Bovine spongiform encephalopathy is a brain disease that affects cattle. It is also known as mad cow disease. The full nature of this disease is not fully understood, but scientists believe it is caused by a protein called a prion rather than some type of bacterial infection or virus. This protein gradually causes tissue in the brain to become spongy, eventually leading to death. Bovine spongiform encephalopathy can be transmitted to humans who eat meat from infected cattle, and it is always fatal in both animals and humans.
When cattle are infected with this disease, the first thing that changes is their behavior. They may become aggressive or nervous. After a while, they begin to develop motor difficulties and may have trouble walking or standing. Eventually, they begin to lose weight and waste away.
When people have the disease, their motor skills deteriorate and they may begin to gradually lose their memory. When the disease starts, they often have emotional or psychiatric problems and changes in their behavior. Sometimes they can get depressed or they can get angry with their family members.
It can take years after exposure for symptoms to appear in both humans and animals. Scientists believe that the disease is spread by eating the brain tissue of an infected animal. Sometimes small amounts of brain tissue can show up in ground beef, and that's how people get the disease. It is very difficult for bovine spongiform encephalopathy to be transmitted to humans, even if they eat contaminated tissue.
Cows also get bovine spongiform encephalopathy from eating diseased brain tissue, and this happened because a lot of animal feed was made using cattle scraps. Laws have been passed to restrict the use of this type of food, and these measures have been quite successful in reducing cases of bovine spongiform encephalopathy worldwide.
Most of the cases have been reported in Britain, and at one point there was a huge epidemic with thousands of new infected cattle being reported every week. The first cows to get this disease were infected in the 1970s, but they did not get sick until the mid-1980s. The British bovine spongiform encephalopathy epidemic peaked during 1992 and 1993.
Most of the human cases have also been British citizens. Scientists say that people can limit their chances of developing the disease by focusing on steaks and roasts instead of ground meat, because those meats are much less likely to become contaminated. There is no way to test for the disease until someone dies, but scientists can usually zero in on it as a likely diagnosis based on symptoms.