‘The truth about bovines, badgers and the spread of TB’

Posted on November 11, 2012

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Today (11th November), an item was posted on guardian.co.uk titled ‘The truth about bovines, badgers and the spread of TB’, written by Professor Alice Roberts of the University of Birmingham.

‘… Convention held that humans had caught tuberculosis from cattle – but the DNA record tells a different story –

Mycobacteria and TB have been in the news a lot recently. In fact, one particular species has been hogging the limelight: Mycobacterium bovis. As its name suggests, it likes to infect cows, but as we’re recently all too aware, it’s quite happy in badgers too …

Not that long ago, TB in humans was thought to have been a fairly recent affliction, dating back to the neolithic and the origins of farming. This oft-repeated idea seemed reasonable – there didn’t seem to be any convincing cases of TB in skeletons dating to earlier periods. Perhaps close contact between early farmers and their cattle exposed them to M bovis, which then evolved into M tuberculosis in its new host …

In 1999, an early genetic study cast doubt on the ancestor-descendant relationship between the bovine and human forms of TB. More studies confirmed the new story. If anything, the ancestor of both human and bovine forms must have been closer to the human form – with its larger chromosome. It’s even possible that cows caught TB from us (or at least, from another mammal that had caught “human” TB) …

Back to the present, and TB has scarcely been out of the news for the past few weeks. The Great Badger Cull has become one of the hottest political potatoes of the year. So what is the scientific evidence? Well, it seems pretty clear that badgers do help spread bovine TB. But that also seems to be where the certainty ends. Bovine TB in the UK has been going up and up – but how much of that is due to better diagnosis? And could culling badgers really help to reduce it? A study published in the journal Nature in 2006 showed that culling badgers reduced the rates of TB among cattle in the area where the cull took place – but increased it in neighbouring areas. In 2011, based on the results of previous trials, scientists advised the current government that culling 70% of badgers in large areas could result in a 16% reduction in bovine TB. For the government, that was enough.

But some scientists are now concerned that the cull – particularly if carried out by free shooting, which hasn’t been trialled, or if targets are missed – could make matters worse.

For this winter, the badgers are safe. Like Caesar presiding over a bizarre gladiatorial contest, environment secretary Owen Paterson granted the badgers a stay of execution, at the eleventh hour. There are just too many of them to make a 70% cull achievable this late in the year.

So the debate continues. It’s an argument about science, politics and economics. It centres on protecting food animals from harm, just as our ancestors have done since farming first got started. But, to me, it also raises interesting questions about how we see ourselves and other animals. It’s about how much we see ourselves as a “dominant” species, entitled to subjugate the needs of other animals beneath our own. It’s about how much room we demand as a human population (with a taste for milk and beef) and how much room we’re prepared to make for wildlife.

And let’s not forget, if it hadn’t been for us, cattle and badgers might not have had TB in the first place …’

Read the item in full and add your comment online at www.guardian.co.uk/science/2012/nov/11/alice-roberts-bovine-tb-badgers

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