Since the last edition a few people have asked us about the rationale behind badger vaccination, so we thought this newsletter would be a good opportunity to look in a bit more detail at why the Wildlife Trusts support badger vaccination as an alternative to culling. So, here is our case for vaccination.
To look at the evidence in context, we have to go back to the first principles of the problem of bovine TB, which exists in both the cattle and badger populations (and in many other species).
If we want to reduce levels of bovine TB in the long term, or even eradicate it, we have to reduce the percentage of animals in each population that carry the disease- in other words, reduce the disease prevalence. Although other species are susceptible to bTB, the focus is on cattle and badgers because it is within and between these species that the risk of transmission is highest, thus perpetuating the problem.
To reduce the percentage of badgers with bTB, vaccination is undoubtedly the best way forward. Culling reduces the number of badgers- it does not, and cannot, reduce the prevalence of disease within the population. This is because with cattle you can cull only animals that have tested positive for the disease, but in badgers the culling has to be universal, because they are wild animals and any other approach is either unfeasible or risks perturbation, and hence the spread of the disease.
In fact, evidence from the ten year, £50m Randomised Badger Culling Trial (RBCT) showed that badger culling increases (in fact, approximately doubled) the prevalence of bTB in the few remaining badgers, probably due to perturbation and interaction between the surviving badgers. So there is a higher rate of infection in the remaining badgers, which will form the basis of the recovering population- taking you back to square one- or much worse.
Vaccination in the most general sense is a tried and tested technique of disease control in both human and animal populations. In addition, the vaccine that will be used- BCG- is the same one that is used on humans to vaccinate against TB. It has been tested on badgers and has been shown to reduce symptoms. What has not yet been proven is how this will translate into improvements in TB levels in cattle- but unlike culling, we know it can’t make anything worse, because it does not cause perturbation and the movement of badgers.
Specifically compared to culling, vaccination has many advantages resulting from the fact that it cannot make bTB worse. For culling to stand any chance of reducing bTB, it has to meet strict criteria on geographical extent, hard boundaries badgers cannot cross, high percentage of land accessed and of animals trapped- failure to meet any of these could cause an increase in bTB. With vaccination, none of these are risks- every badger vaccinated is a step in the right direction, but there are no critical thresholds.
One common case made against vaccination is that it ‘can’t cure sick animals’. Everyone knows vaccination is preventative not curative, so the point of fact is valid. But over time, vaccination reduces the prevalence of disease by protecting young animals and allowing the infected part of the population to die out. The task will undoubtedly be slower and harder where infection rates are higher, but the trend will be a reduction in prevalence, unlike with culling, where the trend is of increased infection rates.
Another common criticism of vaccination is the cost, as the BCG currently has to be injected, since there is not yet a method of oral delivery. However, trapping and vaccinating is comparable in cost to trapping and culling; in fact, even during assessments for the development of the previous culling policy, vaccination was deemed a slightly cheaper option. Vaccination costs more than shooting, but with vaccination there is no cost of carcass disposal or testing. Therefore differences in cost should be modest, and in time, a much cheaper oral bait method of administering the vaccine will be available.
There has also been a lot of publicity recently surrounding the possibility that some landowners may choose to act illegally and control badgers on their own land in response to a bTB breakdown, including coverage of illegal killing of badgers on a recent edition of Y Byd Ar Bedwar. Some believe that such action, if legal, would resolve the bTB problem by taking out ‘sick setts’. However the RBCT demonstrated such compelling evidence that the localised culling of badgers increased the bTB problem that they closed down that trial early, because of the negative impacts it was having. It is imperative that this message is spread as widely as possible if we are to reduce bTB rates.
What is clear is that if collectively we are serious about the aim of eradicating bTB, we must reduce the prevalence of the disease in all species that carry it. That means taking action to reduce the disease in both cattle and badgers. At the moment, the only mechanism for reducing the percentage of badgers catching the disease is vaccination, and that is why the Wildlife Trusts believe that this is the best outcome- not only for our wildlife, but for cattle and for those that own them.