Prions Health Dictionary

  1. Health Encyclopedia
  2. Prions

Prions: From 1 Different Sources

Formally known as the “slow viruses”. Prions are in reality transmissible abnormal proteins infecting the CNS. They cause such human diseases as Kuru, Creutzfeld-Jacob Disease (CJD), bovine spongiform encephalitis (‘mad cow disease’) – all of which are characterised by their ext remely long incubation period.
Health Source: Dictionary of Tropical Medicine
Author: Health Dictionary

Prion

An aberrant variety of one of the proteins, called PrP, in a brain cell. The result of a gene mutation (see GENES), prions are stable, resistant to radiation and impervious to the normal cellular processes of degradation. They seem to react with normal PrP, turning it into an abnormal type that then accumulates in brain tissue. Prions are believed to be the infectious agents that cause a group of serious neurological disorders called spongiform encephalopathies. CREUTZFELDT-JAKOB DISEASE (CJD), the new variant of CJD linked with BOVINE SPONGIFORM ENCEPHALOPATHY (BSE), and KURU – a neurological disorder found in a cannibal tribe in New Guinea – are all diseases in this group that occur in humans. The prion disorders have a long latent period between infection and manifestation of symptoms; they are hard to diagnose until autopsy and there is no cure as yet.... prion

Creutzfeldt-jakob Disease (cjd)

A rapidly progressive, fatal, degenerative disease in humans caused by an abnormal PRION protein. There are three aetiological forms of CJD: sporadic, IATROGENIC, and inherited. Sporadic CJD occurs randomly in all countries and has an annual incidence of one per million. Iatrogenic CJD is caused by accidental exposure to human prions through medical and surgical procedures (and cannibalism in the case of the human prion disease known as kuru that occurs in a tribe in New Guinea, where it is called the trembling disease). Inherited or familial CJD accounts for 15 per cent of human prion disease and is caused by a MUTATION in the prion protein gene. In recent years a new variant of CJD has been identi?ed that is caused by BOVINE SPONGIFORM ENCEPHALOPATHY (BSE), called variant CJD. The incubation period for the acquired varieties ranges from four years to 40 years, with an average of 10–15 years. The symptoms of CJD are dementia, seizures, focal signs in the central nervous system, MYOCLONUS, and visual disturbances.

Abnormal prion proteins accumulate in the brain and the spinal cord, damaging neurones (see NEURON(E)) and producing small cavities. Diagnosis can be made by tonsil (see TONSILS) biopsy, although work is under way to develop a diagnostic blood test. Abnormal prion proteins are unusually resistant to inactivation by chemicals, heat, X-RAYS or ULTRAVIOLET RAYS (UVR). They are resistant to cellular degradation and can convert normal prion proteins into abnormal forms. Human prion diseases, along with scrapie in sheep and BSE in cattle, belong to a group of disorders known as transmissible spongiform encephalopathies. Abnormal prion proteins can transfer from one animal species to another, and variant CJD has occurred as a result of consumption of meat from cattle infected with BSE.

From 1995 to 1999, a scienti?c study of tonsils and appendixes removed at operation suggested that the prevalence of prion carriage may be as high as 120 per million. It is not known what percentage of these might go on to develop disease.

One precaution is that, since 2003, all surgical instruments used in brain biopsies have had to be quarantined and disposable instruments are now used in tonsillectomy.

Measures have also been introduced to reduce the risk of transmission of CJD from transfusion of blood products.

In the past, CJD has also been acquired from intramuscular injections of human cadaveric pituitary-derived growth hormone and corneal transplantation.

The most common form of CJD remains the sporadic variety, although the eventual incidence of variant CJD may not be known for many years.... creutzfeldt-jakob disease (cjd)

Pathogens

Micro-organisms that cause diseases, parasitising plants, animals and humans (see PARASITE). Some organisms are frequently PATHOGENIC, whereas others rarely cause disease. Opportunistic pathogens are those which rarely cause serious infection in healthy people but can do so in patients with weakened immune systems (immunocompromised – see IMMUNITY). Pathogens include BACTERIA, viruses (see VIRUS), prions (see PRION), fungi (see FUNGUS), PROTOZOA and metazoa (multicellular microorganisms called HELMINTHS or worms). The pathogenicity of an organism is called its virulence, which is measured by the number of organisms required to cause disease. The 50 per cent of lethal dose (LD50) is the quantity of a particular pathogen needed to cause infection in half of the hosts invaded.... pathogens

Encephalopathy

Any disorder affecting the brain, especially chronic degenerative conditions.

Wernicke’s encephalopathy is a degenerative condition of the brain caused by a deficiency of vitamin B1 (see Wernicke–Korsakoff syndrome).

Hepatic encephalopathy is caused by the effect on the brain of toxic substances (see toxin) that have built up in the blood as a result of liver failure. It may lead to impaired consciousness, memory loss, a change in personality tremors, and seizures.

Bovine spongiform encephalopathy, or , is a disorder contracted by cattle after they are given feed containing material from sheep or cattle.

The cause seems to be an infective agent known as a prion.

Some cases of new variant Creutzfeldt–Jakob disease in humans have been attributed to infection with the prions responsible for , probably transmitted in meat products.... encephalopathy

Kuru

A rare, fatal infection of the brain that affects some inhabitants of New Guinea.

The disease is caused by a “slow” virus or prion, which has a long incubation period and is spread by cannibalism.

Symptoms include progressive difficulty in controlling movements and dementia.

The study of kuru led to the identification of prions, which also play a role in Creutzfeldt–Jakob disease and BSE.... kuru

Slow Virus

one of a group of infective disease agents that resemble *viruses in some of their biological properties but whose physical properties (e.g. sensitivity to radiation) suggest that they may not contain nucleic acid. They are now more commonly known as *prions.... slow virus

Health encyclopedia icon Health Encyclopedia

Recent Searches