THURSDAY, Aug. 5, 2004 (HealthDayNews) -- British authorities report new evidence that the brain-destroying condition widely known as human mad cow disease can be spread by blood transfusion.
The distorted protein called a prion that causes the condition was detected in an elderly person who received a blood transfusion in 1999 from a donor who developed the disease after the donation and died in 2001, said a report in the Aug. 7 issue of The Lancet.
The person, whose age and sex were not disclosed, did not have symptoms of the disease and died this year of other causes, said the report from the National Creutzfeldt-Jakob Surveillance Center. The prion was detected in the patient's spleen in an autopsy.
One case of transmission linked to a transfusion was reported earlier this year in Britain. The victim in that case developed symptoms of the disease 6.5 years after receiving a transfusion from a donor who developed symptoms three years after the donation and died of the disease. But the victim in that case also died of the disease, in December 2003.
The latest report is worrisome because the infected person had a genetic variant not seen before, meaning that the number of people vulnerable to infection is much greater than had been thought, the report said.
Seventeen cases of the disease, formally called variant Creutzfeldt-Jakob disease, have been diagnosed in the United Kingdom. Creutzfeldt-Jakob disease is literally a one-in-a-million condition of unknown cause that destroys mental function.
Variant Creutzfeldt-Jakob disease is a human version of an animal disease, bovine spongiform encephalitis, which has led to the destruction of thousands of cattle in the United Kingdom. No human equivalent of mad cow disease have been reported in the United States, but the nation's first animal case, a single infected cow, was reported in the state of Washington last December.
Because of the risk of spreading the disease by transfusion, the United States does not accept blood donations from people who have spent at least five months in Europe since 1980 or spent three months in the United Kingdom between 1980 and 1996.
The United Kingdom has taken aggressive steps against the disease, including importing plasma to produce medical blood products and deferring donations from individuals who have received suspect transfusions.
Those steps illustrate the difficulty of protecting people in a situation where the scientific evidence of risk is uncertain, said Dr. Kumanan Wilson, an assistant professor of medicine at the University of Toronto in Canada and co-author of an accompanying editorial in the journal.
The conventional method "would require clear evidence of a risk, particularly when the action could have a harmful effect -- in this case, reduction of the blood supply," Wilson said.
Instead, the United Kingdom chose "a new model of policy making," which was to take measures even though it is still not clear how big the risk of transfusion transmission is, he added.
It was the right decision, Wilson said. "By acting in advance of complete certainty, policy makers have potentially protected against variant Creutzfeldt-Jakob disease emerging as a major new large-scale blood-borne epidemic," he said.
While it still is not certain that the disease can be spread through transfusions, "this is the correct way to make policy, rather than waiting until all the evidence is in," Wilson said. "By then, thousands of people might be exposed."
Another study in the same issue of The Lancet reported disappointing results in testing one measure designed to prevent the spread of the disease by transfusion. Leucoreduction -- the removal of white blood cells -- reduced infectivity by only 40 percent in animal tests, said the report by a group headed by Luisa Gregori, an assistant professor of neurology at the University of Maryland.
Leucoreduction is being practiced in the United Kingdom, Canada, and other countries, Gregori said.
"It should be continued, but other methods of removal should also be investigated," she said. "We need methods of removal from plasma, which is more difficult to achieve."
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