Unconventional pathogens causing spongiform encephalopathies absent in blood products.

To determine whether unconventional pathogens causing subacute spongiform encephalopathy may be present in blood products, a newly developed hepatitis B vaccine and a widely used blood product were injected into mice and rats. As only a few aged mice in the test and the control groups showed spongiform encephalopathic change of a sparse or mild degree and which differed from that seen in rodents infected with Creutzfeldt-Jakob disease, the presence of unconventional pathogens in the tested inocula can be ruled out.