SPONTANEOUS TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHY TSE PRION AKA MAD COW
TYPE DISEASE, DOES IT EXIST NATURALLY IN THE FIELD?
*** We describe the transmission of spongiform encephalopathy in a
non-human primate inoculated 10 years earlier with a strain of sheep c-scrapie.
Because of this extended incubation period in a facility in which other prion
diseases are under study, we are obliged to consider two alternative
possibilities that might explain its occurrence. We first considered the
possibility of a sporadic origin (like CJD in humans). Such an event is
extremely improbable because the inoculated animal was 14 years old when the
clinical signs appeared, i.e. about 40% through the expected natural lifetime of
this species, compared to a peak age incidence of 60–65 years in human sporadic
CJD, or about 80% through their expected lifetimes. ***Moreover, sporadic
disease has never been observed in breeding colonies or primate research
laboratories, most notably among hundreds of animals over several decades of
study at the National Institutes of Health25, and in nearly twenty older animals
continuously housed in our own facility.***
>>> Moreover, sporadic disease has never been observed in breeding
colonies or primate research laboratories, most notably among hundreds of
animals over several decades of study at the National Institutes of Health25,
and in nearly twenty older animals continuously housed in our own facility.
<<<
Transmission of scrapie prions to primate after an extended silent
incubation period
Emmanuel E. Comoy1 , Jacqueline Mikol1 , Sophie Luccantoni-Freire1 ,
Evelyne Correia1 , Nathalie Lescoutra-Etchegaray1 , Valérie Durand1 , Capucine
Dehen1 , Olivier Andreoletti2 , Cristina Casalone3 , Juergen A. Richt4 n1 ,
Justin J. Greenlee4 , Thierry Baron5 , Sylvie L. Benestad6 , Paul Brown1 […]
& Jean-Philippe Deslys1 - Show fewer authors Scientific Reports 5, Article
number: 11573 (2015) doi:10.1038/srep11573 Download Citation
Epidemiology | Neurological manifestations | Prion diseases Received: 16
February 2015 Accepted: 28 May 2015 Published online: 30 June 2015 ABSTRACT
Classical bovine spongiform encephalopathy (c-BSE) is the only animal prion
disease reputed to be zoonotic, causing variant Creutzfeldt-Jakob disease (vCJD)
in humans and having guided protective measures for animal and human health
against animal prion diseases. Recently, partial transmissions to humanized mice
showed that the zoonotic potential of scrapie might be similar to c-BSE. We here
report the direct transmission of a natural classical scrapie isolate to
cynomolgus macaque, a highly relevant model for human prion diseases, after a
10-year silent incubation period, with features similar to those reported for
human cases of sporadic CJD. Scrapie is thus actually transmissible to primates
with incubation periods compatible with their life expectancy, although fourfold
longer than BSE. Long-term experimental transmission studies are necessary to
better assess the zoonotic potential of other prion diseases with high
prevalence, notably Chronic Wasting Disease of deer and elk and atypical/Nor98
scrapie.
snip...
Discussion
We describe the transmission of spongiform encephalopathy in a non-human
primate inoculated 10 years earlier with a strain of sheep c-scrapie. Because of
this extended incubation period in a facility in which other prion diseases are
under study, we are obliged to consider two alternative possibilities that might
explain its occurrence. We first considered the possibility of a sporadic origin
(like CJD in humans). Such an event is extremely improbable because the
inoculated animal was 14 years old when the clinical signs appeared, i.e. about
40% through the expected natural lifetime of this species, compared to a peak
age incidence of 60–65 years in human sporadic CJD, or about 80% through their
expected lifetimes. Moreover, sporadic disease has never been observed in
breeding colonies or primate research laboratories, most notably among hundreds
of animals over several decades of study at the National Institutes of Health25,
and in nearly twenty older animals continuously housed in our own
facility.
The second possibility is a laboratory cross-contamination. Three facts
make this possibility equally unlikely. First, handling of specimens in our
laboratory is performed with fastidious attention to the avoidance of any such
cross-contamination. Second, no laboratory cross-contamination has ever been
documented in other primate laboratories, including the NIH, even between
infected and uninfected animals housed in the same or adjacent cages with daily
intimate contact (P. Brown, personal communication). Third, the cerebral lesion
profile is different from all the other prion diseases we have studied in this
model19, with a correlation between cerebellar lesions (massive spongiform
change of Purkinje cells, intense PrPres staining and reactive gliosis26) and
ataxia. The iron deposits present in the globus pallidus are a non specific
finding that have been reported previously in neurodegenerative diseases and
aging27. Conversely, the thalamic lesion was reminiscent of a metabolic disease
due to thiamine deficiency28 but blood thiamine levels were within normal limits
(data not shown). The preferential distribution of spongiform change in cortex
associated with a limited distribution in the brainstem is reminiscent of the
lesion profile in MM2c and VV1 sCJD patients29, but interspecies comparison of
lesion profiles should be interpreted with caution. It is of note that the same
classical scrapie isolate induced TSE in C57Bl/6 mice with similar incubation
periods and lesional profiles as a sample derived from a MM1 sCJD
patient30.
We are therefore confident that the illness in this cynomolgus macaque
represents a true transmission of a sheep c-scrapie isolate directly to an
old-world monkey, which taxonomically resides in the primate subdivision
(parvorder of catarrhini) that includes humans. With an homology of its PrP
protein with humans of 96.4%31, cynomolgus macaque constitutes a highly relevant
model for assessing zoonotic risk of prion diseases. Since our initial aim was
to show the absence of transmission of scrapie to macaques in the worst-case
scenario, we obtained materials from a flock of naturally-infected sheep,
affecting animals with different genotypes32. This c-scrapie isolate exhibited
complete transmission in ARQ/ARQ sheep (332 ± 56 days) and Tg338 transgenic mice
expressing ovine VRQ/VRQ prion protein (220 ± 5 days) (O. Andreoletti, personal
communication). From the standpoint of zoonotic risk, it is important to note
that sheep with c-scrapie (including the isolate used in our study) have
demonstrable infectivity throughout their lymphoreticular system early in the
incubation period of the disease (3 months-old for all the lymphoid organs, and
as early as 2 months-old in gut-associated lymph nodes)33. In addition, scrapie
infectivity has been identified in blood34, milk35 and skeletal muscle36 from
asymptomatic but scrapie infected small ruminants which implies a potential
dietary exposure for consumers.
