Scientific Opinion on a request for a review of a scientific publication concerning the zoonotic potential of ovine scrapie prions
Subject:
Scientific Opinion on a request for a review of a scientific publication
concerning the zoonotic potential of ovine scrapie prions
Scientific Opinion on a request for a review of a scientific publication
concerning the zoonotic potential of ovine scrapie prions
EFSA Journal 2015;13(8):4197[58 pp.]. doi:10.2903/j.efsa.2015.4197
EFSA Panel on Biological Hazards (BIOHAZ)
Panel Members Acknowledgment Contact
Type: Opinion of the Scientific Committee/Scientific Panel
On request from: European Commission
Question number: EFSA-Q-2015-00048
Adopted: 09 July 2015
Published: 05 August 2015
Affiliation: European Food Safety Authority (EFSA), Parma, Italy
Article (1.0 Mb)
Send Print Cite
Abstract
The factors that modulate the transmissibility of Transmissible Spongiform
Encephalopathies (TSE) and the approaches for the study of their zoonotic
potential are reviewed. The paper ‘Evidence for zoonotic potential of ovine
scrapie prions’ by Cassard et al. (2014) is scientifically appraised, focussing
on the experimental design, the results and the conclusions. The paper provides
evidence in a laboratory experiment that some Classical scrapie isolates can
propagate in humanised transgenic mice and produce prions that on second passage
are similar to those causing one form of sporadic Creutzfeldt-Jakob disease
(sCJD). It is concluded that the results from the study raise the possibility
that scrapie prions have the potential to be zoonotic, but do not provide
evidence that transmission can or does take place under field conditions. The
conclusions of the 2011 ECDC-EFSA ‘Joint Scientific Opinion on any possible
epidemiological or molecular association between TSEs in animals and humans’ are
reviewed in the light of the new scientific evidence available since its
publication. This supports and strengthens the conclusions of that opinion with
regard to the potential for some animal TSE to be zoonotic, but does not provide
evidence of a causal link between Classical or Atypical scrapie and human TSE.
Current evidence does not establish this link, and no consistent risk factors
have been identified for sCJD. The possibility of scrapie-related public health
risks from the consumption of ovine products cannot be assessed. Recommendations
are formulated on further studies and data that are needed to investigate the
zoonotic potential of animal TSE and to estimate the amount of infectivity from
TSE-infected products sourced from small ruminants and entering the food chain
in the European Union.
© European Food Safety Authority,2015
Summary
Following a request from the European Commission (EC), the EFSA Panel on
Biological Hazards (BIOHAZ Panel) was asked to deliver a scientific opinion on
the review of a scientific publication concerning the zoonotic potential of
ovine scrapie prions.
The EC asked the BIOHAZ Panel to scientifically appraise the paper
‘Evidence for zoonotic potential of ovine scrapie prions’ by Cassard et al.
(2014), considering the limitations, assumptions and uncertainties associated
with the study design and outputs. In addition, the BIOHAZ Panel was asked to
advise whether the outcomes of the 2011 EFSA-ECDC ‘Joint Scientific Opinion on
any possible epidemiological or molecular association between TSEs in animals
and humans’ (EFSA BIOHAZ Panel, 2011), with regard to the zoonotic potential of
both Classical and Atypical scrapie, were still valid. Finally, the BIOHAZ Panel
was requested, based on the answers to the above questions, to advise whether
the natural exposure of consumers to ovine products represents a non-negligible
risk for public health.
This Opinion reviews the factors that modulate the transmissibility of
animal Transmissible Spongiform Encephalopathies (TSE) and the approaches for
the study of the zoonotic potential of TSE. It is concluded that there is no
evidence of an absolute species barrier. Many factors influence the ability of
any TSE agent to infect a host, regardless of whether the infection occurs
across a species barrier, and it is impossible to define an experimental model
that encompasses this potential variability and to directly measure zoonotic
potential.
The scientific literature available since the publication of the 2011
EFSA-ECDC Joint Scientific Opinion is also reviewed to allow the appraisal of
the paper by Cassard et al. (2014) as well as the review of the conclusions of
that Scientific Opinion in the context of current knowledge.
