Kuru - A Reason Not to Eat Each Other's Brains

Kuru is a neurodegenerative disease that was observed to occur among indigenous peoples in Papua New Guinea in the South Pacific.  Many of these tribes practiced forms of ritualistic cannibalism and researchers in the early to mid 20th century noticed a peculiar set of neurological problems developing among these people  These included movement disorders, unusual behaviors (such as inappropriate laughing fits), difficult walking, and rapidly progressive and ultimately deadly dementia.  


A virologist, named Daniel Carleton Gajdusek, and an accompanying medical doctor, Vincent Zigas, started looking into the disease in 1957.  They initially thought it was a genetic disorder.

In 1967, researchers formed the hypothesis that the disease may have been linked to ritualistic cannibalism.  The practice was banned by the Australian government overseeing Papua New Guinea at the time and the incidence of kuru was decreasing, further lending credibility to the link between eating human tissue and spread of this disorder.  

Improving upon his earlier work, Gajdusek found that exposing a chimpanzee to the brain tissue from a deceased tribes-person who died from kuru, led to the development of the disease in that same chimpanzee, years later.  Though the transmitting agent was not understood, Gajdusek won a Nobel Prize in Physiology or Medicine in 1976 for demonstrating that kuru could be transmitted–thus showing it was not a genetic condition.

In the 1960’s and 1970’s, researchers made the association with the appearance of brain tissue affected by kuru to those found in other unusual diseases such as scrapie–a neurodegenerative condition seen in sheep and goats.  This led to the suspicion that the diseases were linked or at least spread in a similar way.  Research seemingly excluded other infectious agents–such as bacteria or viruses–as being the cause of these types of diseases.

In 1982, neurologist and biochemist Stanley B. Prusiner purified what appeared to be an infectious protein molecule at the University of California, San Francisco.  This was a landmark discovery that added the term “prion” to the medical lexicon.  The word comes from a combination of “protein” and “infection.”  He later won a Nobel Prize in 1997 for this work.

Prions are fascinating and terrifying.  They are single proteins that are folded or configured in such a way that they cause normal similar proteins to change shape to mimic the prion’s structure.  This causes those normal proteins not only to malfunction, but to cause neighboring proteins to change in similar fashion.  This seems to particularly affect neurologic tissues and many now identified prion diseases–such as kuru–share characteristics of causing rapid neurologic damage over time.  Unlike bacteria or viruses, prions do not hold or need genetic material to replicate themselves.  Prions can exist in the environment for years.  Normal disinfectants and hygienic procedures do not get rid of prions.  Diseases caused by prions are often called “transmissible spongiform encephalopathies.”  Spongiform refers to the appearance of brain tissue under a microscope as damaged or sponge-like with holes.  Encephalopathy refers to a condition impairing brain function.

Though many people may not have heard of kuru or scrapie, Mad Cow Disease may be the most recognizable prion disorder in popular knowledge.  

Research is ongoing to discover a treatment or cure for these diseases.  To date, there is none and prion diseases are fatal.

As frightening as this all sounds, the good news is that these diseases are very rare.  The most common prion disease in humans in the U.S. is called Creutzfeldt-Jakob disease and even it is a one-in-a-million diagnosis.  

Look forward to an episode in the near future on a similarly fascinating topic.  Stay tuned!

Sources: 
-https://en.wikipedia.org/wiki/Kuru_(disease)
-https://www.cdc.gov/prions/cjd/index.html
-Kuru, The First Human Prion Disease: https://www.mdpi.com/1999-4915/11/3/232/htm

Images: 
-Chimpanzee Brain with kuru: Courtesy of D. Carleton Gajdusek via https://www.mdpi.com/1999-4915/11/3/232/htm
-Dr. Carleton Gajdusek: Courtesy of D. Carleton Gajdusek via https://www.mdpi.com/1999-4915/11/3/232/htm
-Histology slides with kuru-infected brain tissue: https://www.sciencedirect.com/topics/nursing-and-health-professions/kuru

Max

Doctor with a mustache.