Title: Prion diseases in humans: Oral and dental implications
Author(s): P. Jayanthi , Priya Thomas , P. Bindhu and Rekha Krishnapillai
Source: North American Journal of Medical Sciences. 5.7 (July 2013): p399.
Document Type: Disease/Disorder overview Copyright : COPYRIGHT 2013 Medknow
Publications and Media Pvt. Ltd.
http://www.najms.org/aboutus.asp
Full Text: Byline: P. Jayanthi, Priya. Thomas, P. Bindhu, Rekha.
Krishnapillai
Prion diseases are a group of neurodegenerative disorders characterized by
accumulation of abnormal prion proteins in the central nervous system. The
prions resist conventional sterilization procedures especially when infected
tissue becomes dried onto metal or glass surfaces. This article, a review of
literature collected using Pubmed as search engine, describes the oral
manifestations of prion diseases in addition to studying the possibility of
cross contamination in the dental office. The article emphasizes the importance
for dentists to be aware of these diseases, to identify the high-risk patients
by obtaining adequate medical history and to know the appropriate deactivation
procedures to be followed.
Introduction
Prion diseases also known as transmissible spongiform encephalopathies
(TSEs), are a group of fatal neurodegenerative diseases occurring in both humans
and animals. Stanley B. Prusiner was the first person to purify the infectious
agent of prion disease and won the 1997 Nobel Prize in Physiology/Medicine.
Prusiner defined prions as infectious, transmissible proteinaceous particles
that lack nucleic acid. The normal cellular prion protein (PrP [sup]c ) is
encoded by PrP [sup]c gene, which is located on the short arm of chromosome 20.
PrP [sup]c has predominantly alpha helical structure, is soluble and proteinase
sensitive. The normal function of PrP [sup]c is not well-known, but the
suggested functions are signal transduction, cell adhesion, regulation and
distribution of acetylcholine receptors. [sup][1]
PrP [sup]c is transformed into abnormal isoform of the protein (PrP [sup]Sc
) due to post translational modification or mutation in the PrP [sup]c gene. PrP
[sup]Sc has predominantly beta structure, is insoluble and partially proteinase
resistant. This mutated PrP [sup]Sc gives rise to TSEs, including bovine
spongiform encephalopathy (BSE) in cattle, scrapie in sheep and goats and
Creutzfeldt-Jakob disease (CJD) in humans. These diseases are characterized by
vacuolization of the gray matter and these vacuoles are located in the neuropils
between the nerve cell bodies. [sup][2],[3]
Although the risk of transmission of CJD through dental procedures is still
unclear, the theoretical possibility of transmission through contaminated dental
instruments should be kept in mind. This article aims to give a brief overview
of the clinical characteristics, risk of transmission and infection control
methods of prion diseases for dentists using data obtained from literature
search in Pubmed search engine.
Etiopathogenesis
The infectious agents for prior disease are composed of a 35-kD brain
sialoglycoprotein called PrP [sup]Sc that is essential for the transmission and
pathogenesis of several neurodegenerative diseases. PrP [sup]Sc is able to
propagate itself in the host by stimulating the conversion PrP [sup]c to PrP
[sup]Sc , leading to its accumulation. [sup][4]
Accumulation of PrP [sup]Sc can result either from exposure to infectious
prions iatrogenically or through ingestion, or because of mutations in the PrP
gene. Sporadic CJD has an unknown cause; that is, thus far no apparent
infections or mutations of the PrP gene have been found in association with such
cases, although the brain in these patients also accumulates PrP [sup]Sc .
[sup][2]
Human Transmissible Spongiform Encephalopathies
Based on the etiopathogenesis, different types of human TSEs have been
recognized. [Table 1] describes the transmission routes and clinical features of
TSEs in humans.{Table 1}
Sporadic Creutzfeldt-Jakob disease
This is the most common type of CJD accounting for 85% of all CJD cases,
occurring in middle or older age group. The disease is characterized by
progressive dementia, ataxia, myoclonus, cortical blindness, akinesia and speech
loss, followed by death within 4 months. [sup][5]
Iatrogenic Creutzfeldt-Jakob disease
The disease occurs following neurosurgery, duramater transplantation,
corneal grafting, and injection of pituitary hormones obtained from human
cadavers. This type of prion disease is important to dentists due to the risk of
cross contamination after the use of infected dental instruments. The incubation
period is variable ranging from 2 to 35 years. The clinical features are similar
to sporadic form, but cerebellar motor symptoms are predominant in this type.
[sup][5]
Variant Creutzfeldt-Jakob disease
vCJD is associated with the intake of BSE-contaminated beef and beef
products. The disease is characterized by depression, delirium, hallucinations,
paresthesia and dysesthesia in hands, feet and mouth followed by dementia and
akinesia. Deposition of amyloid plaques in the lymphatic tissues throughout the
body is a prominent feature. [sup][5]
Kuru
Kuru is endemic in Papua New Guinea and is transmitted by intake of
infected nervous tissue in cannibalistic practices. The disease is characterized
by ataxia, tremors, dysarthria and death. Though cannibalism is banned in 1950,
the incubation period is more than 40 years and the chance of appearance of new
cases is still possible. [sup][4]
Fatal familial insomnia
The disease presents with progressive insomnia, dysautonomy in the form of
hyperthermia, myosis and loss of sphincter control, followed by dysarthria,
tremors, motor dysfunction and cognitive deterioration. Death occurs within 7-18
months. [sup][6]
Gerstmann-Straussler-Scheinker syndrome
Gerstmann-Straussler-Scheinker syndrome gives rise to lack of coordination
leading to ataxia, dysarthria and nystagmus. Death occurs after 1-10 years.
[sup][6]
Oral Manifestations
Oral manifestations are rarely seen in prion diseases. Dysphagia
(difficulty in swallowing) and dysarthria (poor articulation of speech) are
noticed in all forms of human TSEs. Dysphagia and dysarthria could be early
symptoms of the disease and occur as a consequence of pseudobulbar paralysis.
[sup][7] In vCJD, parasthesia (tingling, pricking or numbness), orofacial
dysesthesia (abnormal sensations in the absence of stimulation) and one case of
loss of taste and smell have been reported in the literature. [sup][8],[9]
Infectivity of human oral tissues
Studies on human oral tissues for the presence of PrP [sup]Sc showed
positivity in limited number of oral tissues. Various human tissues like tonsil,
tongue, submandibular and parotid salivary glands, trigeminal ganglia, inferior
alveolar nerve, dental pulp and gingiva taken from different post mortem cases
of vCJD were analyzed for the presence of PrP [sup]Sc . Majority of the cases
showed positive PrP [sup]Sc in tonsils and trigeminal ganglia, while the other
human tissues were negative for PrP [sup]Sc . Western blot, paraffin-embedded
tissue blot, and immunohistochemical techniques were used for the study and the
sensitivity of these assay indicated that PrP [sup]Sc must have been at the
level of less than 1% of that found in the brain tissue. [sup][10]
Presence of PrP [sup]Sc in trigeminal ganglia may raise concerns about the
extent of deposition of PrP [sup]Sc along the cranial nerves and possible
extension into oral and nasal cavities which are innervated by the ganglia.
Guiroy et al., [sup][11] have noted positive PrP immunostaining of axons in the
nerve root and around the degenerating ganglion cells of trigeminal ganglion,
suggesting centripetal or centrifugal extension of the infectious agent along
the axons.
Blanquet-Grossard et al., [sup][12] have investigated the presence of
protease-resistant PrP [sup]Sc in pulp tissues from eight patients with sCJD
using specific monoclonal antibody by Western blotting. Though the authors were
unable to detect protease-resistant PrP [sup]Sc in pulpal tissues, they
suggested that the negative results could be due to low sensitivity of the
technique used and the potential for transmission of CJD via dental procedures
could not be dismissed. The authors have calculated that 1 g of sCJD infected
pulp would be expected to contain 40 log [sub]10 LD [sub]50 /g of infectivity,
compared to 10 [sub]8-9 LD [sub]50 /g of infectivity in brain tissue.
Prions and Dentistry
There is no evidence to show that TSE is transmissible from one person to
other by normal social contact, sexual contact or airborne droplets. Studies
have failed to show evidence of transmission of sCJD by blood components or
plasma products. On the contrary, there have been four reports of probable
transmission of vCJD via blood transfusion, where the donors were at preclinical
phase of the disease at the time of blood donation [Table 1]. [sup][13]
Occupational exposure
There is no risk of transmission of TSE to health care workers including
medical doctors and dentists through clinical contact or noninvasive clinical
investigative procedure. A total of 24 cases of sCJD have been reported in
health care workers as of 2005. [sup][14] Theoretically, it is possible that the
health care workers may acquire prion diseases from affected patients through
needle stick injuries. However, there is no epidemiological evidence to prove an
association between occupational exposure and sCJD. The health care personnel
should be informed about the nature of the hazard as well as the relevant safety
procedures. The World Health Organization (WHO) has recommended "common-sense"
actions in case of an occupational exposure while performing dental procedures
on TSE patients [Table 2]. [sup][15]{Table 2}
Dental procedures
To date, there are no reported definite or suspected cases of human TSEs
arising from dental procedures. Bourvis et al., [sup][16] had theoretically
assessed the risk of iatrogenic transmission of sCJD during endodontic
treatment. They estimated that the risk of being infected during endodontic
treatment ranged from 3.4 to 13 per million procedures, if no effective prior
deactivation procedures were used. However, the probability that more than one
case was infected secondary to endodontic treatment ranged from 47% to 77%
depending on the quantity of the infective material. The results of this study
showed that the risk of sCJD transmission is higher because of the reuse of
endodontic instruments in the absence of effective prion decontamination
procedures.
Achieving appropriate decontamination of endodontic instruments intended
for reuse is extremely difficult. Therefore, there is a possibility that these
decontaminated instruments that were in contact with dental pulpal tissue may
transfer the prion proteins from the infected patients to other patients.
[sup][17]
There are two possible mechanisms assessed for the transfer of CJD via
dental instruments:
*Accidental abrasion of lingual tonsil during dental procedures. Such a
chance is extremely low (10 [sup]4 -10 [sup]9 times less likely than
tonsillectomy). *Contact of dental instruments with pulp tissue. As dental pulp
originates from richly innervated neural crest cells, it is theoretically
possible that the dental pulp of individuals infected with CJD may be
infectious. [sup][12] General recommendations for dentists
The role of the dentist is to identify the patients with different forms of
CJD and to take appropriate measures to reduce the possible risk of cross
contamination. This can be achieved by obtaining: (a) complete medical history
of the patient, (b) family history of prion diseases, (c) travel history to know
about the possible exposure during visits to endemic areas like United Kingdom.
Based on this information, patients can be classified as being at high risk or
low risk for developing the disease. [sup][2]
High-risk patients
Patients with diagnosis or suspicion of CJD; asymptomatic patients with a
gene mutation; all members of the family with a case of hereditary CJD ; all
members of a family with a case of vCJD.
Low-risk patients
Patients with undiagnosed progressive neurological disease with or without
dementia; members of a family with history of undiagnosed dementia or
neurological disease; recipients of human pituitary hormone or duramater;
patients undergoing transdural surgery between 1972 and 1989 as infectious agent
could be transmitted during those procedures.
Prion inactivation methods
The routine physical and chemical sterilizing procedures are ineffective
against prion agents, as they are heat resistant and bind tightly to surgical
steel instruments. The prions also become more resistant to inactivation when
dried and have shown to transmit disease experimentally and clinically, even
after disinfection. [sup][18]
It is advisable to use disposable instruments whenever possible and
incinerate reusable instruments that are difficult to clean (endodontic files,
broaches, carbide and diamond burs and dental matrix bands). Endodontic files
used in the treatment of pulp cavity contain blood and peripheral nerves known
to carry the prion proteins and their intricate surface topography enable to
trap the proteins. Therefore, a recent communication in 2007 titled "Advise for
dentists on re use of endodontic instruments and variant Creutzfeldt-Jakob
Disease" issued by UK Department of Health, has advised dentists to ensure
single use of endodontic reamers and files as a precaution to reduce any
potential risk of transmission of vCJD. The nondisposable instruments should be
mechanically cleaned and passed thorough stringent decontamination protocols
before reuse, as recommended by WHO in 2000 [Table 3]. [sup][15]{Table 3}
The handling of instruments depends on the risk of the patient being
treated. When treating high-risk patients, all materials must be incinerated.
