What is Creutzfeldt-Jakob disease?
Creutzfeldt Jakob disease (CJD) is a degenerative brain disorder that causes rapidly progressive dementia.
It is thought the disease is caused by abnormal versions of brain proteins known as prions. We all have prion proteins in our bodies, but in CJD normal prions are converted to abnormal forms of the protein. These misshapen abnormal forms of prions damage brain cells, eventually creating many holes in the brain tissue, giving it the appearance of a sponge.
There are 2 main types of CJD — classical and variant.
Classical CJD (cCJD) was first described in 1920, and typically affects older people (median age 68 years). About one case occurs per million people per year. Most cases (more than 85 per cent) are sporadic, and occur without any explanation. In a small proportion of cases (5-10 per cent), the disease is inherited.
Variant CJD (vCJD) is a new form of the disease, and was first reported in the United Kingdom in 1996. It is thought to be contracted by eating meat from cows that have bovine spongiform encephalopathy (BSE) — commonly known as ‘mad cow disease’.
vCJD produces similar symptoms to cCJD, but the course of the illness is generally longer, and younger people (median age 28 years) have been affected. As of June 2008, there were 208 cases of vCJD reported worldwide, and 167 of those cases occurred in the UK.
What are the symptoms of CJD?
Both cCJD and vCJD have a long incubation period, which means that symptoms may not start to appear until many years after contracting the disease.
The initial stage of the disease can be subtle, with symptoms of depression, confusion, and personality and behavioural changes. Other symptoms that occur early on are strange physical sensations, such as a feeling of ‘sticky’ skin, and sensations of cold or pain. Psychiatric and sensory symptoms such as these are often more pronounced in people with vCJD.
Problems with memory, balance, coordination and sight soon develop. As the disease advances, the person experiences a rapidly progressive dementia, and in most cases, involuntary and irregular jerking movements known as myoclonus. People with cCJD usually progress to dementia and myoclonus more quickly than those with vCJD.
In the final stage of the disease, all mental and physical functions are lost, and the person usually lapses into a coma. The average time between onset of symptoms and death of someone with cCJD is 7 months; however, some people have survived up to 2 years. People with vCJD usually survive a little longer, usually about 12-14 months after the onset of symptoms. All forms of the disease are invariably fatal.
Is there a cure for CJD?
At the present time, there is no known effective treatment or cure for CJD. However, research is continuing, and it is hoped that there will be an effective treatment within the next 5 to 10 years.
Am I at risk of CJD?
You may have a higher risk if you have a family history of the disease.
Although it is very rare, cCJD has been transmitted as a result of some medical procedures. This is because the prions that cause CJD are resistant to the usual sterilisation techniques used to disinfect surgical instruments, so it is possible for CJD to be transmitted via the use of contaminated medical instruments used in brain surgery.
There have also been cases of cCJD inadvertently being passed from person to person as a result of cornea transplants; human dura mater (brain membrane tissue) transplants; and injections of human-derived growth hormone used to treat short stature and infertility. (Human growth hormone injections are no longer given, and a synthetic growth hormone has been used since the mid-1980s.)
There have been no cases of mad cow disease reported in Australian cattle, and no cases of vCJD in Australia at the time of writing. However, with the ease of travel, in addition to the length of time that contaminated beef was available in the UK (and possibly elsewhere), it is possible that there will be cases of vCJD in Australia at some point in the future.
Alongside the UK, countries that have reported cases of BSE in cattle include: Canada, Japan, USA, and European countries including Portugal, Spain, Belgium, Germany, Italy and France.
The risk of contracting vCJD from eating beef or beef products from the UK is currently extremely low (about one case per 10 billion servings). In order to reduce your risk when travelling to the UK, other European countries, or any country that has reported cases of BSE, you may want to consider either not eating beef products, or only eating low-risk beef products, such as solid muscle meat, rather than sausages or burgers.
Evidence from the UK has shown that vCJD may be transmitted from person to person via blood transfusions.
Variant CJD: disease control
It is now generally agreed that the practice of feeding meat and bone meal (some of which derived from BSE-infected cattle) to livestock cattle was driving the BSE epidemic in the UK.
There are now bans on feeding meat and bone meal from ruminants (for example, cows, sheep and goats) to cattle in most countries. There are also other measures in place to reduce the risk of humans being exposed to BSE. In addition, imports of beef and beef products to Australia have been banned from the UK since 1996, from other European countries since 2001, and from Japan since 2001.
Although there is no definitive scientific proof, it is possible that vCJD may rarely be transmitted by blood transfusions. There have been 4 probable cases of blood transfusion-associated transmission of vCJD in the UK to January 2007. As a result, to protect Australians, there are some restrictions on who can give blood in Australia. You are currently not eligible to give blood if:
- you lived in the UK for a cumulative period of more than 6 months between 1980 and 1996; or
- you received a transfusion of blood or blood products in the UK from 1980 onwards.
2. Health Protection Agency. 4th case of variant CJD infection associated with blood transfusion [updated 2007, Jan 18; accessed 2009, Apr 27]. Available at: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAweb_C/1195733711457?p=1171991026241