Mad cow disease also known as bovine spongiform encephalitis (BSE) or Creutzfeldt–Jakob disease (CJD) is a degenerative brain disorder that can be transmitted. Mad cow disease is the common name and often inappropriate, but is still the more popular term globally. It causes dementia and is potentially fatal. This disease is transmitted by an agent called prion. As the name suggest, this disease usually affects cows. Mad cow disease is transmitted to humans by direct consumption of beef contaminated with the nervous system tissue of animals infected with mad cow disease. This is a variant of CJD called vCJD. This sease can also occur sporadically in humans at a low rate, and is known as classic CJD. The reason for this is still unknown.
Mad cow disease usually results in a rapid mental deterioration due to degeneration of the nervous system. It is called transmissible spongiform disease because of the spongy cheese like appearance of the infected tissue of the nervous system. Death can occur within months of the first symptoms. The symptoms can take a long time to develop, sometimes, up to several decades. The symptoms include a change in personality, anxiety, memory loss, blurred vision, insomnia, and difficulty in thinking, impaired speech, and sudden involuntary jerky movements of the body.
vCJD usually starts with an impaired ability of thinking, reasoning and memory (dementia) which then develops into the full disease. With the progress of the disease the symptoms become more severe. The patient can lapse into a coma. Cause of death is usually heart failure, respiratory failure or other infections such as pneumonia. The life expectancy is very low and death usually occurs within the year of the initial symptoms. In vCJD life expectancy is about 1 to 2 years.
Mad cow disease is caused by prions. Prions are proteins, which under normal conditions do not cause any disease but due to some reason when they get mis-folded they cause the disease. This disease is transmissible and can be spread in several ways.
- Some forms of the disease such as familial CJD can be inherited.
- Variant CJD is transmitted from infected cows, by direct consumption of the nervous system tissue or meat from animals infected with the prionse. Cooking does not destory the disease-causing agent. It is not transmitted through milk or milk products.
- Sporadic CJD can develop sporadically for no known reason. The chance of this occurrence is one in a million people, equally likely in vegetarians and non-vegetarians. It occurs in people over 60 years of age. Sporadic CJD can also be transmitted through contaminated surgical instruments or transplant tissue.
- Another form of the disease, kuru, is found among the tribes of New Guinea where cannibalism is a part of the ritual. This transmitted the disease from the infected individual to healthy people.
However, the exact reasons why some people are more prone to developing this disease than others consuming the same meat is till unclear.
There is no known treatment for mad cow disease. Steroids, antibiotics, antivirals are not effective in treating this disease. The treatment comprises of managing the symptoms and alleviating pain. Prevention of this disease is hence very important. Precaution should be taken during surgery, blood transfusion and during processing meat.