Creutzfeldt–Jakob disease (CJD) is a fatal, degenerative brain disorder that causes rapidly progressive dementia and loss of muscle control. It is a rare disease, affecting 1–2 people in every million in Australia.
What causes CJD?
CJD occurs when prion protein – a self-replicating protein found mainly in your brain and nervous system – mutates and becomes misshapen. The mutated form of the protein cannot be broken down by your body in the usual way so it accumulates in your brain over time, killing brain cells in the process. Eventually, the damage caused by the rogue protein makes your brain resemble a sponge.
Prion proteins can behave similarly to a virus. They can be transmitted from one host (person or animal) to another, and can replicate themselves in an infected person or animal causing disease.
Types of CJD
CJD can be sporadic, hereditary or acquired.
About 90% of people with CJD in Australia and elsewhere have sporadic CJD. It occurs when the prion protein in your body spontaneously mutates without any obvious cause. It typically affects older people (median age at death 67 years).
CJD is hereditary in about 7% of cases in Australia. It results from a mutation in the prion protein gene on chromosome 20, which causes your body to produce abnormal prion protein. Again, it largely affects older people (median age at death 59 years).
Acquired variant CJD
Acquired variant CJD was first reported in the United Kingdom in 1996 when people became infected from eating meat from cows with a related disease to CJD, bovine spongiform encephalopathy (BSE) – commonly known as ‘mad cow disease’. No cases of this type of CJD have ever been reported in Australia.
Acquired iatrogenic CJD
Acquired iatrogenic CJD usually occurs as a result of accidental infection from contaminated instruments during surgery, or from infected human tissue products. However, the stringent measures introduced to combat transmission of CJD this way means that there have been no deaths from acquired iatrogenic CJD in Australia since 2000. CJD is not transmitted through normal everyday contact between people, or sexually transmitted.
Symptoms of CJD
CJD has a long incubation period so symptoms may not appear until years after you have contracted the disease. Once symptoms appear, most people will die within 1–2 years depending on the type of CJD they have.
Early symptoms can be subtle and as the symptoms are not unique to CJD, it can be difficult to diagnose at this stage.
- Problems with balance and coordination, affecting ability to walk
- Slurred speech
- Problems with vision (seeing double)
- ‘Pins and needles’
- Personality changes
- Behavioural changes
- Anxiety and depression
- Problems sleeping
These symptoms are common and only a minute proportion of people experiencing them will have CJD.
More advanced symptoms
As the disease advances, a person will experience a rapidly progressive dementia, and in most cases, involuntary and irregular jerking movements known as myoclonus. As the disease continues to affect the nervous system, a person may experience loss of bladder and bowel control, lose the ability of speech and become blind. In the final stage of the disease, all mental and physical functions are lost, and an infected person will usually lapse into a coma. Death usually results from an infection like pneumonia or from respiratory failure.
Currently, there are no definitive tests that diagnose CJD although blood and urine tests are being developed. If your doctor suspects from your symptoms that you have CJD they may recommend one or more of the following tests to help them establish the likelihood of you having CJD.
- Electroencephalogram (EEG) – this is used to detect abnormal brain activity and can help diagnose sporadic CJD.
- Magnetic resonance imaging (MRI) – this creates an image of your brain that enables doctors to detect prion protein build up and any brain damage that is characteristic of CJD.
- 14-3-3 protein test – a sample of your cerebrospinal fluid (the protective fluid that surrounds your brain and spinal cord) is analysed for the presence of this protein in your body. It indicates damage to your nervous system. As nerve damage can occur for many reasons, it is not conclusive for CJD unless you have symptoms that strongly suggest CJD as well.
- Prion protein amplification – a sample of your cerebrospinal fluid is taken and tested for the presence of the abnormal prion protein.
- Genetic analysis of the prion protein gene – to help with diagnosis if you have suspected hereditary CJD.
- Very rarely, a brain biopsy may be requested where a tiny sample of your brain is taken for analysis. As brain biopsy may be harmful and may not be from an infected area of brain, and as there is no treatment biopsy is hardly ever indicated
There is no treatment available that cures CJD. You may be given drugs to help manage the involuntary muscle spasms and you may be prescribed opiates drugs to help with any pain.
What are your chances of contracting CJD in Australia?
Like other infectious diseases, the occurrence of CJD in Australia is closely monitored and investigated. The last surveillance report published in 2012 was still able to report that there has never been a case of variant CJD in Australia. With countries in Australia and around the world addressing livestock feeding practices to ensure variant CJD does not enter our food chain, variant CJD appearing in Australia this way is unlikely.
The main risk factor for contracting CJD in Australia is whether you received a human pituitary hormone product before 1986. If this is the case you will have most likely received a letter from the Health Department informing you of this risk. Similarly, you may also have received a letter if you were previously exposed to surgical instruments that could potentially have been infected with CJD. However, the risk of having contracted CJD this way is very low.
There are now stringent protocols in place in Australian hospitals to prevent transmission of CJD through surgical instruments, human tissue products and blood transfusion. As there has been no transmission of CJD this way since 2000, it seems that the preventative measures in place are working.
Sporadic CJD affects approximately 1 in every million Australians every year.
Donating blood and CJD
Although there is no definitive scientific proof, it is possible that variant CJD may rarely be transmitted by blood transfusions. 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.