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Chemicals / Complex Chemical Agents /Chemical:

Prion Protein

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INDEX - INFORMATION AVAILABLE

GENERAL & REFERENCES

CHEMICAL STRUCTURE & IDENTIFICATION

PHARMACOKINETICS

CHEMICAL PRODUCTION, TRANSFER, PHYSICAL FACTORS & BIOGEOGRAPHICAL RANGE

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THE FOLLOWING INFORMATION IS HELD ON THE DISEASE INFORMATION PAGE CWD - The Disease in Deer and Elk:

  • Epidemiology, Disease Characteristics & Diagnosis
  • Treatment & Control

General and References

Chemical Summary

  • A protein found normally on cells of the nervous system and elsewhere, a relatively protease-resistant form of which is associated with the transmissible spongiform encephalopathy (TSE) diseases.

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Names and Formulae (Synonyms)

  • Slow Virus

The prion protein, in different forms, is known by a variety of terms, including:

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Associated Diseases

  • Bovine Spongiform Encephalopathy (BSE, "Mad Cow Disease")
  • Chronic Wasting Disease (CWD)
  • Feline Spongiform Encephalopathy (FSE)
  • Scrapie (Rida)
  • Slow Virus
  • Transmissible Mink Encephalopathy (TME)
  • Transmissible Spongiform Encephalopathies (TSEs)
  • Creutzfeldt-Jakob Disease (CJD)
  • Fatal Familial Insomnia (FFI)
  • Gerstmann Straussler Scheinker syndrome (GSS)
  • Kuru
  • New-variant-Creutzfeldt-Jakob Disease (nv-CJD, variant-Creutzfeldt-Jakob Disease, v-CJD)

See also CWD CONTROL: Understanding Prions for CWD of Deer and Elk (Overview of Techniques)

Linked Diseases

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References

Species Author

Dr Debra Bourne MA VetMB PhD MRCVS (V.w5)

Referee

Suzanne I Boardman BVMS MRCVS (V.w6), Chris Brand (V.w52), Dr Terry Kreeger (V.w49), Dr Julie Langenberg (V.w50), Bruce Morrison (V.w48), Michael Samuel (V.w53), Scott Wright (V.w54)

References

Detailed references are provided attached to specific sections.

ORGANISATIONS
(USA Contacts for Managing CWD)

ELECTRONIC LIBRARY
(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

Click here for further reading on "Chronic Wasting Disease"
Library

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Structure & Identification

Physical Properties / Chemistry
Structure
  • PrPC is a protein which is highly conserved in all mammalian species. (J248.2.w1)
  • From an original length of 254 amino acids (Syrian hamster PrP), following processing of the NH2 and COOH termini, both PrPC and PrPSc consist of a chain of amino acids 209 residues long. Following partial proteolysis, truncation of the NH2 terminus of PrPSc produces the form PrP27-30, composed of approximately 142 amino acids, and with a molecular weight of 27-30 kDa. (J135.95.w1)
  • The three-dimensional structure of PrPC consists at its carboxyl terminal half of three alpha helices and a short beta-pleated sheet, forming a stable globular structure, while the amino terminal half of the molecule is forms a random coil. (J251.4.w1)
  • PrPSc has a structure including about 43% beta-sheet and 34% alpha-helical structure, while the normal PrPC has a structure which is about 43% alpha-helix and only 3% beta-sheet. (J251.4.w1)
  • The precise three dimensional structure of PrPSc has yet to be determined. (J251.4.w1)
Appearance
  • --
Melting point
  • --
Boiling point
  • --
Density
  • --
Water solubility
  • Purified preparations of PrPSc are insoluble. (J251.4.w1)
Other solubility
  • --
Acid/Base
  • --

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Chemical Formula Diversity (Sub-type)

Recognised Sub-types
  • There are a variety of strains of abnormal prion protein. These vary in a number of in vitro and in vivo characteristics. 
  • Investigations to date have indicated that the strain of prion protein associated with CWD is different from the strain associated with BSE and from known scrapie strains. It is not yet known whether there are different strains of CWD prions.

(References are available in the detailed literature reports below)

In vitro differences (Laboratory test: differentiation)
  • Differences in the glycoform profiles of different strains of PrPres can be used to distinguish between strains of TSE agents.
  • Studies of glycosylation patterns have not yet identified patterns able to distinguish reliably between strains associated with CWD in deer and elk, scrapie in sheep and cattle and BSE in cattle.
  • Work using a conformation-dependant assay noted a possible conformation difference between PrPCWD in North American elk (Cervus elaphus nelsoni - Rocky Mountain Elk (Cervus elaphus - Red deer)) and that in Odocoileus spp. deer.

