Atypical scrapie in Australia.
BACKGROUND
Since its initial detection in Norway in 1998, atypical scrapie ('atypical/Nor98 scrapie') has been reported in sheep in the majority of European countries (including in regions free of classical scrapie) and in the Falkland Islands, the USA, Canada, New Zealand and Australia.


METHODS
The diagnosis in Australia of atypical scrapie in four Merino and one Merino-cross sheep showing clinical signs of neurological disease was based on the detection of grey matter neuropil vacuolation (spongiform change) in the brain (particularly in the molecular layer of the cerebellar cortex) and associated abnormal prion protein (PrPSc) deposition in both grey and white matter. Changes were minimal in the caudal brainstem, the predilection site for lesions of classical scrapie.


CONCLUSIONS
The distinctive lesion profile of atypical scrapie in these five sheep highlights the diagnostic importance of routine histological evaluation of the cerebellum for evidence of neuropil vacuolation and associated PrPScdeposition in adult sheep with suspected neurological disease.
Regional Veterinary Laboratory, NSW Department of Primary Industries, Wollongbar, New South Wales 2480, Australia.
R W
RW
Cook
CSIRO, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
J
J
Bingham
Animal Health Laboratories, Department of Agriculture and Food, South Perth, Western Australia, Australia.
A S
AS
Besier
Gribbles Veterinary Pathology, Clayton, Victoria, Australia.
C L
CL
Bayley
Department of Economic Development, AgriBio Centre, Bundoora, Victoria, Australia.
M
M
Hawes
Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, New South Wales, Australia.
P L
PL
Shearer
CSIRO, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
M
M
Yamada
CSIRO, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
J
J
Bergfeld
CSIRO, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
D T
DT
Williams
CSIRO, Australian Animal Health Laboratory, Geelong, Victoria, Australia.
D J
DJ
Middleton
D000818:Animals; D001315:Australia; D001921:Brain / Q000473:pathology*; D005260:Female; D019581:Neuropil / Q000473:pathology; D018620:PrPSc Proteins / Q000032:analysis; D012608:Scrapie / Q000175:diagnosis* / Q000473:pathology; D012756:Sheep; D014617:Vacuoles / Q000473:pathology
D018620:PrPSc Proteins
atypical scrapie; prion disease; sheep; transmissible spongiform encephalopathy