Q1. Can badgers get bTB?

Yes, but so can cattle, goats, sheep, pigs, horses, alpacas, llamas, deer, dogs, cats, rats, humans etc..

Q2. Do badgers pass bTB on to other badgers?

Presumably. I have not found any papers explicitly confirming this. It is assumed they do (all other animals seem to do this) and would be surprising if it didn’t happen. The question is perhaps, how easily and how often. There seems a lot of uncertainty about this.

Q3. Does bTB persist in badger populations without regular re-infection from cattle?

Unknown. No clear evidence that it does. “Crucially, it is not known whether TB is self-sustaining in badgers” (SGM, 2008).

Q4. Do badgers pass bTB to cattle?

Possibly. No irrefutable evidence of direct badger to cattle transmission. More guilt by association. Evidence that large scale removal of badgers in a defined area can lead to a reduction in bTB (Randomised Badger Culling Trial - RBCT). Therefore, it is assumed that the badgers were responsible for some of the bTB in cattle. One study showed that in laboratory conditions of close proximity, bTB can move from badgers to cattle, although it was not established exactly how.

Q5. How is bTB transmitted to cattle from badgers?

Nobody knows. The route of transmission is unknown. Strains of bTB are localised and the same strain has been found in badgers and cattle in specific locations. Most bTB lesions are found in lung and throat in both species so it has been assumed that transmission is largely airborne. However, evidence for frequent close contact between species is weak, with recent studies suggesting this is unlikely. So, is transmission indirect via environmental contamination? Again, no clear evidence. It is believed that the bacillus persists in urine in the environment for 14 – 21 days, and in faeces for up to 6 months. What has not been established is how this would cause infection.

Q6. What level of bTB in cattle can be directly attributed to badgers?

Uncertain. Clearly this would depend on a reliable answer to Q5. Figures vary widely and all are estimates based on statistical analysis and modelling. One paper said this was “unquantified and unquantifiable”. Despite this, a figure which seems to be used by Defra is ~4-6% directly, which it is said through subsequent cattle to cattle transmission could account for up to 38% of bTB breakdowns. This seems odd as that suggests the other 95% is only responsible for 62%??! Others argue that as no case of bTB in cattle has been conclusively proven to have been transmitted from badgers, any figure is meaningless as it derives from assumption and association.

Q7. What is main cause of bTB in cattle?

All the evidence points to this being cattle to cattle.

Q8. Why is bTB persisting and increasing if all infected cattle are regularly removed from herds?

This is the $64k question. The obvious answer, which the ISG gave, is that all infected cattle are NOT being removed. The main reason for this is that the TB test is not accurate enough (max 80%, min 50%). At best, 20% of test results are wrong – specifically, because the problem is with sensitivity rather than specificity, that means up to 20% could test as clear even when infected (false negatives). False negatives would lead to infected animals remaining with the herd, and could explain continuing outbreaks which are instead attributed to badgers.

Q9. Is a better test available?

Yes. There are two blood tests. One which is now used that is 90% accurate (gamma interferon). An even newer one (phage) may be 99% or better, but it has yet to be approved. It can give a result in 6 hours.

Q10. Why is it not being used everywhere?

The phage test is brand new and needs to go through proper testing before approval. The Interferon test is being used in Wales, and in some places in England (in high risk areas with existing breakdowns). It isn’t used routinely, possibly because as a blood test it takes more effort and cost, and the system is set up for the skin test. Hopefully the new phage test which should be cheap as well as fast and highly accurate, will replace the skin test eventually.

Q11. Would culling badgers lead to the end of bTB in cattle?

No. Given everyone agrees that at least the majority of bTB is transmitted between cattle, even the total eradication of badgers in the UK would not lead to the end of bTB in cattle. Even supporters of the cull say it would only reduce it a bit, while the science suggests it would have no discernible effect. What would undoubtedly help is better testing, better movement control and quarantine, improved farm hygiene, and enhanced biosecurity.

Q12. Is better movement control and quarantine, improved farm hygiene, and enhanced biosecurity being introduced?

Yes, but at the same time as badger culling, which means that the effects of the two are intertwined and impossible to disentangle. This means that it won’t be scientifically possible to say which approach had what or how much effect. Any reduction in bTB could be a result of one or the other or both.

Q13. Are there any adverse effects, in bTB terms, of culling badgers?

Yes. In certain circumstances, culling is believed to cause an increase in bTB in cattle, as well as in badgers. This is thought to be because it disrupts the social structure and makes badgers roam more, and thus more likely to spread bTB if infected. This effect is magnified where badgers live in low density (such as in many “low” risk areas). That said, the failure to conclusively demonstrate direct badger to cattle bTB transmission remains a problem which could suggest that the so-called “perturbation” effect is merely a misinterpretation of the statistics.

Q14. Is there another way of dealing with bTB in badgers, apart from culling?

Yes. A vaccine is available and proven to work reasonably well (i.e. it protects badgers from catching bTB). It has been used in various parts of England, and is the chosen method of bTB management in badgers in Wales. It has even been approved by Defra as part of the bTB eradication strategy for England.

Q15. Does vaccination cause badger behaviour to change (as culling does)?

No. Badger behaviour and social structure is unaffected.

Q16. Has vaccination been subjected to the equivalent of the RBCT to see how effective it could be in reducing bTB in cattle?


Q17. Why not?

Good question. Perhaps you should ask Defra.

Q18. Is vaccination more expensive than culling?

No, it is considerably cheaper.

Q19. Why is vaccination not being rolled out across England?

Possibly because of 16. But then see 15 and 18 and ask if this is a good enough answer.

Q20. If culling badgers may not have a significant impact on bTB, why is it happening?

The simple answer is I don’t know. The longer answer is that over the past 45 years the idea that badgers are to blame for the otherwise “unexplained” breakdowns has become embedded in Defra and the veterinary profession. This despite the fact that Defra accepts that the skin test is at best 80% accurate. There is also an argument that cattle become infectious before they become sensitive to the skin test, and that some cattle do not become sensitive at all. These appear to be uncontested facts that were widely accepted in the field before the badger theory arrived and supplanted them. It is something of a mystery to me that given this, which strongly suggests that so called “unexplained” breakdowns were simply the result of undetected infectious cattle, badgers have become so central to the argument. There does not seem to be any need to include them.

One argument is that badgers are a spillover host (like pigs) which means they catch bTB from cattle, but that it does not spread much within the badgers and tends to “die” out, unless re-infection from cattle occurs. That would fit with the fact that bTB infected badgers tend to be associated with significant bTB breakdowns. In spillover hosts, the disease is not sustained or spread within the host population, they catch it from outside. There is no clear evidence that badgers can sustain bTB within their population in the absence of local bTB infected cattle. This rather suggests that they may indeed be spillover hosts.

Badgers seem to have become implicated through guilt by association. Their highest population density is in the areas with the highest density of cattle, which are also, perhaps not surprisingly if bTB is exclusively a cattle to cattle issue, the areas with the most bTB. bTB was almost eradicated in the past by a more extreme herd slaughter policy, without any badger involvement. It has been eradicated in Scotland without any badgers being killed. In Ireland, where large numbers of badgers have been culled, bTB stubbornly remains a problem (although they have introduced better testing methods which would explain any decline in bTB).


compiled by M W D'Arcy MSc

March against the Badger cull

West Surrey Badger Group banner and members at the Stop the Cull March on June 1st 2013

Anti-Cull March