Badger cull science failure, denials and confusion

Since mid-March of this year, Defra has persisted with its claims regarding an independent scientific paper (1) that extensively analysed government data on herd bTB incidence and prevalence in the High Risk Area of England since 2010. The paper compares areas subject to badger culling with those that were not culled in each year of the controversial mass badger culls from 2013-2019.The paper concludes that badger culling has had no measurable benefit in bovine TB disease reduction, and Defra continue to claim that the paper is flawed.

Defra’s and Natural England’s position on this new analysis, including apparently that of the Defra chief scientist (CSA), Gideon Henderson and chief vet (CVO) Christine Middlemiss, seems to be based on their dislike of the statistical approach of the new paper, which differs from Defra’s traditional approach to badger cull evaluation.

Defra/APHA prefer to try to mimic the analytical methods of the Randomised Badger Culling Trial (RBCT). They take cull areas and compare them with different unculled areas, adjusting the data considerably to try to take account of the subtle or sometimes profound differences between compared areas. The new study took a different approach. This study looked at the same (or 97% of) herds over the years of study, so spatial differences were minimized. The analysis used data from herds when they were in unculled areas, and then again when they were in culled areas following their transition from one to the other. This simple approach, dictated by Defra secrecy over cull area locations, brings different strengths and requires less interference with the data. The approach enabled all the data available to be used, not just selected parts of it that might lead to skewed, inaccurate results and conclusions. Just look, for example, at the tangled caveats in the Downs paper from 2019 of just three culled areas and multiple unculled areas.

But Defra are very bold in their criticism : “the analysis was scientifically flawed. It manipulated data in a way that makes it impossible to see the actual effects of badger culling and therefore its conclusions are wrong.” Confident claims, but do they have merit?

Defra’s ‘inappropriate grouping’ claim

Defra’s main objection surrounds the issue of what they call ‘inappropriate grouping’ of data. This is the key point in the letter that they pressed the Veterinary Record journal to publish alongside the shortened printed version of the paper on 18th March. This was reported on in more detail here.

The problem in Defra’s claim  goes beyond the calculation mistakes in their 18 March Vet Record graph, that they subsequently (in May) apologised for, retracted & replaced with results more similar to those in the new paper. Defra’s presented data shows the herd bTB incidence reducing dramatically in the first and second years from cull commencement. This is the same data as used in the new paper, so this is no surprise. But the point is, Defra say that you cannot group data from years one and two of culling with that from the third and later years because the level of decline in years one and two are too small, and this will remove all signs of effect. However, the Defra graphs do not show that the level of decline in years one and two in cull areas is small, and this is the contradiction that they refuse to talk about.

Similarly, the analysis presented by APHA staffer Colin Birch at the IVSEE16 conference in Nova Scotia, Canada earlier this month, (2) Figure 1, does not show that the level of decline in years one and two is small either.  It showed sustained decline  over 4 years, with a similar level of decline each year right from the start. Yet it provided no comparison of data from the 25% of the HRA that remains unculled. To the audience’s complaint, here, he quite wrongly tried to attribute these declines to badger culling.

Figure 1. Marginal effects on confirmed bTB incidence rate associated with duration of badger control. Error bars indicate 95% confidence intervals. From Birch abstract ISVEE 2022

So where did the ‘inappropriate grouping’ comment come from? Well, it is likely that Defra have fallen back on RBCT advice and the 2006 and 2007 (3,4) papers that presented the findings of 10 treatment-control area comparisons of small cull areas. These papers showed large variation in the estimated levels of decline in bTB herd incidence in culling areas, so much so that the confidence intervals (CI) on the presented graph figure 2A (Figure 2.) passed through 0 in most years.

Figure 2. Fig 2 (A) from Donnelly et al. 2007

Estimated average declines were 3.5% in year 1 and 12.8 % in year 2, with 39% in year 3. So, you can see that by using the RBCT as a prior reference source (this the point of reference used in Defra/APHA documents), there could be an expectation that there isn’t much disease reduction in years 1 and 2.  However, while the drop may not  have been projected to show significance until year 3, the decline trend should be present and visible by the end of year 2.

So looking again at Figure 1 (Birch 2022 abstract), government is now turning this on its head and claiming, in contradiction, that bTB incidence among cattle herds reduced by around 15% per year in each of the first two years of badger culling.

Defra’s unsupported point was also made by Cambridge vet James Wood on Radio 4 Farming Today on 19th March 2022, but it simply doesn’t stack up. Even if there was just a modest (say 8% average) annual benefit in years 1 and 2, it would still have shown up in the new paper analysis in comparison with unculled areas when using such a huge amount of data, as is possible using the 2016 onwards rolled-out HRA badger culls.

