Creutzfeldt-Jakob Disease (CJD) is a rare and ultimately fatal progressive degenerative brain disease. It is one of a group of diseases called Transmissible Spongiform Encephalopathies (TSEs) that affect humans and animals. TSEs are thought to be caused by the build up in the brain of an abnormal form of the naturally occurring 'prion' protein.
CJD was initially described in its classical, or sporadic, form in 1920. A new classification, known as variant CJD (vCJD), was first identified in 1996. Variant CJD is strongly linked to exposure, probably through food, to a TSE of cattle called Bovine Spongiform Encephalopathy (BSE).
Early symptoms of vCJD are often psychiatric, including anxiety, withdrawal, behavioural changes and depression. Persistent pain and odd sensations in the face and limbs are other early indicators. More obvious neurological symptoms, such as unsteady gait and sudden, jerky movements then develop, along with progressive dementia. All movement and speech is eventually lost and the patient will require 24 hour nursing care. Death occurs within an average of 14 months after the first onset of symptoms. The incubation period is unknown.
Many people with haemophilia have received letters informing them that they have received treatment made in part from the plasma of people who have subsequently developed vCJD. In addition, haemophilia centres wrote to patients in 2004 to inform them of a universal risk status if they had been treated with British-source plasma concentrate between 1980 and 2001.6 This letter, which appeared without warning and contained no offer of support or counselling, brought back painful memories for many haemophilia patients. It also triggered new fears about potential health risks, which still cannot be quantified. This concern is exacerbated by the fact that there is still no licenced test or treatment for vCJD.
In August 2009 the UK Government called for coroners to test the brain and spleen of young people during autopsies so that they could be tested for the presence of the infectious prion believed to cause vCJD. The Haemophilia Society is supporting this call, providing appropriate consents are obtained, as we believe it will help establish a clearer picture of the potential number of vCJD carriers in the wider UK population. We have also reiterated our call for any test for vCJD to be brought in as soon as it is available - not only for people currently 'at risk for public health purposes but also for blood donors to protect the blood supply.
In February 2009, following the finding of abnormal prions (which are associated with vCJD) at autopsy in the tissues of a man with haemophilia who died of other causes, the UK Government updated its risk assessment for people treated with plasma products between 1980 and 2001. This update has now been published.
As you probably know, everyone who lived in the UK between these dates who ate beef or other contaminated food products has a very low but continuing risk of developing vCJD. There is an additional slight increase in risk for people who received plasma products in the same period. If you are in this group you would have received a letter in 2004 explaining that all persons with haemophilia who were treated with UK derived plasma products between 1980 and 2001 are ‘at risk for public health purposes’ in relation to vCJD. The letter would also have offered you a chance to find out if you had received product from an ‘implicated’ batch. These were batches that had been manufactured from a plasma pool which contained at least one donation from a person who later developed vCJD. 802 people with bleeding disorders are known to have been treated with a product from an implicated batch.
Nobody with a bleeding disorder has died of vCJD anywhere in the world. The UK case of finding prions in the man at autopsy is the only time vCJD prions have been found in someone with a bleeding disorder.
The Department of Health have been trying to work out how it is most likely he was infected with the vCJD prion. The possible routes of infection include:
- The ‘implicated’ plasma products
- Blood transfusions
- The consumption of beef or other contaminated food products
- During an operation
- Other ‘non-implicated’ plasma products
Scientifically, it is not possible to tell with certainty where the vCJD prion came from, so the new risk assessment concentrates on which one is most likely. To try and work this out the Department of Health had to make some assumptions, many of which cannot be proved one way or the other. Where there is doubt the risk assessment uses the precautionary principal and is pessimistic. For example:
Assumption 1 – 1 in every 4,500 to 10,000 people are carrying the vCJD prion.
However, the estimated number of people who carry the vCJD prion range from 1 in 4,500 people to 1 in 300,000 people. Only 168 people in the UK have been diagnosed with vCJD. To be on the safe side the risk assessment is working on the assumption of a high possible number of potential blood donors carrying the vCJD prion.
Assumption 2 – People who are carrying the vCJD prion but have not developed the disease, can pass on the infection through plasma products.
Actually, nobody knows if this is true. So far only 3 people who have developed vCJD have been given it from a blood related source. None of these cases were from someone who was carrying the vCJD prion but hadn’t developed the disease.
The risk assessment then makes the following conclusions:
- The most likely cause of infection for this individual case was that he was infected from a plasma product (Factor VIII).
- That it was more likely that the infection came from a ‘non-implicated’ batch product than from an ‘implicated’ batch product. In other words from the product that was not made from a plasma pool containing a donation from someone who later went on to die from vCJD.
So how is it possible for the risk to be higher from batches that seems safer?
In this case, the man with haemophilia had received 9,000 units of treatment from implicated batches, compared to 390,000 units from the non-implicated batches. Obviously, the risk is higher for an individual dose from the implicated batch. However, because he received many more doses from the other batches, the risk from them builds up over time until it is more likely that it was one of these batches that caused the infection. Therefore, the Department of Health are saying that, because they are assuming that so many people carry the prion protein, the amount of product you took, rather than the batch it came from, is more important in deciding your risk. However if, as the understanding of vCJD improves over time, any of the assumptions turn out to be too pessimistic these conclusions could turn out to be wrong. The truth is that too little is known about this disease to be able to say for certain which route of infection was responsible.
As everyone who was treated with plasma products between 1980 and 2001 are already designated ‘at risk for public health purposes’ this new assessment doesn’t mean that there will be any change in the way people with bleeding disorders are treated. It is also important to note that these issues refer to plasma derived factor concentrates manufactured before 2001 and not the currently available products.
As more information becomes available, we will update you.
If you have further questions or concerns about what this new risk assessment might mean in your own case please get in touch with your Haemophilia Centre or contact the Haemophilia Society on 0800 018 6068 or info@haemophilia.org.uk .
