Christine Middlemiss, Gideon Henderson and the Defra bovine TB data fiasco

In March 2022 the Chief Veterinary Officer (CVO) Christine Middlemiss & Chief Scientific Advisor (CSA) Gideon Henderson joined Defra Media Centre in attacking a peer-reviewed, freshly published scientific paper on bovine TB control (Langton et al.), stating that they thought it was flawed, and had ‘inappropriate’ analysis, see here.

The graph the CVO & CSA produced (top right) looked odd, and the authors of the original paper immediately suspected an error in the data, and wrote to Defra with an enquiry to this effect.  In addition, much of their written rebuttal seemed invalid. Further, the CVO wrote a personal blog highlighting her criticisms of the new paper. The blog then received a number of posted comments from external observers and academics which reiterated the papers’ authors’ concerns about potential errors in Defra’s analysis and incorrect conclusions. A response to the CVO & CSA from the authors of the paper was printed in Vet Record on 02 April, see here.

It took more than six weeks before Defra admitted that it had got it wrong and published a new graph of data (above, bottom right). But they maintained that this did not change their overall conclusions about the new paper; basically that it was ‘wrong’. They did not respond to the rebuttal arguments that the authors put forward in the 02 April issue of the journal Veterinary Record. On this there is still strange silence.

The authors of the paper had a further letter published in Vet Record on May 21st responding to Defra’s admission of data errors and their replacement graph. You can read this here

This week, CVO Christine Middlemiss made a small adjustment to her blog, but did not change her faulty graph. She added some wording to the following paragraph (in bold).

“Our analysis indicates a clear reduction in OTFw cattle breakdowns, relative to unculled areas, in culled areas from cull year 2 onwards (Fig 1). For example, TB incidence in the areas where culling started in 2016 has dropped from 17.2 OTFw breakdowns per 100 herd years at risk in 2016/17, to 8.7 in 2019/20.

Similarly in the areas where culling started in 2017 it has dropped from 15.3 in 2017/18 to 8.4 in 2019/20.

In contrast, in the parts of the high-risk area (HRA) where no culling took place, incidence has only fluctuated slightly from year to year, from 10.9 in 2015/16 rising to 12.8 in 2016/17 before returning to 10.9 in 2019/20.”

It is a shame that the CVO does not seem to have grasped that the first bar in the graph represents the first year data after culling and not pre-cull incidence. Incidence levels before culling began are missed off, and these better shows the pattern of change in the first two years that they focus on.

The CVO & CSA’s main criticism of the new paper is that (they imply) bTB does not come down enough in the first two years for those years to be grouped with later years of culling. Looking at their graph, this is clearly not the case and the CVO and CSA’s position is a paradox and nonsense. There is a drop in culled and unculled areas if you examine all the culled and unculled data, and not just a sample of unculled (never-culled) area. The steady decline in incidence, as shown in the Langton, Jones and McGill paper, is attributable to cattle testing and movement control measures. Defra’s attempt to show otherwise falls at the first hurdle. It is something Middlemiss and Henderson seem reluctant to address. It is understood that Defra intend to ignore their own faulty response, and endorse an APHA study at a disease conference in July in Canada as justification to carry on culling in September.

Christine Middlesmiss doubled down on her position in an interview on Farming Today on 26th May (the focus of which was Defra’s badger vaccination licensing scheme), using very strong language and stating that in the Langton, Jones and McGill paper, “the whole methodology was wrong and so the conclusion was wrong.” Again, she claimed that the authors had not used a robust methodology to examine and assess it and therefore the conclusions are wrong, they’re not scientifically valid.”

This is a bold claim about a rigorously peer reviewed paper in a leading scientific journal, and one that it could be said she should be able to clearly and concisely articulate in a debate, or at least to the authors. It is not good enough for the CVO to just claim, as she did in her interview, that “it is complex“.

Further she said we believe that culling is effective, apparently relying on faith rather than understanding of published science. She must be able to explain her reasoning for dismissal of peer reviewed science. She also said that “It’s not absolutely my decision to release it [the data], implying political interference? The authors are still waiting for a response to their April invitation to discuss the CVO’s criticism with her.

You can listen to the CVO’s interview on Farming Today, available here.

The CVO & the CSA must look again and accept the findings of the new robust peer-reviewed research. Prevailing science shows the current badger culling policy to have failed, with no detectable impact from it on the incidence of bovine TB in cattle herds in the High Risk Area. The 29 Supplementary Badger Culling licences authorised this Wednesday were issued on the back of a government veterinary service in denial.

