Torgerson Paper Exposes Deep Flaws in Pro-Culling Analysis

Badger Trust welcomes the publication of a new peer-reviewed paper, which dismantles the statistical basis of claims that badger culling reduces bovine tuberculosis (bTB) in cattle. Professor Paul Torgerson and colleagues’ re-evaluation of the Randomised Badger Culling Trial (RBCT) data identifies fundamental errors in analysis — mistakes that undermine the case for continued badger culling.

Professor Paul Torgerson and colleagues [1] have raised serious concerns about the reliability of the RBCT reanalysis by Mills et al., 2024 [2], arguing that fundamental flaws in both the data handling and statistical methods undermine the claim that culling reduces bTB in cattle. The issues raised relate to key areas, including the following: 

Use of Counts Instead of Rates

Mills et al. base their conclusions on counts of herd breakdowns, without properly adjusting for the number of herds in the area or the time each herd was observed (i.e. no incidence rates). For example, if Area A has 200 herds and 10 breakdowns, and Area B has 500 herds and 12 breakdowns, counts would suggest Area B has a bigger problem. Rates would show Area A has a higher incidence per herd. Torgerson points out that this is epidemiologically flawed: herd breakdowns should be expressed as rates per herd-year, not simple counts. When properly analysed using incidence rates, the effect of culling disappears — suggesting that previous findings of benefit are invalid.

"More plausible approaches to RBCT data analysis strongly suggest that there is no effect of proactive badger culling on the herd incidence of bovine tuberculosis."

Bayesian Analysis Errors

Even more worrying are the coding and reporting mistakes in the Mills team’s use of Bayesian models — the kind used to estimate how likely it is that culling has any impact. Torgerson’s team reviewed eight of these models and found that five had serious flaws. In two key cases, the models were supposed to adjust for how long herds were at risk (a crucial factor), but the code left this out entirely — a basic error that undermines any conclusions drawn. These mistakes mean that Mills et al.’s headline claim — that badger culling reduces bTB in cattle— cannot be supported.

When Torgerson’s team used models that fit the data best — including simpler, more transparent versions — they found no meaningful benefit of culling at all. This doesn’t just challenge Mills’ conclusions; it undermines the scientific case for the entire culling policy. If the numbers don’t hold up, the policy shouldn’t either.

Torgerson and his team raise other serious concerns. They point out that some of the models used by Mills were simply too complex for the small amount of data available, meaning they may have picked up patterns that aren’t real. Additionally, Mills didn’t properly compare their models to basic alternatives that assumed culling had no effect — a key step in checking whether the results really stand up. Taken together, these problems suggest the analysis behind the pro-culling argument is not just flawed in parts — it is fundamentally unreliable.

What is the Randomised Badger Culling Trial (RBCT)?

The RBCT was a major government-funded study launched in the late 1990s to test whether badger culling could help control bTB in cattle. Spanning 30 trial areas across England, it compared the effects of widespread culling, localised ‘reactive’ culling and no culling at all. The study concluded that proactive culling could reduce bTB rates in cattle, but increases in bTB rates outside of the culling areas were also discovered due to social perturbation. Furthermore, despite serious concerns raised by the scientists involved about how their results translated into policy [3], the trial became the foundation for much of the policy that has led to over 247,000 badgers being culled in England. 

In 2024, Professor Torgerson and colleagues revisited the data of the RBCT using a range of statistical models, and concluded that the original analysis was flawed, as they could find no evidence to support an effect of badger culling on confirmed bTB herd incidence [4]. In response, Mills et al., re-examined their own work, and defended their approaches [2]. Now, this latest paper by Torgerson et al. further highlights the major inadequacies with the RBCT analysis [1].

What Next?

These findings demand immediate action. Badger Trust calls for:

• A formal audit of the statistical analyses used to justify the culling policy.

• A moratorium on the licensing of new culls and immediate suspension of existing licences, pending a fully independent review.

• Greater investment in cattle-focused interventions — enhanced biosecurity and improved testing.

  
  

The Torgerson paper is not an academic disagreement — it exposes fundamental errors in the evidence base driving a controversial and damaging wildlife policy. It is now the duty of policymakers and scientists to act on these findings, and ensure future bTB strategies are grounded in robust, transparent science.

References:

1. Torgerson, Paul R., Hartnack, Sonja, Rasmussen, Philip, Lewis, Fraser I., O’Donnell, Peter, & Langton, Thomas E. S. (2025). Randomised Badger Culling Trial—No effects of widespread badger culling on tuberculosis in cattle: Comment on Mills, Woodroffe and Donnelly (2024a, 2024b). Royal Society Open Science, 12, 241609

2. Mills, Cathal L., Woodroffe, Rosie, & Donnelly, Christl A. (2024). An extensive re-evaluation of evidence and analyses of the Randomised Badger Culling Trial (RBCT) I: Within proactive culling areas. Royal Society Open Science, 11, 240385.

3. Bourne, F. J., Donnelly, C. A., Cox, D. R., McInerney, J. P., Gettinby, G., Morrison, W. I., & Woodroffe, R. (2010). Bovine Tuberculosis: The Government’s approach to tackling the disease and consultation on a badger control policy. Independent Scientific Group on Cattle TB 1998‐2007. Available from: www.bovinetb.info/docs/isg_response.

4. Torgerson, P. R., Hartnack, S., Rasmussen, P., Lewis, F., & Langton, T. E. (2024). Absence of effects of widespread badger culling on tuberculosis in cattle. Scientific Reports, 14(1), 16326.