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Tuesday, 21 December, 1999, 15:01 GMT
CJD: What is the risk?
Mice
The scientists tested their theory on mice
BBC Environment Correspondent Margaret Gilmore explains the significance of the latest research into the link between BSE and its human form, CJD.


What are BSE and CJD?

BSE, Bovine Spongiform Encephalopathy, is a degenerative brain disease in cattle.

CJD stands for Creitzfeldt-Jakob disease and was named after the men who discovered it. This is also a degenerative brain disease that generally affects elderly people.


In 1996, scientists confirmed that they had discovered a new strain or variant of the disease among young people that they have until now referred to as nvCJD.

In future, this disease will be known as vCJD. Because the disease is no longer regarded as new, scientists are dropping the n prefix.

vCJD is both mentally and physically degenerative. It leads to vacuoles, or holes, in the brain and cannot, as yet, be cured.

Symptoms can include depression, blurred vision, slurred speech, sometimes aggressiveness, followed by loss of control over limbs and eventually of the entire body.

The emergence of vCJD came after the biggest ever epidemic of BSE in cattle. Since that epidemic was in the UK and most vCJD victims lived in the UK, most scientists believed the two were linked.

They say the most likely cause of vCJD in humans was eating BSE-infected beef between the years of 1986 and 1989, when contaminated meat probably got into the food chain in large quantities.

What is the significance of the new research?

According to the authors, it provides the most "compelling evidence" of the link between BSE in cattle and vCJD in humans.

Prion
Prions are thought to cause CJD and BSE
The ultimate proof would be to inject BSE infected material directly into humans and wait to see what happened - an unethical experiment that is clearly not going to happen.

There is still discussion about the origins of BSE in cattle. Its spread coincided with a change in cattle feed preparation methods when cattle remains were processed and fed to other cattle. It is possible that BSE infection entered the food chain then.

The new research indicates more clearly than ever that vCJD is caused by eating BSE-infected material.

How many people have died of vCJD in the UK?

The official figure for the number of people who have died from vCJD since 1995 is 48. Two others have died in the Irish Republic and in France.

Several other people in the UK have developed the disease and are currently being nursed. Because the incubation period for the disease could be 15 or 20 years, we do not know how many more of us could also eventually fall ill.

Scientists believe they will not have a clear idea of whether the final figure will be a few hundred or a few thousand, or many thousands, until the end of the year 2002.

Some members of the population appear to be more at risk than others. Most of those who have so far died are young. This is baffling the scientists.

What measures have been taken to reduce risk?

The government has slaughtered millions of cattle at risk of being infected with BSE. They continue to allow only young cattle into the food chain.

They also banned beef-on-the-bone because in the highly unlikely event of BSE-contaminated meat still getting into the food chain, the most infectious part would be the meat closest to the bone.

All cattle have to be traced from birth to death to prove they are BSE free. They are all issued with ID cards or passports and they are tagged in the ear.

Is there anything people can do to reduce the risk?

Scientists believe if people are going to get the disease they will, in nearly all cases, already be incubating it.

They believe very little if any contaminated beef is now reaching the food chain. Therefore, there is very little individuals can now do.

However, if large quantities of the adult population are to develop vCJD, the government wants to ensure the disease does not spread unnecessarily across the population.

They have recommended contact lenses used by opticians for tests should not be re-used. They have taken measures to ensure blood is safe.

And they've recommended surgical instruments in certain operations should not be re-used.

How can you tell if you have vCJD?

At present there is no way of telling whether you are incubating the disease.

Scientists have developed a tonsil test which if you are showing symptoms will confirm whether you have vCJD.

The experiment has not yet been used widely enough to become accepted practice - but scientists believe it soon will be.

Before the introduction of the tonsil test, the only confirmation of vCJD came with a brain autopsy - generally after death.

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See also:

21 Dec 99 | Sci/Tech
CJD-BSE link 'indisputable'
21 Dec 99 | Sci/Tech
CJD epidemic fear
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