Scrapie: A Year in Review

By Dr. Diane Sutton, National Scrapie Program Coordinator, U.S. Department of Agriculture/Animal and Plant Health Inspection Service/Veterinary Services

Dec. 2003 -- If you?re a regular reader of Sheep Industry News, you may have read some or all of the scrapie feature articles that have appeared in this tabloid over the past several months. Hopefully, you will also have read the Scrapie Question-and-Answer column, which is making its seventh consecutive appearance in this month?s edition.

Both the feature articles and scrapie Q-and-A?s have been brought to you by the U.S. Department of Agriculture?s Veterinary Services (VS), a component of USDA?s Animal and Plant Health Inspection Service. This month, VS is supplying Sheep Industry News readers with a recap of various USDA-driven, scrapie-related efforts, as well as future priorities, that will bring you up-to-date and illustrate USDA?s commitment to eradicating this serious and export opportunity-inhibiting disease. I hope you will spend a few minutes reading this invaluable information as well as that which VS will continue to bring to you during upcoming months.
Dr. Diane Sutton

In the last year, the National Accelerated Scrapie Eradication Program focused on:

1. developing a genetic-based approach to flock clean-up plans;
2. cleaning up infected and source flocks;
3. tracing and testing exposed animals and flocks;
4. completing the Scrapie Ovine Slaughter Surveillance (SOSS) study to determine the prevalence of scrapie in mature cull ewes;
5. implementing Regulatory Scrapie Slaughter Surveillance (RSSS);
6. providing producer education;
7. expanding scrapie diagnostic capacity;
8. setting up a method for evaluating, approving and monitoring laboratories that want to conduct official genotype tests for scrapie resistance;
9. increasing field personnel and State cooperation to enhance service to producers;
10. increasing the number of producers applying official eartags; and
11. reaching a consensus on the Scrapie Eradication Uniform Method & Rules for FY 2004. (A 2003 report, the method & rules and producer information can be found on the internet at http://www.aphis.usda.gov/vs/nahps/scrapie/)

Use of Genetic-Based Flock Clean-up Plans
During the last year, genetic-based plans have been used nationwide to clean up infected flocks. These plans were discussed in the June 2003 edition of Sheep Industry News. A brochure describing them can also be accessed at http://animalagriculture.org/scrapie/Scrapie.htm.

Official Genotype Testing at Private Laboratories
This winter, accredited veterinarians will be able to draw blood for their clients, at the client?s expense, and have official genotype tests run at USDA-approved labs. For a test to be official, the sheep will need to be officially identified and the blood collected and submitted by an accredited veterinarian using the USDA-provided form.

Expanded Scrapie Diagnostic Capacity and Field Personnel
VS has increased the number of approved diagnostic labs to 25. VS has added 21 people and intends to add an additional 15 for the scrapie program. This will allow VS to collect and test the 50,000 tissue samples from the field, research and slaughter surveillance this year, and to complete flock clean-up plans faster.

Producer Education
During the past year, Sheep Industry News, in cooperation with VS, published several articles and monthly scrapie Q&A?s. This effort will be expanded in 2004 to include outreach at state producer meetings and an industry roundtable at which program progress and direction will be discussed. The National Institute for Animal Agriculture, in cooperation with VS, has developed for producers a brochure and slide presentation on genotyping for scrapie resistance that is available on CD. This information can be accessed at http://animalagriculture.org/scrapie/Scrapie.htm.

Scrapie Flock Certification Program
The Scrapie Flock Certification Program monitors participating flocks and certifies those flocks as free of scrapie once they have been in continuous compliance with the program standards for five years. As of Sept. 30, 2003, there were 1,776 flocks participating in the Scrapie Flock Certification Program (SFCP), of which 105 are certified, 1,663 are complete monitored and eight are selective monitored flocks (figure 1). During Fiscal Years 1997 to 2003, the program made significant improvements in the number of new enrollments (chart 1). There were 310 flocks newly enrolled or certified in the certification program in FY 2003 (figure 2).

Infected and Source Flocks
As of Sept. 30, 2003, there were 50 scrapie infected and source flocks (figure 3). There were 73 newly infected flocks reported in FY 2003 (figure 4). In addition, 351 scrapie cases were confirmed and reported by the National Veterinary Services Laboratories in FY 2003 (figure 5). These included 249 regular necropsy cases, 66 validation necropsy cases, 32 regulatory third eyelid cases, and four validation third eyelid cases. It is important to note that these numbers represent multiple cases within individual infected flocks, and that no cases of scrapie in goats were reported in FY 2003. The last case in a goat was confirmed in August 2002. Sixty flocks, or 82 percent of the scrapie-infected and source flocks identified in FY 2003, were released or put on clean-up plans in FY 2003.

Scrapie: Ovine Slaughter Surveillance (SOSS)
VS?s Center for Epidemiology and Animal Health has released the first results of the SOSS study. The objective of SOSS was to estimate the national and regional prevalence of scrapie in mature cull ewes. The SOSS study estimate for the national scrapie prevalence in mature ewes is 0.20 percent. A more in-depth discussion of the SOSS study was published in the November edition of Sheep Industry News.

Regulatory Scrapie Slaughter Surveillance (RSSS)
RSSS started April 1, 2003. RSSS involves targeted slaughter surveillance, which is designed to identify infected flocks for clean-up. During FY2003 6,600 sheep were sampled, of which test results have been reported for 5,160. There were 17 positive or suspect sheep, of which 3 were white face and 14 were black face. Seventeen plants submitted samples. This work was also discussed in greater detail in the November edition of Sheep Industry News.

Scrapie Testing Summary
During FY 2003, 16,803 animals were sampled or tested for scrapie, and included: 3,724 regular necropsy cases, 42 third eyelid biopsies for the test validation project, 244 necropsy test validations, 579 third eyelid biopsies for the regulatory program and approximately 12,214 animals for SOSS and RSSS (chart 4).

Assignment of Premises ID Numbers and Distribution of Official Ear Tags
As of Sept. 30, 2003, 79,810 sheep and/or goat premises were in the Scrapie National Generic Database, of which 55,776 have requested and been shipped official premises ear tags. If you have not yet requested eartags, please call 1-866-USDA-TAG to receive free official eartags. (Please note that VS is now taking compliance action when violations of the identification requirements are discovered and not corrected.)

What are the APHIS priorities for fiscal year 2004?

1. Expand surveillance testing to 45,000 sheep and goats and assist in cleaning up the infected flocks that are identified as a result.
2. Increase producer outreach and education
3. Enhance ID compliance when sheep and goats change ownership.
4. Work with the States to deliver an effective and uniform program nationwide.
5. Work with the Agricultural Research Service and others to develop new test methodologies and gain insight into disease mechanisms that may assist in the eradication of scrapie.

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