Transmissible Spongiform Encephalitis
“Scrapie” in Domestic Sheep and Goats
Scrapie is a family of fatal, degenerating neurological disease in domestic sheep and goats. Scrapie was first recognized in domestic sheep in Scotland over 200 years ago.* All breeds of sheep are susceptible, but the Suffolk breed in the US is at the highest risk due to their genetics. The cause of scrapie is a small piece of protein, called a prion that can be found in lymph and neural tissues. Unfortunately, it is a very resilient protein that is not easily destroyed. The disease can be transmitted genetically- adult to lamb, and between sheep from infected placentas- adult to adult. The disease can take 2 to 5 years to develop in an animal; so many generations of an entire flock could be infected well before the disease is identified on the farm. Genetic testing can be evaluated by blood samples sent to specific laboratories – consult your veterinarian.
Sheep clinically infected with scrapie may have an abnormal gait, they may “bunny-hop”, have spastic hind legs (hypermetric), or not be aware of where their front legs and feet are (proprioceptive deficits). They are generally weak, eating but emaciated, and can rub their wool off of their hindquarters and flanks until they are raw – hence the name “scrapie”. There is no known treatment for scrapie in sheep or goats.
Scrapie costs the United States sheep industry $20 million annually in direct loses and millions more in lost potential markets and flock productivity. Many programs have been instituted since 1952 to control scrapie. The current federal program is the Scrapie Flock Certification Program**. A flock has to be monitored for 5 years to be certified for the program.
The zoonotic potential (transmissible to people) of scrapie is unknown, but there is evidence that some variants of Creutzfeldt-Jakob disease are caused by ingestion of beef products contaminated with scrapie or scrapie-like organisms. Remember the “Mad Cow” outbreak in England? This was believed to be the result of cattle eating sheep offal in the feed rations. So, sheep by-products are now banned from the feed production market until we can certify our flocks as “Scrapie Free” nation wide - a great challenge for everyone involved in the sheep industry !!
The primary method of prevention is maintenance of a closed ewe flock, purchase of genetically resistant stock, or buying from a certified flock. There are already many certified flocks, and purchasing breeding stock from these producers is recommended. Information about participation in the federal program can be acquired through the CT Department of Agriculture and the Federal APHIS USDA.
*Terry R. Spraker, DVM, PhD, Diplomate ACVP
**Sheep and Goat Medicine, D.G. Pugh