(References are available in the detailed literature reports below)

In vivo differences (Affected animal: variation in toxicity)
  • A given strain of prion produces its own characteristic incubation period and profile of histopathological lesions when inoculated at high titre into mice of known genotype
  • The main method of strain typing prions is by examining the incubation periods and the profile of histopathological lesions produced when they are inoculated into a panel of mice with a variety of known genotypes. 
    • This technique has shown that prions from cattle with bovine spongiform encephalopathy (BSE) are different from known scrapie strains. It has shown also that prions from cases of spongiform encephalopathy in exotic ungulates, feline spongiform encephalopathy (FSE) and new-variant Creutzfeldt-Jakob disease (nvCJD) in humans are of the same strain as those causing BSE in cattle. 
    • The same method has shown that the strain of prions associated with chronic wasting disease (CWD) in deer and elk is different from BSE and from known scrapie strains.

(References are available in the detailed literature reports below)

Literature Reports

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Chemical Detection and Identification

Editorial Comment The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 
  • For detection of prions associated with CWD (chronic wasting disease) in deer and elk the "gold standard" test is immunohistochemistry, particularly of the parasympathetic vagal nucleus at the obex, in the dorsal portion of the medulla oblongata.
  • ELISA and Western blot tests developed for BSE detection have been tested for use in detection of CWD in cervids. To date [January 2004] ELISA-based test kits from three different companies have been approved by USDA Center for Veterinary Biologicals for use as screening tests for the detection of CWD in free-ranging cervid populations, but none has been approved for use for testing of farmed cervids in regulatory programmes. 

Sampling:

  • "Traditionally, confirmation of Transmissible Spongiform Encephalopathy (TSE) disease in humans or animals is by conventional light microscopy of stained tissue sections prepared from specific sites of formalin-fixed tissue after embedding in paraffin wax." (B297.5.w5)
  • For the diagnosis of CWD in deer and elk the most important site of the brain which must be examined is the dorsal portion of the medulla oblongata at the obex. This area is involved early in infection in both deer and elk. (J40.66.w1, P10.67.w1) 
    • It is critically important that the correct portion of the brain is sampled if the results of testing are to be meaningful. (J40.66.w1, P10.67.w1)
    • It is important that specimens are preserved appropriately; the obex sample [intended for histopathology/immunohistochemistry] must be placed in 10% buffered formalin and the remainder of the brain should be frozen. (J40.66.w1)
  • In Odocoileus spp. deer samples of the tonsils, and samples of the retropharyngeal lymph nodes in Odocoileus spp. deer and in Cervus elaphus nelsoni - Rocky Mountain Elk (Cervus elaphus - Red deer), provide additional useful specimens in which PrPCWD can be detected at an early stage using immunohistochemistry (IHC).
    • Studies have shown that in Odocoileus spp. deer PrPCWD can be detected by IHC in the retropharyngeal lymph nodes before it can be detected at the obex. (P10.67.w1, J64.21.w17, J84.8.w1)
    • Studies have shown that in Cervus elaphus nelsoni - Rocky Mountain Elk (Cervus elaphus - Red deer) PrPCWD can be detected by immunohistochemistry (IHC) in the retropharyngeal lymph nodes before it can be detected at the obex. (J212.15.w2)
    • Tonsillar and retropharyngeal lymph node tissue should be preserved in 10% neutral buffered formalin for storage prior to IHC. (J40.66.w2)
    • Fresh, not formalin-preserved, tissue is used for the various "rapid tests". (P50.1.w4)

ANTIBODY DETECTION:

  • TSE diseases produce no known specific immune response. It is not possible to use detection of antibodies (serological response) for detection of abnormal prion proteins or TSE disease.

