Last updated on 24 February 2012
About BSE and other TSEs
Bovine spongiform encephalopathy, or BSE, is one of a group of diseases known as Transmissible Spongiform Encephalopathies (TSEs), or prion diseases. They result from the build-up of abnormal prion proteins in the brain and nervous system. TSEs get their name from the spongy appearance of the infected brain, and the fact that they are transmissible via infected material.
BSE affects the central nervous system of adult cattle, particularly the brain, and eventually causes death. It is often referred to as 'Mad-Cow Disease' because it causes disorientation, clumsiness and, occasionally, aggressive behaviour towards other animals and humans. It has a long incubation period, which means that it usually takes four to six years for cattle infected with BSE to show signs of the disease.
BSE was first confirmed in cattle in 1986; however, no one can say with certainty how and why BSE first occurred, although several theories exist.
Cattle are grazing animals that do not naturally eat meat. Most experts agree that BSE was most likely spread by cattle eating feed that contained meat-and-bone meal, made from BSE-infected tissues. Meat and bone meal was produced in a process called rendering; this turned otherwise unused animal products into animal feed.
Research has shown that cattle can contract BSE if they are fed infected brain tissue. This supports the theory that BSE was transmitted to cattle through their feed. This is backed up by the fact that the number of cases of BSE has reduced significantly since the introduction of a ban on feeding meat and bone meal to cattle, and all other farm livestock. The ban remains in place.
BSE develops in cattle, but it belongs to a family of prion diseases, several of which can affect humans. The most commonly known disease in this group among humans is Creutzfeldt-Jakob Disease (CJD). This is a rare and fatal form of dementia that mainly occurs in individuals between the ages of 40 and 80.
CJD is not a new disease among humans, but in 1996, scientists discovered a new strain of CJD that occurs predominantly in younger people. This is known as variant CJD or vCJD.
The protein that accumulates in the brains of individuals with vCJD is similar to the protein found in cattle infected with BSE, rather than that found in classical CJD.
The occurrence of a new form of CJD in the UK, where there was a high incidence of BSE, suggested that there might be a direct link between BSE and vCJD. Some individuals who developed vCJD were known to have eaten potentially BSE-infected meat products. Researchers have concluded that the most likely origin of this new disease was human exposure to the BSE agent through the consumption of infected meat products before the introduction of BSE controls.
Like BSE in cattle, vCJD is always fatal in people. As of January 2012, 176 cases of vCJD had been diagnosed in the UK. The majority (more than 80%) occurred before 2005.
Since 1989, cases of BSE have been reported in many European and Scandanavian countries and also in Canada, Japan and the United States.
The number of BSE cases in the UK has been in decline for many years. In 2011 only six cases were diagnosed, compared with 37,000 in 1992.
The decline in BSE cases combined with the food safety controls mean that the risk to human health from BSE is now extremely low.
Classical scrapie is a commonly occurring disease in sheep and goats and has been seen in UK flocks for more than 250 years. Classical scrapie is a type of TSE and the signs of the disease are similar to BSE; however, unlike BSE, there does not appear to be any link between scrapie and human illness.
In 2002, the introduction of improved testing methods led to the identification of another TSE disease in sheep and goats, known as atypical scrapie, which comes from the same family of diseases as classical scrapie and BSE.
There is no evidence that atypical scrapie is transmissible to people. Also because of precautionary controls in place for BSE, the parts of the sheep most likely to be infected with atypical scrapie are not allowed into the food chain. For these reasons, the Agency does not advise that people need to change their eating habits with regard to sheep or goat meat. The Agency and Defra is continuing to fund research in the UK to improve our understanding of atypical scrapie.
For further information on BSE and to find out about the latest research, please call the Food Standards Agency on 020 7276 8829, or email: email@example.com.