Scrapie in the United States. Jona Fletcher Summer 2018

Transcription

1 Scrapie in the United States Jona Fletcher Summer 2018

2 Known prion Diseases (1) Human Diseases: Creutzfeldt-Jakob Disease (CJD) Variant Creutzfeldt-Jakob Disease (vcjd) Gerstmann-Straussler-Scheinker Syndrome Fatal Familial Insomnia Kuru Animal Diseases: Bovine Sponigiform Encephalopathy (BSE, aka Mad Cow Disease )- cows Chronic Wasting Disease (CWD)- deer, elk, and moose Scrapie- goats and sheep Transmissible mink encephalopathy- mink Feline spongiform encephalopathy- felines Ungulate spongiform encephalopathy- exotic ungulates What is Scrapie? Scrapie is a TSE (Transmissible Spongiform Encephalopathy) Caused by a prion (pathogenic protein) Leads to death of infected victim Scrapie was the first recognized prion disease Prevalence in sheep has went down in US by 99% since 2003 Last known case of scrapie in goats was detected in 2015

3 Prion Transmission When diseased prion protein (PrPSc protein) comes in contact with a healthy prion protein (PrPC protein) then the healthy protein changes shape and becomes diseased and also infectious to other healthy prion proteins. PrPSc Protein (4) PrPC Protein (4)

4 Prion Transmission Certain prion diseases, such as CJD, kuru, and BSE are only somewhat transmissible, if transmissible at all. They are generally transmitted by contaminated food, or for some cases, genetically. Scrapie, on the other hand, appears to spread readily and rapidly from individual to individual. Routes of infection include: contaminated skin, feces, urine, mucosal secretions, or placental remnants There is also a level of persistence within the environment not seen with BSE Scrapie spreads easily probably due to lymph tissue involved with infection

5 Known Species of Goats Affected with Scrapie (5) Alpine Angora Boer Nigerian Dwarf Nubian Saannen Toggenburg Cross Other crosses Symptoms of Scrapie in Domestic Goats Tremors (notably of head and neck) Gait abnormalities including loss of coordination, high stepping, and swaying of back end Pruritus (urge to scratch) Weight loss with retained appetite Biting of extremities (6) Head pressing Star-gazing Sensitivity to sudden noise or movement Difficulty rising (7) 5

6 Diseases with Similar Symptoms Because there are many different diseases that can cause scrapie-like symptoms, it is important to have goats tested for scrapie if no other diagnosis is confirmed. listeriosis exposure to toxins pregnancy toxemia pneumonia rabies lice mites Goat polio heavy worm loads Johnes disease.

7 Linignathus stenopsis goat sucking louse

8 Cost of Scrapie Testing If you have a goat that exhibits symptoms of scrapie that is over 12 months of age, the Animal and Plant Health Inspection Service will cover the cost of shipping labels, shipping of tissues, and testing of the tissues. They will pay of the testing of up to 30 animals from a flock per year. This means there is no cost to the producer to send in samples of suspected scrapie cases (up to 30 animals) (8).

9 Why does Scrapie matter to you? Costs $10-20 million (or more) in lost revenue due to exportation loss and production cost increases Many countries including Canada ban the import of sheep and goats unless the animal comes from a farm enrolled in the voluntary scrapie eradication program Although scrapie has never been proven to be transmissible to humans, the WHO has recommended all countries attempt to remove prion diseases from animals raised for meat (9).

10 Why does Scrapie matter to you? Europe and Eastern Bloc countries have banned all live sheep and goats, semen, and embryos from being imported from the United States. This is a huge potential market for breeding stock in both the goat and sheep industry China and Japan ban the import of sheep and goat bone meal and tallow Isreal, a previously active importer of US goats, banned their import due to confirmed scrapie cases Mexico, a huge importer of US products, requires all rendered meat to be extensively heat treated before import (10). Possibility of BSE infecting goats/sheep

11 Scrapie Surveillance Methods Regulatory Scrapie Slaughter Surveillance (RSSS) Non-slaughter Surveillance The Scrapie Free Flock Certification Program Surveillance activities Enhancing awareness of the disease Ensuring samples from targeted and clinical animals reach approved laboratory testing facilities Expanding existing slaughter surveillance to include new collection sites Increase efforts to reach underrepresented flocks and geographical areas Increase compliance with identification requirements (7) Goal of Scrapie Surveillance: Eradicate Classical Scrapie in the United States 11

