Human Mad Cow Disease (CJD) Can Spread By Blood Transfusion
Paris – The human version of mad-cow disease can be spread by blood transfusion, according to preliminary research published.These early findings place a question mark over the safety of blood transfusions, as the agent can be transmitted even before a blood donor shows any symptoms of the disease, the researchers suggest. Variant Creutzfeldt-Jakob disease (vCJD) is caused by the same agent as mad-cow disease, in which a mutant form of a protein called a prion proliferates crazily, causing sponge-like holes to form in the brain.
Eating beef contaminated by bovine spongiform encephalopathy (BSE), as mad-cow disease is called, is an identified path of catching vCJD. But until now, data has been unclear or contested as to whether it can also be passed on in blood transfusions. Reporting in issue of The Lancet, scientists at the Institute for Animal Health in Edinburgh say they fed a breed of British sheep a sample of brain from cattle infected with BSE. Sheep were chosen as they harbour the infectious agent in tissues other than the brain and spinal cord, as do humans. Blood was taken from 19 infected sheep before any symptoms were apparent, and was transfused into healthy sheep imported from New Zealand. After 610 days, one of the transfused sheep began to show signs of the disease. All the others are healthy at present, although most are at an earlier stage after transfusion than the affected sheep. While acknowledging that their study still had several years to run and so far only one animal had fallen sick, the scientists said this early finding was “sufficiently important” to announce right now. “This report suggests that blood donated by vCJD-infected human beings may represent a risk of spread of vCJD infection among the population of the UK,” they said. It should now be possible to identify which cells are infected and develop a diagnostic test for vCJD based on a blood sample, they said. That would also help to test the effectiveness of a two-year-old British policy which seeks to eliminate the likeliest source of vCJD transmission by stripping out white blood cells from blood donations. As its name suggests, vCJD is a form of Creutzfeldt-Jakob disease (CJD), for which there is no evidence of a risk of transmission by blood transfusion.
However, vCJD “has a different pathogenesis (from CJD) and could represent different risks,” the scientists caution. Meanwhile, researchers from France’s National Centre of Scientific Research (CNRS) report that vCJD may be promoted by normal prions as well as abnormal ones. Three types of non-mutant prions play a role in a complex “cascade” of enzyme signals that govern brain-cell functions, they say in work published in the US weekly Science. This discovery could ultimately throw up possible treatments for vCJD by designing drugs that block or alter the signalling process. People with vCJD suffer jerky movements, forgetfulness, dementia and finally death. There is no cure or vaccine at present.