Two earlier studies have reported the occurrence of clinical TSE in
cynomolgus macaques after exposures to scrapie isolates. In the first study, the
“Compton” scrapie isolate (derived from an English sheep) and serially
propagated for 9 passages in goats did not transmit TSE in cynomolgus macaque,
rhesus macaque or chimpanzee within 7 years following intracerebral challenge1;
conversely, after 8 supplementary passages in conventional mice, this “Compton”
isolate induced TSE in a cynomolgus macaque 5 years after intracerebral
challenge, but rhesus macaques and chimpanzee remained asymptomatic 8.5 years
post-exposure8. However, multiple successive passages that are classically used
to select laboratory-adapted prion strains can significantly modify the initial
properties of a scrapie isolate, thus questioning the relevance of zoonotic
potential for the initial sheep-derived isolate. The same isolate had also
induced disease into squirrel monkeys (new-world monkey)9. A second historical
observation reported that a cynomolgus macaque developed TSE 6 years
post-inoculation with brain homogenate from a scrapie-infected Suffolk ewe
(derived from USA), whereas a rhesus macaque and a chimpanzee exposed to the
same inoculum remained healthy 9 years post-exposure1. This inoculum also
induced TSE in squirrel monkeys after 4 passages in mice. Other scrapie
transmission attempts in macaque failed but had more shorter periods of
observation in comparison to the current study. Further, it is possible that
there are differences in the zoonotic potential of different scrapie
strains.
The most striking observation in our study is the extended incubation
period of scrapie in the macaque model, which has several implications. Firstly,
our observations constitute experimental evidence in favor of the zoonotic
potential of c-scrapie, at least for this isolate that has been extensively
studied32,33,34,35,36. The cross-species zoonotic ability of this isolate should
be confirmed by performing duplicate intracerebral exposures and assessing the
transmissibility by the oral route (a successful transmission of prion strains
through the intracerebral route may not necessarily indicate the potential for
oral transmission37). However, such confirmatory experiments may require more
than one decade, which is hardly compatible with current general management and
support of scientific projects; thus this study should be rather considered as a
case report.
Secondly, transmission of c-BSE to primates occurred within 8 years post
exposure for the lowest doses able to transmit the disease (the survival period
after inoculation is inversely proportional to the initial amount of infectious
inoculum). The occurrence of scrapie 10 years after exposure to a high dose (25
mg) of scrapie-infected sheep brain suggests that the macaque has a higher
species barrier for sheep c-scrapie than c-BSE, although it is notable that
previous studies based on in vitro conversion of PrP suggested that BSE and
scrapie prions would have a similar conversion potential for human PrP38.
Thirdly, prion diseases typically have longer incubation periods after oral
exposure than after intracerebral inoculations: since humans can develop Kuru 47
years after oral exposure39, an incubation time of several decades after oral
exposure to scrapie would therefore be expected, leading the disease to occur in
older adults, i.e. the peak age for cases considered to be sporadic disease, and
making a distinction between scrapie-associated and truly sporadic disease
extremely difficult to appreciate.
Fourthly, epidemiologic evidence is necessary to confirm the zoonotic
potential of an animal disease suggested by experimental studies. A relatively
short incubation period and a peculiar epidemiological situation (e.g., all the
first vCJD cases occurring in the country with the most important ongoing c-BSE
epizootic) led to a high degree of suspicion that c-BSE was the cause of vCJD.
Sporadic CJD are considered spontaneous diseases with an almost stable and
constant worldwide prevalence (0.5–2 cases per million inhabitants per year),
and previous epidemiological studies were unable to draw a link between sCJD and
classical scrapie6,7,40,41, even though external causes were hypothesized to
explain the occurrence of some sCJD clusters42,43,44. However, extended
incubation periods exceeding several decades would impair the predictive values
of epidemiological surveillance for prion diseases, already weakened by a
limited prevalence of prion diseases and the multiplicity of isolates gathered
under the phenotypes of “scrapie” and “sporadic CJD”.
Fifthly, considering this 10 year-long incubation period, together with
both laboratory and epidemiological evidence of decade or longer intervals
between infection and clinical onset of disease, no premature conclusions should
be drawn from negative transmission studies in cynomolgus macaques with less
than a decade of observation, as in the aforementioned historical transmission
studies of scrapie to primates1,8,9. Our observations and those of others45,46
to date are unable to provide definitive evidence regarding the zoonotic
potential of CWD, atypical/Nor98 scrapie or H-type BSE. The extended incubation
period of the scrapie-affected macaque in the current study also underscores the
limitations of rodent models expressing human PrP for assessing the zoonotic
potential of some prion diseases since their lifespan remains limited to
approximately two years21,47,48. This point is illustrated by the fact that the
recently reported transmission of scrapie to humanized mice was not associated
with clinical signs for up to 750 days and occurred in an extreme minority of
mice with only a marginal increase in attack rate upon second passage13. The low
attack rate in these studies is certainly linked to the limited lifespan of mice
compared to the very long periods of observation necessary to demonstrate the
development of scrapie. Alternatively, one could estimate that a successful
second passage is the result of strain adaptation to the species barrier, thus
poorly relevant of the real zoonotic potential of the original scrapie isolate
of sheep origin49. The development of scrapie in this primate after an
incubation period compatible with its lifespan complements the study conducted
in transgenic (humanized) mice; taken together these studies suggest that some
isolates of sheep scrapie can promote misfolding of the human prion protein and
that scrapie can develop within the lifespan of some primate species.
In addition to previous studies on scrapie transmission to primate1,8,9 and
the recently published study on transgenic humanized mice13, our results
constitute new evidence for recommending that the potential risk of scrapie for
human health should not be dismissed. Indeed, human PrP transgenic mice and
primates are the most relevant models for investigating the human transmission
barrier. To what extent such models are informative for measuring the zoonotic
potential of an animal TSE under field exposure conditions is unknown. During
the past decades, many protective measures have been successfully implemented to
protect cattle from the spread of c-BSE, and some of these measures have been
extended to sheep and goats to protect from scrapie according to the principle
of precaution. Since cases of c-BSE have greatly reduced in number, those
protective measures are currently being challenged and relaxed in the absence of
other known zoonotic animal prion disease. We recommend that risk managers
should be aware of the long term potential risk to human health of at least
certain scrapie isolates, notably for lymphotropic strains like the classical
scrapie strain used in the current study. Relatively high amounts of infectivity
in peripheral lymphoid organs in animals infected with these strains could lead
to contamination of food products produced for human consumption. Efforts should
also be maintained to further assess the zoonotic potential of other animal
prion strains in long-term studies, notably lymphotropic strains with high
prevalence like CWD, which is spreading across North America, and atypical/Nor98
scrapie (Nor98)50 that was first detected in the past two decades and now
represents approximately half of all reported cases of prion diseases in small
ruminants worldwide, including territories previously considered as scrapie
free. Even if the prevailing view is that sporadic CJD is due to the spontaneous
formation of CJD prions, it remains possible that its apparent sporadic nature
may, at least in part, result from our limited capacity to identify an
environmental origin.
