Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalitis (TSEs), which are related to bovine spongiform encephalopathy (BSE or “mad cow disease”). Forms of TSEs include the above mentioned bovine spongiform encephalopathy (BSE) in cattle, chronic wasting disease in deer and elk, and Creutzfelt-Jakob disease in humans. While the exact cause of scrapie is still debated, the disease is associated with the presence of an abnormal form of a protein called a prion. According to Health Canada, there is no known link between scrapie and human health. Nevertheless, there is evidence to suggest that some TSEs — such as mad cow disease or BSE — that affect animals affect humans. Any animal known to be infected with scrapie is currently kept out of the food chain. There is no treatment or vaccine currently available for this disease.
See Signs/Symptoms
Scrapie is slow to develop, usually takes more than a year and a half for clinical signs to appear in an infected animal, although it has been known to take up to eight years to develop. Typically, cases occur in animals between two and five years of age. Once an animal appears ill, however, it will die in one to two months.
Symptoms vary tremendously between cases of scrapie. One may observe an older animal with changes in general behaviour such as aggression or apprehension, tremors, incoordination or abnormal gaits. However scrapie can also present as a mature poor doing animal with a poor wool coat or even simply as a found dead.
A difference in the predominant presentation of the clinical disease has been documented between countries. Wasting and debility appear to be more prominent clinical features in North America. Pruritis remains the most prominent clinical feature in Europe.
One or more of the following clinical signs may be present in affected animals. It is important to note that not all sheep or goats show all the signs of scrapie. Sometimes these signs can be so subtle that they are missed or misdiagnosed until they have progressed.
This dramatic wool loss can develop over a short period of time in animals who are Scrapie positive. The wool loss can be accompanied by proprioceptive deficits and a classic lip-smacking response.
See Control MeasuresScrapie is found in countries all over the world. Diagnosed for the first time in sheep in 1938, it was made a reportable disease in Canada in 1945. There has been a control program in place since that time. Incidents of scrapie are reported annually to the Office international des épizooties (World Organization for Animal Health), referred to as OIE.
Scrapie is spread through fluid and tissue from the placentas of infected females. It can be transmitted from an infected female to her offspring at birth, or to other animals exposed to the same birth environment. Males can contract scrapie, but they do not transmit the disease to other animals. A sheep’s genes affect both its susceptibility to the disease and the length of the incubation period.
Scrapie is diagnosed after death by microscopic examination of the brain tissue, tonsils, lymph nodes, or spleen that have been treated with a special stain. Biopsies of peripheral lymphoid tissue from live sheep can accurately identify certain animals that have scrapie. However, a negative lymphoid biopsy does not rule out that a particular animal has the disease.
Sheep with certain genetic types are less likely to become infected with scrapie. Blood tests can determine the genetic profile of a sheep. Producers that want to minimize the risk of scrapie in their sheep flock can consider selective breeding for genetic resistance to scrapie. However it should be remembered that even genetic resistant sheep can get scrapie.
Alternatively, sheep producers and goat producers can eliminate or severely restrict the introduction of females and commence scrapie surveillance by having animals over 12 months of age that die on their farm tested for scrapie. Specific efforts towards managing the risk of scrapie on individual premises can be recognized through formal participation in a scrapie flock certification program.
In the absence of adopting specific measures to minimize the risk of scrapie on their farm, a producer is encouraged to implement general good management and biosecurity practices such as individual animal identification, record keeping, prompt isolation of sick animals, separation of females giving birth, increased cleanliness of birthing environment, disinfection of equipment between animals and single use needles for injections.
Scrapie is a reportable disease under the federal Health of Animals Act, and a control program exists to prevent its spread. As scrapie is a reportable disease, any suspect scrapie case must be reported to a CFIA veterinarian immediately. Canadian veterinarians and livestock producers have been alerted to the symptoms/ signs of scrapie. When an animal is identified with scrapie, all the animals that were exposed to the same birthing environment and are deemed at risk to developing the disease are ordered destroyed. Producers are compensated for the loss of their animals. The maximum amount of compensation paid for sheep ordered destroyed under the Health of Animals Act is $825 for non-registered animals and $1200 for registered animals. The maximum amount of compensation paid for goats ordered destroyed under the Health of Animals Act is $600 for non-registered animals and $1000 for registered animals. Sheep or goats that are known to be infected with scrapie are humanely destroyed, and their carcasses are burned or buried under CFIA supervision. Owners are further compensated for their disposal costs.
