23 November 2001
BSE-in-sheep epidemic possible

By Alistair Driver

BSE may be present in the UK sheep flock today and an ovine BSE epidemic is still a possibility, scientists have warned.

Research published in the US journal, Science, suggests that 1500 sheep could have been infected at the height of the cattle epidemic in 1990.

Scientists at Oxford University and the Institute of Animal Health predict that a small number of sheep could have BSE in 2001.

Their model, which assumes that 10% of ewes pass the disease on to their offspring, predicts there will be fewer than 20 cases this year.

The team, led by Rowland Kao of Oxford University, and including IAH director Chris Bostock, say “all indications are that current prevalence is low”.

But they warn: A simple model of flock-to-flock BSE transmission shows that horizontal transmission, if it has occurred, could eventually cause a large epidemic.”

Dr Kao believes that, unlike in cattle, BSE may spread from sheep to sheep, which he says happens with scrapie, a similar disease.

He is quoted in UK journal Nature as saying that even getting rid of meat and bonemeal (MBM) might not eradicate BSE in sheep.

“Thats the thing that really concerns everyone,” he says.

His team considered a variety of factors that they believed would indicate levels of BSE in sheep.

These included the number of cattle infected, the dose of infected material that would cause BSE in sheep and the exposure of sheep to infected MBM.

Laboratory experiments have shown that BSE could theoretically exist in sheep.

Sheep were fed the same MBM believed to have caused BSE in cattle and there are fears the disease has been masked by scrapie.

But no evidence has been found in the national flock.

Separate new research has indicated that less people than originally anticipated may be affected by the human equivalent of BSE, variant CJD.

British and French researchers predict there will be around 200 victims. Earlier models suggested that the total could reach hundreds of thousands.