The publication by Cassard et al. (2014) is reviewed, focussing on the
experimental design, the results and the conclusions. The paper uses a
combination of intracerebral inoculation, transgenic mice overexpressing human
prion protein and serial passages that maximises the chance of detecting the
propagation of TSE agents, but does not mimic natural exposure. It provides
evidence in a laboratory experiment that some Classical scrapie isolates can
propagate in humanised transgenic mice and produce prions that on second passage
are similar to those causing one form of sporadic CJD (sCJD). This Opinion
concludes that the paper under appraisal raises the possibility that scrapie
prions have the potential to be zoonotic, but does not provide evidence that
transmission can or does take place under field conditions.
The conclusions of the 2011 ECDC-EFSA Joint Scientific Opinion are reviewed
in detail. Most of the conclusions formulated in that Opinion remain valid at
present; only four require minor amendments. The new scientific evidence
available supports and strengthens the conclusions of the previous Opinion with
regard to the potential for some animal TSE to be zoonotic, but does not provide
evidence of a causal link between Classical or Atypical scrapie and human
TSE.
When considering the public health risks associated with exposure of
consumers to scrapie agents through ovine products, the BIOHAZ Panel indicates
that the level of exposure is largely determined by the prevalence of the
disease in ovines and by the amount of infectivity in ovine tissues entering the
food chain. The latter is reduced by the current specific risk material (SRM)
measures. From the available epidemiological evidence it is not possible to
conclude that the exposure of consumers to ovine products has resulted in the
transmission of prion diseases to humans. A quantitative assessment of the
overall amount of infectivity from TSE-infected ovine products entering the food
chain would require data on infectivity distribution in small ruminants, disease
frequency at population level, and sensitivity of detection of TSE-infected
small ruminants at slaughter, among others. Data on these parameters and a
mathematical model developed and applied previously by EFSA could be used for
this purpose. An individual exposure to scrapie agents could be assessed only by
combining the results from such an assessment with additional information such
as consumption data and ovine product information.
It is concluded that current evidence does not establish a causal link
between scrapie and sCJD, and that the possibility of scrapie-related public
health risks from the consumption of ovine products cannot be assessed.
Recommendations are formulated on further studies and data that are needed
to investigate the zoonotic potential of animal TSE and to estimate the amount
of infectivity from TSE-infected products sourced from small ruminants and
entering the food chain in the European Union.
Keywords
Atypical scrapie, Classical scrapie, Creutzfeldt-Jakob disease,
transmissible spongiform encephalopathy, zoonosis
Concluding remarks 1.5. There is no evidence of an absolute species
barrier.
PRION 2015 ORAL AND POSTER CONGRESSIONAL ABSTRACTS
THANK YOU PRION 2015 TAYLOR & FRANCIS, Professor Chernoff, and
Professor Aguzzi et al, for making these PRION 2015 Congressional Poster and
Oral Abstracts available freely to the public. ...Terry S. Singeltary Sr.
O.05: Transmission of prions to primates after extended silent incubation
periods: Implications for BSE and scrapie risk assessment in human populations
Emmanuel Comoy, Jacqueline Mikol, Val erie Durand, Sophie Luccantoni,
Evelyne Correia, Nathalie Lescoutra, Capucine Dehen, and Jean-Philippe Deslys
Atomic Energy Commission; Fontenay-aux-Roses, France
Prion diseases (PD) are the unique neurodegenerative proteinopathies
reputed to be transmissible under field conditions since decades. The
transmission of Bovine Spongiform Encephalopathy (BSE) to humans evidenced that
an animal PD might be zoonotic under appropriate conditions. Contrarily, in the
absence of obvious (epidemiological or experimental) elements supporting a
transmission or genetic predispositions, PD, like the other proteinopathies, are
reputed to occur spontaneously (atpical animal prion strains, sporadic CJD
summing 80% of human prion cases). Non-human primate models provided the first
evidences supporting the transmissibiity of human prion strains and the zoonotic
potential of BSE. Among them, cynomolgus macaques brought major information for
BSE risk assessment for human health (Chen, 2014), according to their
phylogenetic proximity to humans and extended lifetime. We used this model to
assess the zoonotic potential of other animal PD from bovine, ovine and cervid
origins even after very long silent incubation periods. We recently observed the
direct transmission of a natural classical scrapie isolate to macaque after a
10-year silent incubation period, with features similar to some reported for
human cases of sporadic CJD, albeit requiring fourfold longe incubation than
BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014), is the third
potentially zoonotic PD (with BSE and L-type BSE), ***thus questioning the
origin of human sporadic cases. We will present an updated panorama of our
different transmission studies and discuss the implications of such extended
incubation periods on risk assessment of animal PD for human health.
