There aren't many known causes of mad cow disease. In fact, this disease has just one known cause, which is called a prion. A prion is a type of protein that is capable of causing infection. Some people compare prions to viruses, but the two are dramatically different; viruses are alive and can be killed using certain types of drugs, disinfectants, and heat generated during cooking. Prions, however, are not living organisms and are very difficult to destroy. Unfortunately, there are no effective treatment options for a person or animal diagnosed with this disease.
When a person talks about the causes of mad cow disease, he may actually mean the methods of transmission, as there is really only one known cause of the disease. The root of mad cow disease is a substance referred to as a prion, which is a unique type of protein. Most people think of healthy substances when they hear about proteins, but prions are the opposite. They are infectious and capable of causing deadly brain diseases.
While there aren't multiple causes of mad cow disease, there is more than one method of transmission. Both methods involve animals. Animals develop the disease when they consume feed that is contaminated with these unique proteins. For example, this may happen when animals are fed feed that contains parts of other animals. The second method of transmission occurs when a person consumes meat that contains prions capable of causing mad cow disease.
Interestingly, only certain animals seem to be vulnerable to mad cow disease. Usually, cows develop the disease, which is scientifically referred to as Bovine Spongiform Encephalopathy (BSE). Humans then contract the disease from these infected cows when they consume the infected beef. Unfortunately, cooking doesn't destroy the infectious proteins, so even properly handled and cooked beef can contain the proteins and spread the disease.
Unfortunately, people cannot destroy prions in the same way as they can other infectious agents. If viruses and bacteria were among the causes of the disease, dealing with it might be easier; disinfectants, drugs, and cooking at high temperatures destroy many disease causers. These methods are not effective against prions, however. Additionally, there is no effective treatment for mad cow disease — it is fatal.
In time, scientists may discover other causes of mad cow disease. Scientists are studying other possible methods of transmission as well and trying to learn whether animals can inherit the infectious proteins. For now, however, prions and transmission through food are the known culprits.