Kuru is called the shaking disease, its name derived from the Fore word for "to shake." Caused by an organism that infects the part of the brain that controls coordination, people afflicted with kuru shake uncontrollably.
First, there is headache and joint pain, then shaking, followed by trouble walking and the inability to walk, stand, or eat. Then dementia sets in. Some lucky victims don't exhibit symptoms for many years after they are infected, others are affected immediately—but all of them die, usually of pneumonia or malnutrition within a year of showing symptoms.
The disease has been confined to a remote region in Papua New Guinea inhabited by the Fore tribe, where 80% of the cases of kuru occurred. It was discovered there in 1957, but because of the isolation of the tribe, it isn't known when the disease first appeared there. Fore oral tribal history puts the first cases of kuru somewhere in the 1920s.
Kuru is a prion disease. In prion diseases, there is an accumulation of an abnormal glycoprotein known as prion protein (PrP). The abnormal PrP gradually destroys the cerebellum, then the rest of the brain and the brain stem. And it's transmissible by ingestion of infected tissue.
Yes, the Fore tribe got kuru by eating the flesh of their tribe mates who died from the disease. Transumption, the ritual of consuming dead family members at mortuary feasts, exists and has been practiced for untold decades in remote areas of the world like Papua New Guinea.
Transumption sounds a lot like cannibalism, doesn't it? To make the distinction, people who practice transumption technically are endocannibals. They don't eat just any old dead body—they eat their dead relatives or tribal members.
A group of University College London researchers, led by J.T. Whitfield from the MRC Prion Unit and Department of Neurodegenerative Diseases at the National Hospital of Neurology and Neurosurgery, set out to learn just what influenced the people of Papua New Guinea to eat their dead and how these practices spread kuru only to a defined region.
The research findings were published on January 11, 2017, in the journal Royal Society Open Science, and finally shed some light on this macabre ritual.
In the 1930s, a million people lived in the highlands of New Guinea, their existence unknown to the rest of the world. The Australian government controlled the island, but since the mountainous interior of the island was considered to be uninhabitable, the Fore tribe was left undisturbed until the 1950s when a medical officer of the Kainantu Sub-District, Eastern Highlands of the Australian Trust Territory of New Guinea, was alerted to a high incidence of paralysis, mostly in females of the Fore linguistic and cultural group.
This was the beginning of the awareness of kuru and the death of over 2,700 people.
To study the spread of kuru by endocannibalism, Whitfield and some of his team traveled to the region of Papua New Guinea inhabited by the Fore tribe, also called the Fore linguistic group—because in this central part of New Guinea, language similarity determined cultural groups. The kuru epidemic had been confined to the Fore linguistic region and to contiguous linguistic regions where tribes intermarried.
Since only an oral history of this primitive culture existed, and because of the extreme isolation of the Fore tribe, researchers had to work to establish relationships where the Fore men felt comfortable enough to share their intimate stories of human endocannibalism.
Why men and not the women? There were very few elderly women in the villages. This was because all the women in the North and South Fore regions took part in transumption. They ate the brains, spinal cord, and internal organs of dead family and community members—many of whom had died of kuru.
And their children joined them. Up to about age eight, it was a normal occurrence to have both male and female children join their mothers and other women in the ritual brain-eating of their dead loved ones.
When tissue containing malformed prion proteins is eaten, it passes from the gut into the brain through the lining of the intestines, through specialized cells called M cells. When the infectious prion reaches the brain, it folds normal PrP proteins into the infectious shape and makes them cluster up, eventually causing paralysis and dementia.
Anthropologists who have studied transumption have theorized that the ritual was practiced because the participants thought it would bring fertility, because it satisfied protein deficiencies, and even because the body parts were tasty. Certainly, the old woman in the video above seems to enjoy the taste of human flesh.
Fore members engaged in transumption out of a cultural tradition to honor the dead. They believed that by ingesting brains and other body parts, they were providing the dead with a sacred "burial." Through cultural traditions, women were the main participants in the practice. Because tribes had different languages and cultural traditions, the practice of endocannibalism was narrowly confined to the Fore linguistic area and to linguistic areas immediately contiguous to the Fore.
The extension of kuru out of the Fore linguistic area followed the movement of Fore women who wed and moved into neighboring communities. Those women brought their cultural practices of mortuary endocannibalism with them—and therefore brought kuru. Movement only ventured into areas where language was similar and that kept the kuru confined to a defined region of the Fore and its immediate neighbors.
According to a 2008 paper in the Philosophical Transactions of the Royal Society of London by Whitfield and his co-authors:
The dying person would normally express their wishes as to how their body was to be disposed of; otherwise the family would decide. In the kuru-affected region, all methods of disposal of the body involved being eaten. If the body was buried it was eaten by worms; if it was placed on a platform it was eaten by maggots; the Fore believed it was much better that the body was eaten by people who loved the deceased than by worms and insects. By eating the dead, they were able to show their love and to express their grief.
Genetics also turned out to play a role in who was infected—and ultimately who lived or died. Previous research had shown that polymorphisms (changes) in the prion protein gene where methionine (M) or valine (V) is inserted at position 129 of the protein can change resistance to prion infections. People with 129MV—heterozygotes—are less susceptible to prion infection, and if they do get infected the incubation period between infection and symptoms is longer.
Genetic testing of the inhabitants of the Fore by the researchers found that children who had kuru were mostly of the 129MM genotype and older people, especially women had the 129MV genotype. This made sense because if the MM or VV types were not resistant to prion infections, they likely would have gotten kuru and died, leaving mostly people with the 129MV genotype who might not get the infection.
Tribal language and cultural boundaries helped kuru spread and a few lucky factors helped it die out. Cultural factors in the villages surrounding the Fore tribal areas did not allow children to take part in the brain- and gut-eating ritual, keeping the infection isolated to (mostly) women who moved to the region and women who participated in endocannibalism.
And as communities came under Australian control in the 1950s, the government officials and missionaries rebuked the local people for practicing transumption and the villagers gave in to the new social pressure to bury their dead. The North Fore tribe began to think of kuru as a contagious disease and stopped the practice of transumption. No deaths have been reported there from kuru since 1985. It took the South Fore tribe more than a decade to stop transumption, and the last kuru death there occurred 24 years after the last recorded death in the North Fore.
Because males were only exposed in the first seven or so years of their lives, scientists now know the incubation period in males can be 50 years or more. That long incubation period explains the last three cases of kuru reported in 2003, 2005, and 2009. They were in males infected decades earlier.
Believing there have been no new infections, the MRC Prion Unit in the UK and the Papua New Guinea Institute of Medical Research, stopped surveillance for the disease in September 2012.
That begs the question, how will we know if there is another outbreak in some remote part of the world still cut off from modern communication? I guess we won't know until we stumble upon it.