The source of refrigeration and aspiration system should be external to the
equipment due to the possibility that some residues might pass via internal
systems and compromise sterilization. The patient should never use the normal
spittoon but a disposable receptacle that is later incinerated. The histological
samples of high-risk patients must be handled by specialized staffs that are
aware of the risk. As routine formalin fixation does not inactivate prion
proteins, the samples must be immediately immersed in 98% formic acid for 1 h
prior to paraffin embedding and labelled as biohazardous. [sup][5]
In patients with suspicion of CJD, all the instruments must be stored
separately in a rigid container labelled with data of the patient, type of
treatment provided and details of the attending clinician until a definitive
diagnosis is arrived. The instruments are incinerated if the diagnosis is
confirmed or sterilized by conventional methods like autoclaving if diagnosis is
ruled out. [sup][5]
Conclusion
TSEs are a group of fatal neurodegenerative disorders with no approved
cure. The prion proteins resist conventional sterilization methods used in
dental clinics and laboratories. Although there appears to be very low risk of
CJD transmission during dental procedures, account must be taken of this
possibility. As a general rule, appropriate medical and family history should be
taken from all the patients before dental procedures. The dental professionals
should have up to date knowledge about transmission, diagnosis, infection
control and decontamination procedures regarding prion diseases.
References
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DC. Neuronal degeneration and neurofilament accumulation in the trigeminal
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12. Blanquet-Grossard F, Sazdovitch V, Jean A, Deslys JP, Formant D, Hauw
JJ, et al . Prion protein is not detectable in dental pulp from patients with
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Creutzfeldt-Jakob disease by blood products. Br J Hematol 2006;132:13-24.
14. Ena J. Prions: Who should worry about them? Arch Med Res 2005;36:622-7.
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WHO/CDS/CSR/APH/2000.
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transmission of sporadic Creutzfeldt-Jakob disease in endodontic practice in
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P. Jayanthi, Priya. Thomas, P. Bindhu, Rekha. Krishnapillai
Source Citation (MLA 7th Edition) Jayanthi, P., et al. "Prion diseases in
humans: Oral and dental implications." North American Journal of Medical
Sciences 5.7 (2013): 399. Academic OneFile. Web. 4 Nov. 2013. Document URL
Gale Document Number: GALE|A340744668
Risk of Prion Disease Transmission through Bovine-Derived Bone Substitutes:
A Systematic Review
Yeoungsug Kim DDS1, Hessam Nowzari DDS; PhD2,*, Sandra K. Rich MPH,
PhD3
Article first published online: 15 DEC 2011
DOI: 10.1111/j.1708-8208.2011.00407.x
© 2011 Wiley Periodicals, Inc.
Issue
Clinical Implant Dentistry and Related Research
Clinical Implant Dentistry and Related Research
Volume 15, Issue 5, pages 645–653, October 2013
Additional Information(Hide All)
How to CiteAuthor InformationPublication History
How to Cite
Kim, Y., Nowzari, H. and Rich, S. K. (2013), Risk of Prion Disease
Transmission through Bovine-Derived Bone Substitutes: A Systematic Review.
Clinical Implant Dentistry and Related Research, 15: 645–653. doi:
10.1111/j.1708-8208.2011.00407.x
Author Information 1 Resident, Advanced Education in Periodontics Program,
Herman Ostrow School of Dentistry, University of Southern California, Los
Angeles, CA, USA
2 professor, Clinical Dentistry and director, Advanced Education in
Periodontics Program, Herman Ostrow School of Dentistry, University of Southern
California, Los Angeles, CA, USA
3 associate professor, Advanced Education in Periodontics Program, Herman
Ostrow School of Dentistry, University of Southern California, Los Angeles, CA,
USA
*Dr. Hessam Nowzari, Herman Ostrow School of Dentistry, University of
Southern California, Norris Dental Science Center-DEN, 925W. 34th Street, Room
119, Los Angeles, CA 90089-0641, USA; e-mail: nowzari@usc.edu
Publication History Issue published online: 7 OCT 2013 Article first
published online: 15 DEC 2011
Keywords:
anorganic bovine bone substitutes; BSE diagnostic test; BSE prion
inactivation; BSE prion infectivity; protein; PrP(27-30); PrPSc
ABSTRACT
Background: Despite the causal association between variant Creutzfeldt –
Jakob disease and bovine spongiform encephalopathy (BSE), bovine origin graft
materials are widely used during dental surgical procedures. The aim of this
study was to assess the risk of BSE transmission through anorganic bovine bone
substitutes.
Methods: Electronic database of MEDLINE was searched to identify relevant
studies regarding our focused questions, presence of BSE prion infectivity in
raw bovine bone, BSE prion inactivation by bone substitute manufacturing
process, protein contents in anorganic bovine bone substitutes, and validity of
current BSE diagnostic methods. Search terms yielded 1,704 titles. After
title/abstract screening and duplicates removal, 36 full-text articles were
screened for inclusion.
Results: A total of 16 studies were included in the final analysis. No
eligible studies were identified regarding the efficacy of BSE prion
inactivation by the treatments used for anorganic bovine bone manufacturing. BSE
infectivity and PrPSc, pathological prion, were detected in bovine bone marrow
and serum samples. Proteins were detected in Tutoplast® (bovine), Bio-Oss®, and
tibia samples treated at the similar condition for Bio-Oss deproteinization.
Inconsistent results of different BSE diagnostic tests were not unusual findings
(Iwata et al. 2006; Arnold et al. 2007; Murayama et al. 2010), and a study by
Balkema-Buschmann and colleagues showed an apparent discrepancy between BSE
infectivity and detection of PrP(27-30), the current surrogate marker for prion
disease infectivity.
Conclusion: This review indicates that bovine-derived graft biomaterials
may carry a risk of prion transmission to patients.
Saturday, November 2, 2013
*** Recommendation of the Swiss Expert Committee for Biosafety on the
classification of activities using prion genes and prion protein January 2013
Tuesday, October 29, 2013
Risk of Prion Disease Transmission through Bovine-Derived Bone Substitutes:
A Systematic Review
Sunday, September 08, 2013
*** Iatrogenic Creutzfeldt-Jakob disease via surgical instruments and
decontamination possibilities for the TSE prion
Sunday, February 10, 2013
Creutzfeldt-Jakob disease (CJD) biannual update (February 2013) Infection
report/CJD
Thursday, January 17, 2013
TSE guidance, surgical, dental, blood risk factors, Part 4 Infection
control of CJD, vCJD and other human prion diseases in healthcare and community
settings (updated January 2013)
4.19 All people who are “at increased risk” of CJD/vCJD are asked to help
prevent any further possible transmission to other patients by following this
advice: Don’t donate blood. No-one who is “at increased risk” of CJD/vCJD, or
who has received blood donated in the United Kingdom since 1980, should donate
blood; Don’t donate organs or tissues, including bone marrow, sperm, eggs or
breast milk; If you are going to have any medical, dental or surgical
procedures, tell whoever is treating you beforehand so they can make special
arrangements for the instruments used to treat you if you need certain types of
surgery or investigation; You are advised to tell your family about your
increased risk. Your family can tell the people who are treating you about your
increased risk of CJD/vCJD if you need medical or surgical procedures in the
future and you are unable to tell them yourself.
4.20 GPs are asked to record their patient’s CJD/vCJD risk status in their
primary care records. The GP should also include this information in any
referral letter should the patient require surgical, medical or dental
procedures.
Transmissible Spongiform Encephalopathy Agents: Safe Working and the
Prevention of Infection: Part 4
4.68 The risks of transmission of infection from dental instruments are
thought to be very low provided satisfactory standards of infection control and
decontamination are maintained. There is no reason why any patient with, or “at
increased risk” of, CJD or vCJD, should be refused routine dental treatment.
Such people can be treated in the same way as any member of the general public.
4.69 Information for dentists about the management of patients with, or “at
increased risk” of, CJD/vCJD can be found here. Advice for dentists on re-use of
endodontic instruments and vCJD can be found here. An advice note concerning
problems with dental care for individuals 'at-risk' of CJD for public health
purposes can be found here.
Transmissible Spongiform Encephalopathy Agents: Safe Working and the
Prevention of Infection: Part 4 Published: 2 June 2003 Amended: January 2013
4.70 Dental instruments used on patients with, or “at increased risk” of,
CJD or vCJD can be handled in the same way as those used in any other low risk
surgery, i.e. these instruments can be reprocessed according to best practice
and returned to use. Dentists are reminded that any instruments labelled by
manufacturers as ‘single-use’ should not be re-used under any circumstances.
4.71 Advice on the decontamination of dental instruments can be found in
the Department of Health guidance HTM01-05 ‘Dental decontamination’. This
guidance has been produced to reflect a reasonable and rational response to
emerging evidence around the effectiveness of decontamination in primary care
dental practices, and the possibility of prion transmission through protein
contamination of dental instruments. It is available here. After death
4.72 Guidance on dealing with the bodies of patients with, or “at increased
risk” of, CJD or vCJD, is contained in Annex H. This includes advice on carrying
out post mortem examinations and transportation of bodies, and advice for
undertakers on embalming, funerals and cremations.
Greetings again HPA et al,
I repeat, what I have said all along, all these human and animal TSE prion
strains must all be made reportable, and there should be no age restrictions
tied to any reporting criteria. TSE prion disease knows no borders, they know no
age groups.
Finally, the infamous UKBSEnvCJD only theory should be put to rest once and
for all.
For the scientific communities to continue to endorse such fallacious, and
misleading science as the UKBSEnvCJD only theory, this will only lead to other,
needless and countless exposures, and I can only guess as to how many in the
future will go clinical and die.
These needless and countless exposures and deaths, in the near future,
years, decades to come, from the Transmissible Spongiform Encephalopathy TSE
prion disease, the Prionpathy, the Prionopathies, the VPSPr’s, the sporadic CJD
and all it’s sub-types, the sporadic FFI’s and all it’s potential sub-types,
what about GSS, what about a case of sporadic Creutzfeldt-Jakob disease with a
Gerstmann-Sträussler-Scheinker phenotype but no alterations in the PRNP gene,
and don’t forget VPSPr. VPSPr, has introduced a novel and very different prion
strain to sporadic human prion diseases which may have similarities with those
associated with GSS.
none of this is possibly tied to iatrogenic TSE in humans and or a zoonosis
source, and or both?
TO continue to base iatrogenic TSE prion safety protocols and guidelines,
and continue to base this only on the UKBSEnvCJD theory, and all the rest a
spontaneous happenstance of bad luck, is NOT scientific in my opinion, and I and
the world will hold you all responsible for future needless exposure and deaths
by basing your scientific advice, on corporate and political science, bought and
paid for by the the livestock industry, and enforced by the OIE, USDA, CFIA,
DEFRA, et al. ...
Ladies and Gentlemen, source references at the bottom of these comments
with links, for anyone that is still interested in the rest of this nightmare.
...
thank you,
with kindest regards,
I am sincerely and respectfully,
Terry S. Singeltary Sr.
layperson
see full text ;
Tuesday, December 18, 2012
Bioassay Studies Support the Potential for Iatrogenic Transmission of
Variant Creutzfeldt Jakob Disease through Dental Procedures
Bioassay Studies Support the Potential for Iatrogenic Transmission of
Variant Creutzfeldt Jakob Disease through Dental Procedures
Elizabeth Kirby1#, Joanne Dickinson1#, Matthew Vassey1, Mike Dennis1, Mark
Cornwall1, Neil McLeod1, Andrew Smith2, Philip D. Marsh1,3, James T. Walker1, J.
Mark Sutton1*, Neil D. H. Raven1
1 Health Protection Agency - Porton Down, Salisbury, Wiltshire, United
Kingdom, 2 College of Medical, Veterinary & Life Sciences, Glasgow Dental
Hospital & School, University of Glasgow, Glasgow, United Kingdom, 3 Leeds
Dental Institute, Leeds, West Yorkshire, United Kingdom
Abstract
Background
Evidence is required to quantify the potential risks of transmission of
variant Creutzfeldt Jakob (vCJD) through dental procedures. Studies, using
animal models relevant to vCJD, were performed to address two questions.
Firstly, whether oral tissues could become infectious following dietary exposure
to BSE? Secondly, would a vCJD-contaminated dental instrument be able to
transmit disease to another patient?
Methods
BSE-301V was used as a clinically relevant model for vCJD. VM-mice were
challenged by injection of infected brain homogenate into the small intestine
(Q1) or by five minute contact between a deliberately-contaminated dental file
and the gingival margin (Q2). Ten tissues were collected from groups of
challenged mice at three or four weekly intervals, respectively. Each tissue was
pooled, homogenised and bioassayed in indicator mice.
