Consuming certain tissues can transmit diseases, leading to unforeseen health consequences. This rare transmission mode highlights how cultural practices have historically influenced disease patterns.
Kuru: The Disease of Endocannibalism
Kuru is a fatal neurodegenerative disorder associated with the Fore people of Papua New Guinea. It emerged from the historical practice of endocannibalism, where deceased relatives were consumed as a funerary rite. The term “kuru” translates to “trembling” or “shivering,” reflecting a prominent symptom. Kuru is a transmissible spongiform encephalopathy (TSE), a rare brain disorder causing characteristic sponge-like changes in brain tissue.
The disease was largely confined to the Fore linguistic group and their neighbors in Papua New Guinea’s Eastern Highlands. Women and children were disproportionately affected. They were the primary participants in preparing and consuming brain tissue, where infectious agents were most concentrated. This practice, intended as a sign of respect, inadvertently spread the disease within the community.
Prions: The Unusual Pathogens
Kuru is caused by prions. Prions are misfolded proteins that induce normal versions of the same protein to misfold. Unlike conventional pathogens (bacteria, viruses, fungi), prions lack nucleic acids like DNA or RNA. Their protein-only composition makes them unique infectious agents.
Misfolded prions accumulate in the brain, leading to tissue damage and nerve cell death. Prions are remarkably resistant to typical sterilization methods, including freezing and high heat, complicating their destruction. This resistance contributes to their persistence and disease-causing ability.
How Kuru Develops and Manifests
Kuru was transmitted through consuming infected brain tissue during funerary rituals. The disease has an exceptionally long incubation period, with symptoms appearing years or even decades after exposure. While the average incubation period was 10 to 13 years, some cases showed latency periods exceeding 50 years. This extended period made it challenging to immediately link the practice to the illness.
Kuru progresses through three distinct stages. The ambulant stage involves a loss of coordination, unsteadiness, and tremors, often affecting balance and gait.
In the sedentary stage, individuals lose the ability to walk, experiencing severe tremors, involuntary muscle jerks, and emotional lability, including inappropriate laughter, earning it the nickname “laughing sickness.” The terminal stage brings bedridden patients, difficulty swallowing (dysphagia), and unresponsiveness, though consciousness often remains. Death usually occurs within 6 to 24 months after symptom onset, often from complications like pneumonia or infections, as there is no effective treatment or cure.
The Decline of Kuru and Its Lessons
D. Carleton Gajdusek began studying Kuru among the Fore people in the 1950s. His work, including transmitting the disease to chimpanzees, provided crucial evidence for its infectious nature and long incubation period. This research established Kuru as the first human transmissible spongiform encephalopathy.
Australian government intervention and local community understanding led to the cessation of endocannibalistic practices by the early 1960s. This ban resulted in a significant decline in new Kuru cases. While new infections ceased, individuals exposed before the ban continued to develop the disease for decades due to its prolonged incubation period. The last known death from Kuru was reported in 2005 or 2009, making cases exceptionally rare.
Kuru’s study provided profound scientific lessons, revolutionizing neurodegenerative disease understanding and leading to prion discovery. It demonstrated a novel disease transmission mechanism involving misfolded proteins, fundamentally changing how scientists viewed infectious agents. This knowledge applies to other prion diseases, such as Creutzfeldt-Jakob disease and bovine spongiform encephalopathy, and informs research into various neurodegenerative conditions.