintended side effect that no-one had anticipated; it disrupted their social lives! [1] Badgers naturally live in close-knit groups, which to a certain extent minimise spread of disease as they don’t seem to move around as much. Culling annually was found to disrupt this rather peaceful picture and so badgers were more likely to wander, meaning that those infected with bTB could spread it further afield.

This result was baffling, not least because the same annual culling technique in Ireland had worked extremely well, but that’s science for you. It has been suggested that the area in Ireland had natural barriers to prevent badger movement though, like rivers. In 2013, despite the results published from the RBCT, badger cull pilots were rolled out for the worst affected areas of the UK. The pilot scheme is to run for four years in total, and government have chosen larger areas with natural barriers, in an attempt to diminish this unfortunate dispersal side effect. In any case, scientists and vets alike had concerns about the validity of the RBCT results and further research has suggested that the so-called “perturbation effect” in badgers diminishes after a few years [2]. This is getting confusing now, but surely policy is clear on some things. Like, the most obvious question, how often do badgers infect cattle? The whole justification of badger culling depends on how often those pesky critters directly infect cows. Well, the most recent answer is 5.7%, although it could be anywhere between 1% and 25%! [3] This is a massive scale of uncertainty to base a culling trial on, which surely suggests that more evidence is needed.

If badgers aren’t the answer though, what is? Recent and controversial (sensing a pattern here?) research suggests that our focus should be towards reducing spread of disease between cows themselves, rather than wildlife. Here, it is suggested that culling should instead take place of the cows, or more specifically entire herds that have tested positive for bTB [4]. Hurrah for badgers, but not so much for the farming industry as a whole, which already saw 25,000 cattle destroyed due to bTB in 2011 alone. The scientists involved admitted that they didn’t really consider how this would work practically or economically. It goes to show that whilst there might be an ideal scientific solution, whether this translates to policy practically is another discussion. Is it worth culling more cattle to squash bTB if it could completely destroy the industry as we know it? I can see where the government’s response to this might lie, and it is understandably too large a risk to take! Meanwhile, the approach with badgers is clearly not as effective as necessary, and whilst appealing to some, is neither as cost effective nor humane as it needs to be. There is no doubt that they do spread TB to cattle, whatever way we look at it, and clearly something needs to be done, but at the very least these animals should not have to suffer.

bTB is a vastly complex issue but both pros and cons of badger culling still lack convincing evidence in my eyes, and are surely not enough to build policy on. It is hoped that the method of culling will be much improved upon in the next trial; as if infected badgers are left in the culling area they may well spread the disease further. However, the sad fact is that tuberculosis infected areas are now so large across England and Wales, the badger culls would need to be on a huge scale. As the debate rages on in the media and politics, it is almost impossible to wade in to the badger culling arena and find some cold hard fact. The crossfire comes from every direction, with the badgers blithely unaware of the storm they have created. Just as well; things are likely to be equally uncertain for the foreseeable future.

Article by Claire Harris

References

[1] Independent Scientific Group on Cattle TB. Bovine TB : The Scientific Evidence [Internet]. 2007. Available from: http://webarchive.nationalarchives.gov.uk/20110911090544/

[2] Donnelly CA, Jenkins HE, Woodroffe R. Analysis of further data (to 28 August 2011) on the impacts on cattle TB incidence of repeated badger culling. PLos ONE. 2011. Available from: http://www.plosone.org/annotation/listThread.action?root=3161

[3] Donnelly CA, Nouvellet P. The contribution of badgers to confirmed tuberculosis in cattle in high-incidence areas in England. PLoS Curr Outbreaks. 2013; 5:1–16. Available from: http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3992815&tool=pmcentrez&rendertype=abstract

[4] Brooks-Pollock E, Roberts GO, Keeling MJ. A dynamic model of bovine tuberculosis spread and control in Great Britain. Nature. 2014; 511(7508):228–31. Available from: http://www.nature.com/doifinder/10.1038/nature13529