12 US Scrapie Eradication Program (11) Identification of Goats Goats that change ownership or cross state lines must be identified with the Scrapie Eradication Program Exceptions Goats raised for meat, fiber, or not for breeding purposes. Castrated goats also do not need to be identified. Means of Identification Ear tags, tattoos, and microchips. Ear tags and microchips must be sufficiently tamper proof and provide a unique identification to each animal

13 US Scrapie Eradication Program Recordkeeping Sex, identification number (and date applied), breed, date animal was acquired, address of previous owner, date sold, and address of new owner must be kept in farm records for 5 years (11). Tracing of Infected Animals Infected animals are traced back to their flock or origin through recordkeeping and scrapie tags (6). Clean-Up Strategies With the goal to keep producers in business and breeding stock alive, live animal testing, genetic testing, and individual destruction of infected flock members is the preferred method of scrapie infection cleanup (6).

14 Scrapie Prevention Tips to Prevent Scrapie Within your Herd Ultimately, prevention of scrapie within a producers flock/herd should be used as a first line of defense in the eradication of scrapie as a whole. Keep a closed flock/heard If you must buy breeding stock from another heard, do so from one that is not known to have scrapie Keep does/ewes that are high risk for scrapie away from other does/ewes at kidding time to reduce exposure to bodily fluids Selectively breed stock with PrP resistant genotypes Cull animals with PrP susceptible genotypes (8).

15 Scrapie Prevention Ultimately, prevention of scrapie within a producers flock/herd should be used as a first line of defense in the eradication of scrapie as a whole. Testing for Scrapie Resistance: S146 gene K222 gene These genes cause significant resistant to scrapie occurring naturally as well as introduced in laboratory settings Detection of these genes allow for selective breeding for scrapie resistant goats Testing currently available at the UC of Davis and soon to be available at NeoGen Genomics Herd cleanup projects based upon genetic testing for these alleles could be considered in the future Discounted testing prices are available for members of the American Boer Goat Association as well as the American Dairy Goat Association (12)

16 Success So Far No classical Scrapie or source flocks have been identified since 2016 Only one positive goat has been found though RSSS since 2003, and only 41 total field cases since This does not include quarantined flocks in Colorado (13). With the continued support of goat and sheep producers, the United States is well on its was to being declared scrapie free.

17 Citations 1) Prion Diseases. Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 17 Aug. 2017, 2) Scrapie. USDA APHIS Research Facility Annual Summary Report, APHIS, 11 July 2017, Reference-Guide/Control-and-Eradication/Scrapie. 3) Why Should You Care About Scrapie. The AMERICAN GOAT FEDERATION, The American Goat Federation, 2018, americangoatfederation.org/education/why-should-you-care-about-scrapie/. 4) Cann, A. J. Prion Structure; ) Gough, Kevin C, and Ben C Maddison. Prion Transmission. Advances in Pediatrics., U.S. National Library of Medicine, 1 Oct. 2010, 6) Scrapie Fact Sheet. NSEI: Scrapie Fact Sheet, National Institute for Animal Agriculture, Aug. 2011, Scrapie/Fact Sheet.html#Clinical_Signs. 7) National Scrapie Surveillance Plan. National Scrapie Eradication Program, United States Department of Agriculture, Sept. 2010, 8) Questions and Answers: Testing for Scrapie. National Scrapie Eradication Program, United States Department of Agriculture, 9) Sutton, Diana USDA-APHIS Update. Youtube. American Goat Federation Seminar, 2 July 2018, 10)Kahler, Susan C. The Rational for Ridding U.S. of Scrapie. Estimated Vehicle Interior Air Temperature v. Elapsed Time, American Veterinary Medical Association, 1 May 2001, 11) National Scrapie Eradication Program: Animal Identification and Recordkeeping Guide for Sheep and Goats. Scrapie Factsheet, United States Department of Agriculture, Sept. 2017, 12)White, Stephen N, and David A Schneider. A New Tool: Genetic Scrapie Resistance in Goats. American Goat Federation, The American Goat Federation, June 2018, americangoatfederation.org/wp-content/uploads/2018/07/white-and-schneider-new-2018-goat-scrapie-resistance-dna-test pdf. 13) National Scrapie Eradication Program: May 2018 Monthly Report Fiscal Year May 2018 Monthly Report Fiscal Year 2018, APHIS, 15 June 2018,