Kuru was first described in a specific tribal group in Papua, New Guinea. The word "kuru" means "to shake or tremble" in this tribal group's language. Individuals in New Guinea are believed to have acquired the infection through a cannibalistic ritual involving the blood and brains of deceased tribal members.
Because infection with kuru may occur years or decades before the advent of actual symptoms of the disease, it belongs to a group of diseases originally known as slow virus infections. Currently, slow virus infections are classed together as transmissible spongiform encephalopathies (TSE). TSEs include kuru, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker syndrome, and fatal familial insomnia. The TSE new variant called Creutzfeldt-Jakob disease (also known colloquially as "Mad Cow Disease") has received a great deal of public attention. The TSEs, including kuru, involve abnormal clumps of protein that accumulate throughout the brain, destroying brain tissue and leaving spongy holes.
Kuru reached epidemic proportions among tribal members in the 1950s. Since the practice of cannibalism was halted, the disease has essentially disappeared. Some sources suggest that as few as zero to 10 cases of kuru are diagnosed each year.
Causes and symptoms
Kuru is caused by an infectious protein particle called a prion, which stands for proteinaceous infectious particle. A prion is similar to a virus, except that it lacks any nucleic acid, which prevents it from reproducing. Prions are abnormal versions of proteins that are found in the membranes of normal cells. These abnormal proteins can be passed directly to individuals through the ingestion of prion-infected tissue or when open sores on the recipient's skin are exposed to prion-infected tissue. In addition to being transmissible (as are other infectious agents like viruses or bacteria), prions are unique because they can also be acquired through genetic inheritance.
Symptoms of kuru tend to begin in later middle age, years or decades after the prion was actually acquired. Early symptoms include lack of energy, intense fatigue, headache, weight loss, joint pain, difficulty walking, twitchy muscles, personality changes, mood swings, memory problems, and bizarre behavior. As the disease progresses, the individual experiences stiff muscles, involuntary movements, problems talking, hallucinations, increased confusion, blindness, and sometimes dementia. Death often occurs within three months to two years of the initial symptoms.
Diagnosis is arrived at through characteristic abnormalities found on the electroencephalogram (EEG), a test of brain waves and electricity. Seventy-five percent of individuals with kuru will display these specific abnormalities on EEG. MRI studies and biopsies (tissue samples) from the brain may also show changes that are characteristic of slow virus infection.
Diagnosis of slow virus infection is usually made by a neurologist.
There are no available treatments for kuru. It is relentlessly progressive, incurable, and fatal. Supportive care for the patient and his or her family is the only treatment.
Kuru is always fatal.
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Murray, T. Jock, and William Pryse-Phillips. "Infectious diseases of the nervous system." Noble: Textbook of Primary Care Medicine, edited by John Noble, et al. St. Louis: W.B. Saunders Company, 2001.
Sy, Man-Sun, Pierluigi Gambetti, and Wong Boon-Seng. "Human Prion Diseases" Medical Clinics of North America 86 (May 2002) 551–571.
National Institute of Neurological Disorders and Stroke (NINDS). Kuru Fact Sheet. Bethesda, MD: NINDS, 2003.
Rosalyn Carson-DeWitt, MD