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Students, ARS Team Up to Fight Sheep
Disease By Jan
November 5, 2002
With a helping hand from science, students-turned-shepherds at
Amphitheater High School (AHS) in
Tucson, Ariz., are leading their state's fight against scrapie disease in
Since 2001, AHS science teacher Jose Bernal and his students
have worked with U.S. Department of
Agriculture researchers to protect the school's small flock from scrapie
using genetic/live-animal testing, record keeping and other measures. Bernal's
class cares for the sheep as part of a hands-on agricultural education course.
But it became a tough lesson in loss starting in 1997, when scrapie claimed its
first victim: a pet ewe called Baby Face. Other ewes later tested positive for
the debilitating nervous system disease--otherwise known as transmissible
spongiform encephalopathy--and had to be destroyed.
With the course facing possible discontinuation, Bernal
contacted Katherine O'Rourke, a microbiologist at the
Agricultural Research Service's
Animal Disease Research
Unit in Pullman, Wash. There, O'Rourke's research included helping develop
a "third-eyelid" test to detect scrapie-causing proteins called prions.
In March 2001, O'Rourke and John Duncan, a veterinarian with
USDA's Animal and Plant Health Inspection
Service, flew to Tucson for a "house call." With help from Bernal's class,
they used the third-eyelid test to check for prions in lymph tissue taken from
special membranes covering the sheeps' eyes. They also drew blood samples for
genetic analysis. From this, they devised a protocol by which Bernal's class
could repopulate the flock's diminished ranks and keep it scrapie-free.
For breeding purposes, the class selected rams having the gene
variant 171R, which gives protection against scrapie. According to O'Rourke,
the students' program mirrors larger, commercial efforts to produce
scrapie-free flocks in other states, particularly Wyoming. There, O'Rourke is
participating in a university study to help producers identify sheep having
both scrapie resistance and important economic traits, including wool fiber
diameter, staple length, meat production and lamb performance.
More information about the program appears in this month's issue
ARS is USDA's chief scientific research agency.