Findings
Challenge via the small intestine gave a transmission rate of 100% (mean
incubation 157±17 days). Infectivity was found in both dental pulp and the
gingival margin within 3 weeks of challenge and was observed in all tissues
tested within the oral cavity before the appearance of clinical symptoms.
Following exposure to deliberately contaminated dental files, 97% of mice
developed clinical disease (mean incubation 234±33 days).
Interpretation
Infectivity was higher than expected, in a wider range of oral tissues,
than was allowed for in previous risk assessments. Disease was transmitted
following transient exposure of the gingiva to a contaminated dental file. These
observations provide evidence that dental procedures could be a route of
cross-infection for vCJD and support the enforcement of single-use for certain
dental instruments.
Citation: Kirby E, Dickinson J, Vassey M, Dennis M, Cornwall M, et al.
(2012) Bioassay Studies Support the Potential for Iatrogenic Transmission of
Variant Creutzfeldt Jakob Disease through Dental Procedures. PLoS ONE 7(11):
e49850. doi:10.1371/journal.pone.0049850
Editor: Noriyuki Nishida, Nagasaki University Graduate School of Biomedical
Sciences, Japan
Received: March 23, 2012; Accepted: October 15, 2012; Published: November
30, 2012
Copyright: © 2012 Kirby et al. This is an open-access article distributed
under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the
original author and source are credited.
Funding: The study was funded by the Department of Health (England),
contract number 007/0099. The funders had no role in study design, data
collection and analysis, decision to publish, or preparation of the
manuscript.
Competing interests: AS has received lecture fees and funding for a PhD
studentship from W&H Ltd, lecture fees from Steris Ltd and travel expenses
for attending a meeting from Schulke and Mayr. PM identified consultancy work
for Johnson and Johnson, UK and Unilever, UK. JMS identified consultancy work
for Advanced Sterilisation Products and funding for research involving TSO3,
CISA SpaA, BES Decon, BiotAK, and Genencor International. JMS also received
travel money to attend a meeting of the British Association for the Study of
Community Dentistry. This does not alter the authors' adherence to all the PLOS
ONE policies on sharing data and materials.
* E-mail: mark.sutton@hpa.org.uk
# These authors contributed equally to this work.
snip...
Implications for public health
Currently there is no evidence for vCJD transmission through either surgery
or dentistry. Transmission of vCJD by blood transfusion [5], [9] highlights that
any procedure contacting nervous or lymphoid tissue must also be considered a
risk given the wider tissue distribution of vCJD infectivity compared to
sporadic CJD [19]–[21]. The highly efficient transmission of BSE strain 301 V
infection through direct inoculation into the murine small intestine in this
study raises similar concerns for vCJD transmission through endoscopic
procedures in man.
The observations in the current study also provide theoretical grounds for
concern in respect to dental procedures. The levels of infectivity observed in
all oral tissues tested (most notably gingival margin with up to ~1000 ID per
mg) were higher than previously considered.
A further element of the study assessed residual protein contamination on a
range of dental instruments after routine cleaning and disinfection in general
dental practice in England [22]). The study showed a number of instrument types
and cleaning procedures where the upper interquartile range for residual protein
was in excess of 100 µg. This could equate to up to 100 ID per instrument in the
case of gingival tissue. Autoclaving has been shown to achieve only a 3-log
inactivation of various TSE agents [23] and an autoclave designed for the dental
market has been tested recently and shown to provide only a 100-fold reduction
in infectivity in the BSE301V/VM model used here (134°C, 18 minutes; Sutton et
al unpublished). A dental instrument soiled with infectious gingival tissue and
disinfected under this regimen would have an inadequate safety margin.
The gingival challenge was designed as a worse-case scenario in respect to
the infectious load on a dental instrument, but to be of limited invasiveness.
The procedure resulted in very high levels of transmission with short incubation
periods indicating that a much lower titre challenge material would also have
caused some transmission. Even if a relatively rare event, the large number of
dental interventions taking place in a younger age profile population (c.f.
surgical procedures) and a carrier population of unknown size means these risks
are not negligible. This would seem to be at odds with the absence of any
reported cases of clinical vCJD transmission linked to dental procedures. This
might be explained by a number of factors, including difficulties in linking
dental records to known vCJD patients [24], asymptomatic cases [5] and extended
incubation periods for patients exposed by blood transfusion (up to 7.8 years;
[25]). As a worse case study, the incubation periods described here would be
expected to be the most rapid giving rise to prion-disease symptoms in this
model, and as a novel low-dose, peripheral model of infection, the incubation
periods might be expected to be considerably longer than those observed for
blood transfusion cases. Given the difficulties in linking dental procedure case
histories to vCJD, such cases may not yet be evident.
see full text and more ;
Tuesday, December 18, 2012
Bioassay Studies Support the Potential for Iatrogenic Transmission of
Variant Creutzfeldt Jakob Disease through Dental Procedures
Friday, August 10, 2012
Incidents of Potential iatrogenic Creutzfeldt-Jakob disease (CJD) biannual
update (July 2012)
Thursday, April 12, 2012
Health professions and risk of sporadic Creutzfeldt–Jakob disease, 1965 to
2010
Eurosurveillance, Volume 17, Issue 15, 12 April 2012
Research articles
Thursday, December 22, 2011
Risk of Prion Disease Transmission through Bovine-Derived Bone Substitutes:
A Systematic Review Clin Implant Dent Relat Res. 2011 Dec 15. doi:
10.1111/j.1708-8208.2011.00407.x. [Epub ahead of print]
Sunday, October 23, 2011
The oral secretion of infectious scrapie prions occurs in pre-clinical
sheep with a range of PRNP genotypes
JVI Accepts, published online ahead of print on 19 October 2011
Monday, May 16, 2011
Does Poor Dental Health Have a Role in the Emergence of Variant Creutzfeldt
Jakob Disease in the United Kingdom?
Thursday, October 23, 2008
ONE HUNDRED AND FIRST MEETING OF THE SPONGIFORM ENCEPHALOPATHY ADVISORY
COMMITTEE
MASTER DENTISTS FALLS VICTIM TO CJD
Subject: MASTER DENTIST FALLS VICTIM TO CJD
From: "Terry S. Singeltary Sr." <[log in to unmask]>
Reply-To: Sustainable Agriculture Network Discussion Group <[log in to
unmask]>
Date: Sat, 31 Mar 2007 15:51:24 –0600
Conclusions
11. A preliminary risk assessment produced by DH suggests that vCJD
transmission via endodontic dentistry may, under certain hypothetical but
plausible scenarios, be sufficient to sustain a secondary vCJD epidemic.
However, there are uncertainties around the data and assumptions underpinning
the assessment. Research underway will address some of these uncertainties and
allow the risk assessment to be refined. Once the research is complete and / or
other data become available, the risks should be reassessed. A watching brief
should be maintained.
12. It is unclear whether or not vCJD infectivity can be transmitted via
endodontic files and reamers. However, given the plausibility of such a scenario
and the large number of procedures undertaken annually, it would be prudent to
consider restricting these instruments to single use as a precautionary measure.
Since sufficiently rigorous decontamination of these instruments is difficult,
single use of these instruments would eliminate this risk, should it exist.
SEAC May 2006
Page updated: 8th May 2006
Dental treatment and risk of variant CJD – a case control study
D. Everington,1 A. J. Smith,2 H. J. T. Ward,3 S. Letters,4 R. G. Will5 and
J. Bagg6
Objective Knowledge of risk factors for variant CJD (vCJD) remains
limited, but transmission of prion proteins via re-useable medical
devices,
including dental instruments, or enhanced susceptibility following
trauma
to the oral cavity is a concern. This study aimed to identify whether
previous dental treatment is a risk factor for development of vCJD.
Design Case control study.
Methods Risk factor questionnaires completed by interview with
relatives of 130 vCJD patients and with relatives of 66 community and
53 hospital controls were examined by a dental surgeon. Responses
regarding dental treatments were analysed.
Results We did not find a statistically signifi cant excess of risk of
vCJD
associated with dental treatments with the exception of extractions
in
an unmatched analysis of vCJD cases with community controls
(p = 0.02). However, this result may be explained by multiple
testing.
Conclusions This is the first published study to date to examine
potential links between vCJD and dental treatment. There was no
convincing evidence found of an increased risk of variant CJD
associated with reported dental treatment. However, the power of the
study is restricted by the number of vCJD cases to date and does not
preclude the possibility that some cases have resulted from secondary
transmission via dental procedures. Due to the limitations of the
data
available, more detailed analyses of dental records are required to
fully
exclude the possibility of transmission via dental treatment.
snip...
DISCUSSION
Many studies have searched for risk factors for the development
of different types of CJD, such as diet, exposure to
animals, surgical treatment, including dentistry, and occupational
exposures. A retrospective case control study15 of 60
definite cases of sporadic CJD, occurring in Japan between
1975 and 1977 found no association with extractions of maxillary
or mandibular teeth. An analysis of 26 sporadic CJD
cases and 40 matched controls from the United States16 failed
to discover a significant odds ratio for endodontic surgery,
though these workers did note statistically significant odds
ratios for intraocular pressure testing, injury to or surgery on
the head, face or neck and trauma to other parts of the body.
However, these findings suffer from low statistical power and,
in the case of the Japanese paper, information was requested
for extractions only during the fi ve year period prior to onset.
This paper attempts to identify an association between vCJD
and reported dental treatment.
Comparison of the reported dental histories of cases and
controls found that extractions were the only dental risk factor
that reached statistical significance (at the 5% level) in the
unmatched analysis with community controls. This may be a
result of multiple testing especially as there are fewer extractions
in the cases than in the hospital controls. It is likely that
the majority of vCJD cases in this cohort were infected through
eating BSE contaminated meat products. Therefore, it is diffi -
cult to detect a small subgroup that may have been infected by
secondary transmission, as in this study, through dentistry.
There are a number of limitations to this study, most importantly
relying on reported data from relatives and the relatively
small numbers of cases and controls resulting in low
power to detect statistical differences. Recruitment of controls
has been problematic,17 although every effort was made to
maximise this group. Selection of controls was not matched for
demographic and socio-economic factors for dental attendance
and this may have resulted in bias. It is possible that some of
the responses of ‘no known treatment’ reflect poor knowledge
or recall on the part of the relatives. This would reduce the
power of the study to pick up significant differences between
groups, but not necessarily introduce bias.
Whilst these preliminary data on a topic of great concern
for public health do not provide evidence supporting reported
dental work as being a major route of transmission of the BSE
agent to humans to date, they do not preclude the possibility
that some vCJD cases have been infected by this route.
Furthermore, the incubation period following infection by
a peripheral route may be relatively long and therefore the
period of observation to date of potential secondary transmission
of vCJD may be too short to detect cases.
A more detailed study of previous treatment based on reviewing
actual dental records rather than relying on reported treatments
is required to gain a wider insight into the dental history
of both cases and controls. We are currently investigating the
possibility of examining dental records of vCJD cases and a
larger group of unmatched controls.18
The National CJD Surveillance Unit is funded by the Department of
Health
and the Scottish Executive Department of Health. The sponsors of the
study
had no role in study design, data collection, data analysis, data
interpretation,
or in the writing of the report. We are also grateful to the families
of
cases, without whose co-operation this study would not have been possible.
FULL TEXT ;
SNIP...
Subject: CJD: update for dental staff Date: November 12, 2006 at 3:25 pm
PST
1: Dent Update. 2006 Oct;33(8):454-6, 458-60.
CJD: update for dental staff.
Scully C, Smith AJ, Bagg J. Eastman Dental Institute, University of
London.
It is almost a decade since the recognition of the emergence of a new
infectious disease termed variant Creutzfeldt-Jakob disease (vCJD) caused by
prions (PrPTSE), abnormal variants of a normal human cell surface protein
(PrP).This disease has a number of similarities to other forms of CJD--lethal
disorders characterized by a prolonged incubation period, and progressive mental
deterioration. In relation to oral tissues, PrPTSE have been found in neural,
gingival, pulpal, lingual, lymphoreticular and salivary gland tissue in animal
models. In both sporadic and variant CJD, PrPTSE is detectable in the trigeminal
ganglion and, in vCJD, in lymphoreticular tissues, but infectivity has not been
tested in other human oral tissues. CLINICAL RELEVANCE: PrPTSE is much more
resistant to the common methods of inactivation than conventional pathogens, and
it adheres avidly to steel whilst retaining its infectivity. Particular
attention must be paid to cleaning and sterilizing re-usable dental instruments.