spontaneous atypical BSE ???
if that's the case, then France is having one hell of an epidemic of atypical BSE, probably why they stopped testing for BSE, problem solved $$$
As of December 2011, around 60 atypical BSE cases have currently been reported in 13 countries, *** with over one third in France.
http://www.biomedcentral.com/1746-6148/8/74
so 20 cases of atypical BSE in France, compared to the remaining 40 cases in the remaining 12 Countries, divided by the remaining 12 Countries, about 3+ cases per country, besides Frances 20 cases. you cannot explain this away with any spontaneous BSe. ...TSS
Sunday, October 5, 2014
France stops BSE testing for Mad Cow Disease
http://transmissiblespongiformencephalopathy.blogspot.com/2014/10/france-stops-bse-testing-for-mad-cow.html
Thursday, July 24, 2014
*** Protocol for further laboratory investigations into the distribution of infectivity of Atypical BSE SCIENTIFIC REPORT OF EFSA New protocol for Atypical BSE investigations
http://bse-atypical.blogspot.com/2014/07/protocol-for-further-laboratory.html
2015PRION CONFERENCE FT. COLLINS
>>>Not a threat to humans<<<
this is completely and absolutely wrong. fact is, scientist have no
absolute clue yet, but science is showing that the risk of humans contracting
CWD is very real, and the science is showing it’s very likely, if it has not
happened already. just look at the recent science coming out of the PRION2015
conference in Ft. Collins, and then you tell me there is no risk of cwd to
humans. ...
*** LATE-BREAKING ABSTRACTS PRION 2015 CONFERENCE ***
O18
Zoonotic Potential of CWD Prions
Liuting Qing1, Ignazio Cali1,2, Jue Yuan1, Shenghai Huang3, Diane Kofskey1,
Pierluigi Gambetti1, Wenquan Zou1, Qingzhong Kong1 1Case Western Reserve
University, Cleveland, Ohio, USA, 2Second University of Naples, Naples, Italy,
3Encore Health Resources, Houston, Texas, USA
Chronic wasting disease (CWD) is a widespread and expanding prion disease
in free-ranging and captive cervid species in North America. The zoonotic
potential of CWD prions is a serious public health concern. Current literature
generated with in vitro methods and in vivo animal models (transgenic mice,
macaques and squirrel monkeys) reports conflicting results. The susceptibility
of human CNS and peripheral organs to CWD prions remains largely unresolved. In
our earlier bioassay experiments using several humanized transgenic mouse lines,
we detected protease-resistant PrPSc in the spleen of two out of 140 mice that
were intracerebrally inoculated with natural CWD isolates, but PrPSc was not
detected in the brain of the same mice. Secondary passages with such
PrPSc-positive CWD-inoculated humanized mouse spleen tissues led to efficient
prion transmission with clear clinical and pathological signs in both humanized
and cervidized transgenic mice. Furthermore, a recent bioassay with natural CWD
isolates in a new humanized transgenic mouse line led to clinical prion
infection in 2 out of 20 mice. These results indicate that the CWD prion has the
potential to infect human CNS and peripheral lymphoid tissues and that there
might be asymptomatic human carriers of CWD infection.
==================
***These results indicate that the CWD prion has the potential to infect
human CNS and peripheral lymphoid tissues and that there might be asymptomatic
human carriers of CWD infection.***
==================
P.105: RT-QuIC models trans-species prion transmission
Kristen Davenport, Davin Henderson, Candace Mathiason, and Edward Hoover
Prion Research Center; Colorado State University; Fort Collins, CO USA
The propensity for trans-species prion transmission is related to the
structural characteristics of the enciphering and heterologous PrP, but the
exact mechanism remains mostly mysterious. Studies of the effects of primary or
tertiary prion protein structures on trans-species prion transmission have
relied primarily upon animal bioassays, making the influence of prion protein
structure vs. host co-factors (e.g. cellular constituents, trafficking, and
innate immune interactions) difficult to dissect. As an alternative strategy, we
used real-time quakinginduced conversion (RT-QuIC) to investigate trans-species
prion conversion.
To assess trans-species conversion in the RT-QuIC system, we compared
chronic wasting disease (CWD) and bovine spongiform encephalopathy (BSE) prions,
as well as feline CWD (fCWD) and feline spongiform encephalopathy (FSE). Each
prion was seeded into each host recombinant PrP (full-length rPrP of
white-tailed deer, bovine or feline). We demonstrated that fCWD is a more
efficient seed for feline rPrP than for white-tailed deer rPrP, which suggests
adaptation to the new host.
Conversely, FSE maintained sufficient BSE characteristics to more
efficiently convert bovine rPrP than feline rPrP. Additionally, human rPrP was
competent for conversion by CWD and fCWD. ***This insinuates that, at the level
of protein:protein interactions, the barrier preventing transmission of CWD to
humans is less robust than previously estimated.
================
***This insinuates that, at the level of protein:protein interactions, the
barrier preventing transmission of CWD to humans is less robust than previously
estimated.***
================
Willingham, Erin McNulty, Kelly Anderson, Jeanette Hayes-Klug, Amy Nalls,
and Candace Mathiason Colorado State University; Fort Collins, CO USA
Chronic wasting disease (CWD) is the transmissible spongiform
encephalopathy (TSE), of free-ranging and captive cervids (deer, elk and moose).
The presence of infectious prions in the tissues, bodily fluids and
environments of clinical and preclinical CWD-infected animals is thought to
account for its high transmission efficiency. Recently it has been recognized
that mother to offspring transmission may contribute to the facile transmission
of some TSEs. Although the mechanism behind maternal transmission is not yet
known, the extended asymptomatic TSE carrier phase (lasting years to decades)
suggests that it may have implications in the spread of prions.
Placental trafficking and/or secretion in milk are 2 means by which
maternal prion transmission may occur. In these studies we explore these avenues
during early and late infection using a transgenic mouse model expressing cervid
prion protein. Na€ıve and CWD-infected dams were bred at both timepoints, and
were allowed to bear and raise their offspring. Milk was collected from the dams
for prion analysis, and the offspring were observed for TSE disease progression.
Terminal tissues harvested from both dams and offspring were analyzed for
prions.
We have demonstrated that
(1) CWD infected TgCerPRP females successfully breed and bear offspring,
and
(2) the presence of PrPCWD in reproductive and mammary tissue from
CWD-infected dams.
We are currently analyzing terminal tissue harvested from offspring born to
CWD-infected dams for the detection of PrPCWD and amplification competent
prions. These studies will provide insight into the potential mechanisms and
biological significance associated with mother to offspring transmission of
TSEs.
