What is the link between badgers and bovine TB?

23 September 2012


I've been a big fan of your show for a few years now and really enjoy how you explain everything scientific so that anyone can understand. When it came to a friend of mine, who is a farmer, talking about the UK Badger cull and the Badger TB crisis I couldn't get my head around all the arguments. Would it be possible for you to explain the science behind why we need the cull? And what ways we could help both the badgers and the farmers?


Kat - Okay, this is a very complicated and very emotive issue, and it mixes science, cute furry animals, commercial interest and politics, and with this kind of complicated issue there's obviously no really simple answer to it. Now, the UK government are proposing a badger cull in England that could see as many as 100,000 badgers killed and that's a third of the national population. So, that's quite a big thing and not great if you're a badger or someone who loves badgers. Now, on the farmers side, they're arguing that the wild badger populations harbour the bacteria responsible for bovine TB, and this is a germ called Mycobacterium tuberculosis. It's very closely related to human TB and it can also cause TB in humans although it's a very low risk. You really have to get very close to cows with it. But it is a big problem for cattle farmers and it's responsible for a huge number of animals having to be destroyed every year. There is some evidence that it can get into milk, but the thing is, if you pasteurise milk, then that's absolutely fine and there's no risk to consumers. But they say that badgers do spread the TB germs around through the badger's urine and faeces and cows only need to pick up a relatively small dose of bacteria to be infected. So in theory, getting rid of badgers would stop them bringing TB onto farms and it would protect cows, it would protect the farmer's interests, and the money that it costs to control TB, and all that kind of stuff, and that would be great.

Now on the other hand, there's a lot of people who say that a cull would not be effective. There was a big randomised trial of badger culling and it showed that culling is only really going to make a small difference to TB infections in cows and it might actually make the problem worse. Because if you start disturbing badgers and trying to kill them, they'll scurry away into other locations. And also, if you do manage to kill a lot of them, then you have all these empty badger sets that could potentially be infected and then new badgers will come in, start interacting with the population there, and it's just going to spread, and potentially, it could get worse. There's also no way of telling whether a random badger has TB or not, so they're proposing that you just shoot badgers on sight. So the problem is, you're not selecting between healthy badgers and diseased badgers. So that's a problem and there's also a public risk of having people out at night with shotguns. Again, it's not a great idea. The only way that it could work to do a cull would be, you'd have to kill a huge number of badgers in a very big area or at least 150 square kilometres in a very short time. So that's at least in two weeks, in less than two weeks. And this is going to be very difficult, very expensive. It's not going to completely reduce TB outbreaks anyway in cows and it would cost farmers probably more than they would lose form bovine TB. It's also worth noting that other animals can actually spread bovine TB and it includes deer and foxes, so it's a bit of an unwinnable battle.

Now, where do we go from here? How can we help farmers? How can we help badgers? There's an argument to say that actual better farming practices could do a lot to curb infection. So, controls on moving cattle around, doing more to keep badgers out of farms and out of the food sheds where they store cow food, and actually, there's a lot of work going on into vaccinating badgers. There's currently an injectable vaccine. It's obviously quite hard to trap and inject quite a lot of badgers, but there are proposals that really should be worked on an oral vaccine for badgers so you could leave out in their food, and that would probably be a really good way forward without having to kill lots of them.

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