Single-use devices, such as endodontic files and matrix bands, must never be
re-used. Advice on the reprocessing of dental instruments used on known CJD
patients must be obtained from local infection control teams. Research into
effective methods of prion inactivation appears promising, although further work
on the applicability to general dental practice is required.
PMID: 17087448 [PubMed - in process]
SNIP...
18 January 2007 - Draft minutes of the SEAC 95 meeting (426 KB) held on 7
December 2006 are now available.
snip...
64. A member noted that at the recent Neuroprion meeting, a study was
presented showing that in transgenic mice BSE passaged in sheep may be more
virulent and infectious to a wider range of species than bovine derived
BSE.
Other work presented suggested that BSE and bovine amyloidotic spongiform
encephalopathy (BASE) MAY BE RELATED. A mutation had been identified in the
prion protein gene in an AMERICAN BASE CASE THAT WAS SIMILAR IN NATURE TO A
MUTATION FOUND IN CASES OF SPORADIC CJD.
snip...
SNIP...
SECTION 7: THE RISK TO PATIENTS UNDERGOING DENTAL
TREATMENT
It is of great concern that there may be a risk of becoming infected with
nv-CJD in the dental
surgery due to cross infection from either the dentist or another patient.
The two main sources of
infectious material in the dental surgery are blood and saliva. As shown in
Table 7 these are of
relatively low infectivity compared to the tissues of the CNS.
As nv-CJD has only recently been discovered, few experiments have been
carried out to discover
whether it can be transmitted. Therefore, we must look at the other TSEs to
get an indication of
likely risk.
The risk of transmission via saliva
Studies to ascertain levels of PrP have shown that salivary gland tissue
contains high levels of
infectivity, much earlier than in brain tissue (Sakaguchi 1993, Eklund
1967). Replication of the
infectious agent first appears in salivary tissue soon after inoculation,
possibly indicating that the
salivary glands are one of the primary sites of replication, rather than
the brain. It was also found
that infectivity declines with time, suggesting that greatest risk from
transmission is likely to be
early in the disease, before clinical signs are present.
There has been no research into the risk of transmission from saliva,
however we must assume
that if salivary gland is infected then so is the saliva it produces.
The effect of gingival scarification on transmission
If it is found that BSE has been transmitted to humans via the oral route
it is essential to ascertain
any factors that may have increased susceptibility and therefore may have
implications for
human to human transmission. Studies into the effect of gingival
scarification on the
transmission of Scrapie (Carp 1982) have shown that a higher proportion of
mice succumbed to
infection if their gingivae had been scarified compared to the controls
(100% and 71%
respectively). It was also shown that the incubation period was
significantly shorter.
Although it has not been possible to transmit Scrapie using dental burs
(Adams 1978) it was
found that the gingivae of infected mice do contain a low level of Scrapie
infection that can be
transmitted using an intra-cerebral approach.
The risk of transmission via blood products
Although most forms of CJD have been considered infectious by the mid-1960s
its
transmissibility through the use of blood products is still
controversial.
Sporadic CJD has been reported to be transmitted to mice by injecting blood
from human
patients directly into mouse brain (Brown, 1994, Manuelidis, 1985). However
this evidence has
not been reproduced and another review of research with non-human primates
indicated that
sporadic CJD-infected human blood did not transmit the disease to primates
(Tateishi, 1985).
Some evidence indicates that blood of experimentally infected animals
contains an infective
agent. PrP infectivity resides predominately or exclusively in lymphocytes
and monocytes rather
than granulocytes (Lavelle, 1972). There has been no evidence of
infectivity in erythrocytes,
platelets or plasma, but low infectivity cannot be excluded. Animal studies
have demonstrated
that the scrapie-agent replicates first in the spleen and other lymphoid
tissues but reaches the
highest concentration in the brain, where it results in the clinical
appearance of the disease
(Kurudail 1983). Hence, peripheral tissues in contact with blood also
harbour PrP infectivity.
Animal transmission data indicate that human spleen, lymph nodes, serum and
cord blood are
irregularly infective for animals, although few cord blood samples have
been tested (Manuelidis,
1979). Studies of experimental sporadic CJD in guinea pigs and mice have
shown that the
infectious agent is present in the brain, viscera and blood before clinical
disease develops
(Lavelle, 1972 & Czub 1986).
Several factors must be considered in reviewing the animal evidence
regarding transmission of
human TSEs in blood: the type of human TSE being tested, the level of PrP
infectivity of the
study tissue, the species barrier, and the route of transmission.
The evidence from animal studies is inconclusive regarding transmission of
sporadic CJD
between humans by transfusion.
Although case reports have provided evidence linking CJD to the receipt of
dura mater and
human growth hormone, no human cases have yet been causatively linked to
blood transfusion.
A number of cases have been seen where patients have undergone organ
transplant and then
developed CJD. It is, however, impossible to determine whether the organ
was the source of the
infection as insufficient information about each case is available.
If CJD is transmissible in blood, cases should occur in young patients,
particularly if the
incubation period is short as in the other iatrogenic cases. Even if the
incubation period were
many years, one would expect to see cases in young persons because of the
transfusions given to
infants and young children. If CJD is transmitted in blood, a detectable
increase in cases in blood
transfusion patients may be expected. There is a ban on the use and export
of blood and blood
products from the UK (February 1998) as a precautionary measure and for the
past two years any
donor with a family history of CJD has been prevented from donating blood.
However this may
be unreliable, as many patients will not know the accurate diagnoses of a
family member's
illness.
As noted by Brown (1996) in reference to blood products, "iatrogenic
disease from this source
would dwarf in importance all other sources by virtue of the sheer numbers
of people who
theoretically have been or could be at risk". The appearance of nvCJD
raises new concerns. Due
to a possible oral route of infection and a novel strain of agent, the
distribution of tissue
infectivity may differ from other forms of CJD. This is supported by
evidence that suggested that
at the palatine tonsil might harbour PrP in nvCJD but not in sporadic
CJD.
In view of the theoretical possibility that blood from patients incubating
a TSE may harbour the
infective TSE agent the World Health Organisation recommends that the
following groups
should be excluded as blood donors:
· Recipients of extracts derived from human pituitary glands (growth
hormone and
gonadotropin).
· Those with a family history of CJD, GSS or FFI.
· Those who have received a human dura mater graft.
Animal studies indicate that the infective agent of human TSEs is present
in blood in low titres,
and sufficient evidence of animal transmission suggests that the disease
has the potential to be
transmitted through blood (Heye 1994). However, to date, epidemiological
evidence indicates
that if blood transmission occurs it is likely to be rare. This may be due
to polymorphism at
codon 129, which could restrict susceptibility. It is also possible that
most transfusions may not
contain sufficient dose to cause infection.
There is no specific scientific evidence to date that nv-CJD will transmit
through blood products.
This is due to the incubation period being many months in laboratory
animals. As infectivity has
only been detected in white blood cells the potential risk from donated
blood can be decreased by
a process known as leuko-depletion, removal white blood cells.
The knowledge that blood may be infected could change the views of both the
medical
profession and patients. Transfusions may only be used if absolutely
necessary and patients may
be given the option of donating their own blood for scheduled
operations.
If CJD were transmitted in pooled blood products or saliva, clusters would
be detected. Most
clusters have usually been attributed to familial disease (Masters, 1979
& Reingold 1996).
Surveillance systems have found cases of CJD among persons who have
received blood
transfusions but none have been linked to blood transmission.
It must be remembered, however, that surveillance systems may not detect
cases when unique
epidemiological or clinical features are present.
SECTION 8: CONCLUSIONS
A number of factors must be taken into consideration when assessing the
risk of transmission of
nvCJD during dental treatment. Dental patients are at risk of infection
from a number of sources,
the most significant being the consumption of infected animal products
during the 1980s. A
small minority of patients will also be at increased risk in their place of
work, such as
neuropathologists, neurosurgeons and laboratory technicians.
The most likely route of infection is via ineffectively sterilised
instruments. If a patient is
suspected of having or has been diagnosed with nv-CJD further precautions
can be taken. The
patient is likely to be showing clinical signs, which are likely to make
dental treatment difficult,
therefore only emergency treatment is going to be appropriate. Where
possible, a treatment
option that involves the least cross infection risk should be undertaken. .
To reduce this risk, all
instruments that have been used on a patient with nvCJD should be
disposable or discarded. This
includes oral surgery equipment, root planing hand instruments and
ultrasonic tips in addition to
needles and blades. In the case of accidental inoculation it is unlikely
that sufficient infective
material will be involved to transmit the disease. As discussed previously,
the peripheral route of
infection is ineffective compared with intracerebral inoculation, and blood
or saliva contains
little infectivity compared to central nervous tissue. All patients should
be treated using universal
precautions, which should be employed in all dental practices as a matter
of routine, providing
the maximum protection equally to clinical staff and patients. This
includes the use of gloves,
masks and eye protection at all times. After each patient all instruments
should be autoclaved and
disposable alternatives should be used where appropriate.
The number of patients likely to be incubating nv-CJD is impossible to
predict at present. Much
depends on the average incubation time, the longer the time, the higher the
figure is likely to be.
At present the average incubation time can not be calculated nor is it
possible to estimate the
dose required to infect a human. With the possibility of a nationwide
epidemic investigation
must be carried out to determine the risk from cross infection. Research
has yet to prove that
there is a risk, however, until all possibility of this can be discounted
caution must prevail.
The resistance of the TSE agent to standard medical sterilisation
procedures is noteworthy.
Experimental evidence demonstrates that the agent shows resistance to the
following: exposure
to boiling, freezing, ethanol, H2O2, permanganate, iodine, ethylene oxide
vapour, detergents,
organic solvents, formaldehyde, UV and gamma irradiation, and standard
autoclaving.
Since conventional methods of sterilisation and disinfection do not
decontaminate the CJD
infectious agent, specific measures must be used, however, many of these
are impractical in the
dental practice.
Although the TSE agent is known to be infectious it is not contagious in
the usual sense.
Individuals exposed to patients with CJD: their spouses, nurses and
doctors, do not appear to
have an increased risk of developing the disease. Furthermore,
professionals who might be
considered 'high risk' in relation to exposure to TSE agents: e.g.
pathologists, neurosurgeons,
butchers etc. also do not appear to be at an increased risk of developing
CJD. No proven instance
of CJD contracted occupationally has yet been identified. However, over 170
cases of iatrogenic
CJD contracted through inoculation of contaminated CNS tissue or corneal
transplantation serve
to remind those of us involved in the management of all CJD patients of the
importance of safety
procedures in relation to the TSE agents.
REFERENCES
snip...
snip...
SOURCE
Subject: MASTER DENTIST FALLS VICTIM TO CJD
From: "Terry S. Singeltary Sr."
Reply-To: Bovine Spongiform Encephalopathy
Date: Sat, 31 Mar 2007 15:51:24 -0600
Content-Type: text/plain
Parts/Attachments: Parts/Attachments text/plain (1440 lines)
Subject: CJD: update for dental staff
Date: November 12, 2006 at 3:25 pm PST
1: Dent Update. 2006 Oct;33(8):454-6, 458-60.
CJD: update for dental staff.
Subject:
CJD: update for dental staff
Date: November 12, 2006 at 3:25 pm PST
1: Dent Update. 2006 Oct;33(8):454-6, 458-60.
CJD: update for dental staff.
Scully C, Smith AJ, Bagg J. Eastman Dental Institute, University of
London.
It is almost a decade since the recognition of the emergence of a new
infectious disease termed variant Creutzfeldt-Jakob disease (vCJD) caused by
prions (PrPTSE), abnormal variants of a normal human cell surface protein
(PrP).This disease has a number of similarities to other forms of CJD--lethal
disorders characterized by a prolonged incubation period, and progressive mental
deterioration. In relation to oral tissues, PrPTSE have been found in neural,
gingival, pulpal, lingual, lymphoreticular and salivary gland tissue in animal
models. In both sporadic and variant CJD, PrPTSE is detectable in the trigeminal
ganglion and, in vCJD, in lymphoreticular tissues, but infectivity has not been
tested in other human oral tissues. CLINICAL RELEVANCE: PrPTSE is much more
resistant to the common methods of inactivation than conventional pathogens, and
it adheres avidly to steel whilst retaining its infectivity. Particular
attention must be paid to cleaning and sterilizing re-usable dental instruments.
