Patients' Mad Cow Disease risk 'substantial'
Pastor Dale Morgan
Patients' Mad Cow Disease risk 'substantial'*
Donors and recipients have been told they may be at risk of vCJD
A study of transfusion patients given blood contaminated with the human
form of mad cow disease has indicated the 24 still alive are at
"substantial" risk.
Prof John Collinge's assessment follows his investigation into the third
person infected from the original group of 66.
The patient, the first to be diagnosed with variant Creutzfeldt-Jakob
disease (vCJD) while alive, has since died.
Two others died before their illness was confirmed. The other 39 died
for reasons unrelated to the disease.
The name of the third patient to be infected has not been released, but
it is known that he received the blood transfusion at the age of 23.
He later became ill, and 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.
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
Prof John Collinge
He joined an experimental Medical Research Council trial for a treatment
called Prion-1 which began in 2004, in which patients were given a drug
called quinacrine, but he died a year later at the age of 32.
The diagnosis of vCJD was confirmed after his death after his tonsil
tissue was examined.
Prion diseases in humans are known to have long incubation periods, and
it is possible that 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.
So prions that enter the body through a blood transfusion rather than
through eating meat infected with BSE (bovine spongiform encephalopathy)
are thought to cause vCJD to develop more quickly.
'Substantial risk'
Experts believe that, based on the cases seen so far, infection from a
blood transfusion can develop in just six or seven years.
Professor John Collinge of the MRC Prion Unit said: "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.
'Efficiently transmitted'
"This information is vital for public health planning given the relative
ease with which prions seem to be passed on by blood transfusion."
He said it was possible people at high risk could have their tonsil
tissue tested in a bid to diagnose if they are infected.
Professor Collinge added: "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."
Writing in the Lancet, Kumanan Wilson of Toronto General Hospital and
Maura Ricketts of the Public Health Agency of Canada said: "This third
case considerably strengthens the inference that transfusion
transmission is possible and suggests that the causative prion can be
efficiently transmitted via this route."