===============
*** Scrapie, as recently evoked in humanized mice (Cassard, 2014), is the
third potentially zoonotic PD (with BSE and L-type BSE), ***thus questioning the
origin of human sporadic cases.
===============
Saturday, May 30, 2015
PRION 2015 ORAL AND POSTER CONGRESSIONAL ABSTRACTS
O35
J. Mikol1, S. Luccantoni-Freire1, E. Correia1, N. Lescoutra-Etchegaray1, V.
Durand1, C. Dehen1, J.P. Deslys1, E. Comoy1
1Institute of Emerging Diseases and Innovative Therapies, Service of Prion
Diseases, Atomic Energy Commission, 18 Route du Panorama 92265 Fontenayaux-
Roses, France
E-mail: jacqueline.mikol@wanadoo.fr
Uncommon prion disease induced in macaque ten years after scrapie
inoculation
Introduction: Bovine Spongiform Encephalopathy (BSE) is the single animal
prion disease reputed to be zoonotic, inducing variant of Creutzfeldt-Jakob
Disease (vCJD) in man, and therefore strongly conditioned the protective
measures. Among different sources of animal prion diseases, we show here that
after more than ten years of incubation, intracerebral injection of a sheep
scrapie isolate can induce a prion disease in cynomolgus macaque, a relevant
model of human situation towards several prion strains. Neuropathological
studies showed classical and uncommon data.
Material and method: The cynomolgus macaque was intracerebrally exposed to
a classical scrapie isolate issued from a naturally infected sheep flock. Upon
onset of clinical signs, euthanasia was performed for ethical reasons. Classical
methods of biochemistry and neuropathology were used.
Results: The three elements of the triad were present:
spongiosis was predominant in the cortex, the striatum, the cerebellum.
Neuronal loss and gliosis were moderate.
The notable data were the following
(i) the brain was small, the atrophy involved mostly the temporal lobe in
which axonal loss was histologically demonstrated
(ii) the spongiosis of the Purkinje cells was so intense that most of them
were destroyed
(iii) there was a neuronal loss and a massive gliosis of the dorsomedialis
nucleus of the thalamus
(iv) iron deposits were present in the lenticular nucleus. PrPres heavily
distributed in the cortex, the basal ganglia and the cerebellum consisted in
synaptic deposits and aggregates. Western Blot exhibited a type 1 PrPres in all
parts of the brain.
Conclusion: We described here the successful transmission of a scrapie
prion disease to a non-human primate after an extended incubation period,
leading to a fatal, non-relapsing neurological disease with all the features of
a prion disease. The cerebral lesional profile we observed was original in
comparison to other animal prion diseases (c-BSE, L-type BSE, TME) we previously
experimentally transmitted in this model.
Tuesday, December 16, 2014
Evidence for zoonotic potential of ovine scrapie prions
Hervé Cassard,1, n1 Juan-Maria Torres,2, n1 Caroline Lacroux,1, Jean-Yves
Douet,1, Sylvie L. Benestad,3, Frédéric Lantier,4, Séverine Lugan,1, Isabelle
Lantier,4, Pierrette Costes,1, Naima Aron,1, Fabienne Reine,5, Laetitia
Herzog,5, Juan-Carlos Espinosa,2, Vincent Beringue5, & Olivier Andréoletti1,
Affiliations Contributions Corresponding author Journal name: Nature
Communications Volume: 5, Article number: 5821 DOI: doi:10.1038/ncomms6821
Received 07 August 2014 Accepted 10 November 2014 Published 16 December 2014
Article tools Citation Reprints Rights & permissions Article metrics
Abstract
Although Bovine Spongiform Encephalopathy (BSE) is the cause of variant
Creutzfeldt Jakob disease (vCJD) in humans, the zoonotic potential of scrapie
prions remains unknown. Mice genetically engineered to overexpress the human
prion protein (tgHu) have emerged as highly relevant models for gauging the
capacity of prions to transmit to humans. These models can propagate human
prions without any apparent transmission barrier and have been used used to
confirm the zoonotic ability of BSE. Here we show that a panel of sheep scrapie
prions transmit to several tgHu mice models with an efficiency comparable to
that of cattle BSE. The serial transmission of different scrapie isolates in
these mice led to the propagation of prions that are phenotypically identical to
those causing sporadic CJD (sCJD) in humans. These results demonstrate that
scrapie prions have a zoonotic potential and raise new questions about the
possible link between animal and human prions.
