Tuesday 31 October, 2000
Understanding vCJD
A major report into the BSE, or mad cow disease, crisis in Britain has recently been published. The official report accuses the British government of the time of misleading the public, and proposes a new compensation package for victims' families.
One of the main allegations is that steps weren't taken quickly enough to stop people eating meat infected with BSE and that people went on to develop a human form of the disease, known as variant Creutzfeld-Jacob Disease or CJD. But as Toby Murcott of BBC Science reports, despite a huge scientific research effort in recent years, many questions about this mysterious illness remain unanswered.
Creutzfeld-Jacob Disease is a distressing and inevitably fatal disease that attacks the brain, turning cells and tissue into a fibrous sponge-like material. The first signs of the disease include difficulty in walking loss of memory. These gradually get worse and eventually people with the disease lose control of all their faculties. One man in Britain, whose wife contracted CJD, described how her condition deteriorated:
‘She's going nearly blind, her head is on her chest, she just about recognises me. I think she's forgot one or two of the children, it is just terrible.’
BSE/vCJD link
Creutzfeld-Jacob Disease spontaneously appears in about one person in a million around the world and is related to a whole variety of animal diseases including scrapie in sheep and BSE or mad cow disease. The focus today is on a new form of the disease, called variant CJD, which appears to be linked to eating meat from cows infected with BSE. Richard Gallaher, of the science journal Nature , has been following the BSE/ vCJD link for some time. He comments:
‘The evidence is very strong but it is not completely conclusive. There are several different strands of evidence. Some of them are very simple epidemiological associations. Some are experiments where things are fed to experimental animals and they also develop very similar symptoms. Primates develop very similar symptoms to human beings. So I think that most scientists accept that this is indeed the link.’
| 'It may seem obvious that if something's wrong cells die and you die, but dying is actually a very complicated process and there's quite a lot of work still to be done' | |
Understanding the disease
The common factor in vCJD, BSE and all the other related diseases is a rogue form of a protein in the brain. This protein, called a prion, is found in many different tissues in the body and is normally harmless. However, it can change shape and when it does so it becomes a lethal disease-causing agent. It spreads by encouraging other prions to undergo the same shape change so starting a chain reaction that leads to the destruction of the brain. This much is understood but neuroscientist Rosalind Ridley of Cambridge University, says a great deal about the rogue proteins remain mysterious:
‘We know that the abnormal protein is a bad thing to have. How it actually destroys cells is a very interesting and much studied problem. It may seem obvious that if something's wrong cells die and you die, but dying is actually a very complicated process and I think there's quite a lot of work still to be done.’
How big is the problem?
While researchers grapple with understanding the disease the biggest question is how many people are going to catch it? Gallaher says there are no clear answers yet.
‘I think it’s a matter of just wait and see at the moment. The worrying news is that the number of cases is going up. I think in the last 18 months there's been almost a doubling in the number of cases although we're still talking about tens rather than hundreds of thousands of cases. What we don't know is what the incubation period of this disease might be. It looks like it might have a long incubation period so there's cause for alarm you might say though there's no real estimates as yet as to how big the problem will be and indeed if it will be an epidemic or not.’
Eighty-Four people are thought to have contracted vCJD in Britain but it will be many years before the true scale of the disease is known. Scientists aren't certain how the rogue prion proteins do their damage or even exactly how it is passed on from infected cow to human. The British government, along with many other international bodies such as the European Union, have taken steps to make sure infected beef does not get into food for human consumption. But as yet, there is no cure for any of the forms of CJD. Clive Evvers at the CJD Support Network says the families of those who have the disease accept it could be some time before there is a realistic chance that one will be found:
‘There are pieces of research currently taking place looking at the potential for one or two drugs that have been around for some time to see whether or not they might have an effect on ameliorating the condition. But really we need a lot more fundamental research about the agent before we can move to effective drug treatments.’
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| Symptoms of vCJD |
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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, vCJD affects much younger people - the average age is 27.6 years, with patients aged between 18 and 41 having contracted it. vCJD also lasts longer - up to two years from onset to death.
The first signs of vCJD 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.
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