The latest development in the long-running TB in cattle saga has been the announcement that frequent testing of cattle is more effective for controlling the disease than culling badgers. Wales, going for the slightly less controversial option of testing herds at least once a year rather than killing a protected species, has seen a decrease in the number of cattle slaughtered due to TB, and Scotland has been TB-free since 2009. England meanwhile has been piloting badger culling for the past few years and has a variable testing policy, with herds in some areas only tested once every four years.
With this being such an emotional issue, and one where the results from one trial is being bandied about by both sides as being proof that badger culling both does and doesn’t work, I thought I’d take a look into the issue and why everybody thinks that they’re in the right.
Managing bovine TB
Mycobacterium bovis isn’t the main cause of TB in humans, with cooking meat and pasteurizing milk removing the risk of infection, but it is a huge issue for the farming industry with an estimated £100 million spent last year on managing bovine TB in England.
The UK government releases frequent results for bovine TB prevalence, with the latest report saying that ‘there has been an overall long-term upward trend in the incidence of TB in cattle herds since [January 1996]’. Both England and Wales are aiming to be TB-free by 2038, with Defra releasing in 2014 a policy paper on its strategy to achieve this, which places significant emphasis on managing the TB reservoir in wildlife; referencing the culling of water buffalo in Australia, white-tailed deer in Michigan, brush-tailed possum in New Zealand and badgers in the Republic of Ireland.
‘Based on first veterinary principles and supported by modelling, one would expect culling to be more effective than a badger vaccination programme; that is why I have decided to continue the policy of badger culling in endemic areas learning lessons from the pilots in 2013,’ says Secretary of State for Environment, Food and Rural Affairs, the Rt Hon Owen Paterson MP, in his introduction to the report, saying that although the government will invest £24.6 million in the development of effective TB vaccines for both cattle and badgers, the badger vaccine, available since 2010, would not tackle the badgers in endemic areas already infected.
Badger culls and the Randomised Badger Culling Trial
So as far as England’s current ruling party is concerned, badger culling is a necessary part of the process of eradicating TB. However, both scientific and public opinion is against them. Badger culling is a highly contentious issue – far more so than the culling in New Zealand and Australia where the brush-tailed possum and water buffalo are introduced species and seen as pests that also damage ecosystems and endanger indigenous animal populations. In Michigan, US the white-tailed deer is already hunted – an industry which generated $15.1 million for the state in the 2014 hunting season.
Killing badgers has completely polarised opinion. A Protection of Badgers Act was passed in 1992 and people love them. But in the Republic of Ireland, badger culling has been taking place since the 1980s with relatively little fuss from the public, and bovine TB has been decreasing. However, as this article points out, it is difficult to determine the effect of culling badgers on bovine TB when other control methods have also been used and in Northern Ireland cases have dropped despite no culling taking place.
What seems to be key to the whole discussion for both sides of the England debate is the Randomised Badger Culling Trial (RBCT), which took place 1998-2006 and was designed to investigate the spread of TB between cattle, badgers and other wildlife. The trial included three measures: culling of badgers at the site of a bovine TB outbreak, culling of badgers in an area irrespective of there being an outbreak or not, and no culling.
Unfortunately for Defra, the introductory letter at the beginning of RBCT’s final report says: ‘First, while badgers are clearly a source of cattle TB, careful evaluation of our own and others’ data indicates that badger culling can make no meaningful contribution to cattle TB control in Britain. Indeed, some policies under consideration are likely to make matters worse rather than better. Second, weaknesses in cattle testing regimes mean that cattle themselves contribute significantly to the persistence and spread of disease in all areas where TB occurs, and in some parts of Britain are likely to be the main source of infection. Scientific findings indicate that the rising incidence of disease can be reversed, and geographical spread contained, by the rigid application of cattle-based control measures alone.’
The study found that although proactive culling (killing badgers before an outbreak in cattle) reduced the incidence of TB, this was offset by badgers ranging more widely as they were disturbed, or immigrating into the culled area, with the result that ‘M. bovis prevalence in badgers rose substantially in response to culling, and infection became more diffuse across the landscape. Reactive culling caused smaller reductions in density, but seems to have had similar consequences for M. bovis prevalence.’
So if an eight-year investigation run by an independent scientific group results in the recommendation that badger culling isn’t economically feasible, increases the prevalence and spread of TB in badgers across an areas, and cites an earlier 1986 report looking at the gassing of badgers over a 20-year period that showed that ‘there was not sufficient evidence to say that gassing had had any discernible effect in reducing TB breakdowns’, why is Defra still culling badgers?
In the government’s 2010-2015 bovine TB eradication plan, it doesn’t go into the evidence it’s using, preferring to instead point to three separate sources: an article written by Defra’s chief scientific adviser Professor Ian Boyd and chief veterinary officer Nigel Gibbens, the conclusions of a Defra scientific experts’ meeting held in 2011 and another article written by Ian Boyd on Defra’s Tackling Bovine TB blog.
