It may be possible to detect the presence of 'mad cow' prions through a blood test, an advance that would help keep the food supply, as well as donated blood and organs safe.

But experts fear that many more could fall victim in years to come as the disease can have an incubation period of up to 40 years.

There is currently no effective way of detecting BSE or vCJD in the blood, with the diseases only confirmed after death.

Easier to Keep Food Supply Safe

Now researchers in the US have developed a way of detecting "mad cow" proteins in the blood -- said to be the first time such "prions" have been detected in this way.

The team from the University of Texas said the blood test would make it much easier to keep BSE-infected beef out of the human food supply.

The researchers said it would help ensure that blood transfusions and organ transplants do not transmit vCJD.

And they said that it would give scientists their first chance to figure out how many people may be incubating the disease.

Screening Donated Blood, Organs

In December 2003, the British Government announced the first case of a patient who died from vCJD after receiving blood from an infected donor --thought to be the first person-to-person transmission of vCJD in the world.

In response to that, anyone who had received a blood transfusion since January 1980 was banned from donating blood in the future.

In 2004, another case emerged of a blood transfusion patient who was later found to be carrying vCJD. The person died from other causes.

The patient received a transfusion in 1999 from a donor who later developed vCJD.

Since then further steps have been taken to protect the UK blood supply from potential contamination with vCJD.

The latest research, published in Nature Medicine, could pave the way for donated blood and organs to be screened for vCJD before use.

.