SCIENCE: Ending scrapie `may be impossible'

Wiping out scrapie, the equivalent in sheep of "mad cow disease", could prove almost impossible in the United Kingdom and Europe. That is because it is caused by an infectious agent rather than genetic defects, British scientists have found.

If the disease was caused by genetic mutation, then it might prove possible to breed it out of flocks. But a comparison by a team from the Institute for Animal Health (IAH) in Edinburgh, of sheep from Australia and New Zealand - where no scrapie has been found for decades - with flocks from the UK found few significant differences in their genetic make-up.

Scientists had suggested that mutations of the PrP gene caused scrapie, but the team found that the scrapie-free sheep from the Antipodes had the same mutations of the gene as the diseased British flocks. The IAH concludes in today's edition of Nature that the development of scrapie in sheep must require an additional factor, probably an infectious agent, making eradication in the UK and Europe very difficult.