Bovine spongiform encephalopathy (BSE) or “mad cow disease” is a progressive brain disease of cattle. It is primarily associated with inclusion in cattle feed of ruminant-derived protein contaminated with the infectious agent of BSE, but sporadic "atypical" cases can arise very rarely that are not associated with a history of tainted feed.
It is generally accepted that the infectious agent is a prion, a "self-replicating" protein, rather than a conventional bacterium or virus. The disease has a long incubation period (5 years on average) and is always fatal. BSE causes the brain to become sponge-like. Brain, central nervous system tissue, and parts of of the small intestine can carry the infective agent, so measures have been taken to exclude these tissues from the animal feed supply and from human food.
BSE is often referred to as "mad cow" disease because animals infected with the disease are often irritable and incoordinated and can react unpredictably to stimuli.
The most extensive outbreak of BSE has been in the United Kingdom where more than 180,000 cases have been recorded, starting in 1986.
There is evidence that consumption of brain and spinal cord tissue from cows with BSE can lead to variant Creutzfeldt-Jakob disease (vCJD) in people. The symptoms of vCJD are similar to those of BSE and include progressive disorientation, personality changes, and progressive paralysis. There is no cure for vCJD and it is fatal. Cassic or non-variant Creutzfeldt-Jakob disease in humans is also a fatal degenerative spongiform brain disease. It is sporadic and rare, affecting just 1 in 1 million people; it is not associated with the consumption of tissues from BSE cattle.
Since the discovery of a BSE-infected cow in Washington State in 2003, the federal government has adopted measures to ensure that meat coming from a cow suspected of having BSE will not be allowed to enter the food supply. Visit the EDEN BSE Issues Pageto learn more about BSE and the measures in place to safeguard our food supply.
The BSE cow identifed in Washington State was imported from Canada. In 2005, a native Texan cow was diagnosed with BSE. Another case was identified in 2006 in a native Alabama cow, but this was diagnosed as an atypical case. Another atypical BSE cow was identified in California in 2012.
The FDA has taken steps to prevent to introduction of BSE into U.S. beef herds by adopting a ruminant-to-ruminant feed ban in 1997 preventing use of mammilian protein in feed for ruminants. In addition, the USDA restricts the entry of cattle and cattle products from countries with BSE to protect the national herd and human health.