vCJD case highlights blood transfusion risk
Friday 8th December 2006
Scientists have confirmed that Variant Creutzfeldt-Jakob disease (vCJD) can be passed from person to person through blood transfusion. A case study published in The Lancet reports on the third person known to have contracted vCJD from blood transfusion. The patient, who has since passed away, is the first to have been diagnosed whilst still alive. Two others from a group of 66 people who received prion-infected blood from donors known to have developed vCJD, died before their illness was confirmed.
At the age of 23, the patient was given a blood transfusion from a donor who later developed vCJD. Seven and a half years later he was referred to the NHS National Prion Clinic at the National Hospital for Neurology and Neurosurgery where his symptoms were confirmed to be caused by vCJD. The patient opted to join the experimental MRC treatment trial Prion-1 which began in 2004, in which patients are given a drug called quinacrine. Sadly, he died a year later at the age of 32.
Professor John Collinge of the Medical Research Council Prion Unit explains:
‘‘That three individuals from this small group of people that we know to have been exposed through blood transfusion have already developed vCJD infection suggests that the infection may be efficiently passed by this route, so the risk to remaining individuals is likely to be substantial.”
‘‘A national tonsil tissue screening study being performed by the Health Protection Agency may soon give estimates of the number of people who are silently infected with prions. This information is vital for public health planning given the relative ease with which prions seem to be passed on by blood transfusion.”
Prion infections in humans are known to have long incubation periods, a person could be silently infected for more than 50 years before developing symptoms of the disease. During this time such a carrier of infection poses a potential risk to others through blood transfusion and contamination of surgical and medical instruments.
The incubation period when prions pass from human to human is thought to be much shorter than when they pass from one species to another. As a result, prions that enter the body through blood transfusion as opposed to eating infected cattle meat, like BSE prions do, probably cause vCJD to develop more quickly. When blood transfusion is the source of prions, vCJD seems, based on these cases, to develop in as little as 6 to 7 years.
Professor Collinge concludes:
‘‘Analysis of samples of the patient’s tonsil tissue after death, confirmed that they were infected with prions. Examining tonsil tissue is an established way to diagnose vCJD early if there is reason to suspect a person has prion disease. There was uncertainty about whether this test would also be helpful in patients infected by blood transfusion. Study of tissue from the patient in this case study was extremely helpful in answering this question. In fact, it is likely that prion infection could be diagnosed by tonsil biopsy in people who are known to be at high risk because they have received blood from an infected donor should they wish. Although we do not yet have an effective treatment for any form of CJD, a reliable tonsil test could allow people with vCJD to access experimental treatments early.”
Key facts
- The prions that cause vCJD are an altered form of one of the body’s own proteins. This is why the immune system fails to recognise the danger prions represent.
- Scientists know that a person’s genetic profile plays a role in their relative risk of developing vCJD.
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