| Popis: |
Epidemiologic data indicate that bovine spongiform encephalopathy (BSE) probably originated in cattle by feeding rendered meat and bone meal that was accidentally contaminated by a scrapie-like agent (1). However, there remain several important questions related to the origin and biologic properties of BSE. First, what is the origin of the agent? Is it a previously unrecognized strain of BSE agent rarely inducing sporadic disease in cattle and artificially spread or is it scrapie transmitted from sheep, goat, or possibly other species and adapted to cattle? Second, how was the disease spread? Third, does the large-scale spread of a possibly new or newly adapted scrapie-like agent represent any risk to humans or nonhuman species? The biologic substrate or carrier of the agent’s strain-like behavior in spongiform encephalopathies is unknown (2) and their biologic properties are defined only indirectly. The possibilities to study them are limited to the characteristics obtained by comparative pathology (3), following the anatomic distribution (4) of PrPsc, comparing their species barrier behavior and by following the incubation time of each strain in genetically defined hosts (3). |