Ridiculously, Defra have previously claimed substantial benefit in years 1 and 2 from the post-2013 cull data, and used this as a basis for claiming badger culling was working. They did this spectacularly in 2017 with the APHA Brunton et al. paper (5) that suggested benefit 32% in Somerset, and 58% benefit in Gloucestershire in the first two years, and again in 2019 with the notorious and heavily caveated Downs et al. paper using data to-2017 (6), that was undone by the 2018 results (7), also published in the veterinary literature, with slightly more claimed benefit (Table 1 below).

Pilot cull Area 2013-2017

Brunton et al. 2017

Downs et al. 2019

Percent est. in Yrs 1 and 2

Gloucestershire 1

58%

66%

88%

Somerset 1

32%

37%

86%

Table 1. Claimed benefit from badger culling in Brunton et al (5) and Downs et al (6).

The Defra Minister and MP’s were told that badger culling was working based on this claimed year 1 and 2 benefit. They told parliament and the public in no uncertain terms that badger culling was working, so they can’t really go back on it now without losing face. James Wood also told Countryfile views that he thought the data showed badger culling was working based on the first two-years of pilot data. So, who is talking in riddles now?

The problem that Defra have, and it is why they have clammed up to the scientists and media, is that if Defra/the CSA/CVO were to communicate beyond the bold claims made in March in Vet Record and on the Defra media blog, they would lose the argument. Defra have written to the first author saying they are not prepared to discuss the matter. Caught, it seems, between their scientific advisors’ comments, legal undertakings to monitor efficacy and policy-mania to keep on badger culling in the face of failure. Even Natural England have gone as far as saying that the situation is unclear “Because these different control measures are being implemented simultaneously, it is difficult to determine the relative contribution each of them is making to disease reduction.”

Insufficient data points?

One argument Government have used to dismiss the validity of the new paper is that it has insufficient data points. While the new study does has few data points, each data point summarises a huge amount of data representing hundreds or thousands of herds, helping to obviate the kind of problems caused by the smaller data sets of APHA studies. The approach is equally or more valid. It did, after all, pass rigorous peer-review (4 reviewers including at least two epidemiological statistical specialists) in a leading veterinary journal.

Basically, Defra lost both arguments, rebutting the paper in short measure, and it is astonishing that CSA Henderson CVO Middlemiss were given this position to hold, let alone to defend. No wonder Middlemiss got muddled on Farming Today over it on 25 May.  This problem is now many months old and Defra and Natural England have carried their unsubstantiated criticisms along to justify the licensing of further supplementary culling licences in May and  intensive culling licenses from August. This means the killing of tens of thousands more largely healthy badgers over the next four years to add to the roughly 200,000 that have been slaughtered to date. This flies in the face of peer-reviewed science, against which Defra have failed to produce anything credible or comprehensive that is peer-reviewed.

At the Birdfair State of the Earth panel debate on 15th July of this year, the retired badger cull architect Prof Ian Boyd: Chief Scientific Adviser at Defra (2012-2019) commented: “Well, if badger culling isn’t working it shouldn’t be done, that’s absolutely clear.  I think there is still an ‘if’ there, but I suspect that the evidence is suggesting it doesn’t work.”

And Prof David Macdonald at Oxford, who chaired the Natural England Scientific Advisory Committee for many years, and who called the Pilot culls an ‘epic fail’ has commented in Chapter 16 of his new Oxford University Press book ‘The Badgers of Wytham Woods’: “ it is hard to see how Middlemiss and Henderson land a knock-out punch on Langton et al’s analysis..”

There is nothing very dramatic or complicated here in Defra’s last stand. Defra has lost the scientific argument. They must surely now face abandoning the failed badger culling policy altogether. They really should talk openly about it.

References

1. Langton TES, Jones MW, McGill I. Analysis of the impact of badger culling on bovine tuberculosis in cattle in the high-risk area of England, 2009–2020. Vet Rec 2022; doi:10.1002/vetr.1384.

2. Birch, C. Prosser, A. and Downs S.  An analysis of the impact of badger control on bovine tuberculosis in England. Abstract oral presentation to ISVEE16, Halifax, Nova Scotia, Canada. 2022.

3. Donnelly, C. A. et al. Positive and negative effects of widespread badger culling on tuberculosis in cattle. Nature 439, 843–846 (2006).

4. Donnelly CA, Wei G, Johnston WT, Cox DR, Woodroffe R, Bourne FJ, Cheeseman CL, Clifton-Hadley RS, Gettinby G, Gilks P, Jenkins HE, Le Fevre AM, McInerney JP, Morrison WI. Impacts of widespread badger culling on cattle tuberculosis: concluding analyses from a large-scale field trial. Int J Infect Dis. 2007 Jul;11(4):300-8. doi: 10.1016/j.ijid.2007.04.001. Epub 2007 Jun 12. PMID: 17566777.

5. Brunton LA, et al. Assessing the effects of the first 2 years of industry-led badger culling in England on the incidence of bovine tuberculosis in cattle in 2013–2015. Ecol Evol. 2017;7:7213–7230. doi: 10.1002/ece3.3254. – DOI – PMC – PubMed.

