Creutzfeldt-Jakob Disease - Causes
The search for the agent that causes the spongiform encephalopathies is one of the great medical stories of the twentieth century. At first, researchers suspected that the disease was caused by some kind of virus. But they had no success in locating a virus that could cause infections of this kind.
A disease that belongs to the spongiform encephalopathies family is kuru. At one time, kuru was very common among the Fore tribe in Papua, New Guinea. The disease was spread in a very unusual way. Members of the Fore tribe were cannibals. As part of their culture, they ate the organs (including the brain) of their dead relatives. They believed this custom was a way of honoring the dead. Thus, the disease spread from infected individuals after their death.
Kuru fascinated medical researchers, who discovered that the incubation period for the disease is incredibly long. The incubation period is the time it takes for symptoms to appear after a person has been infected. In the case of kuru, the incubation period is between four to thirty years or more, which means an individual infected with the disease may not show any symptoms for a very long time. This discovery earned Carleton Gadjusek the Nobel Prize in 1976 and introduced researchers to
One theory proposed as early as 1981 was regarded as a "crackpot" idea by many scientists. This theory was developed by the American biologist Stanley Prusiner. Prusiner suggested that spongiform encephalopathies might be caused
by certain kinds of protein molecules. Proteins are chemicals that perform many essential functions in the body. Prusiner suggested the name prion for the infectious forms of proteins.
Many researchers did not take Prusiner's idea seriously because no form of protein had ever been found to cause any infectious disease. After more than fifteen years of research, however, Prusiner's theory was confirmed. Unusual types of protein were finally discovered in the brains of animals with various kinds of spongiform encephalopathies. Scientists now believe that kuru, BSE, nvCJD, and related diseases are caused by the transmission of prions from an infected person to a healthy person. In the vast majority of cases (sporadic CJD), no one knows how this transmission occurs.
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