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2 Kuru among the South Fore 3 Misinterpretations of Kuru 4 Symptoms of Kuru 5 The Prion Protein 6 References 7 External Links 8 Acknowledgements |
Kuru (also known as "Laughing Sickness"), an elusive and hitherto unknown disease first appeared in New Guinea in the early 1900’s. By the 1950’s anthropologists and government officials reported that this disease termed Kuru (The word means "trembling" in the language of the Fore) was rampant among the South Fore. The South Fore were identified by Australian government officials in the 1950’s as a single census division consisting of approximately 8,000 individuals within the Okapa subdistrict.
This particular group was partaking in ritual acts of mortuary cannibalism, and this conduct was later held to be responsible for the transmission of the fatal Kuru epidemic. This distinctive aspect of the illness made it even more fascinating to the various Western scholars who devoted their time to conquering it. Many efforts have been made to understand and describe Kuru, and the knowledge of the dynamics of the disease has continued to grow, even though the disease all but disappeared in New Guinea with the termination of cannibalism. Scientists have now identified Kuru as a prion disease, one of several known Transmissible spongiform encephalopathies. Understanding the structure and replication of the prion is crucial to interpreting the dynamics of Kuru and several other prion diseases, which exist today. The onset of Kuru led to a study of an unfamiliar disease that has lasted almost five decades. This particular disease serves as an example of the procedures scientists undergo in order to understand and appreciate all of the aspects of a disease and how potential therapies and solutions can be found.
The Kuru epidemic reached its height in the 1960’s. Between 1957 and 1968, over 1,100 of the South Fore died from Kuru. The vast majority of victims among the South Fore were women. In fact, eight times more women than men contracted the disease. It later affected small children and the elderly at a high rate as well. It is currently believed that Kuru was transmitted among the South Fore through participation in such cannibalism. Upon the death of an individual, the maternal kin were in charge of the dismemberment of the corpse. The women would remove the arms and feet, strip the limbs of muscle, remove the brains, and cut open the chest in order to remove internal organs. Lindenbaum, one of the early Kuru researchers, states that Kuru victims were highly regarded as sources of food, because the layer of fat on victims who died quickly resembled pork. Women also were known to feed morsels such as human brains and various parts of organs to their children and the elderly (Lindenbaum, 1979).
Studies on chimpanzees injected with brain material from a victim led scientists to believe the agent was a slow virus, because the chimps developed a very similar condition after a long incubation period. Gajdusek was responsible for conducting these tests on chimps. He defined a slow virus as a viral disease with an abnormally long incubation period. In humans, Kuru had an incubation period with a minimum of two years and maximum of 23 (Gajdusek et al., 1966). Gajdusek’s results also confirmed the infectious, transmittable nature of the prion.
Gajdusek studied Kuru, and he found the condition of Kuru victims to be an upsetting sight. He explains, "...to see them, however, regularly progress to neurological degeneration in three to six months (usually three) and to death is another matter and cannot be shrugged off" (Gajdusek, 1996:10). Gajdusek reported three main stages in the progression of symptoms. The first stage is called the ambulant stage, and it includes unsteadiness of stance, gait, voice, hands, and eyes; deterioration of speech; tremor; shivering; in- coordination in lower extremities that moves slowly upward; and dysarthria (slurring of speech). The second stage is also known as the sedentary stage, and Gajdusek defines it with the following symptoms: patient can no longer walk without support, more severe tremors and ataxia (loss of coordination of the muscles), shock-like muscle jerks, emotional lability, outbursts of laughter, depression, and mental slowing (it is important to note that muscle degeneration has not occurred in this stage, and tendon reflexes are usually still normal). The third stage is the terminal stage, which is marked by the patient’s inability to sit up without support; more severe ataxia (loss of muscle coordination), tremor, and dysarthria (slurring of speech); urinary and faecal incontinence; difficulty swallowing (dysphagia); and deep ulcerations appear. Cerebellar dysfunction is the cause of these conditions. Symptoms are generally common among prion diseases, such as Creutzfeldt-Jakob disease(CJD).
The exact nature of Kuru perplexed scholars for decades after the discovery of the ailment, until Prusiner identified and defined prion diseases in 1982 (Prusiner, 1995). Prusiner (1991) classified a prion as an infectious particle composed of a protein that causes neurodegenerative disorders. According to Cashman (1997), prions are infectious agents by biological and medical criteria. However, they are also fairly unique, and properties of prions differ from those of conventional microbes. All known prion diseases are fatal. Such diseases are often called spongiform encephalies, because they frequently cause the brain to become spongy and riddled with holes (Prusiner, 1995). Well known prion diseases include Scrapie, Bovine spongiform encephalopathy (Mad Cow Disease or BSE), and Creutzfeldt-Jakob disease (CJD). Less well-known prion diseases include the following: Transmissible mink encephalopathy, Chronic wasting disease, Feline spongiform encephalopathy, Exotic ungulate encephalopathy, Gerstmann-Sträussler-Scheinker syndrome (GSS), and Fatal familial insomnia (Krakauer et al., 1997). Of these infirmities, four affect humans: Creutzfeldt-Jakob disease, Gerstmann-Strässler-Scheinker syndrome, Fatal familial insomnia, and Kuru. The most common form of prion disease is Scrapie, expressed in sheep and goats (Prusiner, 1995). According to Cohen et al. (1994), prions cause a variety of degenerative neurologic diseases that can be infectious, inherited, or sporadic in origin. The cause of the sporadic forms is unknown; inherited forms are caused by up to twenty different mutations of the human PrP gene; and the infectious forms are transmitted through contact with or consumption of previously infected tissues (Prusiner, 1997).
Since the 1950's, scientists have worked on the prion puzzle. Microbiologists and epidemiologists have been confused by the prions. Advancements have been made, especially in the 1990's. This can be evidenced by Prusiner's reception of the Nobel Prize for Physiology or Medicine in 1997. However, it has still been difficult to detect prion infection, track its transmission, and type the different strains (Cashman, 1997). The Fore experienced a long struggle with kuru, which serves as a poignant example.
Introduction
Kuru among the South Fore
Kuru is a neurodegenerative disorder that surfaced among the South Fore of New Guinea, and the dynamics of this disease have been explored by various scholars. Lindenbaum worked with the South Fore and studied the Kuru disease. Zigas worked in New Guinea, and Gajdusek also traveled there in 1957 to study disease patterns in primitive and isolated populations (Gajdusek, 1996). Lindenbaum, Zigas, and Gajdusek were all crucial to explaining the marked, specific properties of Kuru to the rest of the world.Misinterpretations of Kuru
Scholars who first studied the disease among the South Fore initially had two major misconceptions concerning the nature of the disease. They first incorrectly postulated that it was a genetic disorder. After this possibility was ruled out, scientists next asserted that Kuru was the manifestation of a slow virus. Genetic disorders can be fully understood through application to population genetics. Mutations provide variation and fuel natural selection. A genetic disorder is one that is caused by a mutation that is passed on to subsequent offspring. Since Kuru had a tendency to occur among family members, the original notion that it was a genetic disorder seems somewhat appropriate. This possibility was eventually ruled out, because Kuru was too common and too fatal (Lindenbaum, 1979). A completely lethal genetic disorder would drastically reduce the fitness of a population. Sooner or later it would die out of the gene pool. This fact led scholars to seek additional possible explanations to describe the dynamics of the disease. Symptoms of Kuru
The Prion Protein
References
External Links
Acknowledgements