Blood donors, mad cow disease linked
Friday, February 6, 2004
LONDON -- British scientists studying how the human form of mad cow disease is transmitted say some people could be passing the illness through blood donations.
Although it has not been proven that the brain-wasting variant Creutzfeldt-Jakob Disease can be transmitted through transfusion, the scientists did find a case in which a blood donor and the recipient died of it.
In that case, the donor gave blood more than three years before he developed symptoms, the scientists said in their report in today's Lancet medical journal.
The researchers, led by professor Robert Will at the National CJD Surveillance Center in Edinburgh, wrote that "although the epidemic of vCJD presently seems to be in decline, a proportion of the U.K. population could be incubating vCJD and acting as blood donors."
The scientists based their study on records from United Kingdom blood services and also the national CJD surveillance unit.
The report said 48 people had been identified as having received blood from 15 donors who later developed the variant disease.
By December 2003, all but 17 of the recipients had died but vCJD was the cause of death in only one case. The disease can only be confirmed during an autopsy by examining brain tissue.
"Our findings raise the possibility that this infection was transfusion transmitted," the report says, adding that infection also "could have been due to past dietary exposure" to BSE.
Scientists already believe people can get variant CJD from eating products from cows infected with a similar illness, bovine spongiform encephalopathy -- BSE -- or mad cow disease.
Statistical analysis indicated that the odds of the man not being infected by his blood transfusion were between one in 15,000 and one in 30,000.
In an accompanying independent commentary, Dr. Adriano Aguzzi and Dr. Markus Glatzel from the University Hospital of Zurich in Switzerland, said, "the chance that this case is not transfusion-related is very small."
"Shocking as it may be," they wrote, "the finding that vCJD can be transmitted via blood transfusion is not surprising. Stringent studies in sheep show that prion diseases" -- such as CJD -- "can be transmitted via blood, even if blood is collected in preclinical stages of prion disease."
Besides the transfusions, 20 units of plasma from people who later developed variant CJD were used to make blood products before 1998, when Britain stopped using British blood, the Lancet report said.
The scientists said that before 1998, "many thousands of individuals may have been exposed" to blood products "derived from pools containing a donation from an individual incubating vCJD."
So far, they said, no case of variant CJD has been identified as connected to exposure to such plasma products. The risks from plasma products are probably less than from transfusion, they added.
All blood products for use in operations in Britain are now based on plasma imported from the United States, where there have been no cases of human mad cow disease blamed on American beef. The human form of mad cow disease so far has claimed 143 victims in Britain and 10 elsewhere.