In the eastern highland of Papua New Guinea, live a tribe known as the Fore people. The term Fore is an ethno-lingustic term as it also stand for language spoken. First encountered by gold prospectors in the early 1930s and one of the earliest people to describe the encounter was a European gold prospector named Ted Ubank. What made the Fore people all the rage to anthropologists at the time was the ritual in how they honoured the dead in their community – By cooking and eating them.
However, this observation was only the beginning of a more peculiar yet important discovery. Between 1952 to 1953, two anthropologists named Ronald Berndt and Catherine Berndt noticed that some of the Fore people were manifesting a symptom known by them as Kuru. Kuru literally means ‘to shake’ and they noticed that some of the Fore people were very shaky especially as they walk, making their gait unstable and wobbly. Among these people, some even have symptoms of dementia such and bizarre behavioural changes such as sudden burst of laughter and delirium. Another important observation made was that a significant proportion of the affected people were women and children. The last important observation made was that these people would shortly die after manifesting these symptoms, in less than a few months.
Kuru as a form of sorcery by Tukabu
Within the Fore community, they believe that Kuru is a form of sorcery and witchcraft brought upon by the witch known as Tukabu in their language and those who suffered from Kuru were thought to have done something wrong in the past either to the community or to the Tukabu. Moreover, sufferers need not be guilty of anything as it is also believed that Kuru may just be brought upon by Tukabu out of anger, jelousy or plain evil. Due to this belief in the role of witchcraft, kinsmen of the affected would often kill the Tukabu if they did not manage to reverse their spell. Such notion gained quite a traction that even the patrol officer, John McArthur, in his description of the Fore people concluded that the psychological disturbance in people with Kuru were indeed the result of Tukabu’s sorcery.
Scrapie and Kuru, similarities in different species
Vincent Zigas, a district medical officer at the time, told about the Kuru epidemic to D.C. Gajdusek, a medical researcher and virologist. When Gajdusek arrived in Papua New Guinea in 1959, he received a letter from a veterinarian named William Hadlow who informed him about the striking similarities between Kuru and a neurodegenerative disease in sheep known as Scrapie, after Hadlow had examined the changes in behaviour as well as a Kuru plaque sample.
After reviewing the opinion, observation as well his own research and autopsy, Gajdusek proposed a hypothesis, stating that Kuru is a form of infectious disease acquired from the cannibalistic ritual of the Fore people. Noticing that women and children are disproportionately affected compared to adult men, with a rate of almost 9 times, Gajdusek suspected learned one fine detail about the ritual in which the women and children are given the right to eat the brain of the dead., leading him to refine his hypothesis.
Interspecies experiment that brought about a Nobel prize
To prove that Kuru was infectious in nature, the determine Gajdusek conducted an interspecies experiment by exposing brain sample of those who died from Kuru into the brain sample of other nearly-similar species, a chimpanzee. He would then record his observation and look for changes in behaviour and Kuru symptoms in the Chimp. True enough, his suspicion was confirmed when a Chimp named Daisy that had been previously exposed to the sample, developed Kuru symptoms in less than 2 years after exposure and died shortly after. Daisy’s brain was even found to have the same surface changes consistent with other brains affected by Kuru in which, multiple small holes decorated the surface of the brain, giving a sponge appearance.
This experiment was a huge success in the effort of understanding Kuru because it helped to build the understanding that Kuru was indeed infectious and spreads from exposure to Kuru-contaminated biomaterial. This pioneering work eventually led Gajdusek to receive a Nobel prize in medicine and physiology in the year 1976. However, despite his enthusiasm and relentless effort in identifying the etiology of the infection which was thought to be viral origin, no viral sample was consistently isolated to suggest the role of virus in the disease. Like Kuru, Scrapie and Creutzfeldt-Jakob disease were found to have striking similarities as well, leading to the suspicion that a mysterious infective agent is behind these diseases.
His theory would eventually proved to be correct many years afterward as more and more research on this enigmatic condition took place including in Scrapie and Creutzfeldt-Jakob disease.
Stanley B. Prusiner was one of the earliest to coin the Prion hypothesis, stating the existence of an abnormal misfolded Prion protein that behaves in an infectious manner by influencing other nascent Prion protein to also become misfolded before eventually aggregating on the brain surface, forming holes and causing degenrative brain disease along the way. Autopsies of human brain, sheep with Scrapie and cows with mad cow disease found consistent brain changes known as Spongiform Encephalopathy, describing the sponge-like changes on the surface of the brain.
Such breakthrough was historical as it shaped our understanding of infectivity to be beyond the realm of bacteria and viruses and taught us a separate entity of diseases altogether known as Transmissible Spongiform Encephalopathies (TSE). TSE is a wide group of Prion disease distinguished by the type of species and method of infection that is not limited to human and included a separate classification for the zoonotic version such as the Bovine Spongiform Encephalopathy or Mad Cow disease. By far the most abundant human form of the disease the Creutzfeldt-Jakob disease with Kuru being termed as a variant of Creutzfeldt-Jakob (vCJD). Though many years had passed, this was a legacy left behind by Gajdusek and until this very day, he will be synonymous with the Kuru disease.
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Alpers MP. A history of kuru. P N G Med J. 2007 Jun;50(1–2):10–9.