==============
P.157: Uptake of prions into plants
Christopher Johnson1, Christina Carlson1, Matthew Keating1,2, Nicole
Gibbs1, Haeyoon Chang1, Jamie Wiepz1, and Joel Pedersen1 1USGS National Wildlife
Health Center; Madison, WI USA; 2University of Wisconsin - Madison; Madison, WI
USA
Soil may preserve chronic wasting disease (CWD) and scrapie infectivity in
the environment, making consumption or inhalation of soil particles a plausible
mechanism whereby na€ıve animals can be exposed to prions. Plants are known to
absorb a variety of substances from soil, including whole proteins, yet the
potential for plants to take up abnormal prion protein (PrPTSE) and preserve
prion infectivity is not known. In this study, we assessed PrPTSE uptake into
roots using laser scanning confocal microscopy with fluorescently tagged PrPTSE
and we used serial protein misfolding cyclic amplification (sPMCA) and detect
and quantify PrPTSE levels in plant aerial tissues. Fluorescence was identified
in the root hairs of the model plant Arabidopsis thaliana, as well as the crop
plants alfalfa (Medicago sativa), barley (Hordeum vulgare) and tomato (Solanum
lycopersicum) upon exposure to tagged PrPTSE but not a tagged control
preparation. Using sPMCA, we found evidence of PrPTSE in aerial tissues of A.
thaliana, alfalfa and maize (Zea mays) grown in hydroponic cultures in which
only roots were exposed to PrPTSE. Levels of PrPTSE in plant aerial tissues
ranged from approximately 4 £ 10 ¡10 to 1 £ 10 ¡9 g PrPTSE g ¡1 plant dry weight
or 2 £ 105 to 7 £ 106 intracerebral ID50 units g ¡1 plant dry weight. Both stems
and leaves of A. thaliana grown in culture media containing prions are
infectious when intracerebrally-injected into mice. ***Our results suggest that
prions can be taken up by plants and that contaminated plants may represent a
previously unrecognized risk of human, domestic species and wildlife exposure to
prions.
===========
***Our results suggest that prions can be taken up by plants and that
contaminated plants may represent a previously unrecognized risk of human,
domestic species and wildlife exposure to prions.***
SEE ;
Friday, May 15, 2015
Grass Plants Bind, Retain, Uptake, and Transport Infectious Prions
Report
============
P.19: Characterization of chronic wasting disease isolates from freeranging
deer (Odocoileus sp) in Alberta and Saskatchewan, Canada
Camilo Duque Velasquez1, Chiye Kim1, Nathalie Daude1, Jacques van der
Merwe1, Allen Herbst1, Trent Bollinger2, Judd Aiken1, and Debbie McKenzie1
1Centre for Prions and Protein Folding Diseases; University of Alberta;
Edmonton, Canada; 2Western College of Veterinary Medicine; University of
Saskatchewan; Saskatoon, Canada
Chronic wasting disease (CWD) is an emerging prion disease of free ranging
and captive species of Cervidae. In North America, CWD is enzootic in some wild
cervid populations and can circulate among different deer species. The
contagious nature of CWD prions and the variation of cervid PRNP alleles, which
influence host susceptibility, can result in the emergence and adaptation of
different CWD strains. These strains may impact transmission host range, disease
diagnosis, spread dynamics and efficacy of potential vaccines. We are
characterizing different CWD agents by biochemical analysis of the PrPCWD
conformers, propagation in vitro cell assays1 and by comparing transmission
properties and neuropathology in Tg33 (Q95G96) and Tg60 (Q95S96) mice.2 Although
Tg60 mice expressing S96- PrPC have been shown resistant to CWD infectivity from
various cervid species,2,3
***these transgenic mice are susceptible to H95 C CWD, a CWD strain derived
from experimental infection of deer expressing H95G96-PrPC. The diversity of
strains present in free-ranging mule deer (Odocoileus hemionus) and white-tailed
deer (Odocoileus virginianus) from Alberta and Saskatchewan is being determined
and will allow us to delineate the properties of CWD agents circulating in CWD
enzootic cervid populations of Canada.
References
1. van der Merwe J, Aiken J, Westaway D, McKenzie D. The standard scrapie
cell assay: Development, utility and prospects. Viruses 2015; 7(1):180–198;
PMID:25602372; http://dx.doi.org/10.3390/v7010180
2. Meade-White K, Race B, Trifilo M, Bossers A, Favara C, Lacasse R, Miller
M, Williams E, Oldstone M, Race R, Chesebro B. Resistance to chronic wasting
disease in transgenic mice expressing a naturally occurring allelic variant of
deer prion protein. J Virol 2007; 81(9):4533–4539; PMID: 17314157; http://dx. doi.org/10.1128/JVI.02762-06
3. Race B, Meade-White K, Miller MW, Fox KA, Chesebro B. In vivo comparison
of chronic wasting disease infectivity from deer with variation at prion protein
residue 96. J Virol 2011; 85(17):9235–9238; PMID: 21697479; http://dx.doi.org/10.1128/JVI.00790-11
=========
***these transgenic mice are susceptible to H95 C CWD, a CWD strain derived
from experimental infection of deer expressing H95G96-PrPC.
==========
P.136: Mother to offspring transmission of CWD—Detection in fawn tissues
using the QuIC assay
Amy Nalls, Erin McNulty, Clare Hoover, Jeanette Hayes-Klug, Kelly Anderson,
Edward Hoover, and Candace Mathiason Colorado State University; Fort Collins, CO
USA
To investigate the role mother to offspring transmission plays in chronic
wasting disease (CWD), we have employed a small, polyestrous breeding, indoor
maintainable cervid model, the Reeves’ muntjac deer. Muntjac doe were inoculated
with CWD and tested positive by lymphoid biopsy at 4 months post inoculation.
From these CWD-infected doe, we obtained 3 viable fawns. These fawns tested
IHC-positive for CWD by lymphoid biopsy as early as 40 d post birth, and all
have been euthanized due to clinical disease at 31, 34 and 59 months post birth.
The QuIC assay demonstrates sensitivity and specificity in the detection of
conversion competent prions in peripheral IHC-positive tissues including tonsil,
mandibular, partotid, retropharyngeal, and prescapular lymph nodes, adrenal
gland, spleen and liver. In summary, using the muntjac deer model, we have
demonstrated CWD clinical disease in offspring born to CWD-infected doe and
found that the QuIC assay is an effective tool in the detection of prions in
peripheral tissues. ***Our findings demonstrate that transmission of prions from
mother to offspring can occur, and may be underestimated for all prion
diseases.
===============
***Our findings demonstrate that transmission of prions from mother to
offspring can occur, and may be underestimated for all prion diseases.
===============
I strenuously once again urge the FDA and its industry constituents, to
make it MANDATORY that all ruminant feed be banned to all ruminants, and this
should include all cervids as soon as possible for the following
reasons...
