EXPERIMENTAL LATENCY OF SCRAPIE AGENT

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 tile central nervous system characteristic df 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 ill disease.; Scrapie superinfection of animals inoculated previously but not fallin g in revealed a similar susceptibility to infection in these animals i n comparison with 2-3-week-old intact mice. Basing on their findings a nd published data, the authors discuss the problem of latent infection in,transmission spongiform encephalopathies and its possible contribu tion to the epidemic process.