August 6, 2024

expert reaction to study on a farmer-led badger vaccination programme for bovine tuberculosis (bTB)

A study published in People & Nature looks at a badger vaccination programme for bovine TB.

Prof Malcolm Bennett, Professor of Zoonotic and Emerging Disease, University of Nottingham, said:

“This is an interesting and useful study. The authors rightly point out that it is a relatively small scale (although requiring a huge amount of work) but it backs up limited past experimental and field studies from Britain and Ireland showing that vaccination can drive down TB in badger populations.  An important aspect of the study is that vaccination was undertaken in partnership with local farmers and landowners in an area where culling has been the usual policy approach. The practicalities of vaccinating badgers have been demonstrated previously, but Defra licenses for vaccination were pretty much limited to areas where there was no TB in cattle (or badgers) and therefore no way to test whether or not the vaccination really worked, i.e. stopped transmission among and to badgers.

“Badgers and their role in the epidemiology of bovine TB are controversial matters, with the ‘debate’ perhaps generating more heat than light. So that people who might take very different views – and the paper is strong on this – worked together is itself a hopeful sign.  Some critics of the study might point out that the reason for vaccinating badgers is to prevent infection in cattle, and no such effect on the incidence in cattle was seen.  However, the best-controlled study of culling badgers found that after five years culling badgers, bTB only reduced by around 20% in cattle – and such a small effect would not be picked up in a study of this size.  What’s more, recent studies investigating transmission through comparing the sequences the Mycobacterium bovis (the cause of bovine TB) from both badgers and cattle suggests that cross species transmission rates are very low in both directions compared to within species transmission.  Of course, vaccination, if protective, will help prevent transmission both between badgers and to badgers (from cattle), unlike culling which relies on reducing the number of badgers and in consequence onward transmission. Those against culling might argue that if none of the badgers are infected, then they can’t infect cattle.  This is true, but the diagnostic assays used in the study is for antibody rather than infection, and so not sensitive enough to suggest that no badgers were infected at the end of the study, despite the reduction in those testing positive dropping from 16 to 0%.  Indeed, few vaccines, and particularly TB vaccines in any species, are completely protective.

“So in summary this is an important study, that fits with other evidence of the efficacy of badger vaccination and, importantly, shows that vaccination of badgers is practicable and acceptable in areas where bovine TB is endemic.  Now is the time for further, bigger trials. Coming soon after other studies showing that vaccination of cattle, if carried out over several years, can also be effective, maybe things are finally looking up for badgers, cattle and farmers.”

Prof James Wood, Infectious Disease Epidemiologist at the University of Cambridge and Co-Director of Cambridge Infectious Diseases, University of Cambridge, said:

“These results provide very positive, albeit small scale, findings in relation to the practicability of delivering badger vaccination against bovine TB. The paper is well written and the results are presented with appropriate levels of caution regarding their applicability. Of note is that none of the tested badgers at the end of the trial had antibodies to Mycobacterium bovis, the cause of bovine TB, but the small scale of the sampling means that there was poor statistical power to detect low levels of infection (e.g. a prevalence of 5% could have been missed).

“As the authors suggest, the findings vindicate that a larger scale study of badger vaccination, especially if farmer led, would be warranted. Scaling up this work is regarded by many as a particular challenge.”

‘Farmer-led badger vaccination in Cornwall: Epidemiological patterns and social perspectives’ by Rosie Woodroffe et al. was published in People and Nature at 05:01 UK time on Tuesday 6 August 2024.

DOI: 10.1002/pan3.10691

Declared interests

Prof James Wood: like the first author, Rosie Woodroffe, I provide independent advice on bTB control to Defra through its bTB partnership. I have held funding for bovine TB research from Defra, UKRI, FCDO and the Gates Foundation over the last 5 years.

Prof Malcolm Bennett: I have had funding from Defra to study TB in badgers in the ‘Edge’ area – ie where the cattle epidemic is expanding.