ANTIGEN (PrP) DETECTION:

IMMUNOHISTOCHEMISTY:

  • Immunohistochemistry, using antibodies to PrPres (anti-scrapie amyloid antibodies), has been used for the detection of PrPres and the diagnosis of TSE diseases for many years. A variety of antibodies are used, both monoclonal antibodies (MAbs) and polyclonal antibodies. When used in immunohistochemistry such antibodies allow anatomical localisation of where the PrPres is found within the tissue being tested.
  • Immunohistochemistry is more sensitive than histopathological examination of tissues using standard stains such as haematoxylin and eosin. It can detect PrPres in mildly to moderately autolysed tissues and in tissues such as lymph nodes and tonsils where there are no visible histopathological lesions.
  • In deer and elk immunohistochemistry has been used for the detection of PrPCWD in brain, retropharyngeal lymph node, and (in deer) in tonsil and has been shown to detect PrPCWD in animals which do not yet have histopathological spongiform change in the brain.
  • Immunohistochemistry of the obexhas the advantage that it allows visualisation of PrP in association with specific tissue architecture for high confidence of diagnosis.
  • The recent production of an antibody specific for the pathological form of PrP may lead to the development of new detection capabilities. 

IMMUNOBLOTTING/WESTERN BLOTTING:

  • Immunoblotting, particularly Western blotting, has been used for the detection of PrPres in tissues of individuals with TSE diseases. 

  • Western blotting may be used for the detection of PrPCWD in cervids infected with CWD.

ELISA:

  • Various ELISAs have been developed for the detection of TSEs, in particular for the detection of BSE. 
  • To date [January 2004] ELISA-based test kits from three different companies have been approved by USDA Center for Veterinary Biologicals for use as screening tests for the detection of CWD in free-ranging cervid populations, but none has been approved for use for testing of farmed cervids in regulatory programmes.

OTHER IMMUNOASSAYS:

  • A variety of tests have been and are being developed for the detection of abnormal prion proteins.
  • One test has been described, using capillary electrophoresis and fluorescent labeled peptides, which suggested the possibility of detecting abnormal prion proteins in the blood of elk (Cervus elaphus - Red deer) with CWD and sheep with scrapie. 
  • A conformation-dependent immunoassay (CDI) has been developed which may be used on a variety of ungulates and which was considered to have a sensitivity approaching that of bioassay in cattle and in transgenic mice.

ELECTRON MICROSCOPY: PRESENCE OF SCRAPIE-ASSOCIATED FIBRILS:

  • Scrapie-associated fibrils (SAF) are found only in individuals with TSE diseases.
  • In deer and elk with CWD SAF may be found in the brain and spleen.

BIOASSAY:

  • Detection of the agent by bioassay - transmission of the disease from the suspect case to other animals by inoculation - is used to assay the presence of TSE-associated infectivity and to confirm that disease present in an animal is a TSE. Following inoculation the recipient animals are monitored for the development of clinical disease and examined at necropsy for the presence of lesions of spongiform encephalopathy. In most cases inoculation into rodents is used. 
  • There are limitations to bioassay:
    • Sensitivity of bioassay is optimum when the recipient is of the same species as the donor animal; this is often impractical due to prolonged incubation times and levels of biosecurity required for experimental animals. 
    • There is a limit to the amount of inoculum which can be used, particularly when using small species such as mice and inoculating by e.g. the intracerebral route. 
    • Not all TSEs will transmit to commonly used laboratory species.

(References are available in the detailed literature reports below)

Literature Reports
Types of Techniques recorded as useful for prion identification
ANTIGEN DETECTION
  • Immunohistochemistry
  • ELISA
  • Immunoblotting (particularly Western blotting)
OTHER
  • Presence of Scrapie-associated fibrils
  • Bioassay (important for detection of infectivity)

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Chemical Inactivation

Editorial Comment The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 

"Prions are inactivated by 1N NaOH, 4.0 M guanidinium hydrochloride or isocyanate, sodium hypochlorite (2% free chlorine concentration), and steam autoclaving at 132C for 4.5 h." (D131)

  • The abnormal prions associated with the transmissible spongiform encephalopathy (TSE) diseases are generally resistant to chemical inactivation. 
  • Sodium hypochlorite solution containing 20,000 ppm available chlorine is considered effective for inactivation of TSE agents.
  • Sodium hydroxide (1M) is also considered effective, particularly in combination with gravity-displacement autoclaving.
  • Chemicals which have been shown to considerably, but not entirely, reduce infectivity, include the epoxide glycidol (GLD, 2,3-epoxy-1-propanol) at 3% or 5%, the detergent sarkosyl at high concentration and sodium dichloroisocyanurate solution containing the same level of available chlorine as sodium hypochlorite solution (20,000 ppm).
  • A variety of chemicals have been shown not to inactivate the TSE agents, including acetylethyleneimine, ethanol, ethylene oxide, chlorine dioxide, hydogen peroxide, peracetic acid, phenolic disinfectants, potassium permanganate, urea, formalin/formaldehyde, B-propriolactone and ethylene oxide gas.
  • PrPres shows considerable resistance to degradation by proteases.
  • Purified scrapie prions have been shown to resist inactivation by chemicals which disrupt nucleic acids.

