title: The natural atypical scrapie phenotype is preserved on experimental transmission and sub-passage in PRNP homologous sheep.
abstract: BACKGROUND
  Atypical scrapie was first identified in Norwegian sheep in 1998 and has subsequently been identified in many countries. Retrospective studies have identified cases predating the initial identification of this form of scrapie, and epidemiological studies have indicated that it does not conform to the behaviour of an infectious disease, giving rise to the hypothesis that it represents spontaneous disease.However, atypical scrapie isolates have been shown to be infectious experimentally, through intracerebral inoculation in transgenic mice and sheep. The first successful challenge of a sheep with 'field' atypical scrapie from an homologous donor sheep was reported in 2007.
  
  
  RESULTS
  This study demonstrates that atypical scrapie has distinct clinical, pathological and biochemical characteristics which are maintained on transmission and sub-passage, and which are distinct from other strains of transmissible spongiform encephalopathies in the same host genotype.
  
  
  CONCLUSIONS
  Atypical scrapie is consistently transmissible within AHQ homozygous sheep, and the disease phenotype is preserved on sub-passage.
authors.affiliation: Department of Pathology, Veterinary Laboratories Agency Weybridge, New Haw, Addlestone KT15 3NB, UK. m.m.simmons@vla.defra.gsi.gov.uk
authors.forename: Marion M
authors.initials: MM
authors.lastname: Simmons
authors.forename: Timm
authors.initials: T
authors.lastname: Konold
authors.forename: Lisa
authors.initials: L
authors.lastname: Thurston
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Bellworthy
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Chaplin
authors.forename: S Jo
authors.initials: SJ
authors.lastname: Moore
mesh_terms: D000818:Animals; D005838:Genotype; D010641:Phenotype; D011328:Prions / Q000235:genetics*; D012608:Scrapie / Q000235:genetics* / Q000635:transmission*; D012756:Sheep
chemical_list: D011328:Prions