Single-use devices, such as endodontic files and matrix bands, must never be
re-used. Advice on the reprocessing of dental instruments used on known CJD
patients must be obtained from local infection control teams. Research into
effective methods of prion inactivation appears promising, although further work
on the applicability to general dental practice is required.
PMID: 17087448 [PubMed - in process]
Subject: PrPSc in salivary glands of scrapie-affected sheep
Date: February 15, 2007 at 9:33 am PST
J. Virol. doi:10.1128/JVI.02148-06 Copyright (c) 2007, American Society for
Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
PrPSc in salivary glands of scrapie-affected sheep
Marta Vascellari*, Romolo Nonno, Franco Mutinelli, Michela Bigolaro,
Michele Angelo Di Bari, Erica Melchiotti, Stefano Marcon, Claudia D'Agostino,
Gabriele Vaccari, Michela Conte, Luigi De Grossi, Francesca Rosone, Francesco
Giordani, and Umberto Agrimi Istituto Zooprofilattico Sperimentale delle
Venezie, Histopathology Department, Viale dell'Università 10, 35020 Legnaro
(PD), Italy; Istituto Superiore di Sanità , Department of Food Safety and Animal
Health, Viale Regina Elena 299, 00161 Roma, Italy; Istituto Zooprofilattico
Sperimentale delle Regioni Lazio e Toscana, Strada Terme, 01100 Viterbo,
Italy
* To whom correspondence should be addressed. Email:
mvascellari@izsvenezie.it .
Abstract
The salivary glands of scrapie-affected sheep and healthy controls were
investigated for the presence of the pathological prion protein (PrPSc). PrPSc
was detected in major (parotid and mandibular) and minor (buccal, labial and
palatine) salivary glands of naturally and experimentally infected sheep. By
western blot, PrPSc concentration in glands was estimated as 0.02-0.005% of
brain. Immunohistochemistry revealed intracellular deposition of PrPSc in ductal
and acinar epithelium and occasional labeling into the lumen of salivary ducts.
The presence of PrPSc in salivary glands highlights the possible role of saliva
in the horizontal transmission of scrapie.
SEAC 99th meeting on Friday 14th December 2007
snip...
© SEAC 2007
New research
4. Preliminary, unpublished results of research from the Health Protection
Agency, aimed at addressing some of the uncertainties in the risk assessments,
were reviewed by SEAC (SEAC 97, May 2007). The prion agent used in these studies
is closely related to the vCJD agent. This research, using a mouse model, shows
that following inoculation of mouse-adapted bovine spongiform encephalopathy
(BSE) directly into the gut, infectivity subsequently becomes widespread in
tissues of the oral cavity, including dental pulp, salivary glands and gingiva,
during the preclinical as well as clinical stage of disease.
5. It is not known how closely the level and distribution of infectivity in
the oral cavity of infected mice reflects those of humans infected with vCJD, as
there are no comparable data from oral tissues, in particular dental pulp and
gingiva, from human subclinical or clinical vCJD cases. Although no abnormal
prion protein was found in a study of human dental tissues, including dental
pulp, salivary glands and gingiva from vCJD cases22, the relationship between
levels of infectivity and abnormal prion protein is unclear23. Infectivity
studies underway using the mouse model and oral tissues that are presently
available from human vCJD cases will provide some comparable data. On the basis
of what is currently known, there is no reason to suppose that the mouse is not
a good model for humans in respect to the distribution of infectivity in oral
tissues. Furthermore, the new data are consistent with published results from
experiments using a hamster scrapie model24.
6. A second set of experiments using the same mouse model showed that
non-invasive and transient contact between gingival tissue and fine dental files
contaminated with mouse-adapted BSE brain homogenate transmits infection very
efficiently. It is not known how efficient gingival transmission would be if
dental files were contaminated with infectious oral tissues and then
subsequently cleaned and sterilised, a situation which would more closely model
human dental practice. Further studies using the mouse model that would be more
representative of the human situation, comparing oral tissues with a range of
doses of infectivity, cleaned and sterilised files and the kind of tissue
contact with instruments that occurs during dentistry, should be considered.
7. SEAC considered that the experiments appear well designed and the
conclusions justified and reliable, while recognising that the research is
incomplete and confirmatory experiments have yet to be completed. It is
recommended that the research be completed, submitted for peer-review and widely
disseminated as soon as possible so others can consider the implications.
Nevertheless, these preliminary data increase the possibility that some oral
tissues of humans infected with vCJD may potentially become infective during the
preclinical stage of the disease. In addition, they increase the possibility
that infection could potentially be transmitted not only via accidental abrasion
of the lingual tonsil or endodontic procedures but a variety of routine dental
procedures.
20 Department of Health (2006) Dentistry and vCJD: the implications of a
carrier-state for a self-sustaining epidemic. Unpublished. 21 SEAC (2006)
Position statement on vCJD and endodontic dentistry.
22 Head et al. (2003) Investigation of PrPres in dental tissues in variant
CJD. Br. Dent. J. 195, 339-343. 23 SEAC 90 reserved business minutes.
Implications for transmission risks
snip...PLEASE SEE DISTURBING FINDINGS FULL TEXT HERE ;
A RE-ASSESSMENT OF THE POTENTIAL RISK OF VCJD TRANSMISSION VIA DENTISTRY
ISSUE
1. The Department of Health (DH) has asked SEAC to consider an interim
assessment of the potential risk of vCJD transmission via dental procedures.
This work builds on previous risk assessments on possible dental transmission
considered by SEAC.
BACKGROUND
Previous SEAC considerations of vCJD transmission via dentistry
snip...
The New DH Risk Assessment
8. The research on infectivity just noted forms one strand of a wider
programme at the HPA, which is also intended to quantify protein residues found
on dental instruments and the effectiveness of sterilisation in reducing
infectivity. Following SEAC 97 (May 2007), DH commissioned a comprehensive
re-assessment of the potential risks of vCJD transmission associated with
dentistry to take account of research at the HPA and elsewhere. The assessment
aims to clarify the range of plausible scenarios for vCJD transmission via
dental instruments that could occur, given what is currently known, and to
identify the most important factors affecting this risk. The assessment will be
used to identify the most important areas of further work to address the
uncertainties and any robust ways of cost effectively reducing risks
further.
9. This new interim risk assessment has been produced by DH analysts (annex
3) in collaboration with a Scientific Reference Group of independent experts
(Chaired by Professor Graham Medley). Members of the Group have expertise in
dentistry, instrument decontamination, human and animal prion diseases, anatomy,
public health, risk assessment modelling and epidemiology. This group met three
times to review and refine the modelling framework and agree the risk
assessment. The group provided advice on the inputs and assumptions incorporated
into the risk assessment, particularly where expert judgement was required due
to a lack of hard data. Under circumstances where key data are absent,
precautionary assumptions were agreed. As a number of large uncertainties that
strongly influence the quantification of risk remain, the risk assessment is
considered as interim and will be updated in the future when new scientific
evidence becomes available.
10. The assessment examines the risk that vCJD may be transmitted via
dental procedures by establishing plausible ranges for key parameters, including
(see sections 2 and 3 of the risk assessment):
• the vCJD infectivity of tissues of the oral cavity of infected
patients
• the deposition of that material onto different types of dental
instruments and the effectiveness of standard cleaning and sterilisation
processes used in dental practice
• the mechanisms and efficiency of transfer of vCJD infectivity from
contaminated instruments used on subsequent patients
• the probability of transmission based on assessments of the number and
types of dental procedure conducted and the number of people who might be
carrying an asymptomatic vCJD infection.
Findings 11.
As there is lack of substantial data with which to accurately quantify many
of these parameters, plausible ranges for these parameters have been established
to take account of the often large uncertainties in the data. The large
uncertainties in many of these parameters strongly influence the quantification
of the risk.
12. Plausible scenarios built up using ranges for each of these factors
include many in which dental transmission would have no detectable effect on the
course of the vCJD outbreak (see section 4 of the risk assessment). However,
there are some which include a combination of pessimistic assumptions as regards
the infectivity of dental / oral tissues and the effects of instrument
decontamination which suggest that:
• there could be some hundreds of vCJD transmissions per annum via
dentistry - albeit against a background of several thousand existing vCJD
infections (not clinical cases of vCJD), or where
• dental transmission could generate a self-sustaining reservoir of vCJD
infection within the population.
13. The distinction between vCJD infections and clinical cases of vCJD is
important. If a large proportion of secondary transmissions result in
subclinical infections (either never developing into clinical disease or doing
so over an extended time-scale) and those infected are infectious, the
likelihood of a self-sustaining epidemic increases. The proportion of
individuals who might enter such a subclinical “carrier state” is unknown. Key
Assumptions and areas of uncertainty
14. Work on the risk assessment is on-going and new data should enable some
of the inputs and assumptions underpinning these scenarios to be revised. Key
areas of uncertainty are:
• Infectivity in relevant tissues. Of all the unknowns, that of overriding
importance is whether dental/oral tissues in patients incubating vCJD would be
infective, and if so at what level.
There are as yet no results of studies using human gingival and dental pulp
tissues, and these studies may extend into 2009 and 2010 respectively. This is
examined in section 2.3 of the risk assessment.
• Protein Residues on dental instruments. This is examined in section 2.2
of the risk assessment.
• Efficacy of Autoclaving. This is examined in section 2.3 of the risk
assessment.
• Current prevalence of vCJD infection. This is examined in section 3.3 of
the risk assessment.
• Epidemiology of vCJD. This is examined in section 4 of the risk
assessment.
15. Suggested areas of further work to reduce the uncertainty in these key
areas are described in section 5 of the risk assessment together with a
preliminary analysis of possible interventions and risk reduction
measures.
ADVICE SOUGHT FROM THE COMMITTEE
snip...
POSITION STATEMENT vCJD AND ENDODONTIC DENTISTRY
snip...
Endodontic instruments
5. Evidence suggests that the files and reamers used in endodontic
procedures are reused and are difficult to reliably decontaminate4. Appreciable
quantities of residual material remain adherent to the surface after normal
cleaning and sterilisation5. Thus, there is potential for transfer of dental
pulp between patients undergoing endodontic procedures.
vCJD infectivity in dental tissues
6. There are no data on vCJD infectivity in dental pulp. Although no
abnormal prions were found in a study of dental tissues, including dental pulp,
from vCJD cases6, dental pulp includes blood and peripheral nerve tissue known
to carry vCJD infectivity7,8. In addition, appreciable infectivity has been
found in the dental pulp of hamsters with hamster scrapie9. Although it is
possible that the peripheral nerve may only become infective close to, or after,
the onset of clinical vCJD, inflammation may promote the propagation of
prions10. Thus, although the data are limited and indirect, it is reasonable to
assume that the dental pulp of individuals subclinically-infected with vCJD may
be infectious although the level of infectivity is unknown. Studies underway
will provide direct data on the infectivity in dental tissues from vCJD cases.
level of infectivity is unknown.
4 Letters et al. (2005) A study of visual and blood contamination on
reprocessed endodontic files from general dental practice. Br. Dent. J. 199,
522-525. 5 Smith et al. (2005) Residual protein levels on reprocessed dental
instruments. J. Hosp. Infect. 61, 237-241. 6 Head et al. (2003) Investigation of
PrPres in dental tissues in variant CJD. Br. Dent. J. 195, 339-343. 7 SEAC 91
minutes paragraph 9.
www.seac.gov.uk/papers/papers.htm 8
Department of Health (2005) Assessing the risk of vCJD transmission via
surgery: an interim view. Unpublished. 9 Ingrosso et al. (1999) Transmission of
the 263K scrapie strain by the dental route. J. Gen. Virol. 80, 3043-3047. 10
Heikenwalder et al. (2005) Chronic lymphocytic inflammation specifies the organ
tropism of prions. Science. 307, 1107-1110.
Subclinical carrier state
7. A study of humanised mice showed that vCJD infections may not always
progress to clinical disease within the normal lifespan of the animals11.
Another study suggested that prion infections in mice that remain at a
subclinical level can be transmitted to other mice, resulting in clinical
disease12. Thus, there is evidence to suggest that individuals infected with the
BSE / vCJD agent may remain in a subclinical infection carrier state instead of
developing vCJD. A discrepancy between prevalence estimates based on a survey of
abnormal prion protein in appendix and tonsil tissue and data on vCJD cases
supports this hypothesis13. As no diagnostic test exists to identify such
individuals, they could over the course of their lives be potential sources of
numerous secondary infections arising from invasive medical or dental
procedures.