For information on compounds causing inhibition of PrPres accumulation in vitro and prolongation of the incubation period in rodents see: CWD of Deer and Elk - Prophylactic Treatment (other than vaccines)

(References are available in the detailed literature reports below)

Literature Reports

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Pharmacokinetics

 Pharmacology / Cellular Reactions

Editorial Comment The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 

DIFFERENCE BETWEEN NORMAL CELLULAR PrP AND ABNORMAL PrP

  • PrPC and PrPSc do not differ from one another in their amino acid sequence. However the two forms of PrP are different from one another in their three-dimensional conformation.

CONVERSION OF PrPC TO PrPSc

  • It is known that conversion of PrPC to PrPSc takes place post-translationally
  • The process of conversions appears to involve direct interactions of the cellular protein with existing PrPSc, but the exact mechanism of the conversion is unknown. 
  • It is possible that only an as-yet unidentified form of PrP (which may be denoted as PrP*) is responsible for infectivity .
  • It is possible that an as-yet unidentified additional protein molecule or other substance is required for infectivity.
EFFECT ON CELLS
  • The role of normal cellular PrP is not yet understood. 
  • In the prion diseases astrocytosis, microglial activation and loss of neurons by apoptosis are known to occur, however the precise way in which these diseases cause such cellular and brain damage is not known.

(References are available in the detailed literature reports below)

Literature Reports
Editorial Overviews Available

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Species Specific Responses

Editorial Summary for Degree of Toxicity for other Species The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 
  • Natural hosts of CWD to date include only cervids: Odocoileus hemionus - Mule deer, black-tailed deer (Odocoileus hemionus columbianus), Odocoileus virginianus - White-tailed deer, mule deer x white-tailed deer hybrids and Cervus elaphus nelsoni - Rocky Mountain Elk (Cervus elaphus - Red deer) and Alces alces - Moose. The susceptibility of other subspecies of (Cervus elaphus - Red deer) has not been tested.
  • To date there is no evidence that humans can be infected with CWD; however it is not possible at this time to state categorically that humans cannot become infected.
  • Experimentally, using intracranial inoculation of brain homogenates, it has been possible to infect domestic ferrets, American mink, squirrel monkeys, cattle, and a domestic goat, but not raccoons (Procyon lotor - Common Raccoon). 
  • Initial trials failed to transmit infection to laboratory mice or hamsters, although infection of hamsters was possible following two or more passages in ferrets, indicating that the host range was expanded by such passage, and infection of a few mice has been achieved.

Other TSE Diseases:

(References are available in the detailed literature reports below)

The literature reports are subdivided into the following sections:

  • CWD of Deer and Elk

    • Negative data

  • Other TSE Diseases

Literature Reports of Species Infected
ORDERS recorded overall as containing Definitive Host Species (incl. Experimental, captive and free-ranging) (Not including infection unconfirmed by Laboratory diagnosis)

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Degree of Hazard (Risk to Humans / other Species)

  • The World Health Organisation (WHO) makes the following conclusions and recommendations regarding CWD:

    • "It is advised that any tissue which may come from deer or elk with Chronic Wasting Disease (CWD, a transmissible spongiform disease of North American mule deer and elk) is not used in animal or human food; however, at this time there is no evidence to suggest that CWD in deer and elk can be transmitted to humans." (W244.25Feb2004.CWD1)
  • In the USA the following Biosafety level classifications for TSE agents are suggested in the CDC's "Biosafety in Micribiological and Biomedical Laboratories":

