New research suggesting that BSE is now a greater risk in sheep than cattle has led British scientists at London’s Imperial College to call for immediate action to protect consumers and screen the 40 million strong national flock for the disease.

After the well-publicised fiasco at the end of last year, which revealed that scientists searching for BSE in sheep had actually spent an embarrassing four years looking at bovine brains, still only 180 sheep in the country have been tested for BSE – leaving a true picture of the potential spread of BSE among sheep unclear.

If sheep have become infected with the disease however, the scientists warned in science journal Nature yesterday [Wednesday], a large epidemic could be on its way – and the total number of human deaths from vCJD could triple to a predicted 150,000.

Team leader Professor Neil Ferguson explained: “We were not trying to evaluate the probability that BSE has entered the sheep flock, but rather, given the pessimistic assumption that infection has occurred, to explore its potential extent and pattern of spread.”

This theoretical risk of BSE-infected sheep could however be slashed by 90% if control measures comparable to those used on cattle were implemented on sheep flocks. These include placing restrictions on the age of sheep slaughtered for human consumption and stating that certain offal and tissues from the carcass be kept out of the food supply.

“Our estimates are ultimately dependent on the quality and quantity of information that is gathered by other researchers and we feel that large-scale testing of the national flock, and additional experimental research are urgent priorities,” Ferguson said.

The Food Standards Agency responded to the scientists’ fears by insisting that their conclusions are only “one piece of a [research] jigsaw” that needed examination to see if sheep safeguards are essential. Chairman Sir John Krebs commented in Nature: “In the light of such scientific uncertainty, there is no easy formula for deciding on the right level of precautionary risk management.”

Scientists first diagnosed BSE in 1986, and in October 2000 the BSE inquiry report concluded that the possibility of the disease’s spread into sheep was “perhaps the most important unanswered question about the BSE epidemic”.