What is scrapie and why do I need to worry about it?


Scrapie is a fatal, degenerative disease affecting the central nervous system of sheep/goats. It is in a family of diseases called transmissible spongiform encephalopathies (TSEs). Other TSEs include bovine spongiform encephalopathy (BSE; aka "mad cow disease"), chronic wasting disease (in deer and elk), and Creutzfeldt-Jacob disease (in humans). Scrapie is the oldest known TSE, having existed for centuries. Under natural conditions, only sheep/goats can become infected.

Scrapie was first diagnosed in the US in 1947 in a flock of Suffolk sheep (of UK origin) that had been imported via Canada. The first case of scrapie in a goat was diagnosed in 1969. From 1947 through July 2001, scrapie was diagnosed in over 1000 flocks/herds, with 1600 individual cases of sheep scrapie (87% Suffolk) and 7 cases of goat scrapie. While important, the incidence of scrapie was/is considered to be very low relative to other diseases. Despite this, the disease costs the industry millions of dollars each year. Eradication is close.

The disease
Scrapie is transmitted during the lambing/kidding season from infected dams via ingestion of infected placenta or birth fluids by other ewes/does or newborn lambs/kids. Infected males are not know to transmit the disease. Lambs/kids delivered via caesarian section remain disease-free, as scrapie is not known to infect the embryo or fetus. Previous contamination of premises is believed to be another source of scrapie infection, as there are anecdotal reports of animals getting reinfected on farms that were previously depopulated.

While any breed of sheep/goat can get scrapie, it is known to infect mostly blackface sheep and their crosses (in the US). Early signs of scrapie are subtle changes in temperment or behavior, followed by scratching or rubbing against fixed objects (hence the name scrapie: scraping). Other signs include loss of coordination, weight loss despite good appetite, biting of feet and limbs, and lick smacking. Gait abnormalities are common. Scrapie has a very long incubation period. Signs do not usually appear until 2 to 5 years after the animal was infected. Once the symptoms start, the animal usually only lives for 1 to 6 months. There is no treatment or cure for scrapie. Scrapie is always fatal.

While scrapie is not a genetic disease, a sheep/goat's genetics determine if it will get scrapie, if it is exposed to the infective agent (believed to be a prion). Genetic testing has been available for sheep for many years. In more recent years, similar testing has become available for goats. Testing involves sending a blood or hair sample to a lab. The genetic tests are for scrapie susceptiblity, not the disease itself.

Live animal testing
Initially the only way to confirm that a sheep/goat had scrapie was to examine brain tissues post-mortem. In more recent years, it has become possible to diagnose scrapie in the live animal by testing lymphoid tissue from the third eyelid or rectum. Combining genetic testing with live animal testing has reduced the number of exposed animals that have had to be destroyed as a result of exposure to scrapie-positive animals.

Scrapie eradication
There are two kinds of scrapie: classical and non-classical. Nonclassical scrapie is referred to as Nor98 or Nor98-like scrapie. It was first identified in Norway in 1998. It occurs sporadically in all genotypes and does not appear to be transmissible. The first case of nonclassical scrapie was identified in the US in 2007. Scrapie eradication focuses on classical scrapie.

Most countries have programs for eradicating scrapie. Only Australia and New Zealand are recognized as being scrapie-free. Scrapie limits the movement of sheep/goats between countries and even states. The most recent efforts to eradicate scrapie from the United States began in 2002. One of the key features of the national scrapie eradication program is that sheep/goats must be officially identified. Identification allows animals to be traced back to the farm where they were born (and potentially exposed to scrapie).

For many years, USDA APHIS provided free ear tags and applicators. Free tags are no longer available. Producers must purchase their own tags. Before you get ear tags, you need to have an official premise ID. To get a premise ID, call 1-866-USDA-TAG (1-866-873-2824). You will be connected with the office in your state. Once you have a premise ID, you can order scrapie program tags from approved vendors: Premier 1 Supplies, EZid, Allflex, Alliance, National Band & Tag Company, and Shearwell Data USA. Be sure to get tamper-proof tags that are approved for scrapie ID.

Which sheep/goats require individual scrapie ID has changed over the years and may differ by state. There are a few exceptions, but most sheep/goats should be tagged before leaving the farm/ranch on which they were born. Some sale barns are approved to apply scrapie tags, but they will charge you to do so. It is better that animals be tagged on the farm/ranch where they were born. Many producers use the scrapie tags for their flock/herd ID, so there is no extra cost.

Visual ear tags are the most common form of scrapie identification. There are different colors and styles of tags that can be used. Electronic (RFID) tags are an increasingly popular option. Tattoos (accompanied by registration papers) are acceptable, but not for slaughter channels. In addition to the mandatory tagging requirements, producers are required to keep records regarding the disposition of animals. These records need to be kept for a minimum of 5 years.

There is also a voluntary scrapie-free flock certification program. The program enables sheep/goat producers to have their flocks/herds certified as scrapie-free. The program includes an export category. The standards for the voluntary program were last changed in 2016.

Since slaughter surveillance began in 2003, the percent of cull sheep found positive for scrapie (at slaughter) has decreased by 99 percent. The last 1 percent will be the hardest to find. In more recent years, the slaughter surveillance of goats has increased. There have been 44 confirmed positive goats since 2002. Even though scrapie is less common it goats, it is just as important in goats.

Do your part
Every sheep/goat owner needs to do their part to help eradicate scrapie and enable the US to be declared scrapie-free by the World Organization for Animal Health. The responsiblity starts with official scrapie ID. Be sure to apply the ID before animals leave your farm/ranch. Protect your flock/herd by closing it to female additions or by purchasing females from certified scrapie-free flocks/herds and/or with resistant genotypes. Remove placentas and bedding soiled by birthing right away and keep birthing pens clean. Scrapie is a reportable disease. Report any animal with scrapie-like symptoms to your veterinarian or animal health official. Consider submitting dead or euthanized animals (or whole heads) for scrapie testing.

Zoonotic potential
There is no evidence that scrapie can be transmitted to humans, either by working with infected animals or by consuming their meat or milk. Regardless, any animal known to be infected with scrapie is kept out of the food chain.



Additional reading
National Scrapie Eradication Program
What is Nor98-like (nonclassical) scrapie?
Scrapie: the program - American Goat Federation
Scrapie-free flock certification program (2016)
Scrapie eradication is in sight: you are the key to finding the last cases