======
In the USA, under the Food and Drug Administrations BSE Feed Regulation (21
CFR 589.2000) most material (exceptions include milk, tallow, and gelatin) from
deer and elk is prohibited for use in feed for ruminant animals. With regards to
feed for non-ruminant animals, under FDA law, CWD positive deer may not be used
for any animal feed or feed ingredients. For elk and deer considered at high
risk for CWD, the FDA recommends that these animals do not enter the animal feed
system.
***However, this recommendation is guidance and not a requirement by law.
======
31 Jan 2015 at 20:14 GMT
*** Ruminant feed ban for cervids in the United States? ***
31 Jan 2015 at 20:14 GMT
cwd environmental load factor in the land and surrounding plants and
objects.
transportation of cervids and HUMANS from cwd zone should be regarded as a
great risk factor, and environmental contamination.
PL1
Using in vitro prion replication for high sensitive detection of prions and
prionlike proteins and for understanding mechanisms of transmission.
Claudio Soto
Mitchell Center for Alzheimer's diseases and related Brain disorders,
Department of Neurology, University of Texas Medical School at Houston.
Prion and prion-like proteins are misfolded protein aggregates with the
ability to selfpropagate to spread disease between cells, organs and in some
cases across individuals. I n T r a n s m i s s i b l e s p o n g i f o r m
encephalopathies (TSEs), prions are mostly composed by a misfolded form of the
prion protein (PrPSc), which propagates by transmitting its misfolding to the
normal prion protein (PrPC). The availability of a procedure to replicate prions
in the laboratory may be important to study the mechanism of prion and
prion-like spreading and to develop high sensitive detection of small quantities
of misfolded proteins in biological fluids, tissues and environmental samples.
Protein Misfolding Cyclic Amplification (PMCA) is a simple, fast and efficient
methodology to mimic prion replication in the test tube. PMCA is a platform
technology that may enable amplification of any prion-like misfolded protein
aggregating through a seeding/nucleation process. In TSEs, PMCA is able to
detect the equivalent of one single molecule of infectious PrPSc and propagate
prions that maintain high infectivity, strain properties and species
specificity. Using PMCA we have been able to detect PrPSc in blood and urine of
experimentally infected animals and humans affected by vCJD with high
sensitivity and specificity. Recently, we have expanded the principles of PMCA
to amplify amyloid-beta (Aβ) and alphasynuclein (α-syn) aggregates implicated in
Alzheimer's and Parkinson's diseases, respectively. Experiments are ongoing to
study the utility of this technology to detect Aβ and α-syn aggregates in
samples of CSF and blood from patients affected by these diseases.
***Recently, we have been using PMCA to study the role of environmental
prion contamination on the horizontal spreading of TSEs. These experiments have
focused on the study of the interaction of prions with plants and
environmentally relevant surfaces. Our results show that plants (both leaves and
roots) bind tightly to prions present in brain extracts and excreta (urine and
feces) and retain even small quantities of PrPSc for long periods of time.
Strikingly, ingestion of prioncontaminated leaves and roots produced disease
with a 100% attack rate and an incubation period not substantially longer than
feeding animals directly with scrapie brain homogenate. Furthermore, plants can
uptake prions from contaminated soil and transport them to different parts of
the plant tissue (stem and leaves). Similarly, prions bind tightly to a variety
of environmentallyrelevant surfaces, including stones, wood, metals, plastic,
glass, cement, etc. Prion contaminated surfaces efficiently transmit prion
disease when these materials were directly injected into the brain of animals
and strikingly when the contaminated surfaces were just placed in the animal
cage. These findings demonstrate that environmental materials can efficiently
bind infectious prions and act as carriers of infectivity, suggesting that they
may play an important role in the horizontal transmission of the disease.
Since its invention 13 years ago, PMCA has helped to answer fundamental
questions of prion propagation and has broad applications in research areas
including the food industry, blood bank safety and human and veterinary disease
diagnosis.
Wednesday, June 10, 2015
Zoonotic Potential of CWD Prions
LATE-BREAKING ABSTRACTS
Friday, January 30, 2015
*** Scrapie: a particularly persistent pathogen ***
98 | Veterinary Record | January 24, 2015
EDITORIAL
Scrapie: a particularly persistent pathogen
Cristina Acín
Resistant prions in the environment have been the sword of Damocles for
scrapie control and eradication. Attempts to establish which physical and
chemical agents could be applied to inactivate or moderate scrapie infectivity
were initiated in the 1960s and 1970s,with the first study of this type focusing
on the effect of heat treatment in reducing prion infectivity (Hunter and
Millson 1964). Nowadays, most of the chemical procedures that aim to inactivate
the prion protein are based on the method developed by Kimberlin and
collaborators (1983). This procedure consists of treatment with 20,000 parts per
million free chlorine solution, for a minimum of one hour, of all surfaces that
need to be sterilised (in laboratories, lambing pens, slaughterhouses, and so
on). Despite this, veterinarians and farmers may still ask a range of questions,
such as ‘Is there an official procedure published somewhere?’ and ‘Is there an
international organisation which recommends and defines the exact method of
scrapie decontamination that must be applied?’
From a European perspective, it is difficult to find a treatment that could
be applied, especially in relation to the disinfection of surfaces in lambing
pens of affected flocks. A 999/2001 EU regulation on controlling spongiform
encephalopathies (European Parliament and Council 2001) did not specify a
particular decontamination measure to be used when an outbreak of scrapie is
diagnosed. There is only a brief recommendation in Annex VII concerning the
control and eradication of transmissible spongiform encephalopathies (TSE
s).
Chapter B of the regulation explains the measures that must be applied if
new caprine animals are to be introduced to a holding where a scrapie outbreak
has previously been diagnosed. In that case, the statement indicates that
caprine animals can be introduced ‘provided that a cleaning and disinfection of
all animal housing on the premises has been carried out following
destocking’.
Issues around cleaning and disinfection are common in prion prevention
recommendations, but relevant authorities, veterinarians and farmers may have
difficulties in finding the specific protocol which applies. The European Food
and Safety Authority (EFSA ) published a detailed report about the efficacy of
certain biocides, such as sodium hydroxide, sodium hypochlorite, guanidine and
even a formulation of copper or iron metal ions in combination with hydrogen
peroxide, against prions (EFSA 2009). The report was based on scientific
evidence (Fichet and others 2004, Lemmer and others 2004, Gao and others 2006,
Solassol and others 2006) but unfortunately the decontamination measures were
not assessed under outbreak conditions.
