Fact sheet - Scrapie

Introduction

Scrapie is a fatal disease that affects the central nervous system of sheep and goats. It belongs to the family of diseases known as transmissible spongiform encephalopathies (TSE). Other TSEs include bovine spongiform encephalopathy (BSE) in cattle, chronic wasting disease in deer and elk and Creutzfeldt-Jakob Disease in humans.

The infectious agent of the TSEs is now widely accepted to be an abnormal form of a protein called a prion. Normal prions are present in every mammal and bird. When an abnormal prion enters a healthy animal, it alters existing prions and changes them into the disease-associated form.

There are two forms of scrapie, classical scrapie and atypical scrapie. Atypical scrapie is thought to be a spontaneous degenerative condition of older sheep and is not believed to transmit to animals under natural conditions. Classical scrapie can be transmitted to other animals.

In Canada, classical scrapie is a reportable disease. Reportable diseases are outlined in the Health of Animals Act and Reportable Diseases Regulations. Producers and veterinarians that suspect an animal may be infected with scrapie must contact the Canadian Food Inspection Agency (CFIA). This is required by law.

The number of sheep flocks and/or goat herds confirmed to be infected with classical scrapie in Canada are reported to the World Organisation for Animal Health (WOAH; founded as Office International des Épizooties (OIE)).

Is scrapie a risk to human health?

According to Health Canada, there is no known link between scrapie and human health.

Clinical signs

Scrapie is a disease that develops slowly. Clinical signs are only seen in adult animals, typically between two and five years of age, and in some animals, the disease has taken up to eight years to develop. However, once an animal appears ill, it will typically die within a few months.

Signs vary tremendously between cases of scrapie. An older animal can show changes in general behaviour such as aggression or apprehension, tremors, incoordination or abnormal gaits. However, a mature animal with a poor coat, or one that is found dead, can also be diagnosed with the disease.

The disease seems to present itself differently in different countries. Wasting and debility (weakness) appear to be more prominent clinical features in North America, while pruritus (intense itching) remains the most noted clinical feature in Europe.

Owners of scrapie infected animals may be unaware that there is a problem with their flock or herd. Over time, especially in infected herds/flocks that contain a high percentage of susceptible sheep or goats, owners may experience significant production losses. Infected animals sold from these herds/flocks can spread the disease to other herds/flocks.

Geographical distribution

Scrapie is found in countries all over the world. New Zealand and Australia are two countries recognized as free from the disease. Scrapie was detected in Canada for the first time in sheep in 1938 and has been detected routinely since then. Scrapie was made a reportable disease in Canada in 1945. There has been a control program in place since that time.

Transmission

Animals become infected with classical scrapie through exposure to other scrapie-infected animals and their scrapie-contaminated environment. Scrapie is most commonly spread from an infected female to her offspring or other animals exposed to the birth environment. Fluid and tissue from the placenta can contain large quantities of infectious scrapie prions. Healthy animals become infected by eating or licking any contaminated material in the birth environment. Newborn lambs and kids are very susceptible to infection when born into a contaminated environment.

Animals incubating the disease without clinical signs can also be a source of infection to others. Infectious prions have been found in the milk, feces, saliva and urine of infected animals so transmission may also occur by these routes. Exposure to an environment inhabited by scrapie infected animals could put healthy animals at risk of contracting the disease.

Research shows that sheep with a particular genetic makeup are more at risk of developing scrapie. Using genetic testing, sheep producers can breed for resistance to scrapie. At this time, genetic profiles that can consistently predict a high risk of developing scrapie for goats are still being researched.

Diagnosis

Scrapie is diagnosed after death by detecting abnormal scrapie prions in the brain tissue or lymph nodes. Biopsies of rectal or third eyelid lymphoid tissue from live sheep or goats can accurately identify some animals that have scrapie. These live animal biopsy tests can be useful for screening flocks or herds for the presence of infection, but are not reliable to confirm an individual is free from disease.

Treatment

There is no treatment or vaccine currently available for this fatal disease.

Protection of Canadian livestock

The CFIA, with the support of the small ruminant industry, is working towards eradicating scrapie in Canada. The CFIA, under the National Scrapie Eradication Program, conducts active surveillance for scrapie, takes action to control disease on infected farms, and provides support to the Scrapie Flock Certification Program (SFCP).

Scrapie is a "reportable disease" under the Health of Animals Act. This means that all suspected cases must be reported to the CFIA for immediate investigation.

The CFIA imposes strict regulations on the import of animals and animal products from countries where scrapie is known to occur. These regulations are enforced through port-of-entry inspections done either by the Canada Border Services Agency or the CFIA.

Sheep of certain genetic types are less likely to become infected with scrapie. A blood or tissue test can determine the genetic susceptibility of a sheep to scrapie. Producers who want to minimize the risk of scrapie in their sheep flock can consider selective breeding for genetic resistance to scrapie.

Alternatively, sheep producers and goat producers can:

• close their herd/flock
• purchase animals from flocks or herds in a scrapie flock certification program
• commence scrapie testing in mature deadstock

Specific efforts towards managing the risk of scrapie on individual premises can be recognized through formal participation in the 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 the birthing environment
• disinfection of equipment between animals
• single use needles for injections

For more information on sheep and goat biosecurity, see:

National Farm-Level Biosecurity Standard for the Goat Industry

• Biosecurity Planning Guide for Canadian Goat Producers

The National Sheep On-Farm Biosecurity Standard

• The National Sheep Producer Biosecurity Planning Guide

CFIA's response to an outbreak of scrapie

When a scrapie-positive test result is confirmed by the CFIA, immediate science-based internationally recognized disease control actions are initiated and usually include the following:

• strict quarantine and animal movement controls to prevent disease spread;
• humane destruction and disposal of all infected and at-risk animals;
• investigation of potentially infected or high-risk animals that could spread the disease to new premises and investigation of potential source farms;
• strict cleaning and disinfection of the infected premises; and
• follow up deadstock surveillance requirement.

Owners whose animals are ordered destroyed may be eligible for compensation.

More detailed information on CFIA's disease response activities is available in What to expect if scrapie has been detected on your farm.

Implementing disease control measures enables owners to return their premises to its previous health status, maintains the health of the national herd/flock and protects the reputation of Canada's sheep and goat industries.

Additional information

• Chronic wasting disease of deer and elk
• Animal Health Offices
• CWD herd certification programs
• CWD – What to expect if your animals may be infected