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From: TSS ()
Subject: BSE transmitted between sheep
Date: August 16, 2005 at 6:22 pm PST


BSE transmitted between sheep

Incident at government test farm fuels new food fear

James Meikle, health correspondent
Wednesday August 17, 2005
The Guardian


BSE has been transmitted naturally between sheep for the first time, a study has shown. Confirmation that such a thing is possible reinforces fears that the disease may have entered sheep as well as cattle on farms in Britain.
The revelation that lambs at a government experimental station appear to have caught BSE from their mothers coincides with plans to relax anti-BSE controls in cattle and was not mentioned at a meeting of the Food Standards Agency in London this week.


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Scientists will now seek to estimate from ongoing experiments whether there was ever enough infection in flocks to make the disease survive for long. No evidence of BSE has emerged from testing sheep in abattoirs or on farms, although this did not begin until well after the BSE epidemic in cattle was in steep decline.
Safety advisers have previously warned that any sheep with BSE entering the food chain would be potentially far more dangerous than a single cow, since there are far more parts of the animal that can carry infection.

The report on infected lambs, in the journal Veterinary Record, also comes as officials review contingency plans in case BSE is ever found in sheep on normal farms. The present worst case scenario assumes that around 25m sheep might have to be destroyed. There would be severe shortages of sheep meat, since an entire year's crop of lamb, some older sheep bred for mutton and many breeding ewes would have to be killed.

But the plans have been based on hypothetical models. Now scientists from the government's Veterinary Laboratories Agency have revealed that two ewes fed 5mg of BSE-infected material had lambs that died of BSE after showing signs of infection in their tonsils, 546 days after birth.

Their mothers had shown no outward signs of the disease at lambing, one showing them 73 days after lambing, and the other 198 days after.

But it is still not certain that the lambs were infected while in the uterus, or shortly before or after lambing. The disease may have spread through the birthing fluids or in some other way. The evidence so far suggests this is far more likely than the lambs catching the disease from other apparently unaffected sheep.

It is already known that BSE-like diseases can be transmitted via blood in humans as well as animals, but there has been no evidence that it has been handed from dam to calf in cattle, or mother to baby in people.

The sheep involved were of a genetic type that in lab tests previously appeared most susceptible to BSE. But it is unclear how many such sheep are in flocks on farms. There are 15 different genetic types, and unlike in BSE in cattle, genetic type seems important.

Unfortunately at present there would be no way of identifying resistant sheep in time for them to go into food, while banning others.

The fear about sheep has existed for years because, until the late 1980s, they were fed the same sort of feed as was fed to cattle. However if it was ever in sheep, there is no suggestion that it ever existed on a large scale.

There is some good news. The lambs that seem to have inherited BSE showed a brain signature similar to BSE in cattle. Officials have been worried that some BSE in sheep, if it existed, might have been masked by a similar disease called scrapie, not known to be dangerous to humans. The relatively small scale of the vCJD epidemic in humans so far might give some reassurance too, given the size of an enormous BSE cattle epidemic.

Peter Jinman, a leading veterinary surgeon on Seac, the scientific body advising the government on anti-BSE measures, said: "This clearly is an important finding. It is another part of the jigsaw." Seac would consider the implications next month.

The Food Standards Agency said the study "adds to the scientific knowledge in an area of continuing scientific uncertainty". It did not advise the public against eating sheep, but would continue to recommed "precautionary and proportionate measures".

The environment department, Defra, pointed out that nearly 2,700 scrapie samples had been tested for BSE since 1998 with no sign of the disease, although two samples with anomalous results were still being tested, using mice.

http://www.guardian.co.uk/uk_news/story/0,3604,1550320,00.html

S. J. Bellworthy, G. Dexter, M. Stack, M. Chaplin, S. A. C. Hawkins, M. M. Simmons, M. Jeffrey, S. Martin, L. Gonzalez, and P. Hill
Natural transmission of BSE between sheep within an experimental flock
Vet Rec. 2005 157: 206. [Full Text] [PDF]

TSS



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