BSE update: ewes to blame?
25 August 2005
BSE or 'mad cow disease' can be passed from ewes to lambs. It's the first time the link has been proved and it raises the possibility that the disease has been spreading undetected among sheep. Antenna asks, is BSE back?
What did the scientists do?
Scientists deliberately infected 30 ewes with BSE and the ewes gave birth to lambs. Two of the lambs died this year of BSE - proving that the disease can spread from one generation to the next.
Scientists deliberately infected 30 ewes with BSE and the ewes gave birth to lambs. Two of the lambs died this year of BSE - proving that the disease can spread from one generation to the next.
We already knew that sheep might have been infected with BSE after eating infected meat, so this feeding practice was stopped back in 1988 and many of our sheep have been tested for BSE.
Why deliberately infect a sheep with BSE?
Some scientists weren't sure our sheep were really BSE-free. They needed to test whether it could be passed from mother to lamb - and the experiment proves it can, so they were right to check.
Some scientists weren't sure our sheep were really BSE-free. They needed to test whether it could be passed from mother to lamb - and the experiment proves it can, so they were right to check.
Is the new discovery bad news for sheep?
It may not be as serious as it sounds because transmission of BSE from ewe to lamb wouldn't be enough to infect a flock and the disease would die out as the lambs died. What would be worse is if BSE can spread between unrelated sheep, so that's what the scientists are testing now.
It may not be as serious as it sounds because transmission of BSE from ewe to lamb wouldn't be enough to infect a flock and the disease would die out as the lambs died. What would be worse is if BSE can spread between unrelated sheep, so that's what the scientists are testing now.
And in the lab experiment the odds were stacked against the sheep more than they would be in the real world...
'It was an experiment with high doses of infectivity and the sheep were genetically susceptible which made them more likely to develop the disease. We have to ask if it is applicable to natural infection on the farm.'
Alastair Macrae, sheep and cow veterinary surgeon, University of Edinburgh
Alastair Macrae, sheep and cow veterinary surgeon, University of Edinburgh
So there could theoretically be sheep out there who've been born with BSE...
'We've been looking for BSE in the national flocks in recent years and haven't found it. We couldn't look for it on such a large scale 10 to 15 years ago as we didn't have the right tools.
'We've been looking for BSE in the national flocks in recent years and haven't found it. We couldn't look for it on such a large scale 10 to 15 years ago as we didn't have the right tools.
'Also, farmers can't distinguish between BSE and another disease called scrapie - clinically they look just the same.'
Danny Matthews, BSE expert, Veterinary Laboratories Agency
Danny Matthews, BSE expert, Veterinary Laboratories Agency
Danny Matthews, BSE expert, Veterinary Laboratories Agency
Image: VLA
What's so bad about BSE?
Eating BSE-infected meat has been linked to the human brain disease vCJD, but it's very hard to prove.
Eating BSE-infected meat has been linked to the human brain disease vCJD, but it's very hard to prove.
'Theoretically it is possible that people could have eaten sheep that were infected with BSE before 1988, but because the incubation period for vCJD is very long, a matter of years rather than days, it is very difficult to associate becoming infected with eating a particular food.' Danny Matthews
Should we have been as wary of lamb kebabs as we were of beefburgers during the height of the BSE scare?
'Given the size of the BSE epidemic in cattle it is far more likely that individuals were infected from cattle rather than sheep, and the Food Standards Agency still considers it safe for sheep meat to be eaten.'
Danny Matthews
To find out more about how sheep can pass BSE to their lambs click on the link below...
Danny Matthews
To find out more about how sheep can pass BSE to their lambs click on the link below...
