Scrapie

Last Modified: April 19, 2024
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Sheep and goat

Scrapie is a fatal, degenerative disease that affects the central nervous system of sheep and goats. It is classified as a transmissible spongiform encephalopathy. Infected flocks typically experience significant production losses. The U.S. sheep and goat industry continues to experience export losses and increased production and disposal costs because the United States is not free of scrapie.

Scrapie is difficult to detect. It can take 2 to 5 years for an animal to show signs of disease, and current diagnostic tests require brain or lymphoid tissue. Animals typically live 1 to 6 months after they begin to show signs. Most are infected as young lambs or kids, but adult animals can get it, too. Apparently healthy animals infected with the disease agent can spread it.

  • Signs of central nervous system problems, most commonly incoordination or poor muscle control (ataxia)
  • Weakness of any kind, including stumbling, falling down, or having difficulty rising (not including animals with visible traumatic injuries and no other signs of scrapie)
  • Behavioral abnormalities
  • Significant weight loss with no decrease in appetite or in an animal with adequate teeth
  • Increased sensitivity to noise and sudden movement
  • Tremors
  • Star gazing
  • Head pressing
  • Abnormal gait that involves both the forelimbs or rear legs such high stepping with forelimbs, bunny-hop movement with rear legs, or swaying of back end. This does not include gait abnormalities involving only one leg or one front and one back leg.
  • Repeated intense rubbing with bare areas or damaged wool in similar locations on both sides of the animal's body or, if on the head, both sides of the poll; abraded, rough, thickened, or hyperpigmented areas of skin in areas of wool/hair loss in similar locations on both sides of the animal's body or, if on the head, both sides of the poll

Less specific clinical signs:

  • Unable to walk prior to slaughter or death
  • Condemned antemortem at slaughter for non-central nervous systems signs
  • Poor body condition despite having good teeth
  • Unknown cause of on-farm death

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One of the best ways to prevent scrapie is to select genetically resistant breeding stock. This practice has significantly reduced scrapie in the United States. Owners of infected flocks should restock with resistant rams and resistant or less susceptible ewes.

We also recommend the following biosecurity measures to reduce the spread of scrapie:

  1. Maintain a Closed Herd. Maintain a closed herd with no external contact with sheep or goats. Minimize outside purchases of sheep or goats to reduce the risk of scrapie exposure. Select replacement animals from another closed herd that has measures in place to prevent scrapie introduction or that are genetically resistant.
  2. Reduce Exposure. Wash and disinfect boots that have been to facilities with other livestock. After removing debris from surfaces, disinfect with a diluted 5.25% bleach solution (add 50 ounces bleach to 78 ounces of water to create 1 gallon of disinfection solution). Use personal protective equipment (PPE), such as boot covers and gloves, and proper handwashing techniques when traveling between livestock. Reduce commingling of herds in locations where livestock come from various places (such as markets, fairs, or exhibits).
  3. Confine Lambing and Kidding. Confine ewes and does that are lambing or kidding so that there is limited contact with other animals. Remove any placental tissues, fluids, and soiled debris as soon as possible after lambing/kidding while wearing PPE. Disinfect the birthing area between births. Ewes and does with unknown scrapie status should remain separated until there is no vaginal discharge. Milk and colostrum from potentially exposed sheep or goats should not be fed to lambs or kids.

There is no treatment for scrapie. To eliminate the disease from an infected flock or herd, genetically susceptible exposed animals and animals showing clinical signs are euthanized and the premises is cleaned and disinfected.

Prions are difficult to decontaminate as they have been shown to tightly bind to surfaces without losing infectivity. They are resistant to most disinfectants including alcohol and formalin. Prion contamination has also been shown to have resistance to heat and radiation. While prion decontamination is difficult, there are methods that can be used. For guidance on cleaning and disinfecting farm equipment and premises, see Appendix 2 in the Scrapie Program Standards Volume 2 (708.43 KB).

Report Signs of Animal Disease

Producers or owners who suspect an animal disease should contact their veterinarian to evaluate the animal or herd. Find an accredited veterinarian.

Animal health professionals (veterinarians; diagnostic laboratories; public health, zoo, or wildlife personnel; and others) report diagnosed or suspected cases of nationally listed reportable animal diseases to APHIS District Offices and to the State animal health official as applicable under State reporting regulations. 