Subject terms: Biological sciences• Medical research At a glance
why do we not want to do TSE transmission studies on chimpanzees $
5. A positive result from a chimpanzee challenged severly would likely
create alarm in some circles even if the result could not be interpreted for
man. I have a view that all these agents could be transmitted provided a large
enough dose by appropriate routes was given and the animals kept long enough.
Until the mechanisms of the species barrier are more clearly understood it might
be best to retain that hypothesis.
snip...
R. BRADLEY
1: J Infect Dis 1980 Aug;142(2):205-8
Oral transmission of kuru, Creutzfeldt-Jakob disease, and scrapie to
nonhuman primates.
Gibbs CJ Jr, Amyx HL, Bacote A, Masters CL, Gajdusek DC.
Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep
and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were
exposed to the infectious agents only by their nonforced consumption of known
infectious tissues. The asymptomatic incubation period in the one monkey exposed
to the virus of kuru was 36 months; that in the two monkeys exposed to the virus
of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the
two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively.
Careful physical examination of the buccal cavities of all of the monkeys failed
to reveal signs or oral lesions. One additional monkey similarly exposed to kuru
has remained asymptomatic during the 39 months that it has been under
observation.
snip...
The successful transmission of kuru, Creutzfeldt-Jakob disease, and scrapie
by natural feeding to squirrel monkeys that we have reported provides further
grounds for concern that scrapie-infected meat may occasionally give rise in
humans to Creutzfeldt-Jakob disease.
PMID: 6997404
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6997404&dopt=Abstract
Recently the question has again been brought up as to whether scrapie is
transmissible to man. This has followed reports that the disease has been
transmitted to primates. One particularly lurid speculation (Gajdusek 1977)
conjectures that the agents of scrapie, kuru, Creutzfeldt-Jakob disease and
transmissible encephalopathy of mink are varieties of a single "virus". The U.S.
Department of Agriculture concluded that it could "no longer justify or permit
scrapie-blood line and scrapie-exposed sheep and goats to be processed for human
or animal food at slaughter or rendering plants" (ARC 84/77)" The problem is
emphasized by the finding that some strains of scrapie produce lesions identical
to the once which characterize the human dementias"
Whether true or not. the hypothesis that these agents might be
transmissible to man raises two considerations. First, the safety of laboratory
personnel requires prompt attention. Second, action such as the "scorched meat"
policy of USDA makes the solution of the scrapie problem urgent if the sheep
industry is not to suffer grievously.
snip...
76/10.12/4.6
Nature. 1972 Mar 10;236(5341):73-4.
Transmission of scrapie to the cynomolgus monkey (Macaca fascicularis).
Gibbs CJ Jr, Gajdusek DC.
Nature 236, 73 - 74 (10 March 1972); doi:10.1038/236073a0
Transmission of Scrapie to the Cynomolgus Monkey (Macaca fascicularis)
C. J. GIBBS jun. & D. C. GAJDUSEK
National Institute of Neurological Diseases and Stroke, National Institutes
of Health, Bethesda, Maryland
SCRAPIE has been transmitted to the cynomolgus, or crab-eating, monkey
(Macaca fascicularis) with an incubation period of more than 5 yr from the time
of intracerebral inoculation of scrapie-infected mouse brain. The animal
developed a chronic central nervous system degeneration, with ataxia, tremor and
myoclonus with associated severe scrapie-like pathology of intensive astroglial
hypertrophy and proliferation, neuronal vacuolation and status spongiosus of
grey matter. The strain of scrapie virus used was the eighth passage in Swiss
mice (NIH) of a Compton strain of scrapie obtained as ninth intracerebral
passage of the agent in goat brain, from Dr R. L. Chandler (ARC, Compton,
Berkshire).
Friday, January 30, 2015
*** Scrapie: a particularly persistent pathogen ***
Thursday, March 26, 2015
Increased Infectivity of Anchorless Mouse Scrapie Prions in Transgenic Mice
Overexpressing Human Prion Protein
Increased susceptibility of human-PrP transgenic mice to bovine spongiform
encephalopathy following passage in sheep
J. Virol. doi:10.1128/JVI.01578-10 Copyright (c) 2010, American Society for
Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Increased susceptibility of human-PrP transgenic mice to bovine spongiform
encephalopathy following passage in sheep.
