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Students, ARS Team Up to Fight Sheep Disease

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 sheep.

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 of Agricultural Research magazine.

ARS is USDA's chief scientific research agency.