Kuru is an incurable degenerative neurological disorder (brain disease) that is a type of transmissible spongiform encephalopathy found in humans.
Kuru is believed to be caused by prions and is related to Creutzfeldt-Jakob disease. It is best known for the epidemic that occurred in Papua New Guinea in the middle of the twentieth century, and earlier.
Although it is considered a transmissible prion disease, there is some evidence that the origin of the outbreak was due to consumption of an individual (cannibalism) with sporadic CJD, thus implying a common pathophysiology.
Kuru causes physiological as well as neurological effects that ultimately lead to death. It was endemic among the Fore tribe of Papua New Guinea and was confined to the Fore population and those nearby populations with whom they intermarried. It is characterized by truncal ataxia, preceded by headaches, joint pains and shaking of the limbs, with the clinical stage lasting an average of 12 months.
Trembling is present in almost all patients with transmissible spongiform encephalopathy.
The word kuru is taken from the Fore word "kuria/guria", 'to shake'. It is also known as the laughing sickness due to the pathologic bursts of laughter people would display when afflicted with the disease.
Kuru was first noted in the Fore tribe of the Eastern Highlands Province of Papua New Guinea as Australian administrators explored the area in 1957–1959. It was in the late 1950s that the full extent of the disease was realized, after it had reached large infection rates in the South Fore of the Okapa Subdistrict, though the agent was unknown.
The disease was researched by Daniel Carleton Gajdusek who, along with Baruch S. Blumberg, was awarded the Nobel Prize in Physiology or Medicine in 1976 for his showing that kuru was transmissible to chimpanzees. This was the first time that this group of encephalopathies had been demonstrated to be infectious and therefore a major step forwards in their investigation. As kuru is the only epidemic of human prion disease in known human history, it has provided important insights into the variant CJD.
It is believed by some that the disease spread easily and rapidly in the Fore people due to their endocannibalistic funeral practices, in which relatives consumed the deceased to return the "life force" of the deceased to his hamlet, a Fore societal subunit. The dysmorphism evident in the infection rates—kuru was 8-9 times more prevalent in women and children than in men at its peak—is because while the men of the village took the choice cuts, the women and children would eat the rest of the body including the brain, where the prion particles were particularly concentrated. There is also the strong possibility that it was passed on to women and children more easily because they took on the task of cleaning relatives after death and may have had open sores and cuts on their hands. Although ingestion itself of the prion particles would not lead to the disease, there was a high degree of transmission if the prion particles could reach the subcutaneous tissue. With elimination of cannibalism because of Australian law enforcement and local Christian missionaries' efforts, Kuru rapidly declined among the Fore. However, the mean incubation period of the disease is 14 years and cases were reported with latencies of 40 years for those who were most genetically resilient.