Chris Plinston, Patricia Hart, Angela Chong, Nora Hunter, James Foster,
Pedro Piccardo, Jean C. Manson, and Rona M Barron* Neuropathogenesis Division,
The Roslin Institute and R(D)SVS, University of Edinburgh, Roslin, Midlothian,
UK; Laboratory of Bacterial and TSE Agents, Food and Drug Administration,
Rockville, MD, USA
* To whom correspondence should be addressed. Email:
rona.barron@roslin.ed.ac.uk .
Abstract
The risk of transmission of ruminant transmissible spongiform
encephalopathy (TSE) to humans was thought to be low due to the lack of
association between sheep scrapie and incidence of human TSE. However a single
TSE agent strain has been shown to cause both bovine spongiform encephalopathy
(BSE) and human vCJD, indicating that some ruminant TSEs may be transmissible to
humans. While the transmission of cattle BSE to humans in transgenic mouse
models has been inefficient, indicating the presence of a significant
transmission barrier between cattle and humans, BSE has been transmitted to a
number of other species. Here we aimed to further investigate the human
transmission barrier following passage of BSE in a sheep. Following inoculation
with cattle BSE, gene targeted transgenic mice expressing human PrP showed no
clinical or pathological signs of TSE disease. However following inoculation
with an isolate of BSE that had been passaged through a sheep, TSE associated
vacuolation and proteinase-K resistant PrP deposition were observed in mice
homozygous for the codon 129-methionine PRNP gene. This observation may be due
to higher titres of the BSE agent in sheep, or an increased susceptibility of
humans to BSE prions following passage through a sheep. ***However these data
confirm that, contrary to previous predictions, it is possible that a sheep
prion may be transmissible to humans and that BSE from other species may be a
public health risk.
Suspect symptoms
What if you can catch old-fashioned CJD by eating meat from a sheep
infected with scrapie?
28 Mar 01
Most doctors believe that sCJD is caused by a prion protein deforming by
chance into a killer. But Singeltary thinks otherwise. He is one of a number of
campaigners who say that some sCJD, like the variant CJD related to BSE, is
caused by eating meat from infected animals. Their suspicions have focused on
sheep carrying scrapie, a BSE-like disease that is widespread in flocks across
Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight
to the campaigners' fears. To their complete surprise, the researchers found
that one strain of scrapie causes the same brain damage in mice as sCJD.
"This means we cannot rule out that at least some sCJD may be caused by
some strains of scrapie," says team member Jean-Philippe Deslys of the French
Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses,
south-west of Paris. Hans Kretschmar of the University of Göttingen, who
coordinates CJD surveillance in Germany, is so concerned by the findings that he
now wants to trawl back through past sCJD cases to see if any might have been
caused by eating infected mutton or lamb...
2001
Suspect symptoms
What if you can catch old-fashioned CJD by eating meat from a sheep
infected with scrapie?
28 Mar 01
Like lambs to the slaughter
31 March 2001
by Debora MacKenzie Magazine issue 2284.
FOUR years ago, Terry Singeltary watched his mother die horribly from a
degenerative brain disease. Doctors told him it was Alzheimer's, but Singeltary
was suspicious. The diagnosis didn't fit her violent symptoms, and he demanded
an autopsy. It showed she had died of sporadic Creutzfeldt-Jakob disease.
Most doctors believe that sCJD is caused by a prion protein deforming by
chance into a killer. But Singeltary thinks otherwise. He is one of a number of
campaigners who say that some sCJD, like the variant CJD related to BSE, is
caused by eating meat from infected animals. Their suspicions have focused on
sheep carrying scrapie, a BSE-like disease that is widespread in flocks across
Europe and North America.
Now scientists in France have stumbled across new evidence that adds weight
to the campaigners' fears. To their complete surprise, the researchers found
that one strain of scrapie causes the same brain damage in mice as sCJD.
"This means we cannot rule out that at least some sCJD may be caused by
some strains of scrapie," says team member Jean-Philippe Deslys of the French
Atomic Energy Commission's medical research laboratory in Fontenay-aux-Roses,
south-west of Paris. Hans Kretschmar of the University of Göttingen, who
coordinates CJD surveillance in Germany, is so concerned by the findings that he
now wants to trawl back through past sCJD cases to see if any might have been
caused by eating infected mutton or lamb.
