A Short Overview of Kuru, its Discovery and Pathology

Source: http://www.darksideofhistory.com/dis...ery-pathology/



Uncontacted Tribes, Unknown Diseases

In the 1950s, explorers were charting the highlands of eastern Papua New Guinea, then officially an Australian territory, encountering many uncontacted tribes. One of these, the Fore people, presented an endemic neurodegenerative disorder, the likes of which had not been seen before, with women and children being the ones predominantly affected. The Australian administration called it a “psychosomatic manifestation” to certain life events, as they thought this was a physical response to stress. The Fore’s explanation for the outbreak was initially possession by the souls of the dead, and later witchcraft.



The condition was called negi-negi, which indicated silliness, since the Fore thought it was a passing ailment of the mind. As the death toll rose and the invariable fatality became evident, they named the sickness kuru, meaning “fear” or “shaking” in their language. Eventually, the Fore blamed the fatal condition on sorcery, a development which led to numerous witch hunts. Anyone who held a grudge against the deceased was suspected, prompting blood feuds which escalated into village wars.

Medical Research & Breakthrough

Medical staff under the jurisdiction of the Australian administration began to observe the disease and keep records of it. Numerous theories were proposed regarding its cause and its nature, ranging from infection to genetic disorders, or even blaming funerary cannibalism, which was widespread among the Fore at the time. None of these theories were accepted, however, due to lack of solid evidence. In addition, any initial attempt at inoculating animals, from snakes to bears, with biological material from infected kuru victims, failed to produce symptoms.

Since the nature of the agent causing the disease was completely unknown at the time, researchers did not get results through conventional methods. The final answer would, in time, open a new chapter in the field of infectious disease. The big breakthrough came when the medical staff studying the disease noticed similarities between kuru and scrapie, a similar disease in sheep. The resemblance in manifestation was uncanny, such as with trouble standing or walking and trembling; microscopic examinations revealed that kuru victims and sheep suffering from scrapie both presented the same brain disorder called spongiform encephalopathy, commonly known as mad cow disease.

Researchers Daniel Carleton Gajdusek and Michael Alpers decided to conduct an experiment in which they would harvest brain tissue from recently deceased kuru victims and inject it directly into the brains of chimpanzees, the closest subject they could get to a human one. They managed to prove it was transmissible when the test subjects developed symptoms between 18 and 30 months from inoculation.


Australian scientist Michael Alpers with two of his Fore friends

Funerary Cannibalism and the Spread of Kuru

This finding, coupled with anthropological studies of the Fore, finally found the cause of the kuru endemic: they had become infected by consuming the disease-bearing brain of their dead. Cannibalism was a common funerary practice among the Fore, as well as among a number of other native cultures. The body of the deceased, after being mourned for 2-3 days, was ritually cut up on a bed of edible greens wasting nothing.

The head was placed over a fire, burning off the hair, the skin was peeled off and ultimately, the skull was de-fleshed with bamboo knives. The brain was removed via a hole at the top of the cranium, cooked in bamboo tubesalong with the flesh from other parts of the body and eaten over the course of the following days. Males over the age of 6 never consumed the brain, however, which explains the lower incidence of kuru among the men; nevertheless, they could potentially still get infected from other tissue, although at a lower rate.


Fore people

Michael Alpers, whose research and fieldwork proved invaluable to the discovery and classification of kuru, proposed a theory about the origins of the disease. He hypothesized that a single person – “patient zero” in epidemiological terms – presented a spontaneous genetic mutation and developed the disease, which then became an epidemic. Furthermore, he followed every single recorded case of kuru, identifying patient zero as a man who died in the 1910s. Despite Alpers’ achievements, it was Gajdusek who received the Nobel Prize in Physiology or Medicine in 1976, while Alpers was completely omitted. This event sparked many controversies.

Prions – the Cause of Kuru

The pathogen causing kuru was discovered later. In 1997, the Nobel Prize in Physiology or Medicine was awarded to Stanley Prusiner for identifying misfolded proteins – prions – as the cause. Proteins are the building blocks of life as they are an essential part of any living organism and are the structural components of body tissue. Every biological function contains proteins at its core. Proteins are created inside cells as long chains of amino-acids that fold into specific, three-dimensional shapes which are required for them to function properly. Therefore, since prions are misfolded proteins, an accumulation of these can lead to neurodegenerative diseases such as kuru.

Prions can appear either spontaneously, inherited genetically (e.g. fatal familial insomnia), or they can be infectious (kuru and Creutzfeldt-Jakob disease in humans, mad cow disease, scrapie, etc.). Normally, erroneous proteins have no biological function and are eventually broken down by natural processes in the body. Prions, however, are resistant to breakdown; even heat, such as cooking, will not eliminate them. How they cause disease is simply by building up into so-called amyloids, an abnormal deposition of proteins in the body.


Spongiform aspect of prion infected brain tissue

These mutated proteins have the property of binding to one another in tight layers and, more importantly, of modifying the shape of the original “normal” protein that the prion originated from into the infectious prion form. As it replicates itself, the result is a buildup that eventually kills neurons, making a myriad of tiny holes in the brain. This was an important discovery, putting prions next to viruses and bacteria as agents of pathogenesis in animals.

Symptoms of Kuru

Kuru manifests as a progressive, irreversible and invariably fatal neurodegenerative disease. The afflicted may present an initial phase of headaches and joint pain, followed by clear signs of the disease, like trouble coordinating motion, trouble standing upright and walking, slurred speech. Patients also present involuntary spasms or a slow, continuous dance-like motion of the limbs, called choreoathetosis. Severe tremor was always present, aggravated by voluntary movement. All this results in a very distressing situation for everyone involved as a strong, autonomous individual is slowly becoming and invalid. Eventually even eating becomes an impossibility.


Children suffering from kuru

Depression or euphoria set in, with loss of control over emotions, hence why it was sometimes called the laughing death. The disease runs its course between 3 months and 2 years, with mean survival at 12 months from the onset. Unlike similar prion diseases, kuru causes only mild dementia, meaning that patients remain conscious until the final stages, becoming trapped into their nonfunctioning bodies, knowing the inevitable outcome. The proximal cause of death is usually emaciation or infection.

Prion Diseases Today

Research into the field of prion diseases is ongoing. For example, the mad cow disease outbreak from 1987 left an unknown number of people infected. Having the extremely long incubation periods in mind that can theoretically exceed the human lifetime, cases of the human form, called Variant Creutzfeldt-Jakob Disease, will continue to appear. The story of prion diseases is far from over.

In Papua New Guinea, the Fore people are still under epidemiological observation today, with cases of kuru appearing over 60 years after the abandonment of cannibalism.


Cows suffering from BSE lose the ability to stand