    • "Biosafety level classification. Human prions and those propagated in apes and monkeys are manipulated at Biosafety Level 2 or 3, depending on the studies being conducted. BSE prions are likewise manipulated at Biosafety Level 2 or 3, due to the possibility that BSE prions have been transmitted to humans in Great Britain and France. All other animal prions are considered Biosafety Level 2 pathogens. Thus, based on our current understanding of prion biology described above, once human prions are passaged in mice and mouse PrPSc is produced, these prions should be considered Biosafety Level 2 prions, even though the human prions are Biosafety Level 3 under most experimental conditions. An exception to this statement is in the case of mice expressing human or chimeric human/mouse transgenes. These transgenic mice produce human prions when infected with human prions and should be treated as Biosafety Level 2 or 3 in accord with the guidelines described above." (D131)
  • In the UK for laboratory work with the agent of CWD (as well as human TSE agents and the agents of BSE, FSE and TME), the recommended Overall Laboratory Containment Level for experimental work is level 3, with Animal Containment Level 3 for small animal work and level 1 for large animal work, although some derogations from full Containment Level 3 may be allowed (subject to local risk assessment) since transmission is considered most likely to occur percutaneously or by ingestion (to a lesser extent). (B320)

Biological Containment Level - USA
  • Biosafety level 2 for CWD prions
  • Biosafety level 2 or 3 for human prions, prions propagated in apes or monkeys and BSE prions.

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Chemical Production, Transfer, Physical Factors and Biogeographical Range

Chemical Production

Editorial Comment The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 

DIFFERENCE BETWEEN NORMAL CELLULAR PrP AND ABNORMAL PrP

  • PrPC and PrPSc do not differ from one another in their amino acid sequence. However the two forms of PrP are different from one another in their three-dimensional conformation.

CONVERSION OF PrPC TO PrPSc

  • It is known that conversion of PrPC to PrPSc takes place post-translationally. 
  • The process of conversions appears to involve direct interactions of the cellular protein with existing PrPSc, but the exact mechanism of the conversion is unknown. 
  • It is possible that only an as-yet unidentified form of PrP (which may be denoted as PrP*) is responsible for infectivity .
  • It is possible that an as-yet unidentified additional protein molecule or other substance is required for infectivity.
Literature Reports

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Mechanisms of Transmission / Contamination

Editorial Comment

The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 

SOURCES OF AGENT

  • It is thought that the agent of CWD is shed in secretions or excretions (e.g. saliva, urine, faeces) and is passed to the next host by the oral route.
  • Environments contaminated by the agent are thought to be an important source of agent for infection, particularly within highly contaminated captive environments. The importance of agent in contaminated environments as a source for free-living cervids has not yet been determined

For the other TSE diseases, sources of agent appear to differ:

  • In scrapie, the placenta has been implicated as a source of infective agent in sheep. Faeces and secretions may also be sources; prions have been detected in intestinal tissue and in nasal mucosa of sheep.
  • In BSE and the related FSE and nvCJD, contaminated foods are considered to be the main source of infective agent.
    • Lateral transmission (i.e. one animal acting as the source for another animal, not via consumption of the infected animal or its products) was considered possible in some cases of BSE in exotic ruminants.
  • In Kuru, brain tissue is considered to have been the main infective agent.
  • In iatrogenic cases of CJD, tissue grafts, hormone products and microscopic amounts of CNS material contaminating instruments have been recognised as sources of the agent.
  • The source of agent, if any, in cases of sporadic CJD is unknown.

ROUTES OF INFECTION

  • It is thought that the CWD agent is passed to the next host by the oral route. 
  • Maternal transmission may occur but if so appears to be minor. 
  • Transmission may occur indirectly via a contaminated environment; the importance of contaminated environments in the transmission of CWD is not clear.
  • Experimentally, transmission has been demonstrated by the oral route (feeding of contaminated material to fawns) as well as by intracerebral inoculation.

Information from the other TSE diseases:

  • In general it is considered that the natural route of uptake of the agent is oral.
  • There may be a role for entry via the conjunctiva or breaks/abrasions in mucosa or skin.
  • Maternal transmission may occur however it is unclear whether this is transmission in utero or during/after birth.
  • Iatrogenic transmission has occurred through subcutaneous and intramuscular injection, grafting of infected tissues and implantation of contaminated electrodes into the brain.
  • Experimentally intracerebral inoculation is generally considered to be the most effective route for transmission of TSEs. Intravenous, intraperitoneal, subcutaneous, scarification, conjunctival and oral routes have also been used successfully. The oral route generally appears to be relatively inefficient compared to e.g. intracerebral inoculation.

ROUTES OF DISSEMINATION IN A NEW HOST

  • CWD agent appears to accumulate initially in lymphoid tissue. 