The EFSA Panel on Biological Hazards recently published its conclusions on
the scrapie situation in the EU after 10 years of monitoring and control of the
disease in sheep and goats (EFSA 2014), and one of the most interesting findings
was the Icelandic experience regarding the effect of disinfection in scrapie
control. The Icelandic plan consisted of: culling scrapie-affected sheep or the
whole flock in newly diagnosed outbreaks; deep cleaning and disinfection of
stables, sheds, barns and equipment with high pressure washing followed by
cleaning with 500 parts per million of hypochlorite; drying and treatment with
300 ppm of iodophor; and restocking was not permitted for at least two years.
Even when all of these measures were implemented, scrapie recurred on several
farms, indicating that the infectious agent survived for years in the
environment, even as many as 16 years after restocking (Georgsson and others
2006).
In the rest of the countries considered in the EFSA (2014) report,
recommendations for disinfection measures were not specifically defined at the
government level. In the report, the only recommendation that is made for sheep
is repopulation with sheep with scrapie-resistant genotypes. This reduces the
risk of scrapie recurrence but it is difficult to know its effect on the
infection.
Until the EFSA was established (in May 2003), scientific opinions about TSE
s were provided by the Scientific Steering Committee (SSC) of the EC, whose
advice regarding inactivation procedures focused on treating animal waste at
high temperatures (150°C for three hours) and high pressure alkaline hydrolysis
(SSC 2003). At the same time, the TSE Risk Management Subgroup of the Advisory
Committee on Dangerous Pathogens (ACDP) in the UK published guidance on safe
working and the prevention of TSE infection. Annex C of the ACDP report
established that sodium hypochlorite was considered to be effective, but only if
20,000 ppm of available chlorine was present for at least one hour, which has
practical limitations such as the release of chlorine gas, corrosion,
incompatibility with formaldehyde, alcohols and acids, rapid inactivation of its
active chemicals and the stability of dilutions (ACDP 2009).
In an international context, the World Organisation for Animal Health (OIE)
does not recommend a specific disinfection protocol for prion agents in its
Terrestrial Code or Manual. Chapter 4.13 of the Terrestrial Code, General
recommendations on disinfection and disinsection (OIE 2014), focuses on
foot-and-mouth disease virus, mycobacteria and Bacillus anthracis, but not on
prion disinfection. Nevertheless, the last update published by the OIE on bovine
spongiform encephalopathy (OIE 2012) indicates that few effective
decontamination techniques are available to inactivate the agent on surfaces,
and recommends the removal of all organic material and the use of sodium
hydroxide, or a sodium hypochlorite solution containing 2 per cent available
chlorine, for more than one hour at 20ºC.
The World Health Organization outlines guidelines for the control of TSE s,
and also emphasises the importance of mechanically cleaning surfaces before
disinfection with sodium hydroxide or sodium hypochlorite for one hour (WHO
1999).
Finally, the relevant agencies in both Canada and the USA suggest that the
best treatments for surfaces potentially contaminated with prions are sodium
hydroxide or sodium hypochlorite at 20,000 ppm. This is a 2 per cent solution,
while most commercial household bleaches contain 5.25 per cent sodium
hypochlorite. It is therefore recommended to dilute one part 5.25 per cent
bleach with 1.5 parts water (CDC 2009, Canadian Food Inspection Agency
2013).
So what should we do about disinfection against prions? First, it is
suggested that a single protocol be created by international authorities to
homogenise inactivation procedures and enable their application in all
scrapie-affected countries. Sodium hypochlorite with 20,000 ppm of available
chlorine seems to be the procedure used in most countries, as noted in a paper
summarised on p 99 of this issue of Veterinary Record (Hawkins and others 2015).
But are we totally sure of its effectiveness as a preventive measure in a
scrapie outbreak? Would an in-depth study of the recurrence of scrapie disease
be needed?
What we can conclude is that, if we want to fight prion diseases, and
specifically classical scrapie, we must focus on the accuracy of diagnosis,
monitoring and surveillance; appropriate animal identification and control of
movements; and, in the end, have homogeneous and suitable protocols to
decontaminate and disinfect lambing barns, sheds and equipment available to
veterinarians and farmers. Finally, further investigations into the resistance
of prion proteins in the diversity of environmental surfaces are required.
References
snip...
98 | Veterinary Record | January 24, 2015
Persistence of ovine scrapie infectivity in a farm environment following
cleaning and decontamination
Steve A. C. Hawkins, MIBiol, Pathology Department1, Hugh A. Simmons, BVSc
MRCVS, MBA, MA Animal Services Unit1, Kevin C. Gough, BSc, PhD2 and Ben C.
Maddison, BSc, PhD3 + Author Affiliations
1Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey
KT15 3NB, UK 2School of Veterinary Medicine and Science, The University of
Nottingham, Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK 3ADAS
UK, School of Veterinary Medicine and Science, The University of Nottingham,
Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK E-mail for
correspondence: ben.maddison@adas.co.uk Abstract Scrapie of sheep/goats and
chronic wasting disease of deer/elk are contagious prion diseases where
environmental reservoirs are directly implicated in the transmission of disease.
In this study, the effectiveness of recommended scrapie farm decontamination
regimens was evaluated by a sheep bioassay using buildings naturally
contaminated with scrapie. Pens within a farm building were treated with either
20,000 parts per million free chorine solution for one hour or were treated with
the same but were followed by painting and full re-galvanisation or replacement
of metalwork within the pen. Scrapie susceptible lambs of the PRNP genotype
VRQ/VRQ were reared within these pens and their scrapie status was monitored by
recto-anal mucosa-associated lymphoid tissue. All animals became infected over
an 18-month period, even in the pen that had been subject to the most stringent
decontamination process. These data suggest that recommended current guidelines
for the decontamination of farm buildings following outbreaks of scrapie do
little to reduce the titre of infectious scrapie material and that environmental
recontamination could also be an issue associated with these premises.
SNIP...
Discussion
Thorough pressure washing of a pen had no effect on the amount of
bioavailable scrapie infectivity (pen B). The routine removal of prions from
surfaces within a laboratory setting is treatment for a minimum of one hour with
20,000 ppm free chlorine, a method originally based on the use of brain
macerates from infected rodents to evaluate the effectiveness of decontamination
(Kimberlin and others 1983). Further studies have also investigated the
effectiveness of hypochlorite disinfection of metal surfaces to simulate the
decontamination of surgical devices within a hospital setting. Such treatments
with hypochlorite solution were able to reduce infectivity by 5.5 logs to lower
than the sensitivity of the bioassay used (Lemmer and others 2004). Analogous
treatment of the pen surfaces did not effectively remove the levels of scrapie
infectivity over that of the control pens, indicating that this method of
decontamination is not effective within a farm setting. This may be due to the
high level of biological matrix that is present upon surfaces within the farm
environment, which may reduce the amount of free chlorine available to
inactivate any infectious prion. Remarkably 1/5 sheep introduced into pen D had
also became scrapie positive within nine months, with all animals in this pen
being RAMALT positive by 18 months of age. Pen D was no further away from the
control pen (pen A) than any of the other pens within this barn. Localised hot
spots of infectivity may be present within scrapie-contaminated environments,
but it is unlikely that pen D area had an amount of scrapie contamination that
was significantly different than the other areas within this building.
