Animal & Plant Health Protection
Nebraska Scrapie Eradication Program
A Program for Nebraska Sheep and Goat Producers
Nebraska Department of Agriculture
In cooperation with United States Department of Agriculture
University of Nebraska Extension
History of Scrapie
The disease known as Scrapie has been recognized for more than 250 years. The unusual name was coined from sheep trying to relieve the intense itching which results in "scraping" off the wool. In 1947, scrapie was introduced into a Michigan flock through sheep imported from Britain. Scrapie has spread throughout the U.S. since that time. In 2002, new cases of scrapie totaled 259 and 5 goats were also found infected. Hundreds more cases have been found since then.
Scrapie is a member of a family of diseases known as Transmissible Spongiform Encephalopathys (TSEs). TSEs are caused by an infectious protein called a prion. After prions are ingested, they enter the lymphatic system and travel to lymph nodes. After many months, the prions are found in the brain where they cause "holes" in the brain tissue giving it a sponge-like appearance. Other TSE-type diseases are Bovine Spongiform Encephalopathy (BSE) in cattle, Chronic Wasting Disease (CWD) in deer, and Creutzfeldt - Jakob disease (CJD) in humans.
A Slow Developing Disease
Sheep (and goats) are infected at a very young age, but may not show symptoms of disease until two - six years of age. Goats are susceptible to scrapie when raised together with sheep but do not appear to spread the disease. Symptoms develop slowly and may go unrecognized at first. Symptoms may include:
Since scrapie affects the central nervous system, it can be confused with other diseases. Remember, symptoms of scrapie may take months to develop and is always fatal.
A positive diagnosis of scrapie in a flock is based on symptoms, duration of illness, and submission of brain tissues from an affected animal. The presence of prions in a microscopic section of brain tissue is the only method to be certain that sheep are infected with scrapie. A test of lymph tissue contained in the third-eyelid of sheep can be performed by a regulatory veterinarian in some instances, but this test is not used for routine scrapie diagnosis. If you suspect that one of your sheep may be infected with scrapie, you should contact your local veterinarian for a diagnosis.
Scrapie and Genetics
Research has shown that certain genes in the DNA of sheep play a role in the development of scrapie. The testing for the resistance or susceptibility of sheep to scrapie can be done with a blood sample drawn from the sheep in question. An approved laboratory can determine the resistance or susceptibility to scrapie by examining the DNA at Codon 171 of the genetic make-up. Letter designations are reported for each strand of the DNA. An "R" at Codon 171 indicates resistance to scrapie, whereas, a "Q" or "H" indicates susceptibility. Three combinations are possible since there are two strands of DNA:
RR = Highly resistantBy knowing the genetics of breeding animals, producers can actually breed more resistance to scrapie into their flock. Producers who retain their own replacement ewe lambs can begin influencing their flock resistance to scrapie by selecting rams that have been DNA tested and certified by an approved lab as carrying the "RR" gene at Codon 171. In a few years, the flock resistance to scrapie will be greatly increased. There is no genetic test available for goats at this time.
QR = Moderate resistance
QQ = Susceptible
USDA's Animal Plant Health Inspection Service (APHIS) launched a new and enhanced Scrapie Eradication Program in November of 2002. All states agreed to be consistent with the program so producers could transport sheep between states. Scrapie costs American sheep producers an estimated $25 million annually. Trade barriers exist with Scrapie-Free countries, such as Australia and New Zealand. Rendering companies will not pick up dead sheep because of scrapie concerns.
The Scrapie Eradication Program utilizes genetics in a flock based clean-up plan. Slaughter surveillance of cull ewes will identify infected flocks. Infected flocks will be DNA tested and the scrapie infected and susceptible sheep removed.
USDA has funds available for the clean-up of infected flocks including the costs associated with DNA testing, and the purchase of infected and susceptible sheep at fair market value.
Other aspects of the eradication program include identification of sheep and goats with official USDA scrapie tags in:
Voluntary Scrapie Flock Certification Program
With the implementation of the Voluntary Scrapie Flock Certification Program in 1992 and modified in 1997, USDA provided producers with the opportunity to protect their sheep from scrapie and to enhance the marketability of their animals through certifying their origin in scrapie-free flocks. The intent of the program is to monitor flocks over a period of five years or more to identify flocks that are free of scrapie. Because there is no live animal test for this disease and scrapie has a long incubation period, a flock is considered free of disease if no sheep have been diagnosed with scrapie over a period of time. The longer a flock is enrolled and following the requirements of the program, the more likely the sheep in the flock are free of scrapie.
The economic value of animals in enrolled flocks increases the longer they are in the program, especially once the flock is certified. Animals from certified flocks are a valuable source for replacement breeding animals, especially when the genetics of the replacements are known.
When participating in the program, flock owners must:
The Nebraska Bureau of Animal Industry (BAI) working together with USDA/APHIS has begun efforts throughout the state to eradicate scrapie.
Genetic Testing for Scrapie available at:
Gene Check, Inc.
1629 Blue Spruce Drive, Ste 106
Fort Collins, CO 80524
More Information Available on the Web at:
United States Department of Agriculture