Scientists show that vCJD can be transmitted through blood

British Medical Journal, Sept 23, 2000 by Roger Dobson

Scientists have warned that variant Creutzfeldt-Jakob disease (vCJD), the human form of bovine spongiform encephalopathy (BSE), could be transmitted through whole blood transfusions by donors who have no symptoms of the disease.

The warning follows new research with animals showing that BSE can be passed from a diseased sheep to a healthy animal.

But the UK Department of Health and the National Blood Service of England and north Wales said there was no evidence that vCJD had ever been transmitted to humans through blood transfusions. They said the risk was theoretical as whole blood was no longer used tot transfusions in the United Kingdom, the white cells being removed by a process called leucodepletion.

In the new study (Lancet 2000;356:955-9) researchers at the Institute for Animal Health in Newbury and Edinburgh took blood from sheep that had been fed brains from cattle infected with BSE. The blood was taken from the 19 sheep before any symptoms of disease appeared in the animals.

The blood was then transfused into healthy sheep from New Zealand, and 610 days later one of the sheep that had received the blood began to show signs of BSE. The other sheep given blood are healthy, said the report, but were mostly given the blood later than the affected animal.

"We have shown that it is possible to transmit BSE to a sheep by transfusion with whole blood taken from another sheep during the symptomless phase of an experimental BSE infection," said the report.

The report, which points out that whole blood is not now used in UK transfusions, adds, "Although this result was in only one animal, it indicates that BSE can be transmitted between individuals of the same species by whole-blood transfusion."

Dr Tim Wallington, medical spokesman for the National Blood Service, said, "We have closely monitored the development in the science of vCJD ever since it was acknowledged that the cause of the disease was most likely to be from exposure to BSE. Systems for reporting are robust, and it remains the case that there is no direct evidence of blood transmission of vCJD in humans."

He added, "The use of UK donated plasmas in the production of blood products has ceased. They are now made from imported plasma from countries where there is a very low incidence of BSE and no vCJD."

The Department of Health has described as "speculative" the reports that an 11 month old baby was born with vCJD after contracting it in the womb from her mother, who later died of the disease.

The Red Cross in Australia is establishing contingency plans in case the country's health ministers accept advice to ban an estimated 30000 people from donating blood. The group includes people who were in Britain for more than six months in the 1980s and early '90s. The US, Canadian, and New Zealand governments have already imposed similar bans.

Full story in News Extra at bmj.com