Scrapie is a TSE
Scrapie is one of the diseases called transmissible spongiform encephalopathies (TSEs) or ‘prion’ diseases. These diseases have long incubation periods during which an abnormal protease-resistant isoform of a prion protein accumulates in the central nervous system.
World distribution of scrapie
Scrapie is present in several European Union member states, especially the United Kingdom, Canada, the United States, Iceland, India, Japan and Brazil. Israel has also reported outbreaks of scrapie, with the most recent being in early 2007. There have been isolated reports of scrapie from a number of countries including New Zealand (1954) and the Republic of South Africa (1972). In these instances, the disease was confined to imported sheep and was eradicated by destruction of the affected group.
For the latest information on the distribution of scrapie, refer to the OIE World Animal Health Information Database.
Australia is free of scrapie
Australia is free of scrapie and is recognised as meeting the World Organisation for Animal Health (OIE) requirements for a scrapie historically free country.
Australia has had one isolated case of scrapie, on a single property in Victoria in 1952. Four of a group of 10 Suffolk sheep imported from the United Kingdom were affected. The disease was eradicated by slaughter of affected and in-contact sheep, ploughing paddocks on which they had grazed and leaving them fallow for a year, and quarantine of the property for a year.
If scrapie occurred in Australia, it would be likely to impact on Australia’s international trade in livestock and livestock products. For this reason Australia protects its status and ensures continued freedom from scrapie through the national TSE Freedom Assurance Program (TSEFAP).
Atypical scrapie is a different disease to ‘classical’ scrapie
Atypical scrapie is a non-contagious, sporadic, degenerative brain condition which can arise spontaneously in older sheep and, less commonly, in goats.
Atypical scrapie is a separate disease to classical scrapie. Australia is free of ‘classical’ scrapie and has a ruminant feed ban and other controls to prevent the entry and use of risk materials in livestock feed.
Atypical scrapie has been diagnosed in more than 20 countries worldwide. Most countries that test large numbers of sheep for classical scrapie have found cases of atypical scrapie.
Sheep that develop atypical scrapie show neurological signs such as lack of coordination, head pressing and circling.
Veterinarians routinely submit samples from sheep exhibiting neurological signs under Australia’s rigorous animal health surveillance program.
Atypical scrapie does not require OIE notification and cases do not impact on trade.
What animals are susceptible to scrapie?
Sheep and goats are susceptible to scrapie. Breeds of sheep vary in their susceptibility to scrapie but all goat breeds appear susceptible.
Scrapie is not considered to pose a human health risk.
How is scrapie spread?
The main mode of transmission of scrapie is from mother to offspring immediately after birth and to other susceptible newborns exposed to the birth fluids and tissues of an infected animal.
The incubation period of scrapie varies but it is usually measured in years. The incubation period can be influenced by host genetics and strain of scrapie.
How could scrapie enter Australia?
Scrapie could be introduced into Australia through the importation of infected sheep or goats or through the use of a veterinary biological product, such as a vaccine that contains a contaminated ingredient. Australia’s strict quarantine requirements are designed to prevent this.
Australia has a ruminant feed ban and other controls to prevent the entry and use of risk materials in livestock feed, as these feeds could potentially introduce scrapie.
What are the signs of scrapie?
Scrapie should be suspected in sheep or goats that develop a slowly progressive neurological disease. Signs observed may include:
- reduced exercise tolerance (usually the earliest sign)
- staggery gait
- tremor, especially of the head and neck and in response to stimulation
- severe persistent itchiness leading to rubbing of wool and skin trauma (although this is not always present)
- excessive nibbling or licking after rubbing along the spine over the rump
- emaciation or obesity may occur in the later stages of the disease.
What other diseases look like scrapie?
Scrapie causes neurological signs with or without itching, so many sheep and goat diseases look similar to scrapie.
Diseases of sheep and goats that may present with signs similar to scrapie are:
- metabolic diseases such as pregnancy toxaemia (twin lamb disease), hypocalcaemia (milk fever) and diseases that cause liver and kidney damage
- diseases that cause itching such as lice and itch mite
- infectious diseases such as listeriosis (circling disease), brain or spinal abscess, focal symmetrical encephalomalacia (the chronic form of pulpy kidney)
- toxicities such as lead poisoning, annual ryegrass toxicity, botulism and urea poisoning
- exotic diseases such as rabies.
There is no treatment for affected sheep and goats. Once the signs develop, the affected animal will eventually die.
Australia’s surveillance program for scrapie
Australia has a TSE Freedom Assurance Program (TSEFAP) to ensure we remain free of scrapie. The program involves controlling the import of live animals, animal products and animal feeds, having a legislated ruminant feed ban in place and conducting targeted surveillance of sheep.
As part of the TSEFAP, Australia must test a certain number of sheep that show signs similar to scrapie in order to show that we continue to remain free of scrapie.
Sheep producers who have a veterinarian investigate neurological signs in their sheep may be eligible for an incentive payment. Producers who participate are supporting their industry to demonstrate that Australia remains free of scrapie and may also find the actual cause of the disease at reduced cost. Veterinarians who investigate cases and submit the required samples may also be eligible for a rebate. Read more on the National TSE Surveillance Program.