Natural and experimental oral infection of nonhuman primates by bovine spongiform encephalopathy agents

Experimental lemurs either were infected orally with the agent of bovine sp ongiform encephalopathy (BSE) or were maintained as uninfected control anim als. Immunohistochemical examination for proteinase-resistant protein (prio n protein or PrP) was performed on tissues from two infected but still asym ptomatic lemurs, killed 5 months after infection, and from three uninfected control lemurs, Control tissues shelved no staining, whereas PrP was detec ted in the infected animals in tonsil, gastrointestinal tract and associate d lymphatic tissues, and spleen. In addition, PrP was detected in ventral a nd dorsal roots of the cervical spinal cord, and within the spinal cord PrP could be traced in nerve tracts as far as the cerebral cortex. Similar pat terns of PrP immunoreactivity were seen in two symptomatic and 18 apparentl y healthy lemurs in three different French primate centers, all of which ha d been fed diets supplemented with a beef protein product manufactured by a British company that has since ceased to include beef in its veterinary nu tritional products. This study of BSE-infected lemurs early in their incuba tion period extends previous pathogenesis studies of the distribution of in fectivity and PrP in natural and experimental scrapie, The similarity of ne uropathology and PrP immunostaining patterns in experimentally infected ani mals to those observed in both symptomatic and asymptomatic animals in prim ate centers suggests that BSE contamination of zoo animals may have been mo re widespread than is generally appreciated.