Scrapie has been around for centuries and until now there has been no
evidence that it poses a risk to human health. But if the French finding means
that scrapie can cause sCJD in people, countries around the world may have
overlooked a CJD crisis to rival that caused by BSE.
Deslys and colleagues were originally studying vCJD, not sCJD. They
injected the brains of macaque monkeys with brain from BSE cattle, and from
French and British vCJD patients. The brain damage and clinical symptoms in the
monkeys were the same for all three. Mice injected with the original sets of
brain tissue or with infected monkey brain also developed the same
symptoms.
As a control experiment, the team also injected mice with brain tissue from
people and animals with other prion diseases: a French case of sCJD; a French
patient who caught sCJD from human-derived growth hormone; sheep with a French
strain of scrapie; and mice carrying a prion derived from an American scrapie
strain. As expected, they all affected the brain in a different way from BSE and
vCJD. But while the American strain of scrapie caused different damage from
sCJD, the French strain produced exactly the same pathology.
"The main evidence that scrapie does not affect humans has been
epidemiology," says Moira Bruce of the neuropathogenesis unit of the Institute
for Animal Health in Edinburgh, who was a member of the same team as Deslys.
"You see about the same incidence of the disease everywhere, whether or not
there are many sheep, and in countries such as New Zealand with no scrapie." In
the only previous comparisons of sCJD and scrapie in mice, Bruce found they were
dissimilar.
But there are more than 20 strains of scrapie, and six of sCJD. "You would
not necessarily see a relationship between the two with epidemiology if only
some strains affect only some people," says Deslys. Bruce is cautious about the
mouse results, but agrees they require further investigation. Other trials of
scrapie and sCJD in mice, she says, are in progress.
People can have three different genetic variations of the human prion
protein, and each type of protein can fold up two different ways. Kretschmar has
found that these six combinations correspond to six clinical types of sCJD: each
type of normal prion produces a particular pathology when it spontaneously
deforms to produce sCJD.
But if these proteins deform because of infection with a disease-causing
prion, the relationship between pathology and prion type should be different, as
it is in vCJD. "If we look at brain samples from sporadic CJD cases and find
some that do not fit the pattern," says Kretschmar, "that could mean they were
caused by infection."
There are 250 deaths per year from sCJD in the US, and a similar incidence
elsewhere. Singeltary and other US activists think that some of these people
died after eating contaminated meat or "nutritional" pills containing dried
animal brain. Governments will have a hard time facing activists like Singeltary
if it turns out that some sCJD isn't as spontaneous as doctors have
insisted.
Deslys's work on macaques also provides further proof that the human
disease vCJD is caused by BSE. And the experiments showed that vCJD is much more
virulent to primates than BSE, even when injected into the bloodstream rather
than the brain. This, says Deslys, means that there is an even bigger risk than
we thought that vCJD can be passed from one patient to another through
contaminated blood transfusions and surgical instruments.
Like lambs to the slaughter
Thursday, December 20, 2012
OIE GROUP RECOMMENDS THAT SCRAPE PRION DISEASE BE DELISTED AND SAME OLD BSe
WITH BOVINE MAD COW DISEASE
Monday, November 30, 2009
USDA AND OIE COLLABORATE TO EXCLUDE ATYPICAL SCRAPIE NOR-98 ANIMAL HEALTH
CODE
Monday, April 25, 2011
Experimental Oral Transmission of Atypical Scrapie to Sheep Volume 17,
Number 5-May 2011
Friday, February 11, 2011
Atypical/Nor98 Scrapie Infectivity in Sheep Peripheral Tissues
Monday, June 27, 2011
Comparison of Sheep Nor98 with Human Variably Protease-Sensitive
Prionopathy and Gerstmann-Sträussler-Scheinker Disease
BSE: TIME TO TAKE H.B. PARRY SERIOUSLY
If the scrapie agent is generated from ovine DNA and thence causes disease
in other species, then perhaps, bearing in mind the possible role of scrapie in
CJD of humans (Davinpour et al, 1985), scrapie and not BSE should be the
notifiable disease. ...
TSS
posted by Terry S. Singeltary Sr. | 12:36 PM
0 Comments:
Post a Comment
Subscribe to Post Comments [Atom]
<< Home