Kuru is a degenerative fatal neurological disorder appeared in Papua New Guinea in the early twentieth century. Kuru belongs to a class of infectious diseases called transmissible spongiform encephalopathies (TSEs), also known as prion diseases. The hallmark of a TSE disease is misshapen protein molecules that clump together and accumulate in brain tissue. The term kuru derives from the Foré word kuria which means to shake or shiver from fever and cold, a reference to the body tremors that are a classic symptom of the disease and is also known among the Foré as the laughing sickness due to the pathologic bursts of laughter people would display when afflicted with the disease. The discovery of kuru opened new windows into the realms of human medicine, was instrumental in the later transmission of other prion diseases, and was one of the greatest contributions to biomedical sciences in the 20th century.
Kuru is caused by prions, an infectious agent composed of protein in a misfolded form. The disease was the result of the practice of ritualistic, endocannibalistic funeral practices, in which relatives prepared and consumed the bodies and tissues, including brain of deceased family members among the Foré. Brain tissue from individuals with kuru was highly infectious, and the disease was transmitted either through eating or by contact with open sores or wounds. The most striking neuropathologic feature of kuru was the presence of numerous amyloid plaques, which are associated with the pathology of over 20 or more human diseases.
For the prion, replication involves converting conventional proteins into prions. Prions replicate by recruiting normal proteins to their cause, flipping them into a rogue prion-like shape that can go on to infect other cells and animals. This change initiates a chain reaction, and newly converted prions convert other proteins which they come into contact with on the interior of their respective cell membrane. The conversion occurred inside neurons from the soluble, monomeric, alpha-helical, protein, PrPC into an insoluble, multimeric, beta-sheeted conformer, PrPSc. The PrPSc collects in lysosomes, which are small, spherical, intracellular membrane-bound compartment vesicular organelles filled with enzymes that act as the digestive system of the cell, digesting bacteria, old organelles, and metabolizing fatty acids. This filling eventually leads to the lysosomes rupturing killing the cell that contains it due to the internal acidic pH 5 of lysosomes, releasing the prions to attack other cells.
Kuru causes physiological as well as neurological effects that ultimately lead to death. It is characterized by truncal ataxia, lack of voluntary coordination of trunk/torso muscle movements, preceded by headaches, joint pains and shaking of the limbs. Trembling is present in almost all patients with a transmissible spongiform encephalopathy.
The symptoms of kuru are broken down into three specific stages. The first stage, the...