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EDITIONS
BSE Inquiry Wednesday, 18 August, 1999, 14:31 GMT 15:31 UK
CJD: The threat to human health
CJD graphic
The evidence of cross-species infection is still shaky
The fact that BSE is one of a group of diseases that are known to transfer from one species to another meant that what started as an agricultural crisis was soon regarded as a threat to human health.


The human equivalent of BSE is thought to be new variant Creutzfeldt -Jakob disease - nvCJD.

It has been described as a disease in its own right, although it is similar to classic CJD. Both diseases are fatal, difficult to diagnose and extremely rare.

But the discovery of nvCJD was particularly alarming as it has only been found in the UK, and only since the BSE crisis started.

Warning to brain specialists

It first emerged during 1994-95, and was first described in detail in a 1996 paper in The Lancet medical journal.

cattle
Although BSE is an animal disease, it has raised fears about human health
Dr Robert Will, the paper's author and head of the UK CJD Surveillance Unit, wrote to all brain specialists in the UK at the time.

He said: "In the past few weeks we believe we may have identified a new clinico-pathological phenotype of CJD which may be unique to the UK.

"This raises the possibility of a causative link between BSE and CJD."

He was in no doubt as to the impact this news might have.

"The identification of a form of CJD that might be causally linked to BSE will result in widespread anxiety and concern," he said.

To date, 38 people have died from nvCJD disease, and it is thought probable that it has been responsible for two other deaths.

Click here for details of death rates from classic CJD.

Classic CJD - which is found in countries around the world - first appears as dementia, and progresses rapidly to destroy brain tissue and cause death. It is marked by a distinct pattern of electrical activity in the brain.

The brain is left riddled with holes like a sponge.

But while CJD typically affects patients aged between 50 and 75, nvCJD affects much younger people - the average age is 27.6 years, with patients aged between 18 and 41 having contracted it.

The new disease also lasts longer - up to two years from onset to death.

The first signs of nvCJD are likely to be anxiety, depression or changes in behavioural patterns, all of which get progressively worse.

After weeks or months the disease affects co-ordination, and patients may have difficulty walking and picking things up.

Later on, patients will develop problems with memory and have difficulty making sense of the world around them.

The typical pattern of brain activity seen in CJD is absent in the new variant.

In search of a cause

Abnormal proteins known as prions are thought to be the cause of both diseases. Other diseases in the same class - such as BSE and scrapie - are also thought to be caused by prions.

Prion rogue
Rogue prions are thought to cause the diseases
However, not all scientists agree on this and some doubt that prions can cause disease at all.

One current research project, funded by the Ministry of Agriculture, suggests bacteria is really to blame for BSE and it would be almost impossible for the disease to pass from cow to cow, let alone from cows to humans.

But the weight of scientific opinion is behind the prion theory.

Prion diseases are also known as "transmissible spongiform encephalopathies" - transmissible because they can be transmitted between humans and animals, and spongiform encephalopathies because they often leave the brain riddled with holes like a sponge.

Researchers have seen the diseases pass from species to species when brain tissue is exchanged, but the risks from blood transfusions and food are uncertain.

Risks of transmission

Nevertheless, blood in the UK is treated to reduce the risks of transmission and surgeons who treat any CJD patient are advised to destroy all instruments.

Authorities in the US and Canada have banned blood donations from people who spent long periods in the UK, and other countries are considering such a move.

On the whole, however, doctors are still in the dark as to what is the root cause of nvCJD and its fellow prion diseases.

Some CJD cases are thought to have been caused by injections of human growth hormone, which came from dead bodies.

This practice has stopped, and an artificial hormone is used. Since its introduction, there have been no more such cases.

Sometimes the diseases develop because there is a family history.

But most instances of CJD and all of nvCJD occur spontaneously, and there is no pattern by region or date to help doctors establish a cause.

An incurable condition

The treatment outlook is bleak. Although there is plenty of research around the world, all doctors can do at present is alleviate symptoms until the patient dies.

The CJD Surveillance Unit offers these words of comfort: "Individuals with CJD may sometimes feel discomfort from for example, sitting in one position too long, but there is no pain associated with the disease itself.

"The most distress is felt by those who know them, as they see a loved one so seriously ill."

Classic CJD deaths in the UK

Although cases of the classic disease have been steadily rising, doctors say this could be down better reporting to the surveillance unit.


CJD graph scot and NI

Click
here to return.
See also:

18 Aug 98 | Health
18 Mar 99 | Health
03 Jun 99 | Americas
02 Oct 98 | Health
18 Aug 99 | Medical notes
19 Mar 99 | Science/Nature
Internet links:


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