2ND PASSAGE OF A US SCRAPIE AGENT IN CATTLE

Scrapie and bovine spongiform encephalopathy are similar chronic neuro degenerative diseases of sheep and cattle. An earlier study showed tha t, on first passage in cattle, a US scrapie agent caused an encephalop athy that was distinct from bovine spongiform encephalopathy (BSE). Th e present report describes a second passage in cattle, carried out bec ause diseases caused by the spongiform encephalopathy agents often cha nge in character with additional passages in abnormal hosts. For this work, young calves were inoculated intracerebrally with a pooled suspe nsion of brain from cattle that had died of encephalopathy after exper imental inoculation with brain from scrapie-affected sheep. The second passage disease was essentially identical with the first passage dise ase, as judged by clinical signs, histopathological findings and distr ibution of ''prion protein scrapie'' (PrPsc). This represents addition al evidence to suggest that the US sheep scrapie agent tested is incap able of causing BSE in cattle.