The Guardian article doesn’t actually cite or link to any actual results, just saying that evidence from Australia and New Zealand shows that to control the disease in cattle, the disease must also be managed in the wild reservoir as well. However, in Boyd’s second article, he says that an update to the RBCT report using an additional two years of cattle testing data showed that the initial detrimental impact of badger culling on the incidence of bovine TB in the immediate surrounding area as badgers moved around, disappeared within 12-18 months. However, in this additional analysis, no further elaboration takes place on the original report’s finding that the financial cost of culling means that it isn’t an economically viable option.
What’s happening now?
At the beginning of this month, pilot culls began in Dorset, Somerset and Gloucestershire, for the third year running in the latter two counties. Rather than focusing on scientific data like the RBCT (shot badgers haven’t been tested for TB), Defra is instead looking into how humane the method of controlled shooting is (where a badger isn’t first trapped), how effective in terms of badger removal, and how safe it was (due to protesters attempting to interrupt the shooting).
The 2013 cull in Gloucestershire and Somerset didn’t go well for Defra, with trained marksmen failing to reach the target of killing 70% of the badger population – the figure reached by the RBCT to result in reduced disease in cattle herds – and an independent panel review concluded that between 7.4% and 22.8% of badgers shot were still alive after five minutes. The cull therefore didn’t meet the criteria for effectiveness and humaneness that Defra set.
The 2014 cull, taking place in the same areas, didn’t do much better, with results showing that in Gloucestershire, just 274 badgers were shot when the minimum target was 615. Defra subsequently released a statement saying that this was due to ‘unlawful protest and intimidation’. In Somerset the minimum target was surpassed with 341 badgers shot, but Professor Rosie Woodroffe, who was involved with the RBCT, said that the target was ‘rubbish’ and not set in line to kill 70% of badgers. Results from the RBCT, which the government is basing its culling programme on, explicitly says that killing fewer than this percentage will increase the spread of TB and make the situation worse. There was also action in the courts as protesters brought legal action against the government for not appointing independent monitoring of the cull as it had the first year, with the case eventually dismissed.
So the cull is starting again this year, having been extended for the first time to Dorset. Queen guitarist Brian May’s not very happy about it, saying he will bring legal action if the culls go ahead. Many influential experts aren’t happy either. Professor Ranald Munro, chair of the independent expert panel who monitored the 2013 cull, Lord Krebs, who studied the link between badgers and the spread of TB and penned the influential 1997 Krebs report and Professor John Bourne, who led the RBCT, are among those who have penned an open letter recently, clearly stating once again that: ‘The efficacy of badger culling was not supported by the ten-year, £50 million government funded field trial (the RBCT).’ They go on to point out that the previous two years have failed to meet the effectiveness or humaneness criteria, the cull is very expensive, costing over £5000 to kill one badger, and that cattle to cattle transmission is of ‘central importance’.
‘Control strategies require wider recognition of other factors, including the limitations of the tuberculin test, more rigid cattle movement controls and heightened on-farm biosecurity,’ they continue, adding: ‘These measures are far more effective at reducing tuberculosis in cattle.’
There is support for the cull though, mainly from farmers, with Farming Minister George Eustice telling the Commons that applications have been received from north Devon and Herefordshire to expand the cull next year, which may mean that the culls could be extended in subsequent years. Comparisons with Wales’ tactics of handling TB are becoming key in the discussion over culling, particularly around cost as £17 million has so far been spent on the culls, but Eustice continues to say that culling is necessary, alongside other measures like vaccines.
Vaccination
Vaccination of both cattle and badgers may be a better way to reduce TB say Munro and the other experts in their open letter. Wales has been vaccinating badgers since 2012 as part of a collection of measures to reduce bovine TB, including the yearly testing which set me off on this article. England started its own badger vaccination scheme last September in areas that are outside high risk TB areas, but are at risk of spreading disease.
Brian May is pushing this option, having launched the Badger and Cattle Vaccination Initiative last year. The website points to a 2012 study by Carter et al, which showed that vaccination led to a significant reduction in the risk of badgers and their cubs becoming infected. But evidence is scarce, so this initiative was set up to further research.
Cattle TB vaccination is currently banned by the EU, with problems arising around vaccinated cattle testing false-positive for TB when the tuberculin skin test is used. Again, further research and long-term trials are needed.
Continue the cull?
For the time being it looks like Defra’s sticking with the cull as part of its overall strategy despite widespread condemnation by a whole raft of wildlife charities, scientists and think tanks, the majority of the public polled by YouGov being against it and Chris Packham risking the wrath of the BBC to speak out against it.
Earlier this year the Badger Trust managed to get documents released that warned of the ‘severe risks’ posed by the badger cull three years before they began. However, Prime Minister David Cameron maintains that despite badger culling being his ‘most unpopular policy’, it is still ‘the right thing to do.’ Newly-elected Labour leader Jeremy Corbyn though has spoken out against the cull in the past and ending the cull was in Labour’s manifesto for the election earlier this year. Politics is clearly playing a major role, with the YouGov poll showing increasing numbers of Conservative voters being in favour of the cull.
In the end, it seems that culling will continue, and more than anything this issue shows how one piece of evidence can be presented and used for completely opposite arguments.
Hypervelocity Science 
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