New test will identify human carriers of mad cow disease

SCIENTISTS have developed the first reliable blood test for the human version of mad cow disease, which could transform diagnosis and screening of the fatal brain disorder.

The test could also identify carriers and help scientists accurately assess for the first time how many people in the UK may be incubating the disease.

Variant Creutzfeldt-Jakob Disease (vCJD) is the human equivalent of Bovine Spongiform Encephalopathy, which affects cattle.

Identified in the 1990s, the illness was traced to the consumption of beef products containing contaminated meat.

In Scotland, between 1990 and 2010, a total of 22 deaths were diagnosed as having been definately or probably as a result of the disease. The total number of victims in the UK was 170.

VCJD progressively causes the brain to become riddled with holes, a condition called spongiosis, leading to mental problems, loss of body function, and eventual death.

There is no cure for the condition, which has a long incubation period. People can harbour prions - the infectious proteins believed to spread the disease - for years while experiencing no symptoms. During this time, victims can potentially transmit the disease by donating blood or undergoing surgery.

Until now there has been no way of telling for sure if someone has the disease other than by examining their brain tissue.

The prototype blood test developed by scientists at the Medical Research Council (MRC) is 100,000 times more sensitive than any studied before.

Details of the research appeared today in The Lancet medical journal.

Lead author Dr Graham Jackson, from the MRC Prion Unit, based at University College London, said: "This test comes at the end of many years of meticulous, painstaking research in our Unit and the NHS National Prion Clinic.

"Although further larger studies are needed to confirm its effectiveness, it's the best hope yet of a successful early diagnostic test for the disease.

"This test could potentially go on to allow blood services to screen the population for vCJD infection, assess how many people in the UK are silent carriers and prevent onward transmission of the disease."

At one stage it was feared that as more people began to develop symptoms there would be a major epidemic of vCJD.

Professor John Collinge, director of the MRC Prion Unit, said: "One of the reasons that vCJD is such a dreaded disease and has caused such disruption and expense to health services is the lack of knowledge of who is and who is not a carrier of this infection.

"The next step will be to test blood donors from a country unaffected by BSE to gain a better idea of how the test fares in practice.

"Longer term studies will also be needed to assess what proportion of individuals who test positive for prion infection will then go on to develop the disease later in life."BRAIN DEATH

VCJD affects proteins, prions, in the central nervous system, causing them to change and form clusters in the brain. When brain cells die, they create holes in the brain matter.

Anxiety and depression are often the first symptoms of the disease, progressing to loss of motor and speech function, and dementia.

Sufferers usually die within six months of early symptoms - often from pneumonia. In a minority of patients, the disease may take two years to run its course. Very rarely, it can last for many years.