Can prion diseases be transmitted between individuals via blood transfusion: evidence from sheep experiments.

We have shown that it is possible to transmit bovine spongiform encephalitis (BSE) to a sheep by transfusion with whole blood taken from another sheep during the pre-clinical phase of an experimental BSE infection when the donor animal appears healthy. BSE and new variant Creutzfeld-Jakob disease (vCJD) in humans are caused by the same infectious agent and the sheep-BSE experimental model has similar pathogenesis, with involvement of the lymphoreticular system, to that of human vCJD. Although we have had only one case of positive transmission of BSE out of a total of 21 transfusions, our studies remain incomplete and further cases could occur. Our studies, however, reinforce the possibility that whole blood donated by pre-clinical vCJD-infected humans may represent a risk of spreading vCJD infection among the human population of the U.K.