8. The prevalence of subclinical infection in the UK population is
uncertain. A recent estimate suggests the number of subclinical carriers may be
of the order of several thousand14. SEAC has strongly recommended that further
studies to ascertain better the prevalence of vCJD infection be urgently
considered15.
Transmission risks
9. The new DH analysis suggests that, on the basis that residual dental
pulp on endodontic files and reamers is transferred relatively efficiently to
patients on reuse, dental pulp is as infective as peripheral nerve tissue and a
subclinical carrier population for vCJD exists, a self-sustaining vCJD epidemic
arising from endodontic surgery is plausible. There are uncertainties about the
efficiency of vCJD transmission via endodontic procedures, the vCJD infectivity
of dental pulp and the existence of a subclinical infection carrier state.
However, even if a self-sustaining epidemic were not possible, clusters of vCJD
infections could arise from the use of instruments contaminated with the vCJD
agent from endodontic procedures on infected patients. Interactions between this
and other routes of secondary transmission, such as blood transfusion and
hospital surgery, would make a self-sustaining epidemic more likely.
Potential risk reduction measures
10. Endodontic files and reamers have a limited lifespan, restricting the
number of possible secondary transmissions. Improving the effectiveness of
procedures used to decontaminate dental instruments would reduce the risk of
transmission. Restricting endodontic files and reamers to single use would
prevent potential secondary transmission via these instruments.
Conclusions
11. A preliminary risk assessment produced by DH suggests that vCJD
transmission via endodontic dentistry may, under certain hypothetical but
plausible scenarios, be sufficient to sustain a secondary vCJD epidemic.
However, there are uncertainties around the data and assumptions underpinning
the assessment. Research underway will address some of these uncertainties and
allow the risk assessment to be refined. Once the research is complete and / or
other data become available, the risks should be reassessed. A watching brief
should be maintained.
12. It is unclear whether or not vCJD infectivity can be transmitted via
endodontic files and reamers. However, given the plausibility of such a scenario
and the large number of procedures undertaken annually, it would be prudent to
consider restricting these instruments to single use as a precautionary measure.
Since sufficiently rigorous decontamination of these instruments is difficult,
single use of these instruments would eliminate this risk, should it
exist.
SEAC May 2006
===================================
© SEAC 2007
New research
4. Preliminary, unpublished results of research from the Health Protection
Agency, aimed at addressing some of the uncertainties in the risk assessments,
were reviewed by SEAC (SEAC 97, May 2007). The prion agent used in these studies
is closely related to the vCJD agent. This research, using a mouse model, shows
that following inoculation of mouse-adapted bovine spongiform encephalopathy
(BSE) directly into the gut, infectivity subsequently becomes widespread in
tissues of the oral cavity, including dental pulp, salivary glands and gingiva,
during the preclinical as well as clinical stage of disease.
5. It is not known how closely the level and distribution of infectivity in
the oral cavity of infected mice reflects those of humans infected with vCJD, as
there are no comparable data from oral tissues, in particular dental pulp and
gingiva, from human subclinical or clinical vCJD cases. Although no abnormal
prion protein was found in a study of human dental tissues, including dental
pulp, salivary glands and gingiva from vCJD cases22, the relationship between
levels of infectivity and abnormal prion protein is unclear23. Infectivity
studies underway using the mouse model and oral tissues that are presently
available from human vCJD cases will provide some comparable data. On the basis
of what is currently known, there is no reason to suppose that the mouse is not
a good model for humans in respect to the distribution of infectivity in oral
tissues. Furthermore, the new data are consistent with published results from
experiments using a hamster scrapie model24.
6. A second set of experiments using the same mouse model showed that
non-invasive and transient contact between gingival tissue and fine dental files
contaminated with mouse-adapted BSE brain homogenate transmits infection very
efficiently. It is not known how efficient gingival transmission would be if
dental files were contaminated with infectious oral tissues and then
subsequently cleaned and sterilised, a situation which would more closely model
human dental practice. Further studies using the mouse model that would be more
representative of the human situation, comparing oral tissues with a range of
doses of infectivity, cleaned and sterilised files and the kind of tissue
contact with instruments that occurs during dentistry, should be
considered.
7. SEAC considered that the experiments appear well designed and the
conclusions justified and reliable, while recognising that the research is
incomplete and confirmatory experiments have yet to be completed. It is
recommended that the research be completed, submitted for peer-review and widely
disseminated as soon as possible so others can consider the implications.
Nevertheless, these preliminary data increase the possibility that some oral
tissues of humans infected with vCJD may potentially become infective during the
preclinical stage of the disease. In addition, they increase the possibility
that infection could potentially be transmitted not only via accidental abrasion
of the lingual tonsil or endodontic procedures but a variety of routine dental
procedures.
20 Department of Health (2006) Dentistry and vCJD: the implications of a
carrier-state for a self-sustaining epidemic. Unpublished. 21 SEAC (2006)
Position statement on vCJD and endodontic dentistry.
22 Head et al. (2003) Investigation of PrPres in dental tissues in variant
CJD. Br. Dent. J. 195, 339-343. 23 SEAC 90 reserved business minutes.
Implications for transmission risks
snip...
11. The new research also suggests that dental procedures involving contact
with other oral tissues, including gingiva, may also be capable of transmitting
vCJD. In the absence of a detailed risk assessment examining the potential for
transmission via all dental procedures, it is not possible to come to firm
conclusions about the implications of these findings for transmission of vCJD.
However, given the potential for transmission by this route serious
consideration should be given to assessing the options for reducing transmission
risks such as improving decontamination procedures and practice or the
implementation of single use instruments.
12. The size of the potential risk from interactions between the dental and
other routes of secondary transmission, such as blood transfusion and hospital
surgery, to increase the likelihood of a self-sustaining epidemic is
unclear.
13. It is likely to be difficult to distinguish clinical vCJD cases arising
from dietary exposure to BSE from secondary transmissions via dental procedures,
should they arise, as a large proportion of the population is likely both to
have consumed contaminated meat and undergone dentistry. However, an analysis of
dental procedures by patient age may provide an indication of the age group in
which infections, if they occur, would be most likely to be observed. Should the
incidence of clinical vCJD cases in this age group increase significantly, this
may provide an indication that secondary transmission via dentistry is
occurring. Investigation of the dental work for these cases may provide
supporting data. There is no clear evidence, to date, based on surveillance or
investigations of clinical vCJD cases, that any vCJD cases have been caused by
dental procedures but this possibility cannot be excluded.
Conclusions
14. Preliminary research findings suggest that the potential risk of
transmission of vCJD via dental procedures may be greater than previously
anticipated. Although this research is incomplete, uses an animal model exposed
to relatively high doses of infectivity, and there are no data from infectivity
studies on human oral tissues, these findings suggest an increased possibility
that vCJD may be relatively efficiently transmitted via a range of dental
procedures. Ongoing infectivity studies using human oral tissues and the other
studies suggested here will enable more precise assessment of the risks of vCJD
transmission through dental procedures.
15. Guidance was issued to dentists earlier this year recommending that
endodontic files and reamers be treated as single use which, provided it is
adhered to, will remove any risk of a self-sustaining epidemic arising from
re-use of these instruments. To minimise risk it is critical that appropriate
management and audit is in place, both for NHS and private dentistry.
16. It is also critical that a detailed and comprehensive assessment of the
risks of all dental procedures be conducted as a matter of urgency. While taking
into account the continuing scientific uncertainties, this will allow a more
thorough consideration of the possible public health implications of vCJD
transmission via dentistry and the identification of possible additional
precautionary risk reduction measures. The assessment will require continued
updating as more evidence becomes available on the transmissibility of vCJD by
dental routes, and on the prevalence of infection within the population. A DH
proposal to convene an expert group that includes dental professionals to
expedite such an assessment is welcomed. Given the potential for transmission
via dentistry, consideration should be given to the urgent assessment of new
decontamination technologies which, if proved robust and effective, could
significantly reduce transmission risks.
SEAC June 2007
27 SEAC Epidemiology Subgroup (2006) position statement of the vCJD
epidemic.
28 DH (2007) Precautionary advice given to dentists on re-use of
instruments
see full text 17 pages ;
13 DH (2007) Precautionary advice given to dentists on re-use of
instruments
Tuesday, August 12, 2008
Biosafety in Microbiological and Biomedical Laboratories Fifth Edition 2007
(occupational exposure to prion diseases)
PLEASE REMEMBER, ALL IATROGENIC CJD IS, IS SPORADIC CJD, UNTIL ROUTE AND
SOURCE OF THE IATROGENIC EVENT, IT’S ROUTE, IT’S SOURCE, DOCUMENTED, AND PUT
INTO THE PUBLIC DOMAIN, DOES ANY EVENT BECOME DOCUMENTED AS IATROGENIC, AND WITH
THE INCUBATION PERIOD SO LONG, THESE EVENTS ARE MOSTLY NEVER CONFIRMED, THUS ALL
IATROGENIC EVENTS GO DOWN AS SPORADIC CJD, problem solved $$$
WHAT about the sporadic CJD TSE proteins ?
WE now know that some cases of sporadic CJD are linked to atypical BSE and
atypical Scrapie, so why are not MORE concerned about the sporadic CJD, and all
it’s sub-types $$$
Sunday, August 11, 2013
Creutzfeldt-Jakob Disease CJD cases rising North America updated report
August 2013
Creutzfeldt-Jakob Disease CJD cases rising North America with Canada seeing
an extreme increase of 48% between 2008 and 2010
Sunday, October 13, 2013
CJD TSE Prion Disease Cases in Texas by Year, 2003-2012
Sunday, October 27, 2013
A Kiss of a Prion: New Implications for Oral Transmissibility
Tuesday, September 24, 2013
NORDION (US), INC., AND BIOAXONE BIOSCIENCES, INC., Settles $90M Mad Cow
TSE prion Contamination Suit Cethrin(R)
Case 0:12-cv-60739-RNS Document 1 Entered on FLSD Docket 04/26/2012 Page 1
of 15
Saturday, June 25, 2011
Transmissibility of BSE-L and Cattle-Adapted TME Prion Strain to Cynomolgus
Macaque
"BSE-L in North America may have existed for decades"
Over the next 8-10 weeks, approximately 40% of all the adult mink on the
farm died from TME.
snip...
The rancher was a ''dead stock'' feeder using mostly (>95%) downer or
dead dairy cattle...
*** Saturday, November 2, 2013 ***
Exploring the risks of a putative transmission of BSE to new species
Wednesday, October 30, 2013
SPECIFIED RISK MATERIAL (SRM) CONTROL VERIFICATION TASK FSIS NOTICE 70-13
10/30/13
***Together with previous experiments performed in ovinized and bovinized
transgenic mice and hamsters [8,9] indicating similarities between TME and
L-BSE, the data support the hypothesis that L-BSE could be the origin of the TME
outbreaks in North America and Europe during the mid-1900s.
with great sadness and disgust, I must inform you that our federal
government has failed us again, and chose the industry over sound science, with
regards to TSE prion disease, aka mad cow type disease...tss
Saturday, November 2, 2013
APHIS Finalizes Bovine Import Regulations in Line with International Animal
Health Standards while enhancing the spread of BSE TSE prion mad cow type
disease around the Globe
Monday, November 4, 2013
R-CALF Bullard new BSE rule represents the abrogation of USDA’s
responsibility to protect U.S. consumers and the U.S. cattle herd from the
introduction of foreign animal disease
CWD TSE prion disease in cervids, humans, iatrogenic, 85%+ sporadic CJD,
???
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
HD.13: CWD infection in the spleen of humanized transgenic mice
Liuting Qing and Qingzhong Kong
Case Western Reserve University; Cleveland, OH USA
Chronic wasting disease (CWD) is a widespread prion disease in free-ranging
and captive cervid species in North America, and there is evidence suggesting
the existence of multiple CWD strains. The susceptibility of human CNS and
peripheral organs to the various CWD prion strains remains largely unclear.
Current literature suggests that the classical CWD strain is unlikely to infect
human brain, but the potential for peripheral infection by CWD in humans is
unknown. We detected protease-resistant PrpSc in the spleens of a few humanized
transgenic mice that were intracerebrally inoculated with natural CWD isolates,
but PrpSc was not detected in the brains of any of the CWD-inoculated mice. Our
ongoing bioassays in humanized Tg mice indicate that intracerebral challenge
with such PrpSc-positive humanized mouse spleen already led to prion disease in
most animals.
