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Journal of Clinical Microbiology, September 2002, p. 3421-3426, Vol. 40, No. 9
0095-1137/02/$04.00+0 DOI: 10.1128/JCM.40.9.3421-3426.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
Department of Veterinary Public Health,1 Research Center for Protozoan Diseases,2 Department of Veterinary Pathology, Obihiro University of Agriculture and Veterinary Medicine, Obihiro,3 Department of Laboratory of Animal Science, Center of Biomedical Research, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan4
Received 22 January 2002/ Returned for modification 21 April 2002/ Accepted 18 June 2002
Due to the apparent absence of an agent-specific nucleic acid genome, scrapie strains cannot be classified by genome characterization, which is commonly used for the classification of many viruses. However, scrapie strains can be distinguished to some extent by biological properties such as transmissibility to experimental animals and distribution of neuropathological lesions and by biochemical properties such as the molecular mass and relative protease-resistance of the disease-specific isoform of prion protein (PrPSc). In order to preliminarily characterize the scrapie strains that are prevalent in Japan, we analyzed the transmissibility of sheep scrapie isolates to mice and the relative proteinase K (PK) resistance of the corresponding PrPSc. The results indicate that Japanese scrapie strains can be divided into at least three groups based on biological and biochemical properties. The first group includes isolates which cause disease in mice with an incubation period of
400 days and possess PrPSc with relatively high PK resistance. Isolates of the second group contain PrPSc that is highly resistant to PK digestion but transmit poorly to mice. The final group consists of isolates that cause disease in mice with an incubation period of less than 300 days and are associated with PrPSc with reduced PK resistance. Sheep scrapie has occurred sporadically in Japan since1982, with only
60 officially reported cases so far. However, the diversity of scrapie strains in the field suggested by our data raises the concern that a scrapie strain similar to the parental agent of bovine spongiform encephalopathy could exist or emerge in Japan. Thus, continuous surveillance for scrapie will be required to prevent the further spread of scrapie, not only among the sheep population but also to other species, and to eliminate any potential risk of sheep scrapie to public health.
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