Scrapie

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. It is a fatal, progressive, degenerative disease of the central nervous system of sheep and goats.

Australia

Australia is free of scrapie and is recognised as meeting the WOAH requirements for a scrapie historically free country.

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 protects its free status and ensures continued freedom from scrapie through border biosecurity controls and the national TSE Freedom Assurance Program (TSEFAP).

Border Controls the import of live ruminants, animal products and animal feeds, and the TSEFAP monitors compliance with a legislated ban on feeding risk feedstuffs such as meat meal to ruminants (sheep, cattle and goats), and conducts and reports targeted surveillance of mature sheep showing neurological signs.

Global

While scrapie has a long history and attempts have been made over the years to control and eradicate the disease, it remains endemic in many countries. Scrapie is present in several European Union member states, especially the United Kingdom, Canada, the United States, Iceland, India, Japan, Brazil and Israel.

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
• excitability
• 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.

Some metabolic diseases can present similarly to scrapie such as pregnancy toxaemia (twin lamb disease) and hypocalcaemia (milk fever), as well as diseases that cause itching such as lice and mites. Infectious disease such as listeriosis (circling disease), a brain or spinal abscess, or focal symmetrical encephalomalacia (the chronic form of pulpy kidney) can also present similarly to scrapie.

Some toxicities can present similarly to scrapie such as lead poisoning, annual ryegrass toxicity, botulism and urea poisoning.

Atypical and ‘classical’ scrapie are different and separate diseases but present with similar signs. Atypical scrapie is a non-contagious, sporadic, degenerative brain condition which can arise spontaneously in older sheep and, less commonly, in goats. It 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. Atypical scrapie does not require WOAH notification and cases do not impact on trade.

Some exotic diseases such as rabies can also present similarly to scrapie.