There are many reasons why people are reluctant to comply with government laws and regulations. However, a cooperative state-federal-industry program for eradicating scrapie in the United States has resulted in excellent progress towards eliminating this disease in sheep and goats. The number of animals testing positive for scrapie in the U.S. has decreased by 99 percent, since analysis of producer-submitted samples began in 2003.
What is Scrapie?
Scrapie is a fatal, neurodegenerative disease that affects the central nervous system of sheep and goats. There is no cure or treatment available for it. The disease is caused by a prion, a protein that can trigger normal proteins in the brain to fold abnormally. The abnormal form of the protein can no longer be broken down, allowing a buildup and damage to brain cells. After an animal becomes infected, there is a two to five-year incubation period. During this time an infected animal may not show signs of illness but can shed the scrapie disease agent. Once clinical signs do appear, the disease progresses and is fatal one to six months later (The Center for Food Security & Public Health, 2016). Scrapie is confirmed through microscopic examinations of brain tissue at death, or by procedures that detect the presence of the abnormal prion protein.
Clinical signs of scrapie include:
- Behavior changes (nervousness, aggression).
- Locomotor incoordination.
- Scratching and rubbing.
- Weight loss with no decrease in appetite.
- Wool pulling.
- Lip smacking.
- Head pressing.
Scrapie can be passed between animals through direct contact with infected animals or by contaminated “fomites”. Fomites are inanimate objects that can transfer infectious disease agents by direct or indirect contact, and may include:
- Water and feeding troughs.
- Objects an infected animal may have rubbed against (a clinical sign, and the origin of the name of scrapie, is animals that often rub on objects and scrape off their wool or hair).
- Soil contaminated with the disease agent.
- Reused syringes.
- Other equipment that is not cleaned between use.
Prions can persist and remain on fomites for many years, posing a long-term risk of infection. This disease can be spread from a ewe to its offspring through contact with the placenta, milk and colostrum. Scrapie is very difficult to get rid of once it is present. (Konold T., Hawkins S. Thurston L. Maddison B. Gough K. et al. 2015).
When Scrapie was First Diagnosed in the U.S.
The first diagnosis of scrapie in the United States was made during 1947 in a Michigan flock of sheep. The flock owners had imported sheep of British origin through Canada for several years, and brought in the infected sheep this way. In 1952, scrapie was identified in two additional states (Scrapie Management Team, 2012). Originally thought to be a disease only of sheep, the first case in a goat was diagnosed during 1969, after the goat was transferred from its herd of origin in Missouri to the scrapie experimental station in Mission, Texas. Producers became concerned about other animals might be at risk, and about the increasing number of scrapie cases. In response, the U.S. Department of Agriculture, Animal and Plant Health Inspection Service (USDA APHIS) created the National Scrapie Eradication Program (NSEP).
National Scrapie Eradication Program
NSEP was created in 2001 to accelerate the eradication of scrapie from U.S. sheep flocks and goat herds.
The NSEP program is based on the following concepts:
- Identification of pre-clinical infected sheep through live-animal testing and active slaughter surveillance.
- Effective tracing of infected animals to their flock/herd of origin made possible as a result of the new identification requirements.
- Providing effective cleanup strategies that will allow producers to stay in business, preserve breeding stock, and remain economically viable. USDA/APHIS will do this by providing the following to exposed and infected flocks/herds that participate in cleanup plans:
- Indemnity for high risk, suspect, and scrapie positive sheep and goats, which owners agree to destroy.
- Scrapie live-animal testing.
- Genetic testing.
- Testing of exposed animals that have been sold out of infected and source flocks/herds.
Since its inception, the NSEP is close to eradicating scrapie in the U.S.
The positive cooperation of livestock producers has enabled the NSEP program to be extremely effective in reducing the prevalence of scrapie. Producers are helping by identifying their sheep and goats according to the federal and state regulations, reporting suspected sheep and goats to an accredited veterinarian, and submitting the heads of dead or euthanized sheep and goats over the age of 18 months for scrapie testing. Livestock producers are also using genetic selection in flocks and herds that are at risk (National Scrapie Education Initiative).
The USDA has tried to make participation in the program as easy as possible. They provide 80 plastic flock tags free of charge to anyone who may not have received tags. The USDA provides genetic testing and scrapie testing for participating producers. The USDA also offers indemnity for high risk, suspect and scrapie positive sheep and goats, which owners agree to destroy.
Preventative Biosecurity for Scrapie
What can sheep and goat owners do to protect their animals from scrapie? Preventative biosecurity is the best solution to minimize the risk of sheep and goats from getting scrapie. Some prevention tips include:
- Maintain a closed flock or herd – do not bring in new animals if necessary, particularly ewes (female sheep).
- Genetic resistance – a ram that has a high genetic resistance to scrapie will pass this on to his offspring.
- Lambing management – the highest risk period of scrapie transmission is at birth or soon afterward, from exposure to infected placenta or birth fluids. Remove placentas right away and remove bedding and manure between each birth.
- Read more about preventative biosecurity measures on the Prevent section of the Healthy Farms Healthy Agriculture website.
Thanks to the combined efforts of the government and livestock producers, the number of scrapie outbreaks in the U. S. has been drastically reduced. Participation in these types of programs is needed to work towards the eradication of other harmful livestock diseases as well.
Konold T., Hawkins S. Thurston L. Maddison B. Gough K. Duarte A. Simmons H.. (2015, September). Objects in contact with classical scrapie sheep act as a reservoir for scrapie transmission. Retrieved from https://doi.org/10.3389/fvets.2015.00032
The Center for Food Security & Public Health. (2016, September). Scrapie [PDF file]. Retrieved from http://www.cfsph.iastate.edu/Factsheets/pdfs/scrapie.pdf
Scrapie Management Team. (2012, September). Scrapie – an overview of the disease and the National Scrapie Eradication Program [PDF file]. Retrieved from https://datcp.wi.gov/Documents/ScrapieAnOverviewoftheDiseaseandtheNSEP.pdf
United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS). (2017, July). Scrapie. Retrieved from https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/nvap/NVAP-Reference-Guide/Control-and-Eradication/Scrapie
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