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Transmissible Spongiform Encephalopathy in Small Ruminants

Posted by Teresa Steckler -

Scrapie has compromised the health of small ruminants for centuries. The disease was first described in 1732 and is now recognized as a transmissible spongiform encephalopathy (TSE). A recent article in Animal Frontiers, by Dr. V. Beringue and Dr. O. Andreoletti, describes how the specter of this "old" disease has remerged in a "new" form. The old, well-known TSE is considered the classical disease, and the newly discovered form is considered the atypical disease.

Scrapie is not a treatable disease, and the prognosis for a sheep or goat that has been diagnosed with scrapie is death. Even though there are no vaccines to prevent or control the spread of scrapie, some control measures have been effective. Research over the last several years has shown clearly that some sheep are less susceptible to classical scrapie than others, and genetic markers associated with the degree of susceptibility to classical scrapie have been described. The authors of the article described how the European Union, United States, and several other countries are using modern genetic technologies to control classical scrapie in sheep. There are good reasons to believe that the same approach will be effective for goats, but more genetic information and testing is needed before that can be determined.

Now that scientists have developed effective control measures for classical scrapie, many are turning their attention to atypical scrapie, which is also called Nor98 because it was first identified in Norway in 1998. There is evidence that atypical scrapie develops spontaneously, with no external cause, and usually in aged animals. The ability of atypical scrapie to be transferred from one animal to another under natural conditions is not well understood, but there is evidence that it can be transmitted under experimental conditions. To further complicate matters, the relationship between the genetics of the animal and susceptibility to atypical scrapie is not known. Thus, considerably more research is needed to begin unraveling the threads of information that will allow scientists to determine whether effective methods can be developed to control or prevent the onset of atypical scrapie.

The newest story on this old problem is available in "Classical and atypical TSE in small ruminants," in the January 2014 issue of Animal Frontiers, found at http://animalfrontiers.org/content/4/1/33.full.pdf+html.  By Gregory S. Lewis


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