August 2, 2005 (ENS): England's Department
of Health has begun to notify 100 people in the United
Kingdom who are newly identified as at increased risk
for the human form of mad cow disease, known as variant
Creutzfeldt-Jakob disease (vCJD).
These are people who have donated blood that was transfused
to three patients who later developed the fatal brain
Dr. Kate Soldan of the Emerging Infections and Zoonoses
Department of the Health Protection Agency Centre for
Infections in London, says vCJD infection has been observed
in two recipients of blood transfusions from donors
who later developed vCJD.
One of these recipients did not develop vCJD and died
of causes unrelated to the disease.
Although other exposures, including dietary exposure
to mad cow disease, known formally as bovine spongiform
encephalopathy, or BSE, cannot be excluded as the source
of these patients' infections, "it is considered
highly probable that these two patients were infected
by blood transfusion," says Dr. Soldan, who is
consultant scientist and scientific secretary to the
CJD Incidents Panel.
These reports added to previous evidence of vCJD infectivity
in blood obtained from experiments in animals and led
to the conclusion that transfusion should be considered
a possible route of vCJD transmission in humans.
The 100 or so individuals involved are being informed
by the UK Blood Services that they are "potentially
at-risk of vCJD for public health purposes" so
that special public health precautions can be taken
to reduce the risk of person-to-person transmission
of vCJD during their healthcare.
They are being asked not to donate blood, organs or
other tissues, and to inform their healthcare providers
of their "at-risk" status in order that infection
control guidance can be implemented for the instruments
used in certain invasive healthcare procedures.
Their general medical practitioners are being briefed
by the Health Protection Agency and Health Protection
Scotland so that they can provide further information
and support to their patients, and assist with implementation
of the recommended public health precautions, as required.
Over two million blood donations are collected each
year in the UK by the blood services, and over half
a million patients receive transfusions annually.
Of the 150 people who have died from vCJD in the UK
to July 1, four have been confirmed as having received
blood transfusions that may be associated with their
subsequent development of vCJD.
For one of these cases, the probable source of infection
has already been identified, as one of the donors went
on to develop vCJD. For the remaining three cases, transfusion
remains a possible source of the recipients' infection.
For two other cases, symptoms developed before or very
shortly after transfusion, and therefore transfusion
is not considered a possible source of their infections.
A risk assessment by the Department of Health looked
at the probability of donors to vCJD cases being the
source of a recipient's infection and, therefore, the
probability that the donors themselves are infected.
The United Kingdom CJD Incidents Panel considered this
risk assessment and recommended that such donors should
be considered as potentially at-risk of vCJD for public
health purposes unless the probability of being infected
with vCJD falls clearly below one percent.
Certain invasive healthcare procedures that have already
been carried out on these 100 people will be considered
by the CJD Incidents Panel.
Where past invasive healthcare procedures have been
conducted on these individuals, and potentially contaminated
instruments may be a risk for other patients, local
health protection staff are asked to consult the CJD
Incidents Panel for advice about whether any actions
should be taken.
Since its establishment in 2000, the CJD Incidents
Panel has issued advice relating to several groups of
patients identified as at increased risk of CJD.
Other groups of patients who are considered to be potentially
at-risk of vCJD for public health purposes include patients
who have been operated on with instruments previously
used for healthcare interventions on a patient with
vCJD; recipients of blood from donors who later developed
vCJD, and patients who have been treated with plasma
products that may have been contaminated with vCJD infection.
The first transfusion case of vCJD was announced in
December 2003. A blood donor, who was well at the time
of donation in 1996, died of vCJD in 2000, according
to the UK Health Protection Agency. A recipient of this
donated blood was diagnosed with vCJD in 2003 and died
in the autumn of that year.
A second case of probable transmission of vCJD infectivity
by blood was announced in July 2004. A patient had received
a blood transfusion in 1999 from a donor who later developed
vCJD. The patient died of causes unrelated to vCJD but
a post mortem revealed the presence of abnormal prion
protein - the infective agent which causes vCJD - in
the patient’s spleen, indicating that the patient
had been infected with vCJD.
The possibility that vCJD can be transmitted from one
person to another by blood transfusion raised the question
of whether transfusion should be considered as a possible
route of infection for other recipients with vCJD. This
in turn raised the question of whether donors to these
recipients might be carrying vCJD.
This new notification of donors to vCJD cases is a
further precautionary measure to reduce the possible
risk of secondary transmission of vCJD in the UK.
Prion diseases, or transmissible spongiform encephalopathies,
are fatal neurodegenerative dieases that affect both
humans and animals. The hallmark of prion diseases is
the accumulation of abnormal misfolded proteins in the
central nervous system which form plaques and holes
in the brain. vCJD has a long incubation period measured
in years, and there are usually no signs of the disease
Currently, there are no sensitive methods for the detection
of infectious prions in potential blood donors that
may be incubating the infectious agent for vCJD.
At an October 2004 symposium at the annual AABB blood
banking conference in Baltimore, Maryland, U.S., Canadian
and British scientists acknowledged that vCJD can be
transmitted through blood transfusion. They raised the
concern that there might be a second wave of the disease
brought about the human to human transmission through
David Asher, MD, chief and supervisory medical officer
with the U.S. Food and Drug Division of Emeging and
Transfusion-Transmitted Diseases at the Center of Biologics
Evaluation and Research expressed heightened concern
about vCJD transmission by blood.
The United States has a number of measures in place
to protect blood safety, but, he said, it is not possible
to remove every blood risk by donor deferral.
"If we attempt to defer every donor who spent
time in the UK from 1980 to 1996, the bood donor loss
would be enormous," he said.
Further information about this notification can be
found on the UK Health Protection Agency site at: http://www.hpa.org.uk/infections/topics_az/CJD/vCJDBloodDonors.htm
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