Diseases of Cattle: BSE or Mad Cow Disease

Bovine Spongioform Encephalopathy (also known as BSE or "mad cow disease") is a progressive degenerative disease that affects to central nervous system of cattle. It belongs to a group of similar but distinct neurological diseases including Creutzfeldt-Jacob disease (CJD) in humans. The cause of BSE is unknown and there is no known treatment for this fatal disease.

Typically, it takes from two to eight years from the time of infection for the clinical signs of BSE to appear.  BSE-affected animals may display symptoms such as nervousness or aggressive behavior, abnormal posture, lack of coordination and difficulty in rising.  When first noticed, clinical signs may resemble those of rabies. Rabies progresses rapidly over a few days while the symptoms of BSE progress over a period of two to six months.  Following the onset of clinical signs, the animal's condition deteriorates until it either dies or is destroyed. 

Great Britain's outbreak is believed to have been caused by the inadvertent feeding to cattle of meat and bone meal supplements that were contaminated with an infectious agent. This occurred in the late 1970s and early 1980s. Once cattle became infected, the BSE agent was recycled in the cattle food chain through the feeding of rendered material from slaughtered animals to other cattle. This increased the magnitude of the epidemic.  Great Britain banned the feeding of ruminant derived protein (from sheep and cattle) to ruminants in 1988. the use of potentially contaminated bovine tissue was prohibited in the manufacture of all animal feed. this ban has had an effect, as the number of BSE cases has declined since the winter of 1992-93.

Diagnosis of BSE is based on clinical signs of the live animal followed by the appearance of characteristic lesions in a post-mortem microscopic examination of the brain. There are no tests for the disease in live animals.