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Badger culling and BTB data:

Middlemiss and Henderson say sorry for getting it wrong

As previously blogged on 18th March here, the respected journal Veterinary Record published a new scientific appraisal of the effect of badger culling on bovine tuberculosis (bTB) in the High Risk Area of England using government data collected from farmers and vets for over a decade. This extensively peer reviewed paper is available open access online, in full here. The paper concluded that badger culling has not been associated with reductions in bovine TB (bTB) incidence or prevalence among cattle herds.

Alongside a one-page summary of the paper in the Vet Record print edition, the Chief Veterinary Officer (CVO) Christine Middlemiss and Chief Scientific Adviser (CSA) Gideon Henderson published an un peer-reviewed letter rebutting the paper’s main findings. They produced their ‘alternative analysis’ in the form of a graph, and claimed it showed that badger culling was ‘working’ in reducing bTB in cattle. The graph indicated very rapid declines in bTB in culled areas following the commencement of culling, with little change in unculled areas. The CVO Christine Middlemiss also posted a blog on the Defra website using the same graph.

The graph could not be reconciled with publicly available data. There followed repeated requests for Defra to supply the data and methodology, but these were not met. Then last week, six weeks after publication, Middlemiss and Henderson  sent an email to the authors of the original paper stating:

“Following your recent correspondence about how incidence in unculled area was calculated we have re-examined our analyses and discovered an error we wish to bring to your attention.  The incidence in the area unculled throughout the period was calculated incorrectly. The incidence in cull areas is unchanged. We attach a corrected graph, with the corresponding data and workings as previously requested. We apologise for this error..”

A new graph was provided (see below). After further requests and delay, we have data from Defra to allow us to reproduce their corrected graph but not to check its origination. Defra’s original published graph shows bTB herd incidence higher in unculled areas in four of the five years, while in the new one it sits at the same levels as in culled areas.

As previously, Defra are still disregarding huge areas of unculled land in their blue-bar ‘never culled’ areas, which is problematic. Notably, however, the error bars between ‘culled’ and ‘never culled’ overlap more extensively, so the difference between the two is unclear.  It seems that Defra’s corrected calculations corroborate the findings in the Langton et al., and that there has indeed been no significant impact from badger culling on bTB incidence among cattle herds.

Defra’s graphs from their 19th March letter and 5th May email:

19th March (withdrawn): Unculled incidence is higher than culled in 4 of the 5 years.
5th May: Now incidence levels in unculled areas are shown well within same levels as culled areas.

Defra’s “never culled” areas are likely to include significant land areas where bTB is less of an issue, with landowners having a lower incentive to coordinate a cull, whilst the “waiting to be culled” portion of the unculled area will have significant areas where bTB is a major problem. Defra is engineering a highly selective use of the available data. It adds up to a misleading picture that is bringing Defra into disrepute. Without access to their full data source, it is not possible to fully understand their rationale.

Further, when you don’t limit the data as Middlemiss and Henderson did, and add “all culled areas” bars (green), and include 2013/14 and 2014/15 (see below), it shows the true extent of decline of bTB incidence in unculled areas that mirrors culled areas.

Revised Defra data with Langton et al’s unculled green bars

The 5th May ‘apology’ email from Middlesmiss and Henderson maintains that “this does not change the overall argument in the letter”, yet over six weeks on, they have failed to address a response by the authors to this criticism (published in Vet Record on 2nd April). This response shows that their main argument on ‘incorrect grouping’ of data does not undermine the peer-reviewed statistical analysis.

Specifically, Middlemiss and Henderson claimed that using data from the first two years of culling ‘masks’ any overall effect from badger culling, making it ‘impossible to see’. But Defra’s counter argument rests upon a steep decline in herd incidence over those first two years! Defra’s argument falls and the answer is that taking all the data, herd breakdowns reduce in culled and unculled areas at similar rates, due to cattle measures both before and after badger culling is rolled out.

So, the senior Defra scientists have no answer, and continue to use delaying tactics, while still providing only limited access to the available data that might enable independent researchers to assess their new graph. This is shocking and does not serve the public interest. Cattle-based measures implemented from 2010, and particularly the introduction of the annual tuberculin skin (SICCT) test have been responsible for the slowing, levelling, peaking and decrease in bovine TB in cattle in the High Risk Area (HRA) of England during the study period, before badger culling was rolled out in 2016.

Last week, the authors of the badger culling paper, Tom Langton, Mark Jones and Iain McGill wrote to George Eustice (read here) about the continuing fiasco and asking for badger culling to be suspended and for additional clarification and dialogue.

This is what all stakeholders and the public deserve. Clear, open government responding to the facts in an honest and professional way.  No more delay, secrecy, and avoidance of the real issues. It is time things changed.

On Friday 20th May, the paper’s authors response to Defra’s apology and clarification was published in Vet Record. You can read this here:

Farming Today featured the debate around Defra’s data miscalculation on 20th May; you can listen here from 7:18 minutes in.

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