In the mid-1990s, the news was full of reports of so-called "Mad Cow Disease", the term coined in Britain for a condition actually called bovine spongiform encephalopathy (BSE). The condition was given its unofficial title by the erratic and uncoordinated behavior of affected cattle--damage done to the nervous system by the disease tends to cause cattle to have great difficulty in walking and eating, and thus tends to lead to premature death (or before identification began to take place, to their early slaughter). The condition itself is actually, as its names might suggest, particular to cows--humans and other animals can in no way contract bovine spongiform encephalopathy. It is believed that the condition arises from the presence of variant versions of protein structures called prions, which are more basic than viruses and bacteria as disease causing agents. Prions actually exist in their normal state in the brains of most cattle and humans, but in a deformed, variant state may be spread along from animal to animal to catalyze the production of more variant prions. The spread occurs namely through the consumption of brain or spinal tissue from infected animals, and conditions similar to the human result of BSE have been identified in cultures that participate in ritualistic cannibalism (particularly the consumption of brain tissue, as in Kuru).
It is by this method that BSE was thought to have first been spread to cows. The practice of using unused animal tissue in cattle feed was once standard practice, as it served as a cheap source of readily-available protein. It has more recently been banned in many countries, as this has been identified as a potential risk factor to the spread of BSE from cattle to cattle.
The human version of the condition is called Creutzfeldt-Jakob disease (CJD), and has been familiar to science for several decades. The sypmtoms are mostly neurological, including eventual dementia and complete failure of phyiscal coordination. The mortality rate, as presently recorded, is one-hundred percent; death occurs, as a rule, within six months of symptom onset. The concern with the BSE outbreak of the mid-1990s was that meat from these cattle would be delivered to humans in Britain and countries to which the meat was exported. While brains aren't really much of a component of your average Big Mac, the prions from infected cows may be found in meat outside that exposed to the central nervous system, and tissue from near the spinal column often does find its way into chuck and other products.
The most blatant concern over the outbreak was the fear that the minor epidemic would spread from British cows to those in Canada, the United States and Japan, some of the world's largest beef importers. This was, as it turned out, an unnecessary worry. Only 153 cases of the variety of CJD linked to BSE or mad cow disease have been reported worldwide, as of 2003, and all of these cases were contained within Britain (save for 10 which were actually experienced outside the nation, but which resulted from meat consumed within). The disease is as such extremely rare, far more rare than its notoriety during the media craze could possibly have warranted. Eating meat in Britain, Australia, Japan, America is as safe as ever, at least as far as prions are concerned.
