Mad Cow Disease

Bovine Spongiform Encephalopathy or Mad Cow Disease (BSE), degenerative brain disorder of cattle. Symptoms in cows include loss of coordination and a typical staggering gait. Affected animals also show signs of senility, for example, lack of interest in their surroundings, the abandonment of routine habits, disinterest in feed and water, or unpredictable behavior. Affected cattle show symptoms when they are three to ten years old.

First identified in Britain in November 1986, over 170,000 cases have since been recorded there. Sporadic incidences have been confirmed in other European countries, with Switzerland (over 260 cases) and Ireland (over 260 cases) identifying the largest number. It has also been recognized in Canada, where cases are confined to dairy cows imported from Britain. BSE has not been officially confirmed in the United States or any other major milk-producing country.

Autopsies of affected cattle reveal holes in the brain tissue that give it a spongy, or spongiform, texture. Similar spongiform diseases have been recognized in humans (for example, Creutzfeldt-Jakob disease or CJD) for over a century and in sheep (scrapie) for over 200 years. The cause of BSE is unproven, although there is strong evidence that prions, which may be infective proteins, are the agent. Other hypotheses suggest that prions work with an as yet undetected virus to cause the infection.

Recycled animal tissue, which had been routinely fed to British dairy cows as a protein supplement, was identified as the source of the infection. The European Commission's Scientific Veterinary Committee and the world control body, the Fédération Internationale des Epizooties (FNE) believes that BSE was originally spread from sheep's brains infected with scrapie and that its spread was accidentally accelerated by the ingestion of brain tissue taken from cows that had become infected with BSE.

Following through with this fodder transmission theory, the British government introduced compulsory destruction of suspect animals and their carcasses beginning in 1988. The feeding of animal tissue to cows was banned in Britain in July 1988 and since mid-1992, monitors working for the United Kingdom Ministry of Agriculture have recorded a persistent decline in the number of confirmed cases. It is estimated that the program will eradicate BSE in Britain by the end of 1999.

Since the initial report of the disease, there has been fear and speculation that it might be transferable to humans through milk or beef products. The appearance of CJD in several dairy farmers in Britain in the early 1990s heightened the alarm.