Ongoing BSE cases linked to dirty feed bins
FORDYCE MAXWELL
VETERINARY scientists now believe that dirty feed bins are the most likely cause of cattle born after the end of July 1996 developing BSE.
That was when a ban was introduced on the use of bonemeal, identified as the source of the BSE epidemic of the early 1990s, in ruminant rations.
But a number of cattle born after the ban started - known as BARB (born after the reinforced ban) cases - have developed the brain disease BSE, linked since March 1996 with the fatal human condition CJD.
Yesterday Charles Milne, Scotland's chief state vet, said nine herds in south-west England, the West Midlands and south-west Wales have produced 20 BARB cases.
Investigations on these farms have revealed a possible source of infection as the BSE agent - still never identified precisely - existing inside feed bins that had not been thoroughly cleaned for years.
Milnes said: "In experiments, as little as one milligram of BSE-infected brain tissue has been enough to infect a calf. In some of these herds, feed was stored in feed bins that were in use before August 1996, and had never been cleaned."
Similarly, he said, recent 2001 and 2002 BARB cases from a single herd in south-west Wales might have been infected by old feed dislodged when a bin was moved in 2002.
He said: "We believe that the current risk of BSE infection as a result of the persistence of the BSE agent in feed bins, from feed produced prior to the feed ban, is extremely low. Nevertheless, we strongly recommend feed bins are cleaned routinely and very thoroughly, particularly those in use before August 1996 and not cleaned out since."
Public health risks from BARB cases are negligible, Milnes said, because of strict controls that take specified risk materials from cattle carcases out of the human food chain. But he added: "Our aim is total eradication of BSE from the national herd by the end of 2010. To do this we need the continued help of farmers and veterinary surgeons throughout the UK."
BSE cases reached a peak in the early 1990s with more than 200,000 cases a year. Fewer than 200 a year are now being found and no cattle born since July 1996 and found to be developing BSE originated in Scotland.
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Last updated: 14-Dec-05 01:20 GMT
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