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United States Department of Agriculture

Agricultural Research Service

Research Project: TRANSMISSION, DIFFERENTIATION, AND PATHOBIOLOGY OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES Title: Characterization of a U.S. Sheep Scrapie Isolate with Short Incubation Time

Authors
item Hamir, Amirali
item Richt, Juergen
item Kunkle, Robert
item Greenlee, Justin
item Bulgin, M - UNIVERSITY OF IDAHO
item Gregori, L - VA MEDICAL CENTER, MD
item Rohwer, R - VA MEDICAL CENTER, MD

Submitted to: Veterinary Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 16, 2009
Publication Date: November 1, 2009
Repository URL: http://vet.sagepub.com/content/46/6/1205
Citation: Hamir, A.N., Richt, J.A., Kunkle, R.A., Greenlee, J.J., Bulgin, M.S., Gregori, L., Rohwer, R.G. 2009. Characterization of a U.S. Sheep Scrapie Isolate with Short Incubation Time. Veterinary Pathology. 46(6):1205-1212.

Interpretive Summary: Scrapie is a naturally occurring fatal disease of sheep and goats. In a previous study it was shown that sheep inoculated with US scrapie inoculum (No. 13-7) induced terminal disease within an average of 19 months. We have since produced an inoculum, No. X124 from pooled brains of US origin sheep scrapie, that results in incubations nearly 3 fold shorter. The present study documents laboratory findings in tissues of sheep inoculated with No. X124. All inoculated sheep developed clinical disease and were euthanized within an average of 7.7 months post inoculation (MPI). Sheep that were genetically susceptible developed the disease faster (within 6 months). Also, the inoculum was able to induce disease in a short time (7 MPI) in a sheep that was supposed to be highly resistant to scrapie. This indicates that inoculum No. X124 appears to be more virulent than inoculum No. 13-7. Importantly this strain of scrapie represents a significant development in that it provides a natural model that requires less than 25 percent of the time for the disease to develop, thus enabling a faster pace for research investigating prion disease pathogenesis and inactivation.

Technical Abstract: Scrapie is a naturally occurring fatal neurodegenerative disease of sheep and goats. Susceptibility to the disease is partly dependent upon the genetic makeup of the host. In a previous study it was shown that sheep intracerebrally inoculated with US scrapie inoculum (No. 13-7) developed terminal disease within an average of 19 months. We have since produced an inoculum, No. x124 from pooled brains of US origin sheep scrapie, that results in incubations nearly 3 fold shorter. The present study documents clinicopathological findings and the distribution of abnormal prion proteins (PrP**Sc) by immunohistochemical (IHC) and Western blot (WB) techniques, in tissues of sheep inoculated with No. x124. All inoculated sheep developed clinical disease and were euthanized within an average of 7.7 months post-inoculation (MPI). Sheep that had VV or AV at codon 136 of prion protein (PRNP) gene developed the disease faster and were euthanized at an average of 4.3 and 5.6 MPI, respectively. Also, the inoculum was able to induce disease in a short time (7 MPI) in a sheep that was relatively resistant (QR at codon 171) to scrapie. This indicates that inoculum No. x124 appears to induce scrapie in shorter time than inoculum No. 13-7, especially in sheep homozygous or heterozygous for valine at codon 136.

Last Modified: 12/20/2014
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