UK blood donors told they may carry human mad cow disease

LONDON, UK, 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 wasting disease.

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 during incubation.

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 transfusions.

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