6. Downs S H, Prosser A, Ashton A, Ashfield S, Brunton L A, Brouwer A, et al. Assessing effects from four years of industry-led badger culling in England on the incidence of bovine tuberculosis in cattle, 2013–2017. 2019. Sci Rep. 2019; 9:14666. 
https://doi.org/10.1038/s41598-019-49957-6. Accessed 16 June 2021

7. Mcgill I, Jones M. Cattle infectivity is driving the bTB epidemic. Vet Record. 2019; 185(22), 699 – 700. 
https://pubmed.ncbi.nlm.nih.gov/31806839/.

Why Defra’s Badger Vaccination Proposals Risk Perpetuating Further Culling

Today, the Government has released its plans for a new and simplified licencing system to facilitate badger vaccination. While on the face of it these plans appear to be helpful for those who wish to see an end to the culling of badgers, wildlife campaigners are concerned that they will be used as a smokescreen, to perpetuate further ‘reactive’ culling, and to prevent those who wish to protect badgers from speaking out against the culls.

Indications are that the government aims to allow vaccination in 2 of around 60 areas where badgers will be killed in 2022, with any further areas covering but a small proportion of the designated High Risk Area for bovine TB in cattle in the west of England. There are concerns that there may be restrictions, such as vaccination being promoted only once badger numbers have been decimated, and ‘gagging orders’ placed upon those who sign up to government funding – including that badger protectors would no longer be able to speak out against the badger cull.

The Government’s announcement claims that its badger vaccination plans form part of its long-term strategy to eradicate bovine TB in England by 2038. However, the strategy relies on the assumption that badger culling is working to reduce bovine TB, when current peer-reviewed scientific evidence suggests otherwise.

Government also claims that badger culling is being phased out. The reality is that it continues to be expanded, with 29 supplementary culls authorised yesterday, 25th May. A further ten new intensive badger culling zones are expected to be announced later in the year. The expected kill figure over the next 4 years is up to another 100,000 badgers. The Government wishes to retain the option to continue killing badgers in perpetuity under its proposals for ‘epidemiological culling’ which has, as anticipated also so far failed to reduce bTB herd breakdowns.

There are several reasons why vaccinating badgers might be desirable – principally to prevent bovine TB spilling over from cattle into healthy badger populations and to protect individual badgers from disease. However, there is little evidence to suggest that vaccinating badgers will prevent or reduce bovine TB among cattle – just as with culling, the move to promote the vaccination of badgers is based on the false assumption that badgers are a significant source of TB for cattle, and that badger intervention is necessary to control cattle TB, when the evidence suggests tighter cattle measures are the answer.

There are also good reasons why vaccination of badger populations previously subjected to culling is unlikely to be successful. Badger culling will reduce a population, but there is some evidence that it may increase the prevalence of TB among surviving badgers. Also, surviving badgers may be trap shy making them much more difficult to trap and vaccinate.

Ecologist Tom Langton, one of the authors of a new peer-reviewed study, With vets Mark Jones and Iain McGill has been closely monitoring & challenging government bTB strategy failures, said:

It is depressing to see the smokescreen approach to Defra’s badger cull policy continuing. There is no evidence that vaccinating badgers, particularly after culling has massacred the population, can hold any benefit to bTB disease eradication in cattle and this was confirmed by the Godfray Review in 2018. Government is trying to normalise badger culling long-term, by initially claiming to the public that it is being phased out, when the plan is to perpetuate the so-called ‘epi-culling’ – the failed reactive culling of old. 

Failed government tactics could see the killing of thousands of badgers per year to 2038 and beyond. It is a disgusting, unethical slaughter of wildlife. It circumnavigates the legal protection of badgers under The Protection of Badgers Act 1992 and does nothing for farmers or cattle. Badger vaccinators should not be induced to mislead farmers into thinking that badger vaccination is known or expected to help control bovine TB in cattle. This is particularly unwelcome as our recently published, extensively peer-reviewed paper using government data* shows how badger culling intervention has failed to influence bovine TB herd breakdowns during the last decade, with the Chief Vet and Scientific Advisor putting out botched data and flawed argument to try to cover their trail.”

Veterinary surgeon Dr Mark Jones, another author of the recent science paper, said:

“From the lockdowns we have all suffered since 2020, we are all only too aware of the movement restrictions, accurate testing and vaccination that were necessary to control Covid 19. These kinds of measures need to be rigorously applied to cattle if bovine TB is to be successfully brought under control. Our recent peer-reviewed research clearly demonstrates that culling badgers is not reducing bovine TB among cattle herds, and while there may be good reasons to vaccinate badgers, it’s highly unlikely that badger vaccination will help control TB in cattle, and the promotion of badger vaccination continues to frame badgers as the culprit. This badger blame game needs to end.”

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