***These results indicate that the CWD prion may have the potential to
infect human peripheral lymphoid tissues.
Oral.15: Molecular barriers to zoonotic prion transmission: Comparison of
the ability of sheep, cattle and deer prion disease isolates to convert normal
human prion protein to its pathological isoform in a cell-free system
Marcelo A.Barria,1 Aru Balachandran,2 Masanori Morita,3 Tetsuyuki
Kitamoto,4 Rona Barron,5 Jean Manson,5 Richard Kniqht,1 James W. lronside1 and
Mark W. Head1
1National CJD Research and Surveillance Unit; Centre for Clinical Brain
Sciences; School of Clinical Sciences; The University of Edinburgh; Edinburgh,
UK; 2National and OIE Reference Laboratory for Scrapie and CWD; Canadian Food
Inspection Agency; Ottawa Laboratory; Fallowfield. ON Canada; 3Infectious
Pathogen Research Section; Central Research Laboratory; Japan Blood Products
Organization; Kobe, Japan; 4Department of Neurological Science; Tohoku
University Graduate School of Medicine; Sendai. Japan; 5Neurobiology Division;
The Roslin Institute and R(D)SVS; University of Edinburgh; Easter Bush;
Midlothian; Edinburgh, UK
Background. Bovine spongiform encephalopathy (BSE) is a known zoonotic
prion disease, resulting in variant Creurzfeldt- Jakob disease (vCJD) in humans.
In contrast, classical scrapie in sheep is thought to offer little or no danger
to human health. However, a widening range of prion diseases have been
recognized in cattle, sheep and deer. The risks posed by individual animal prion
diseases to human health cannot be determined a priori and are difficult to
assess empirically. The fundamemal event in prion disease pathogenesis is
thought to be the seeded conversion of normal prion protein (PrPC) to its
pathological isoform (PrPSc). Here we report the use of a rapid molecular
conversion assay to test whether brain specimens from different animal prion
diseases are capable of seeding the conversion of human PrPC ro PrPSc.
Material and Methods. Classical BSE (C-type BSE), H-type BSE, L-type BSE,
classical scrapie, atypical scrapie, chronic wasting disease and vCJD brain
homogenates were tested for their ability to seed conversion of human PrPC to
PrPSc in protein misfolding cyclic amplification (PMCA) reactions. Newly formed
human PrPSc was detected by protease digestion and western blotting using the
antibody 3F4.
Results. C-type BSE and vCJD were found to efficiently convert PrPC to
PrPSc. Scrapie failed to convert human PrPC to PrPSc. Of the other animal prion
diseases tested only chronic wasting disease appeared to have the capability ro
convert human PrPC to PrPSc. The results were consistent whether the human PrPC
came from human brain, humanised transgenic mouse brain or from cultured human
cells and the effect was more pronounced for PrPC with methionine at codon 129
compared with that with valine.
Conclusion. Our results show that none of the tested animal prion disease
isolates are as efficient as C-type BSE and vCJD in converting human prion
protein in this in vitro assay.
***However, they also show that there is no absolute barrier ro conversion
of human prion protein in the case of chronic wasting disease.
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
***Chronic Wasting Disease CWD risk factors, humans, domestic cats, blood,
and mother to offspring transmission
I thought your readers and hunters and those that consume the venison,
should have all the scientific facts, personally, I don’t care what you eat, but
if it effects me and my family down the road, it should then concern everyone,
and the potential of iatrogenic transmission of the TSE prion is real i.e.
‘friendly fire’, medical, surgical, dental, blood, tissue, and or products there
from...like deer antler velvet and TSE prions and nutritional supplements there
from, all a potential risk factor that should not be ignored or silenced. ...
the prion gods at the cdc state that there is ;
''no strong evidence''
but let's see exactly what the authors of this cwd to human at the cdc
state ;
now, let’s see what the authors said about this casual link, personal
communications years ago. see where it is stated NO STRONG evidence. so, does
this mean there IS casual evidence ????
“Our conclusion stating that we found no strong evidence of CWD
transmission to humans”
From: TSS (216-119-163-189.ipset45.wt.net)
Subject: CWD aka MAD DEER/ELK TO HUMANS ???
Date: September 30, 2002 at 7:06 am PST
From: "Belay, Ermias"
To:
Cc: "Race, Richard (NIH)" ; ; "Belay, Ermias"
Sent: Monday, September 30, 2002 9:22 AM
Subject: RE: TO CDC AND NIH - PUB MED- 3 MORE DEATHS - CWD - YOUNG HUNTERS
Dear Sir/Madam,
In the Archives of Neurology you quoted (the abstract of which was attached
to your email), we did not say CWD in humans will present like variant CJD.
That assumption would be wrong. I encourage you to read the whole article
and call me if you have questions or need more clarification (phone:
404-639-3091). Also, we do not claim that "no-one has ever been infected with
prion disease from eating venison." Our conclusion stating that we found no
strong evidence of CWD transmission to humans in the article you quoted or in
any other forum is limited to the patients we investigated.
Ermias Belay, M.D. Centers for Disease Control and Prevention
-----Original Message-----
From:
Sent: Sunday, September 29, 2002 10:15 AM
To: rr26k@nih.gov; rrace@niaid.nih.gov; ebb8@CDC.GOV
Subject: TO CDC AND NIH - PUB MED- 3 MORE DEATHS - CWD - YOUNG HUNTERS
Sunday, November 10, 2002 6:26 PM ......snip........end..............TSS
Thursday, April 03, 2008
A prion disease of cervids: Chronic wasting disease
2008 1: Vet Res. 2008 Apr 3;39(4):41
A prion disease of cervids: Chronic wasting disease
Sigurdson CJ.
snip...
*** twenty-seven CJD patients who regularly consumed venison were reported
to the Surveillance Center***,
snip...
full text ;
Thursday, May 26, 2011
Travel History, Hunting, and Venison Consumption Related to Prion Disease
Exposure, 2006-2007 FoodNet Population Survey Journal of the American Dietetic
Association Volume 111, Issue 6 , Pages 858-863, June 2011.
Travel History, Hunting, and Venison Consumption Related to Prion Disease
Exposure, 2006-2007 FoodNet Population Survey
Joseph Y. Abrams, MPH, Ryan A. Maddox, MPH , Alexis R. Harvey, MPH ,
Lawrence B. Schonberger, MD , Ermias D. Belay, MD
Accepted 15 November 2010. Abstract Full Text PDF References .
Abstract
The transmission of bovine spongiform encephalopathy (BSE) to human beings
and the spread of chronic wasting disease (CWD) among cervids have prompted
concerns about zoonotic transmission of prion diseases. Travel to the United
Kingdom and other European countries, hunting for deer or elk, and venison
consumption could result in the exposure of US residents to the agents that
cause BSE and CWD. The Foodborne Diseases Active Surveillance Network 2006-2007
population survey was used to assess the prevalence of these behaviors among
residents of 10 catchment areas across the United States. Of 17,372 survey
respondents, 19.4% reported travel to the United Kingdom since 1980, and 29.5%
reported travel to any of the nine European countries considered to be
BSE-endemic since 1980. The proportion of respondents who had ever hunted deer
or elk was 18.5%, and 1.2% had hunted deer or elk in a CWD–endemic area. More
than two thirds (67.4%) reported having ever eaten deer or elk meat. Respondents
who traveled spent more time in the United Kingdom (median 14 days) than in any
other BSE-endemic country. Of the 11,635 respondents who had consumed venison,
59.8% ate venison at most one to two times during their year of highest
consumption, and 88.6% had obtained all of their meat from the wild. The survey
results were useful in determining the prevalence and frequency of behaviors
that could be important factors for foodborne prion transmission.
"These findings indicate that a high percentage of the United States
population engages in hunting and/or venison consumption. If CWD continues to
spread to more areas across the country, a substantial number of people could
potentially be exposed to the infectious agent."
Potential Venison Exposure Among FoodNet Population Survey Respondents,
2006-2007
Ryan A. Maddox1*, Joseph Y. Abrams1, Robert C. Holman1, Lawrence B.
Schonberger1, Ermias D. Belay1 Division of Viral and Rickettsial Diseases,
National Center for Zoonotic, Vector-Borne, and Enteric Diseases, Centers for
Disease Control and Prevention, Atlanta, GA *Corresponding author e-mail:
rmaddox@cdc.gov
The foodborne transmission of bovine spongiform encephalopathy to humans,
resulting in variant Creutzfeldt-Jakob disease, indicates that humans can be
susceptible to animal prion diseases. However, it is not known whether foodborne
exposure to the agent causing chronic wasting disease (CWD) in cervids can cause
human disease. The United States Foodborne Diseases Active Surveillance Network
(FoodNet) conducts surveillance for foodborne diseases through an extensive
survey administered to respondents in selected states. To describe the frequency
of deer and elk hunting and venison consumption, five questions were included in
the 2006-2007 FoodNet survey. This survey included 17,372 respondents in ten
states: California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New
Mexico, New York, Oregon, and Tennessee. Of these respondents, 3,220 (18.5%)
reported ever hunting deer or elk, with 217 (1.3%) reporting hunting in a
CWD-endemic area (northeastern Colorado, southeastern Wyoming, and southwestern
Nebraska). Of the 217 CWD-endemic area hunters, 74 (34.1%) were residents of
Colorado. Respondents reporting hunting were significantly more likely to be
male than female (prevalence ratio: 3.3, 95% confidence interval: 3.1-3.6) and,
in general, older respondents were significantly more likely to report hunting
than younger respondents. Venison consumption was reported by more than half
(67.4%) of the study population, and most venison consumers (94.1%) reported
that at least half of their venison came from the wild. However, more than half
(59.1%) of the consumers reported eating venison only one to five times in their
life or only once or twice a year. These findings indicate that a high
percentage of the United States population engages in hunting and/or venison
consumption. If CWD continues to spread to more areas across the country, a
substantial number of people could potentially be exposed to the infectious
agent.
Monday, May 23, 2011 CDC
Assesses Potential Human Exposure to Prion Diseases Travel Warning
Public release date: 23-May-2011
Contact: Francesca Costanzo adajmedia@elsevier.com 215-239-3249 Elsevier
Health Sciences
CDC assesses potential human exposure to prion diseases Study results
reported in the Journal of the American Dietetic Association Philadelphia, PA,
May 23, 2011 – Researchers from the Centers for Disease Control and Prevention
(CDC) have examined the potential for human exposure to prion diseases, looking
at hunting, venison consumption, and travel to areas in which prion diseases
have been reported in animals. Three prion diseases in particular – bovine
spongiform encephalopathy (BSE or "Mad Cow Disease"), variant Creutzfeldt-Jakob
disease (vCJD), and chronic wasting disease (CWD) – were specified in the
investigation. The results of this investigation are published in the June issue
of the Journal of the American Dietetic Association.
"While prion diseases are rare, they are generally fatal for anyone who
becomes infected. More than anything else, the results of this study support the
need for continued surveillance of prion diseases," commented lead investigator
Joseph Y. Abrams, MPH, National Center for Emerging and Zoonotic Infectious
Diseases, CDC, Atlanta."But it's also important that people know the facts about
these diseases, especially since this study shows that a good number of people
have participated in activities that may expose them to infection-causing
agents."
Although rare, human prion diseases such as CJD may be related to BSE.
Prion (proteinaceous infectious particles) diseases are a group of rare brain
diseases that affect humans and animals. When a person gets a prion disease,
brain function is impaired. This causes memory and personality changes,
dementia, and problems with movement. All of these worsen over time. These
diseases are invariably fatal. Since these diseases may take years to manifest,
knowing the extent of human exposure to possible prion diseases could become
important in the event of an outbreak.
CDC investigators evaluated the results of the 2006-2007 population survey
conducted by the Foodborne Diseases Active Surveillance Network (FoodNet). This
survey collects information on food consumption practices, health outcomes, and
demographic characteristics of residents of the participating Emerging
Infections Program sites. The survey was conducted in Connecticut, Georgia,
Maryland, Minnesota, New Mexico, Oregon, and Tennessee, as well as five counties
in the San Francisco Bay area, seven counties in the Greater Denver area, and 34
counties in western and northeastern New York.