    • In both naturally-occurring CWD and experimental infection via the oral route, PrPCWD accumulation occurs in alimentary associated lymphoid tissues before it is found in the brain.
    • The precise cells involved within lymphoid tissues is not yet known although a role for follicular dendritic cells is probable.
  • The first brain region in which the agent is detected following oral infection is the dorsal motor nucleus of the vagus nerve, in the medulla oblongata, suggesting transmission to the CNS via the vagus nerve.
  • Agent is found in other areas of the brain later during the course of infection.

Information from the other TSE diseases:

  • It is probable that the first site of prion conversion in the body is in lymphoid tissue of the gut or spleen. The agent can be demonstrated in lymphoid tissues before it is detected in nervous tissue.
  • Transmission to the CNS appears to occur via the peripheral nervous system with a rate of transport of about one millimetre per day.
  • The vagus nerve has been implicated in transmission following experimental oral infection in hamsters.
Literature Reports

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Physical Susceptibility (Inactivation)

Editorial Comment The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 
  • The agents causing transmissible spongiform encephalopathies (TSEs) vary in their resistance to inactivation by physical agents. In general TSE agents are much more resistant than are conventional infectious agents, such as bacteria and viruses, to heat, ultraviolet radiation, ionizing radiation and microwave irradiation.
  • The resistance of TSE agents to heat varies with the material in which the agent is present (e.g. tissue size and composition) and has been shown to increase if the agent has been fixed (e.g. by ethanol or formalin) or if material containing the agent becomes attached to glass or metal. It appears that during the early stages of procedures such as autoclaving, designed to inactivate pathogens, a proportion of the agent may become heat fixed onto surfaces, following which this fraction of the original quantity of the agent becomes resistant to further heating.
  • Incineration at high temperatures (e.g. 1,000C) is effective in removing all infectivity although trace infectivity could be detected following incineration at 600C followed by rehydration of the resultant ash.
  • TSE agents also are resistant to acids and alkalis. However a combination of alkali plus heating, e.g. autoclaving at 120C for 30-90 minutes following or in the presence of concentrate alkali (1M or 2M sodium hydroxide), has been reported to be effective for the inactivation of various scrapie strains.
  • Sonication was not effective at deactivation.
Literature Reports

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Environments - External Habitats

Editorial Overview The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 
  • Relatively little work has been done on the survival of the TSE agents in the environment. Work that has been done indicates that they persist for a long time (years) in a variety of environmental conditions.
Literature Reports
Habitat Biomes where chemical plays a significant role
  • --

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Distribution and Geographical Occurrence

Editorial Overview The following editorial comment summarises detailed information given within the LITERATURE REPORTS. Links to the LITERATURE REPORTS are provided at the bottom of this box. 

The distribution of the different TSE diseases, and therefore of their associated prions, varies between the diseases.

  • Chronic wasting disease (CWD) is restricted to North America (USA and Canada), plus one case detected in South Korea in an individual exported from Canada. To date CWD has been detected in wild populations of cervids in the USA (Colorado, Illinois, Nebraska, New Mexico, South Dakota, Utah, Wisconsin, Wyoming) and Canada (Saskatchewan) and in captive populations of cervids in the USA (Colorado, Kansas, Minnesota, Montana, Nebraska, Oklahoma, South Dakota, Wisconsin, Wyoming) Canada (Alberta, Saskatchewan) and South Korea.
  • Transmissible Mink Encephalopathy (TME) has been detected in the USA (Wisconsin, Idaho), Canada (Ontario), Finland, Germany (the former East Germany) and Russia.
  • Scrapie is considered to have a world-wide distribution, with the exception of New Zealand and Australia.
  • Bovine Spongiform Encephalopathy (BSE), including the related Feline Spongiform Encephalopathy (FSE), has been detected mainly in Europe, in UK (Great Britain and Northern Ireland), Eire, France, Switzerland, Portugal, in cattle imported from Britain in Denmark, Italy, Channel Islands, Belgium, Germany and outside Europe in the Falkland Islands, Canada and Oman and in Australia in a cheetah imported from Britain. In 2003 it was detected for the first time in from Canada and the USA.
  • Creutzfeldt-Jakob disease (CJD), including sporadic CJD, iatrogenic CJD and familial forms of human prion disease, has a worldwide distribution.
  • New variant Creutzfeldt-Jakob disease (nvCJD or vCJD), which is related to BSE (identical prion strain) has been detected mainly in the UK, but with a few cases in France and the Republic of Ireland.
  • Kuru has been found only in Papua New Guinea, mainly in the region occupied by the Fore peoples. 
Literature Reports
General Regions with reports of agent in last three years (not including experimental)

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