A new, more effective way of testing sheep for BSE has been devised by a scientist at the University of California San Francisco.

Professor Stanley Prusiner claims that the test has so far proved to be 100 per cent accurate and has been able to identify animals infected with BSE long before they the first symptoms of disease started to show.

Professor Prusiner's said that his laboratory will test sheep samples to see if he can distinguish BSE from sheep scrapie, a naturally occurring brain disease which causes the same symptoms as BSE.

If the test works, it will be put into practise in the UK and will probably then become widespread in sheep rearing regions on a global basis.

"This test has been approved for sheep, and we plan to make it available for sheep and there is this question that everybody is very concerned about, is there BSE in sheep?" Professor Prusiner said. "That's a question that has not been answered yet but it will be answered through commercial testing."

To date Prusiner's work on the detection of BSE has been pioneering. The scientist is credited with identifying prions, or protein fragments that become denatured in the brain, as the agent thought to be responsible for causing mad cow disease.

The testing will be carried out by InPro Biotechnology, a company which was set up by Professor Prusiner, and LGC, formerly the Laboratory of the Government Chemist, in Teddington, south-west London.

So far research into BSE in cattle has been held back because of the lack of a definitive test that can identify the early stages of the infection - before any physical symptoms manifest themselves.

The test, which is called CDI-5, will be the first of a "second generation" of tests that will revolutionise the diagnosis and understanding of neurodegenerative diseases caused by rogue changes in the prion protein of the brain - one of the key elements in diseases such as BSE.

Professor Prusiner said the test could also be carried out on humans to detect whether or not they had picked up the disease after consuming BSE infected meat.

. The key to the test's success is that it can distinguish between the two types of the prion protein - the normal and abnormal forms - and is able to quantify how much of each is present.