Eradicating Scrapie

The National Scrapie Eradication Program (NSEP), a cooperative State-Federal-industry program, is working to eradicate classical scrapie from the United States and meet World Organisation for Animal Health (WOAH) criteria for disease freedom. To date, the program has eliminated scrapie in 99 percent of U.S. sheep and goats. The program is conducting targeted sampling of subpopulations that have a higher prevalence of scrapie than the general sheep/goat population to find the remaining cases.

Modernizing NSEP

APHIS published a final rule in the Federal Register in 2019, updating scrapie program regulations (9 CFR 79). The rule established a more flexible approach to disease investigations and affected flock management and more consistent animal identification and recordkeeping requirements for sheep and goats. The rule also moved specific requirements for official eartags and official identification methods, such as tattoos and implantable electronic ID (microchips), and indemnity calculations to the NSEP Standards.

The NSEP surveys for scrapie in the United States. Surveillance components include:

  1. Regulatory scrapie slaughter surveillance
  2. Non-slaughter surveillance (for example, trace investigations, on-farm testing)
  3. The Scrapie Free Flock Certification Program

Since 2002, the prevalence of scrapie has decreased significantly through existing eradication efforts. This is largely due to effective slaughter surveillance of geographically distributed sampling based on annual population estimates. However, to declare the United States “scrapie free,” we must prove to the world that we have conducted testing in all sheep and goat populations. That is why owner submission of samples from sheep/goats over 18 months of age found dead or euthanized on farm is extremely important. With the help of those who raise sheep and goats, APHIS will be able to declare the U.S. free of scrapie. Scrapie currently costs sheep and goat industries approximately $10 to $20 million in lost export opportunities, annually.

Producers, accredited veterinarians, APHIS representatives, and State animal health employees may collect and submit samples from adult sheep or goats. APHIS provides shipping boxes and pre-printed, postage-paid labels at no cost to producers and accredited veterinarians. APHIS will pay for scrapie testing of up to 30 animals per flock per year. Producers may remove and submit whole heads or report deceased sheep or goats and ask for help with submitting samples. Accredited veterinarians can either remove and submit whole heads or collect and submit specified tissues.

To request a box, or for more guidance on collecting and submitting samples, contact the APHIS Veterinary Services District Office in your State or your State's designated scrapie epidemiologist. 

Shipping Instructions

Whole head samples: Ship the cooler containing the head with frozen cold packs overnight to Remington Locker, APHIS' sample collection facility:

18795 S 580 W Remington, IN 47977 
Phone: 317-347-3100 
Fax: 219-261-2357 
Email: remington.locker@usda.gov

Be sure to inform the facility of the shipment’s delivery date.

Tissue samples: Ship tissue samples to an APHIS-contract laboratory. Contact the APHIS Veterinary Services District Office in your State for instructions.

Test Results

Positive test results will be confirmed by the National Veterinary Services Laboratories (NVSL) or an NVSL-approved laboratory.

In 2021, APHIS published the USDA Commercial Indemnity Table, which supersedes section II.J. 4. (a) of the Program Standards that detail how commercial sheep and goat* indemnity values are calculated. The values are based on nationally recognized market data sources including USDA's Agricultural Marketing Service, USDA's National Agricultural Statistics Service, and the Livestock Marketing Information Center.

* Certain classes of sheep and goats are not represented in this table. A process for valuing these animals is still being finalized.

Approximately 30 percent of U.S. sheep are genetically susceptible to scrapie. Some animals have been bred to be genetically resistant to the disease. Because scrapie persists in the environment for years, owners of previously infected flocks should restock with rams that are resistant and ewes of resistant or less susceptible genotypes. 

Currently all goat breeds are considered genetically susceptible. Researchers are still investigating the possibility of genetic resistance in goats but have not yet identified a resistant genotype.

Major Codons Associated With Scrapie in Sheep

Codon 171 is the major determinant of classical scrapie susceptibility in the United States. It plays a role in sheep susceptibility to the major type of classical scrapie found in the United States, valine-independent scrapie.

