Kuru

Kuru is an incurable degenerative neurological disorder (brain disease) that is a type of transmissible spongiform encephalopathy found in humans. It 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 progression to death over approximately 18 months for the most susceptible victims. It 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. 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. Trembling is present in almost all patients with transmissible spongiform encephalopathy.

History
Kuru is a rare and fatal brain disorder that occurred at epidemic levels during the 1950s-60s among the Fore people in the highlands of New Guinea. The disease was the result of the practice of ritualistic cannibalism among the Fore, in which relatives prepared and consumed the tissues (including brain) of deceased family members. Brain tissue from individuals with kuru was highly infectious, and the disease was transmitted either through eating or by contact with open sores or wounds. Government discouragement of the practice of cannibalism led to a continuing decline in the disease, which has now mostly disappeared.

Kuru belongs to a class of infectious diseases called transmissible spongiform encephalopathies (TSEs), also known as prion diseases. The hallmark of a TSE disease is misshapen protein molecules that clump together and accumulate in brain tissue. Scientists believe that misshapen prion proteins have the ability to change their shape and cause other proteins of the same type to also change shape. Other TSEs include Creutzfeldt-Jakob disease and fatal familial insomnia in humans, bovine spongiform encephalopathy in cattle (also known as mad cow disease), scrapie in sheep and goats, and chronic wasting disease in deer and elk.

The disease was researched by Daniel Carleton Gajdusek who was awarded (along with Baruch S. Blumberg) 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.

Transmission
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 main incubation period of the disease is 14 years and cases were reported with latencies of 40 years for those who were most genetically resilient.

Treatment
There were no treatments that could control or cure kuru, other than discouraging the practice of cannibalism. Currently, there are no cures or treatments for any of the other TSE diseases. What is the prognosis?

Similar to other the TSEs, kuru had a long incubation period; it was years or even decades before an infected person showed symptoms. Because kuru mainly affected the cerebellum, which is responsible for coordination, the usual first symptoms were an unsteady gait, tremors, and slurred speech. (Kuru is the Fore word for shiver.) Unlike most of the other TSEs, dementia was either minimal or absent. Mood changes were often present. Eventually, individuals became unable to stand or eat, and they died in a comatose state from 6 to 12 months after the first appearance of symptoms.