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Ask the Shepherd-Scrapie Disease and Testing for Susceptibility

Scrapie is a fatal, degenerative disease affecting the central nervous system of sheep and goats. There is no cure and there is no treatment for scrapie, though scientists around the world are searching hard for one. Scrapie is classified as a transmissible spongiform encephalopathy (TSE). Both scrapie and bovine spongiform encephalopathy (BSE; a.k.a. “Mad Cow” disease) are TSEs, as is Chronic Wasting Disease in deer and elk. (In humans, it is called Creutzfeldt-Jakob disease (named after the people who discovered it).

Transmission-The scrapie agent is thought to be spread most commonly from the ewe to her offspring and to other lambs in contemporary lambing groups through contact with the placenta and placental fluids. Signs or effects of the disease usually appear two (2) to five (5) years after the animal is infected but may be longer.

Symptoms-Signs of scrapie vary widely among individual animals…Early signs include subtle changes in behavior or temperament….loss of coordination, weight loss despite retention of appetite, biting of feet and limbs, lip smacking, and gait abnormalities, including high-stepping of the forelegs, hopping like a rabbit, and swaying of the back end…Several other problems can cause clinical signs similar to scrapie in sheep, including the diseases ovine progressive pneumonia, listeriosis, and rabies; the presence of external parasites (lice and mites); pregnancy toxemia; and toxins.(NSEI)

(Italics are my edits in above quote.)

It was the late 1990’s and Vermont newspapers were full of stories about the USDA, Scrapie, and one Vermont sheep farm, owned by the Faillace family. Long before acquiring our own flock of sheep, we followed this tragic story, from the initial investigation by the government, to shepherds watching their flock of over 100 sheep pull away in a tractor trailer headed for slaughter on March 23, 2001. Years later, a colleague of my husband’s said that he drove by the Faillace farm every morning on his way to work. He said that on the morning of the seizure of the sheep, the flock of sheep was grazing in the pasture with their guardian llama-it was a typical peaceful Vermont scene. That evening, on his way back home, chills ran down his spine as all that was left was one llama standing in the field. Years later, Linda Faillace went on to write a book to tell their story of their multi-year battle against the USDA for their sheep, and the tragic end to their life-time dream of operating a sheep farm. Linda wrote the book to bring herself “peace of mind” and a sense of “healing”. The pictures tell the story of the heartache, devastation, and injustice felt by this family.

So needless to say, when shepherds in Vermont hear the word “Scrapie”, their hearts quicken, and their palms get sweaty, remembering the tragic ordeal of the Faillace family.

Scrapie prevention has been a topic of discussion among all sheep breeders. Recently, I had asked a fellow Gotland sheep breeder, Polly Matzinger, Ph.D., a researcher at the National Institute of Health, her opinion about Scrapie and Scrapie susceptibility testing. With Polly’s background in science, I asked her to explain the susceptibility testing.

Tell me about Scrapie and why it is so important to understand.

The disease, known as Scrapie, is one that the US government is highly focused on, even though there have been no instances of transmission from sheep to humans in the entire history of human/sheep relations.  No one knows why Scrapie has never been transmitted to humans, but it’s likely that the protein that causes it, is different enough between sheep and humans so that it cannot cross between the two species.  Because Scrapie causes a wasting disease in sheep, it is an economical problem for flocks that have it.  It can also be transmitted to wild sheep (like bighorn sheep) when they visit infected domestic flocks.

How does a sheep get Scrapie and is there a way to tell if a sheep is susceptible to the disease?

In order to get scrapie, a sheep has to carry a susceptibility gene for a protein called a “Prion”.  Some sheep carry forms of the prion gene that confer resistance, while others carry forms that make them susceptible.  If you think of the gene as a long string of letters (a “code” for the protein, with each individual letter called a “codon”), and you numbered the letters from one end to the other, it turns out that the letters at positions 136, 154 and 171 seem to be the critical ones for resistance to scrapie in many species.  (In humans, there is some evidence that position 129 might be important.) In sheep, or at least in Suffolk, Texel and Cheviot  sheep, (the ones that have been studied the most),  the letters A, R, R at positions 136, 154 and 171 are found most often in sheep that are resistant.   The letter (codon) at position 171 is the one that the government has most focused on.  If there is a Q at that position, the sheep is thought to be susceptible.  If there is an R at that position, it is thought to be sensitive. This is an extreme oversimplification, but politicians aren’t usually very good at dealing with complexity, so the government focuses on codon 171.

What happens if your flock has Scrapie?

If your flock becomes infected (because you bought a scrapie infected sheep and put it with the rest of your flock), the government can (and does) come and take away all of the sheep in your flock that are Q at position 171.  So it’s good to have sheep that carry R at position 171.  It’s kind of crazy, because researchers have found that the letters at position 171 are not the whole story, but our government doesn’t really care.  It will come and decimate your flock, if you get scrapie and have animals that are Q at 171.

Have any Gotland sheep ever undergone codon testing?Gotland Ewe

As far as I know most Gotlands have not been tested for their codons at this position, though a few breeders are beginning to test.

Should Gotland breeders be testing their flocks for codon R and Q?

We should consider the codon 171 status of our sheep, and, if we find some that are R at 171, and we like them for other reasons too, we should keep those sheep rather than an equally nice sheep that is Q. When I say “equally nice”, I mean that we shouldn’t be focusing on the scrapie gene so much that we ignore the Gotland breed standard.  The Gotland characteristics come first.  However, if you have enough sheep and you’re choosing between keeping one of two sheep with equally good characteristics of color, fleece and conformation, then keep the one with R at codon 171. I don’t think that we should give it priority above other things, but we should at least be aware, and take note of it when other things are equal. This can be difficult when many of us have small Gotland flocks. By testing and eliminating lines that carry the Q, we must have large flocks, and lots of breeding choices, or perhaps having groups of people who have smaller flocks, but work together.

Personally, I don’t test my sheep, yet, and I don’t have a large enough sample to consider the prion gene as an important enough characteristic on which to make breeder decisions –yet.  There will come a time, however, when I start testing.  Our government can be way too invasive at times, even when working with incomplete data.

 

In further discussions with Polly, she acknowledged that the challenge in building a breed, as in the upbreeding of Gotlands, is to not overlook other more important traits of the sheep, while testing for and breeding for the R gene. She feels it is critical that the breed standards take priority first and then begin looking at the R gene. 

Interesting Links to understanding what happened to the Faillace family:

Eradicate Scrapie!

The USDA’s War on a Family Farm

Mad Sheep Scare

Sheep Farmer Writes About Losing Her Flock

 

 

 

 

 

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One Response

  1. Robyn
    | Reply

    I grew up in Vermont and remember very clearly when the Sheep were taken away from the Faillace family. What a sad event.

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