Scrapie infectivity in hamster blood is not associated with platelets

The infectivity of hamster scrapie strain 263K was measured in platelets isolated from blood pooled from six hamsters with clinical scrapie. The total number of infectious doses present in the blood pool was 220, out of which only 3.5 infectious doses were associated with platelets. A larger proportion of the total infectivity was recovered from the mononuclear leukocyte fraction. This result indicates that platelets are not the source of blood-borne infectivity in transmissible spongiform encephalopathy-infected hamsters.