Thousands of people in the UK could be unwitting carriers of the protein which causes the human form of mad cow disease, according to new research. In a government-funded study scientists examined the appendices and tonsils of 12,500 people and found three of the samples tested positive for variant Creutzfeldt-Jakob-Disease. On that basis they have calculated 3,800 people in Britain could be carrying the infective agent, a prion protein. It is feared individuals could be incubating the disease without showing symptoms while still posing a threat to others. In March, in a bid minimise the risk of spreading the disease, Britain banned people who received transfusions over the past 24 years from donating blood. It is estimated 141 people have died in the UK from CJD - the disease is claiming around 20 lives a year. CJD was first linked to eating beef from cows infected with BSE, or mad cow disease, in 1996.