Infected meat eaten in the late 1980s caused many of the vCJD deaths. Photograph: Matt Dunham/AP
Scientists believe they are a step nearer to developing a reliable blood test for variant CJD, the human form of BSE and say their prototype is 100,000 times more sensitive than any previous attempt.
A team from the government-funded Medical Research Council(MRC) based at University College London, found the infectious prion agents associated with the disease in the blood of 15 of 21 samples from people known to have had vCJD and says it has detected infection in blood spiked with vCJD to within one part per 10m.
More work is needed, including anonymously testing thousands of blood donors in a country not knowingly exposed to infection, as controls. Progress has been reported in the Lancet medical journal as the government continues to ponder the ethics of telling infected people they have a disease for which there is no proven treatment and no cure. There are also uncertainties over how many people carry infection even without ever showing clinical symptoms.
Most of the 170 who have died from the long-incubating disease in the UK since 1995 are thought to have contracted it from eating infected meat in the late 1980s. Controls on the meat industry, not always rigorously observed, were later introduced to protect consumers. But three people are thought to have died because they were unwittingtly given infected blood transfusions years before expensive restrictions on donated blood and blood products were introduced.
Two other people who died from other causes were found to have vCJD infection; one is thought to have had a transfusion of contaminated blood during an operation, and the other, a person with haemophilia, to have received contaminated blood products. Without a reliable test or filter for donations, there is no way of knowing how effective existing safety measures are. Trials of a filter are expected to be completed later this year.
John Collinge, director of the MRC prion unit, said: “We have quite a lot of room for improving this test”. Early diagnosis of vCJD was vital, he said. “At the moment, a firm diagnosis can usually be made only once serious symptoms of the disease have developed which indicate extensive damage to the brain.”
The Department of Health is montoring the research closely while NHS Blood and Transplant said it “may be a first step towards development of a screening test which could be of value in establishing the prevalence of infection, as a blood donor screening test or for testing people considered at risk for public health purposes.”
Sources : Guardian-Health