Similarly, there were no differences in how the biosecurity of pen D was
maintained, or how this pen was ventilated compared with the other pens. This
observation, perhaps, indicates the slower kinetics of disease uptake within
this pen and is consistent with a more thorough prion removal and
recontamination. These observations may also account for the presence of
inadvertent scrapie cases within other studies, where despite stringent
biosecurity, control animals have become scrapie positive during challenge
studies using barns that also housed scrapie-affected animals (Ryder and others
2009). The bioassay data indicate that the exposure of the sheep to a farm
environment after decontamination efforts thought to be effective in removing
scrapie is sufficient for the animals to become infected with scrapie. The main
exposure routes within this scenario are likely to be via the oral route, during
feeding and drinking, and respiratory and conjunctival routes. It has been
demonstrated that scrapie infectivity can be efficiently transmitted via the
nasal route in sheep (Hamir and others 2008), as is the case for CWD in both
murine models and in white-tailed deer (Denkers and others 2010, 2013).
Recently, it has also been demonstrated that CWD prions presented as dust when
bound to the soil mineral montmorillonite can be infectious via the nasal route
(Nichols and others 2013). When considering pens C and D, the actual source of
the infectious agent in the pens is not known, it is possible that biologically
relevant levels of prion survive on surfaces during the decontamination regimen
(pen C). With the use of galvanising and painting (pen D) covering and sealing
the surface of the pen, it is possible that scrapie material recontaminated the
pens by the movement of infectious prions contained within dusts originating
from other parts of the barn that were not decontaminated or from other areas of
the farm.
Given that scrapie prions are widespread on the surfaces of affected farms
(Maddison and others 2010a), irrespective of the source of the infectious prions
in the pens, this study clearly highlights the difficulties that are faced with
the effective removal of environmentally associated scrapie infectivity. This is
likely to be paralleled in CWD which shows strong similarities to scrapie in
terms of both the dissemination of prions into the environment and the facile
mode of disease transmission. These data further contribute to the understanding
that prion diseases can be highly transmissible between susceptible individuals
not just by direct contact but through highly stable environmental reservoirs
that are refractory to decontamination.
The presence of these environmentally associated prions in farm buildings
make the control of these diseases a considerable challenge, especially in
animal species such as goats where there is lack of genetic resistance to
scrapie and, therefore, no scope to re-stock farms with animals that are
resistant to scrapie.
Scrapie Sheep Goats Transmissible spongiform encephalopathies (TSE)
Accepted October 12, 2014. Published Online First 31 October 2014
Monday, November 3, 2014
Persistence of ovine scrapie infectivity in a farm environment following
cleaning and decontamination
PPo3-22:
Detection of Environmentally Associated PrPSc on a Farm with Endemic
Scrapie
Ben C. Maddison,1 Claire A. Baker,1 Helen C. Rees,1 Linda A. Terry,2 Leigh
Thorne,2 Susan J. Belworthy2 and Kevin C. Gough3 1ADAS-UK LTD; Department of
Biology; University of Leicester; Leicester, UK; 2Veterinary Laboratories
Agency; Surry, KT UK; 3Department of Veterinary Medicine and Science; University
of Nottingham; Sutton Bonington, Loughborough UK
Key words: scrapie, evironmental persistence, sPMCA
Ovine scrapie shows considerable horizontal transmission, yet the routes of
transmission and specifically the role of fomites in transmission remain poorly
defined. Here we present biochemical data demonstrating that on a
scrapie-affected sheep farm, scrapie prion contamination is widespread. It was
anticipated at the outset that if prions contaminate the environment that they
would be there at extremely low levels, as such the most sensitive method
available for the detection of PrPSc, serial Protein Misfolding Cyclic
Amplification (sPMCA), was used in this study. We investigated the distribution
of environmental scrapie prions by applying ovine sPMCA to samples taken from a
range of surfaces that were accessible to animals and could be collected by use
of a wetted foam swab. Prion was amplified by sPMCA from a number of these
environmental swab samples including those taken from metal, plastic and wooden
surfaces, both in the indoor and outdoor environment. At the time of sampling
there had been no sheep contact with these areas for at least 20 days prior to
sampling indicating that prions persist for at least this duration in the
environment. These data implicate inanimate objects as environmental reservoirs
of prion infectivity which are likely to contribute to disease transmission.
Friday, May 22, 2015
*** Chronic Wasting Disease and Program Updates - 2014 NEUSAHA Annual
Meeting 12-14 May 2014 ***
Saturday, May 30, 2015
PRION 2015 ORAL AND POSTER CONGRESSIONAL ABSTRACTS
PLEASE SEE LATEST SCIENCE ON SPORADIC CJD POTENTIAL LINKS TO DIFFERENT
ANIMAL TSE PRION DISEASE ;
sporadic CJD now linked to c-BSE, L type BASE BSE (CALIFORNIA), Scrapie,
and atypical Scrapie, with much concern about CWD
***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.
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.
===============
***thus questioning the origin of human sporadic cases...TSS
===============
2014
***Moreover, L-BSE has been transmitted more easily to transgenic mice
overexpressing a human PrP [13,14] or to primates [15,16] than C-BSE.
***It has been suggested that some sporadic CJD subtypes in humans may
result from an exposure to the L-BSE agent.
*** Lending support to this hypothesis, pathological and biochemical
similarities have been observed between L-BSE and an sCJD subtype (MV genotype
at codon 129 of PRNP) [17], and between L-BSE infected non-human primate and
another sCJD subtype (MM genotype) [15].
snip...
Monday, October 10, 2011
EFSA Journal 2011 The European Response to BSE: A Success Story
snip...
EFSA and the European Centre for Disease Prevention and Control (ECDC)
recently delivered a scientific opinion on any possible epidemiological or
molecular association between TSEs in animals and humans (EFSA Panel on
Biological Hazards (BIOHAZ) and ECDC, 2011). This opinion confirmed Classical
BSE prions as the only TSE agents demonstrated to be zoonotic so far
*** but the possibility that a small proportion of human cases so far
classified as "sporadic" CJD are of zoonotic origin could not be excluded.
*** Moreover, transmission experiments to non-human primates suggest that
some TSE agents in addition to Classical BSE prions in cattle (namely L-type
Atypical BSE, Classical BSE in sheep, transmissible mink encephalopathy (TME)
and chronic wasting disease (CWD) agents) might have zoonotic potential.
snip...
