Kuru

Kuru is a rare and fatal infectious disease affecting the nervous system first found among individuals in Papua, New Guinea. The infection is typically transmitted from person-to-person during ritual cannibalism. Kuru is a type of spongiform encephalopathy, which is a group of diseases that causes brain tissue to degenerate and replacement of healthy tissue with clusters of tiny liquid-filled, thin-walled cavities called cysts. The brain of an individual with kuru tends to look like a sponge. 

Kuru is caused by the accumulation of infectious, misfolded proteins called prions in the nervous system. The disease is spread through cannibalism of infected tissue (i.e. when an individual eats the human tissue of an infected individual). Kuru first affected a tribe in the highlands of New Guinea who ate the brain tissues of deceased family members. The misfolded prion proteins were thereby passed from person-to-person. 

Kuru has a very long incubation period (i.e., time between exposure to infectious agent and onset of signs and symptoms), which is typically around 10 to 13 years but can be up to 50 years. 

Early stages of kuru are characterized by tremors, unsteady gait, and ataxia (i.e., impaired coordination of movements). As the disease progresses, tremors and ataxia increase in frequency and intensity, and muscle jerks (i.e., quick, involuntary movements) may also develop. Other signs and symptoms may also include pain in the upper and lower extremities, difficulty walking, slurred speech, and headache. In the late stages of kuru, individuals may also develop dementia or experience difficulty swallowing, or dysphagia, which can lead to malnutrition. Eventually, individuals with kuru end up in a coma. 

Diagnosis of kuru is primarily based on patient history and clinical presentation. Neurological exams can reveal ataxia, muscle jerks, as well as difficulty walking. However, as kuru is very rare, other more common neurological diseases (e.g., Lewy body dementia, fatal familial insomnia, and frontotemporal dementia) need to be excluded, based on brain imaging findings and/or family history. Other spongiform encephalopathies and infectious diseases should also be excluded. These similar encephalopathies include Creutzfeldt-Jakob disease (CJD) , which can be caused by a genetic mutation; blood transfusion from an infected individual; or medical procedures, like when equipment for a procedure gets contaminated and infects healthy individuals. Electroencephalogram (EEG) can help differentiate kuru from CJD. In kuru disease, EEG will typically be unusual but will not demonstrate the characteristic sharp wave complexes seen in CJD. Bovine spongiform encephalopathy (i.e., mad cow disease), which is caused by eating the meat of cows with prions, must also be ruled out. Autopsy can reveal histopathological findings that can confirm the diagnosis of spongiform encephalopathy postmortem.  

There is no cure for kuru, and death usually occurs within 6 to 12 months from symptom onset. Treatment is only supportive and can include analgesics and physical therapy to assist with movements. 

Kuru is a rare and incurable disease caused by prions and spread through cannibalism. It is a member of a group of prion diseases called spongiform encephalopathies. Incubation period is long, anywhere from 13 years up to 50 years. Early signs and symptoms include muscle tremors and loss of coordination. In late stages of kuru, individuals may also develop pain in the extremities, difficulty swallowing, slurred speech, and dementia. Kuru is a diagnosis of exclusion, based on patient history, clinical presentation, neurologic exam, and brain imaging.