What is a TSE?
Transmissible spongiform encephalopathies (TSEs) in animals are a class of rare brain diseases that are associated with the accumulation of abnormal prion protein in the brain and therefore affect the central nervous system. These diseases are very rare, fatal and are characterized by spongy degeneration of the brain. There are no validated live animal tests, no treatments and no vaccines for these diseases.
There are a number of TSEs which affect people and animals. Of most interest to Australia’s livestock industries are:
- Bovine spongiform encephalopathy (BSE) which affects cattle and is commonly referred to as ‘mad cow disease’
- Scrapie is a TSE that affects sheep and goats
- Chronic wasting disease (CWD) is a TSE that affects cervids such as mule deer, white tail deer and Rocky Mountain elk
- Feline spongiform encephalopathy (FSE) found in domestic cats and captive exotic cats
- Transmissible mink encephalopathy (TME) is a very rare disease of farmed mink.
- Exotic ungulate encephalopathy found in captive antelope, Ankole cattle and bison.
- Creutzfeld – Jakob disease (CJD) is a rare and fatal form of TSE that affects humans worldwide. A newly recognized form of CJD, called variant Creutzfeldt-Jakob disease (vCJD), has been diagnosed in a small number of people since 1996 and is thought to be linked to the consumption of certain parts of the carcase of BSE-infected cattle in countries affected by the disease.
BSE and chronic wasting disease have never been recorded in Australia. Scrapie has occurred once, in imported sheep on a single property in 1952 and was promptly eradicated. Two cases of feline spongiform encephalopathy have been diagnosed in imported animals in Australian zoos in 1992 (cheetah) and 2002 (Asiatic golden cat), where exposure before importation to feeds derived from BSE affected cattle are thought to have caused the disease. In both instances, effective response measures were taken. As of January 2014, there have been no reported cases of vCJD in people in Australia, although it is recognised that one or more cases could occur due to overseas exposure.
Australia’s livestock continue to remain free from TSEs. This has been confirmed by national and international risk assessments, for example those conducted by the Food Standards Australia New Zealand, European Food Safety Authority, and the New Zealand Food Safety Authority.
Australia’s status as free from BSE can only be assured if we continue to apply vigorous preventive measures complemented by an ongoing surveillance program meeting international standards. These processes need to be well coordinated, nationally uniform, transparent and auditable in order to maintain our trade access.
Pathways for the introduction of the disease to Australia
Importation of certain animals from TSE-affected countries
Importation of cattle into Australia from the UK ceased in 1988 and from continental Europe in 1991. The cattle and buffalo that are still alive from the limited number of previous imports have been placed under lifetime quarantine. They have been permanently identified utilising the National Livestock Identification System (NLIS) so that they will never enter the human food or animal feed chains and will be disposed of safely at the ends of their lives. There is a very slight risk that these animals were exposed to the BSE agent. Given knowledge of the incubation period of BSE, there remains a low and diminishing risk that they may be infected. The importation of sheep and goats were banned from all countries except New Zealand back in 1952 in response to the detection of scrapie in imported sheep.
Importation of contaminated feedstuff originating from BSE/scrapie-affected countries
The importation of animal-derived Meat and Bone-Meal (MBM) (except for fishmeal) from all countries except New Zealand was banned in Australia in 1966 as a measure against the importation of anthrax spores. Risk based import controls minimise the chance that other imported stockfeeds or stockfeed ingredients have been cross-contamination with MBM.
Importation of biologicals contaminated with the BSE agent
Quarantine risk assessments have been made of vaccines and other biological materials that involve cattle and sheep products in their manufacture and that are intended for use in animals. Restrictions on the importation of these products have been extended in line with emerging knowledge of the BSE status of countries throughout the world. Current Australian Government Department of Agriculture, Water and the Environment policies are detailed on the Department of Agriculture website. For further information on Australia’s ruminant feed ban click here.
Stringent controls are in place against the introduction of TSEs through these three pathways. Furthermore, in the unlikely event that the BSE agent is introduced through one of these pathways, the legislated bans in Australia on the feeding to ruminant animals of MBM derived from mammals, birds or fish will prevent any TSE being propagated and amplified.