  • It codes for the amino acids Glutamine (Q), Arginine (R), Histidine (H) or, rarely, Lysine (K).
  • Q is associated with increased susceptibility to classical scrapie, while R is associated with increased resistance.
    • H is considered to have the same susceptibility as Q. The relative susceptibility of K is still under investigation. Therefore, both H and K are reported as Q by most laboratories and are treated as Q for regulatory purposes.
    • Over 99 percent of the classical scrapie cases in the United States that have been genotyped were QQ.

Codon 136 plays a role in sheep susceptibility to the less common type of classical scrapie found in the United States, valine-dependent scrapie.

  • It codes for the amino acid Alanine (A), Valine (V) or, rarely, Threonine (T).
  • V is associated with increased susceptibility to classical scrapie.
  • The occurrence of T is extremely rare and as of September 2012 has never been reported in the United States. Because its role in susceptibility is unknown, if it were identified in U.S. sheep it would be reported by most laboratories as V and treated as V for regulatory purposes.

Codon 154 plays a minor role in classical scrapie and is not often used in the United States as part of a breeding or regulatory strategy. It is, however, associated with increased susceptibility to Nor98-like scrapie.

Codon 141 is associated with increased susceptibility to Nor98-like scrapie. Its role in classical scrapie, if any, is unknown.

Codon 112 also plays a minor role in classical scrapie, although its association with classical scrapie resistance is still under investigation.

Testing for Genetic Susceptibility

Genotype testing for susceptibility to scrapie is a key component of NSEP. Note: Genetic testing does not tell you whether a sheep or goat is infected with scrapie.

Sample submissions must meet the following requirements for official genotype testing:

  • Sheep or goats are officially identified.
  • The blood is drawn by a Federal or State animal health official or an accredited veterinarian.
  • The sample is submitted with a VS Form 5-29 or State equivalent to an APHIS-approved lab.
  • The sample meets any additional requirements set by the APHIS-approved lab.

Becoming an APHIS-Approved Genotyping Laboratory

Approved genotyping laboratories may conduct privately funded official scrapie genotype testing and compete for NSEP-funded official genotyping. This approval lasts for 1 year and is subject to review and renewal.

Each laboratory must apply to conduct official genotype tests. Interested labs should send an application package to the NVSL. The application must contain the following information about the laboratory:

  • Laboratory name and address
  • Name of the legally responsible official and, if different, the director of the laboratory
  • A description of the laboratory facilities and equipment that will be used in performing genotype tests
  • A list of the types of samples that will be tested
  • The standard operating procedure for each test to be used, including methods, materials, equipment, and other relevant information
  • A list of the names of individuals performing specific tests and a detailed statement of each individual’s qualifications
  • A detailed description of the procedures to satisfy the recordkeeping requirements of the Scrapie Eradication Program
  • A description of the specific procedures for reporting test results
  • The laboratory quality assurance manual
  • A statement authorizing APHIS to inspect the laboratory without notice during normal business hours (inspection may include, but is not limited to, reviewing and copying records, observing tests being conducted, and interviewing personnel)

After submitting a complete application package, the laboratory will have additional tasks such as completing a proficiency test panel and site visits to demonstrate technical competency and evaluate testing and laboratory protocols. Following completion of these tasks, APHIS will extend approval in writing to the laboratory. For more information, contact scrapie@usda.gov.

The National Scrapie Flock Certification Program (SFCP) increases the marketability of sheep and goats from flocks that have demonstrated freedom of scrapie disease by adhering to program standards. This is a voluntary program for producers who are committed to monitoring their flocks for clinical scrapie signs and reporting any suspect animals for testing. Participants in this program benefit by decreasing the risk of introducing classical scrapie into their flocks.

Participants may participate in one of two categories in the SCFP program:

  1. Export Category—Monitors and samples participating flocks. If conditions are met, it may lead to Export Certified status and recognition of negligible scrapie risk.
  2. Select Category—Test samples from mature sheep and goats to identify and remove infected flocks.

How To Apply

To participate in the SCFP program in either category you must complete the SFCP application form (VS Form 5-22).

Note: The Export Category has additional documentation requirements for applying such as a flock inventory and an initial flock inspection.

For more information on this voluntary program, including how to enroll, please contact scrapie@usda.gov.

National Institute of Animal Agriculture Materials