story to find out more.
A sheep's genes determine many of its
characteristicsincluding its susceptibility to diseases like scrapie.
Click the image for more information about it.
Genetics Research Helps Scuttle Scrapie
McGinnis November 7, 2006
More accurate genetic tests for diagnosing scrapie disease in sheep
have been developed by Agricultural Research Service (ARS) scientists in Clay Center, Neb. They
believe this achievement will promote scrapies eventual eradication.
Contagious, incurable and fatal, scrapie is the sheep industrys
chief disease priority, costing U.S. producers an estimated $20 million every
year. Scrapie's name reflects the diseases most distinctive symptom: an
uncontrollable itching sensation that causes afflicted sheep to compulsively
scrape their bodies against nearby objects.
In a diseased animal, abnormally folded prionsproteins that
occur in all mammalscause the naturally produced prions to fold
abnormally as well. As the misfolded proteins amass, they cause neurological
problems and death. Most sheep die one to six months after symptoms appear,
although they may be infected for years without showing any signs.
Genetic predisposition to the disease is related to variations in
amino acid sequences coded within each sheeps DNA. Selective breeding for
resistance could one day reduce the genetic risk of developing scrapie and may
eventually eradicate it.
Carnahan and molecular geneticist Michael Heaton collect blood for DNA
analysis. Click the image for more information about it.
Drawing from a diverse group of U.S. sheep,
P. Heaton, a geneticist at the Roman L. Hruska U.S. Meat Animal Research
in Clay Center, and his colleagues have resequenced the prion gene, identifying
new genetic variation.
This achievement has improved commercially available genotyping tests
and enhanced the national scrapie eradication program run by the U.S.
Department of Agriculture's Animal and
Plant Health Inspection Service. Essentially, this research is improving
the speed, cost and quality of anti-scrapie breeding methods.
The scientists have identified and stored DNA from 15 common sheep
breeds. This information is freely available to researchers and testing labs to
facilitate diagnosis and eventual scrapie eradication.
In short, the ARS researchers have amassed a detailed body of
knowledge allowing them to test sheep for scrapie susceptibility with great
accuracy. With that information, breeders can select less-susceptible sheep and
breed more scrapie-resistant flocks.
more about the research in the November/December 2006 issue of
Agricultural Research magazine.
ARS is the USDA's chief scientific