PrP(Sc) deposition in nervous tissues without lymphoid tissue involvement is frequently found in ARQ/ARQ Sarda breed sheep preclinically affected with natural scrapie

The pathogenesis of natural scrapie in Sarda breed sheep was investigated in 1050 asymptomatic and 49 sick sheep from scrapie-affected flocks.Central and peripheral nervous system, along with lymphoreticular system (LRS)tissues, were subjected to immunohistochemistry (IHC) and Western-blotting(WB) for detection of pathological isoform of the prion protein (PrPSc). A total of 69 of the 1050 clinically healthy sheep were found to be infected with scrapie, with PrPSc being detected in both the central nervous system (CNS) and enteric nervous system (ENS) plexuses of 60 of the sheep, while IHC and WB yielded evidence of PrPSc deposition only in lymphoid tissues of the remaining 9 clinically healthy sheep. PrPSc was also detected in the CNS, as well as in ENS plexuses from allof the 49 clinically affected sheep. Nevertheless, 18 of the 69 clinically healthyanimals (26%, 17 ARQ/ARQ and 1 ARQ/AHQ sheep), along with 3 ARQ/ARQ sheep (6%) of the clinically affected group, showed no IHC or WB evidenceof PrPSc in lymphoid tissues, but PrPSc could be still detected in their CNS and ENSplexuses. The study demonstrates dual CNS and ENS PrPSc deposition in Sardasheep with scrapie, in spite of an apparent lack of lymphoid tissue involvement ina number of cases.[...]