Probable transmission of bovine spongiform encephalopathy to humans has focused intense interest on all of the transmissible spongiform encephalopathies (TSEs) and how they spread. In all TSEs, an abnormal disease-associated, proteinase K-resistant protein referred to as PrP-res or PrPsc accumulates in brain. In some species, PrP-res accumulates in other tissues as well. Sheep placenta, brain, spleen, and lymph node were analyzed in detail for PrP-res and infectivity. Both were detected in all brain and spleen samples and in placenta and lymph nodes of 80% of the scrapie-infected sheep. A perfect correlation was observed between infectivity and PrP-res detection. These results substantiate the probability that placenta plays an important role in natural transmission of scrapie, suggest that analysis of placenta for PrP-res could be the basis for an antemortem test for sheep scrapie, and show that PrP-res, scrapie infectivity, and scrapie disease are closely associated.

Abstract. A distinct strain of scrapie identified in sheep of Norway in 1998 has since been identified in numerous countries throughout Europe. The disease is known as Nor98 or Nor98-like scrapie, among other names. Distinctions between classic scrapie and Nor98 scrapie are made based on histopathology and immunodiagnostic results. There are also differences in the epidemiology, typical signalment, and likelihood of clinical signs being observed. In addition, sheep that have genotypes associated with resistance to classic scrapie are not spared from Nor98 disease. The various differences between classic and Nor98 scrapie have been consistently reported in the vast majority of cases described across Europe. The current study describes in detail the pathologic changes and diagnostic results of the first 6 cases of Nor98 scrapie disease diagnosed in sheep of the United States.

The IHC test for PrP(Sc) in RAMALT was an effective means of detecting subclinical scrapie in live, high-risk sheep.

Control of scrapie, an ovine transmissible spongiform encephalopathy or prion disorder, has been hampered by the lack of conventional antemortem diagnostic tests. Currently, scrapie is diagnosed by postmortem examination of the brain and lymphoid tissues for PrP Sc , the protein marker for this group of disorders. For live, asymptomatic sheep, diagnosis using tonsil or third-eyelid lymphoid tissue biopsy and PrP Sc assay has been described.