Creutzfeldt-Jakob Disease (CJD)
- What is Creutzfeldt-Jakob disease?
- What are the symptoms of CJD?
- How common is CJD?
- What causes CJD?
- Can CJD be treated?
- How does CJD relate to "mad cow disease"?
- Is beef still dangerous?
- Where can I find out more about CJD?
What is Creutzfeldt-Jakob disease?
Creutzfeldt-Jakob disease, commonly known as CJD, is a very rare form of dementia. Dementia is a term that describes any condition which leads to ever-decreasing mental ability. Alzheimers disease is the most common form of dementia, and probably the most well-known.
Some rare types of dementia can be transmitted, and these are known as prion diseases. CJD, along with Kuru (a disease once noted among cannibals in New Guinea) and some animal dementia-type illnesses, is such a disease. This means that, unlike Alzheimers disease, CJD can be "passed on" to others.
Fortunately, CJD cannot be transmitted by air, like influenza or the common cold, nor is it contagious, like measles or mumps. However, it may be possible to catch CJD through exposure to infected blood and tissue, and this has caused a recent fear about dental surgery in the UK. There is no evidence that having dental treatment in Ireland puts you at any risk.
Two German doctors first discovered CJD in the 1920s. They noticed that the brains of people who had died from CJD had lost most of their nerve cells. The nerves had been replaced by fine fibres spotted by microscopic holes that resembled a sponge. This trait has been seen in scrapie, which affects sheep, and BSE, which affects cattle. BSE, the "mad cow" disease, actually stands for Bovine Spongiform Encephalopathy, which means spongy brain disease in cows.
CJD occurs all over the world, but remains very rare, affecting one new person in every two million each year. It tends to affect people between the ages of 50 and 80. However, a new variant of Creutzfeldt-Jakob disease (nvCJD) that afflicts people at a much younger age was identified in the 1990s. Research indicates that this variant of the illness is likely to be caused by cross-infection from cattle infected with BSE in other words, through eating infected beef. New variant CJD is therefore also known as human BSE.
What are the symptoms of CJD?
As with any form of dementia, CJD slowly erodes the mental ability of the affected person. Initially, a person with CJD may demonstrate mood swings and memory lapses. Their ability to work is impaired and they begin to lose interest in social activities. At this stage, CJD symptoms resemble a mild form of depression.
As time goes on, however, they will become unsteady on their feet, their speech will begin to slur and their vision will deteriorate. The disease will then progress rapidly, as the patient experiences jerking limbs, incontinence and tremors. They also lose their ability to speak or move.
This rapid degeneration can be very distressing for relatives, but fortunately the person with CJD will only be aware of the early onset of the illness, possibly complaining of blurred vision and clumsiness. CJD is fatal, and death is usually the result of a secondary illness, such as pneumonia, usually within months.
In one in ten cases, people with CJD may survive for up to five years. On these occasions the onset of the disease is much slower, and the patient may only suffer slight memory loss in the first year or two.
Patients with nvCJD tend to be affected earlier in life and usually survive for longer before finally succumbing to the illness.
How common is CJD?
Creutzfeldt-Jakob disease is extremely rare. Memory loss, blurred vision and all the other such symptoms may have many other causes and are highly unlikely to herald CJD. There have been only 30 cases in Ireland in the last 20 years, and only between 30 and 50 in the UK each year.
The new variant of CJD, which is transmitted by eating infected beef, affects people at a much younger age than standard CJD. In the last decade, there have been 77 definite or probable cases of this new variant in the UK, less than a quarter of all cases of CJD. There are no statistics for nvCJD in Ireland, but 11 of the 30 deaths since 1980 were under the age of 50. None of these cases have been proven to be caused by new variant CJD.
What causes CJD?
There is no simple answer. For many people who contract CJD, there will be no obvious reason why. There have been some circumstances, however, where the cause of CJD can be traced:
- Occasionally, CJD is hereditary, in which case there will have been a close family member who had the illness.
- In the past, some people, who were treated with human growth hormones that had been extracted from corpses, contracted CJD. This hormone is now produced artificially in most parts of the world, including Ireland.
- A few people contracted CJD after receiving corneal transplants from an infected donor. This would be a very unlikely occurrence in Ireland, given the extreme rarity of the condition in this country.
- Three people in Britain died of CJD after brain surgery. It was later discovered that surgical instruments used in their operations had previously been used on CJD-infected patients. It is now common practice to destroy all instruments after surgery on CJD patients, as many forms of sterilisation do not seem to kill the active agent of infection.
- Some people in America have been informed that they may have been infected with CJD through potentially contaminated blood products. There has been no diagnosed case of CJD from this source as yet.
Most of these cases occurred at a time before it was known that CJD could be passed from one human to another.
Can CJD be treated?
Unfortunately not. There is no treatment that can cure CJD or halt its progress. Drug treatments are available to alleviate pain in people with CJD, and to make their lives more comfortable.
How does CJD relate to "mad cow disease"?
BSE, the so-called "mad cow disease", was first discovered in Britain in 1986, and over one million cattle may have been infected during the course of the outbreak. While the British epidemic has receded, its cause remains unclear, but is thought to have been due to cattle being fed sheep products infected with scrapie.
The disease seems to have "jumped" from sheep to cows, and subsequently from cows to humans, where it has been given the name of human BSE, or new variant CJD (nvCJD). Despite British government claims to the contrary during the 1990s, research has proven that nvCJD results from eating infected beef and beef products.
Is beef still dangerous?
Due to different feeding methods for cattle, BSE has been much rarer in Ireland, North and South, than in Britain. For a number of years now, stringent measures have been taken throughout Europe to monitor any outbreak of BSE and carefully to destroy any infected cattle. All European beef products are now carefully monitored and Irish beef, in particular, is considered BSE-free.
However, BSE may have entered the human food chain as early as 1980. Since the incubation period for nvCJD the time between being infected and becoming ill may be between 5 and 40 years, it is impossible to tell how many people may ultimately develop the disease, and estimates in the UK vary considerably.
It is theoretically possible that anyone who ate British beef products during the 1980s and early 1990s may be at risk of contracting the disease at some stage in the next 40 years. However, CJD in any of its variants remains an extremely rare complaint, and researchers at Londons City University believe the disease has an incubation of only 8 years. If this is so, then any BSE epidemic has already reached its peak.
Where can I find out more about CJD?
Due to the diseases rarity in Ireland there is no native support group or information service. However, the tragedy of the BSE crisis in the UK led to the foundation of a CJD surveillance unit based in Edinburgh. They can be found on-line at www.cjd.ed.ac.uk.
Deaths from human BSE in Britain have led to the setting up of a support group for friends and relatives of people who died from the illness. Their website is at www.humanbse.org.uk.
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