Survey participants were asked about behaviors that could be associated
with exposure to the agents causing BSE and CWD, including travel to the nine
countries considered to be BSE-endemic (United Kingdom, Republic of Ireland,
France, Portugal, Switzerland, Italy, the Netherlands, Germany, Spain) and the
cumulative length of stay in each of those countries. Respondents were asked if
they ever had hunted for deer or elk, and if that hunting had taken place in
areas considered to be CWD-endemic (northeastern Colorado, southeastern Wyoming
or southwestern Nebraska). They were also asked if they had ever consumed
venison, the frequency of consumption, and whether the meat came from the wild.
The proportion of survey respondents who reported travel to at least one of
the nine BSE endemic countries since 1980 was 29.5%. Travel to the United
Kingdom was reported by 19.4% of respondents, higher than to any other
BSE-endemic country. Among those who traveled, the median duration of travel to
the United Kingdom (14 days) was longer than that of any other BSE-endemic
country. Travelers to the UK were more likely to have spent at least 30 days in
the country (24.9%) compared to travelers to any other BSE endemic country. The
prevalence and extent of travel to the UK indicate that health concerns in the
UK may also become issues for US residents.
The proportion of survey respondents reporting having hunted for deer or
elk was 18.5% and 1.2% reported having hunted for deer or elk in CWD-endemic
areas. Venison consumption was reported by 67.4% of FoodNet respondents, and
88.6% of those reporting venison consumption had obtained all of their meat from
the wild. These findings reinforce the importance of CWD surveillance and
control programs for wild deer and elk to reduce human exposure to the CWD
agent. Hunters in CWD-endemic areas are advised to take simple precautions such
as: avoiding consuming meat from sickly deer or elk, avoiding consuming brain or
spinal cord tissues, minimizing the handling of brain and spinal cord tissues,
and wearing gloves when field-dressing carcasses.
According to Abrams, "The 2006-2007 FoodNet population survey provides
useful information should foodborne prion infection become an increasing public
health concern in the future. The data presented describe the prevalence of
important behaviors and their associations with demographic characteristics.
Surveillance of BSE, CWD, and human prion diseases are critical aspects of
addressing the burden of these diseases in animal populations and how that may
relate to human health."
###
The article is "Travel history, hunting, and venison consumption related to
prion disease exposure, 2006-2007 FoodNet population survey" by Joseph Y.
Abrams, MPH; Ryan A. Maddox, MPH; Alexis R Harvey, MPH; Lawrence B. Schonberger,
MD; and Ermias D. Belay, MD. It appears in the Journal of the American Dietetic
Association, Volume 111, Issue 6 (June 2011) published by Elsevier.
also, they did not call this CWD postive meat back for the well being of
the ELK ;
Wednesday, March 18, 2009
Noah’s Ark Holding, LLC, Dawson, MN RECALL Elk products contain meat
derived from an elk confirmed to have CWD NV, CA, TX, CO, NY, UT, FL, OK RECALLS
AND FIELD CORRECTIONS: FOODS CLASS II
___________________________________
PRODUCT
a) Elk Meat, Elk Tenderloin, Frozen in plastic vacuum packaging. Each
package is approximately 2 lbs., and each case is approximately 16 lbs.; Item
number 755125, Recall # F-129-9;
b) Elk Meat, Elk Trim, Frozen; Item number 755155, Recall # F-130-9;
c) Elk Meat, French Rack, Chilled. Item number 755132, Recall # F-131-9;
d) Elk Meat, Nude Denver Leg. Item number 755122, Recall # F-132-9;
e) Elk Meat, New York Strip Steak, Chilled. Item number 755128, Recall #
F-133-9;
f) Elk Meat, Flank Steak Frozen. Item number 755131, Recall # F-134-9;
CODE
Elk Meats with production dates of December 29, 30, and 31
RECALLING FIRM/MANUFACTURER
Recalling Firm: Sierra Meats, Reno, NV, by telephone on January 29, 2009
and press release on February 9, 2009.
Manufacturer: Noah’s Ark Holding, LLC, Dawson, MN. Firm initiated recall is
ongoing.
REASON
Elk products contain meat derived from an elk confirmed to have Chronic
Wasting Disease (CWD).
VOLUME OF PRODUCT IN COMMERCE
Unknown
DISTRIBUTION
NV, CA, TX, CO, NY, UT, FL, OK
___________________________________
CJD REPORT 1994 increased risk for consumption of veal and venison and lamb
CREUTZFELDT JAKOB DISEASE SURVEILLANCE IN THE UNITED KINGDOM THIRD ANNUAL
REPORT AUGUST 1994
Consumption of venison and veal was much less widespread among both cases
and controls. For both of these meats there was evidence of a trend with
increasing frequency of consumption being associated with increasing risk of
CJD. (not nvCJD, but sporadic CJD...tss)
These associations were largely unchanged when attention was restricted to
pairs with data obtained from relatives. ...
Table 9 presents the results of an analysis of these data.
There is STRONG evidence of an association between ‘’regular’’ veal eating
and risk of CJD (p = .0.01).
Individuals reported to eat veal on average at least once a year appear to
be at 13 TIMES THE RISK of individuals who have never eaten veal.
There is, however, a very wide confidence interval around this estimate.
There is no strong evidence that eating veal less than once per year is
associated with increased risk of CJD (p = 0.51).
The association between venison eating and risk of CJD shows similar
pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK
OF CJD (p = 0.04).
There is some evidence that risk of CJD INCREASES WITH INCREASING FREQUENCY
OF LAMB EATING (p = 0.02).
The evidence for such an association between beef eating and CJD is weaker
(p = 0.14). When only controls for whom a relative was interviewed are included,
this evidence becomes a little STRONGER (p = 0.08).
snip...
It was found that when veal was included in the model with another
exposure, the association between veal and CJD remained statistically
significant (p = < 0.05 for all exposures), while the other exposures ceased
to be statistically significant (p = > 0.05).
snip...
In conclusion, an analysis of dietary histories revealed statistical
associations between various meats/animal products and INCREASED RISK OF CJD.
When some account was taken of possible confounding, the association between
VEAL EATING AND RISK OF CJD EMERGED AS THE STRONGEST OF THESE ASSOCIATIONS
STATISTICALLY. ...
snip...
In the study in the USA, a range of foodstuffs were associated with an
increased risk of CJD, including liver consumption which was associated with an
apparent SIX-FOLD INCREASE IN THE RISK OF CJD. By comparing the data from 3
studies in relation to this particular dietary factor, the risk of liver
consumption became non-significant with an odds ratio of 1.2 (PERSONAL
COMMUNICATION, PROFESSOR A. HOFMAN. ERASMUS UNIVERSITY, ROTTERDAM). (???...TSS)
snip...see full report ;
Thursday, October 10, 2013
CJD REPORT 1994 increased risk for consumption of veal and venison and lamb
CJD9/10022
October 1994
Mr R.N. Elmhirst Chairman British Deer Farmers Association Holly Lodge
Spencers Lane BerksWell Coventry CV7 7BZ
Dear Mr Elmhirst,
CREUTZFELDT-JAKOB DISEASE (CJD) SURVEILLANCE UNIT REPORT
Thank you for your recent letter concerning the publication of the third
annual report from the CJD Surveillance Unit. I am sorry that you are
dissatisfied with the way in which this report was published.
The Surveillance Unit is a completely independant outside body and the
Department of Health is committed to publishing their reports as soon as they
become available. In the circumstances it is not the practice to circulate the
report for comment since the findings of the report would not be amended. In
future we can ensure that the British Deer Farmers Association receives a copy
of the report in advance of publication.
The Chief Medical Officer has undertaken to keep the public fully informed
of the results of any research in respect of CJD. This report was entirely the
work of the unit and was produced completely independantly of the the
Department.
The statistical results reqarding the consumption of venison was put into
perspective in the body of the report and was not mentioned at all in the press
release. Media attention regarding this report was low key but gave a realistic
presentation of the statistical findings of the Unit. This approach to
publication was successful in that consumption of venison was highlighted only
once by the media ie. in the News at one television proqramme.
I believe that a further statement about the report, or indeed statistical
links between CJD and consumption of venison, would increase, and quite possibly
give damaging credence, to the whole issue. From the low key media reports of
which I am aware it seems unlikely that venison consumption will suffer
adversely, if at all.
CWD transmission to humans.
NEVER ???
never say never with the TSE prion.
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
HD.13: CWD infection in the spleen of humanized transgenic mice
Liuting Qing and Qingzhong Kong
Case Western Reserve University; Cleveland, OH USA
Chronic wasting disease (CWD) is a widespread prion disease in free-ranging
and captive cervid species in North America, and there is evidence suggesting
the existence of multiple CWD strains. The susceptibility of human CNS and
peripheral organs to the various CWD prion strains remains largely unclear.
Current literature suggests that the classical CWD strain is unlikely to infect
human brain, but the potential for peripheral infection by CWD in humans is
unknown. We detected protease-resistant PrpSc in the spleens of a few humanized
transgenic mice that were intracerebrally inoculated with natural CWD isolates,
but PrpSc was not detected in the brains of any of the CWD-inoculated mice. Our
ongoing bioassays in humanized Tg mice indicate that intracerebral challenge
with such PrpSc-positive humanized mouse spleen already led to prion disease in
most animals. ***These results indicate that the CWD prion may have the
potential to infect human peripheral lymphoid tissues.
Oral.15: Molecular barriers to zoonotic prion transmission: Comparison of
the ability of sheep, cattle and deer prion disease isolates to convert normal
human prion protein to its pathological isoform in a cell-free system
Marcelo A.Barria,1 Aru Balachandran,2 Masanori Morita,3 Tetsuyuki
Kitamoto,4 Rona Barron,5 Jean Manson,5 Richard Kniqht,1 James W. lronside1 and
Mark W. Head1
1National CJD Research and Surveillance Unit; Centre for Clinical Brain
Sciences; School of Clinical Sciences; The University of Edinburgh; Edinburgh,
UK; 2National and OIE Reference Laboratory for Scrapie and CWD; Canadian Food
Inspection Agency; Ottawa Laboratory; Fallowfield. ON Canada; 3Infectious
Pathogen Research Section; Central Research Laboratory; Japan Blood Products
Organization; Kobe, Japan; 4Department of Neurological Science; Tohoku
University Graduate School of Medicine; Sendai. Japan; 5Neurobiology Division;
The Roslin Institute and R(D)SVS; University of Edinburgh; Easter Bush;
Midlothian; Edinburgh, UK
Background. Bovine spongiform encephalopathy (BSE) is a known zoonotic
prion disease, resulting in variant Creurzfeldt- Jakob disease (vCJD) in humans.
In contrast, classical scrapie in sheep is thought to offer little or no danger
to human health. However, a widening range of prion diseases have been
recognized in cattle, sheep and deer. The risks posed by individual animal prion
diseases to human health cannot be determined a priori and are difficult to
assess empirically. The fundamemal event in prion disease pathogenesis is
thought to be the seeded conversion of normal prion protein (PrPC) to its
pathological isoform (PrPSc). Here we report the use of a rapid molecular
conversion assay to test whether brain specimens from different animal prion
diseases are capable of seeding the conversion of human PrPC ro PrPSc.
Material and Methods. Classical BSE (C-type BSE), H-type BSE, L-type BSE,
classical scrapie, atypical scrapie, chronic wasting disease and vCJD brain
homogenates were tested for their ability to seed conversion of human PrPC to
PrPSc in protein misfolding cyclic amplification (PMCA) reactions. Newly formed
human PrPSc was detected by protease digestion and western blotting using the
antibody 3F4.
Results. C-type BSE and vCJD were found to efficiently convert PrPC to
PrPSc. Scrapie failed to convert human PrPC to PrPSc. Of the other animal prion
diseases tested only chronic wasting disease appeared to have the capability ro
convert human PrPC to PrPSc. The results were consistent whether the human PrPC
came from human brain, humanised transgenic mouse brain or from cultured human
cells and the effect was more pronounced for PrPC with methionine at codon 129
compared with that with valine.
Conclusion. Our results show that none of the tested animal prion disease
isolates are as efficient as C-type BSE and vCJD in converting human prion
protein in this in vitro assay. ***However, they also show that there is no
absolute barrier ro conversion of human prion protein in the case of chronic
wasting disease.
PRION2013 CONGRESSIONAL ABSTRACTS CWD
Sunday, August 25, 2013
***Chronic Wasting Disease CWD risk factors, humans, domestic cats, blood,
and mother to offspring transmission
Sunday, July 21, 2013
*** As Chronic Wasting Disease CWD rises in deer herd, what about risk for
humans?
I’m just saying. ...
TSS
