After studying sheep for nine years, researchers at the University of Edinburgh have found evidence that vCJD can be transmitted through blood transfusion in humans.
The researchers say that their findings highlight the significance of precautions against vCJD transmission, such as the Government decision in 2004 to ban blood donations from anyone who had received a blood transfusion since 1980.
During the study, the researchers looked at BSE transmission between sheep through infected blood to quantify how vCJD - the human form of BSE - could be spread through transfusions.
They observed that the likelihood of BSE being transmitted between sheep through transfusion of infected sheep blood was 36 per cent, with rates of 43 per cent found for scrapie.
"It is apparent that the stage of disease incubation in infected donors played a large role in the likelihood of transmission. The longer that BSE or scrapie had been carried by donors, the greater the likelihood of the disease being transmitted with transfusions of infected blood," said lead researcher Fiona Houston, presently at the University of Glasgow.
BSE is one of a group of rare neurodegenerative disorders called transmissible spongiform encephalopathies (TSEs), which include scrapie and vCJD.
The researchers said that eight of the 22 sheep that received BSE infected blood showed evidence of infection, while nine out of 21 sheep receiving scrapie-infected blood developed the disease.
"The study shows that, for sheep infected with BSE or scrapie, transmission rates via blood transfusion can be high, particularly when donors are in the later stages of infection. This suggests that blood transfusion represents an efficient route of transmission for these diseases and justifies the current control measures put in place to safeguard human blood supplies," Houston said.
The study has been published in the journal Blood.