Efforts to differentiate
bovine spongiform encephalopathy (BSE) from
scrapie in
prion infected sheep have resulted in effective methods to decide about the absence of BSE. In rare instances uncertainties remain due to assumptions that BSE, classical
scrapie and CH1641-a rare
scrapie variant-could occur as mixtures. In field samples including those from fallen stock, triplex Western blotting analyses of variations in the molecular properties of the
proteinase K resistant part of the disease‑associated form of
prion protein (
PrP(res)) represents a powerful tool for quick discrimination purposes. In this study we examined 7 deviant ovine field cases of
scrapie for some typical molecular aspects of
PrP(res) found in CH1641‑scrapie, classical
scrapie and BSE. One case was most close to
scrapie with respect to molecular mass of its non-glycosylated fraction and N-terminally located 12B2‑epitope content. Two cases were unlike classical
scrapie but too weak to differentiate between BSE or CH1641. The other 4 cases appeared intermediate between
scrapie and CH1641 with a reduced molecular mass and 12B2‑epitope content, together with the characteristic presence of a second
PrP(res) population. The existence of these 2
PrP(res) populations was further confirmed through deglycosylation by PNGaseF. The findings indicate that discriminatory diagnosis between classical
scrapie, CH1641 and BSE can remain inconclusive with current biochemical methods. Whether such intermediate cases represent mixtures of TSE strains should be further investigated e.g. in bioassays with rodent lines that are varying in their susceptibility or other techniques suitable for strain typing.