[Experimental latency of scrapie].

BALB/c mice infected with the scrapie agent without apparent symptoms of the disease for 12 to 14 months after inoculation were examined by virological and histological methods. Changes in the central nervous system characteristic of the pathohistological picture of scrapie were detected in two out of 66 mice. Intracerebral challenge of mice with the examined material from these animals did not result in disease. Scrapie superinfection of animals inoculated previously but not falling ill revealed a similar susceptibility to infection in these animals in comparison with 2-3-week-old intact mice. Basing on their findings and published data, the authors discuss the problem of latent infection in transmission spongiform encephalopathies and its possible contribution to the epidemic process.