KURU

fatal degenerative disorder of the central nervous system. Kuru has been found only among the Fore people and related ethnolinguistic groups in Papua New Guinea (kuru is a Fore word for trembling, or shivering). The first symptoms of the disease include joint pain and headaches, which typically are followed by loss of coordination, tremor, and dementia. After the onset of symptoms the disease progresses steadily, and death occurs within two years of the onset of symptoms. For many years medical investigators suspected that the disease was hereditary rather than infectious, although its pattern of incidenceit struck adult females and children of both sexes but rarely adult maleswas unusual for a hereditary condition. The American physician D. Carleton Gajdusek established the infectious nature of the disease by injecting samples of brain tissue from subjects who had died from kuru into the brains of chimpanzees; the primates eventually developed and succumbed to the disease. The transmission of kuru is attributed to the Fore's cannibalistic rituals of mourning in which the brain of the dead was handled and eaten, especially by women and children. Since this practice was discontinued, the disease has virtually disappeared. The exact nature of the infectious agent was difficult to discern. Originally a virus was believed to be the culprit, but research has revealed that an unusual infectious agent called a prion is responsible. A prion is a deviant form of a harmless protein normally found in the brain. The prion is thought to convert the conformation of the normal protein molecule to its own modified form. Unlike the normal protein, the aberrant prion protein is much more resistant to enzymatic breakdown. As a result, prions accumulate within nerve cells, damaging them and causing the characteristic neurodegeneration of the disease. Kuru is one of a group of prion diseases sometimes referred to as spongiform encephalopathies because the brains of those with the disease become riddled with holes. Spongiform encephalopathies include diseases of humans, such as Creutzfeldt-Jakob disease, and those that affect animals, such as bovine spongiform encephalopathy, also known as mad cow disease.