Detection of PrPSc in sheep at the preclinical stage of scrapie and its significance for diagnosis of insidious infection.

A field sheep insidiously infected with natural scrapie was diagnosed at the preclinical stage through detection of the core fragment of PrpSc (PrPcore) in peripheral lymph nodes by the biopsy method. Three out of 32 euthanized healthy sheep were found positive for PrPcore in the spleen and lymph nodes. Mice that were inoculated with spleen homogenate of one of these sheep showed clinical signs of scrapie and were positive for PrPcore in their brain samples. These results suggest that the detection of PrPcore is significant for diagnosis in the preclinical phase of scrapie.