BSE has been transmitted naturally between sheep for the first time. This confirmation reinforces fears that the disease may have entered sheep on farms in Britain. 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. Now the Veterinary Laboratories Agency scientists have revealed that 2 ewes fed 5 milligrams of BSE-infected material had lambs that died of BSE after showing signs of infection. Their mothers had shown no outward signs of the disease at lambing, 1 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. 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 farms. 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 because, until the late 1980s, they were fed the same sort of feed as cattle. However if it was ever in sheep, there is no suggestion that it ever existed on a large scale. Officials have been worried that some BSE in sheep, if it existed, might have been masked by scrapie, not known to be dangerous to humans. The relatively small scale of the vCJD epidemic in humans so far might give some reassurance, given the size of an enormous BSE cattle epidemic. The Department of the Environment and Rural Affairs pointed out that nearly 2700 scrapie samples had been tested for BSE since 1998 with no sign of the disease, although 2 samples with anomalous results were still being tested, using mice. The UK Food Standards Agency has not placed any restrictions on the sale of sheep products (mutton, lamb and wool).
For more information read the paper by J. Bellworthy et al., available at: http://veterinaryrecord.bvapublications.com/cgi/content/full/157/7/206
(Promed 8/19/05)