Thursday, August 12, 2010
Seven main threats for the future linked to prions
First threat
The TSE road map defining the evolution of European policy for protection
against prion diseases is based on a certain numbers of hypotheses some of which
may turn out to be erroneous. In particular, a form of BSE (called atypical
Bovine Spongiform Encephalopathy), recently identified by systematic testing in
aged cattle without clinical signs, may be the origin of classical BSE and thus
potentially constitute a reservoir, which may be impossible to eradicate if a
sporadic origin is confirmed.
*** Also, a link is suspected between atypical BSE and some apparently
sporadic cases of Creutzfeldt-Jakob disease in humans.
*** These atypical BSE cases constitute an unforeseen first threat that
could sharply modify the European approach to prion diseases.
Second threat
snip...
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
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
emphasised by the finding that some strains of scrapie produce lesions identical
to the once which characterise 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 acrapie 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, March 8, 2013
Dogs may have been used to make Petfood and animal feed
Chronic Wasting Disease Susceptibility of Four North American Rodents
Chad J. Johnson1*, Jay R. Schneider2, Christopher J. Johnson2, Natalie A.
Mickelsen2, Julia A. Langenberg3, Philip N. Bochsler4, Delwyn P. Keane4, Daniel
J. Barr4, and Dennis M. Heisey2 1University of Wisconsin School of Veterinary
Medicine, Department of Comparative Biosciences, 1656 Linden Drive, Madison WI
53706, USA 2US Geological Survey, National Wildlife Health Center, 6006
Schroeder Road, Madison WI 53711, USA 3Wisconsin Department of Natural
Resources, 101 South Webster Street, Madison WI 53703, USA 4Wisconsin Veterinary
Diagnostic Lab, 445 Easterday Lane, Madison WI 53706, USA *Corresponding author
email: cjohnson@svm.vetmed.wisc.edu
We intracerebrally challenged four species of native North American rodents
that inhabit locations undergoing cervid chronic wasting disease (CWD)
epidemics. The species were: deer mice (Peromyscus maniculatus), white-footed
mice (P. leucopus), meadow voles (Microtus pennsylvanicus), and red-backed voles
(Myodes gapperi). The inocula were prepared from the brains of hunter-harvested
white-tailed deer from Wisconsin that tested positive for CWD. Meadow voles
proved to be most susceptible, with a median incubation period of 272 days.
Immunoblotting and immunohistochemistry confirmed the presence of PrPd in the
brains of all challenged meadow voles. Subsequent passages in meadow voles lead
to a significant reduction in incubation period. The disease progression in
red-backed voles, which are very closely related to the European bank vole (M.
glareolus) which have been demonstrated to be sensitive to a number of TSEs, was
slower than in meadow voles with a median incubation period of 351 days. We
sequenced the meadow vole and red-backed vole Prnp genes and found three amino
acid (AA) differences outside of the signal and GPI anchor sequences. Of these
differences (T56-, G90S, S170N; read-backed vole:meadow vole), S170N is
particularly intriguing due its postulated involvement in "rigid loop" structure
and CWD susceptibility. Deer mice did not exhibit disease signs until nearly 1.5
years post-inoculation, but appear to be exhibiting a high degree of disease
penetrance. White-footed mice have an even longer incubation period but are also
showing high penetrance. Second passage experiments show significant shortening
of incubation periods. Meadow voles in particular appear to be interesting lab
models for CWD. These rodents scavenge carrion, and are an important food source
for many predator species. Furthermore, these rodents enter human and domestic
livestock food chains by accidental inclusion in grain and forage. Further
investigation of these species as potential hosts, bridge species, and
reservoirs of CWD is required.
Veterinary Pathology Onlinevet.sagepub.com Published online before print
February 27, 2014, doi: 10.1177/0300985814524798 Veterinary Pathology February
27, 2014 0300985814524798
Lesion Profiling and Subcellular Prion Localization of Cervid Chronic
Wasting Disease in Domestic Cats
D. M. Seelig1⇑ A. V. Nalls1 M. Flasik2 V. Frank1 S. Eaton2 C. K. Mathiason1
E. A. Hoover1 1Department of Microbiology, Immunology, and Pathology, Colorado
State University, Fort Collins, CO, USA 2Department of Biomedical Sciences,
Colorado State University, Fort Collins, CO, USA D. M. Seelig, University of
Minnesota, Department of Veterinary Clinical Sciences, Room 339 VetMedCtrS,
6192A (Campus Delivery Code), 1352 Boyd Ave, St Paul, MN 55108, USA. Email
address: dseelig@umn.edu
Abstract
Chronic wasting disease (CWD) is an efficiently transmitted, fatal, and
progressive prion disease of cervids with an as yet to be fully clarified host
range. While outbred domestic cats (Felis catus) have recently been shown to be
susceptible to experimental CWD infection, the neuropathologic features of the
infection are lacking. Such information is vital to provide diagnostic power in
the event of natural interspecies transmission and insights into host and strain
interactions in interspecies prion infection. Using light microscopy and
immunohistochemistry, we detail the topographic pattern of neural spongiosis
(the “lesion profile”) and the distribution of misfolded prion protein in the
primary and secondary passage of feline CWD (FelCWD). We also evaluated cellular
and subcellular associations between misfolded prion protein (PrPD) and central
nervous system neurons and glial cell populations. From these studies, we (1)
describe the novel neuropathologic profile of FelCWD, which is distinct from
either cervid CWD or feline spongiform encephalopathy (FSE), and (2) provide
evidence of serial passage-associated interspecies prion adaptation. In
addition, we demonstrate through confocal analysis the successful
co-localization of PrPD with neurons, astrocytes, microglia, lysosomes, and
synaptophysin, which, in part, implicates each of these in the neuropathology of
FelCWD. In conclusion, this work illustrates the simultaneous role of both host
and strain in the development of a unique FelCWD neuropathologic profile and
that such a profile can be used to discriminate between FelCWD and FSE.
prion chronic wasting disease immunohistochemistry interspecies cat feline
spongiform encephalopathy transmissible spongiform encephalopathy adaptation
species barrier
Monday, August 8, 2011 Susceptibility of Domestic Cats to CWD Infection
Oral.29: Susceptibility of Domestic Cats to CWD Infection
Amy Nalls, Nicholas J. Haley, Jeanette Hayes-Klug, Kelly Anderson, Davis M.
Seelig, Dan S. Bucy, Susan L. Kraft, Edward A. Hoover and Candace K.
Mathiason†
Colorado State University; Fort Collins, CO USA†Presenting author; Email:
ckm@lamar.colostate.edu
Domestic and non-domestic cats have been shown to be susceptible to one
prion disease, feline spongiform encephalopathy (FSE), thought to be transmitted
through consumption of bovine spongiform encephalopathy (BSE) contaminated meat.
Because domestic and free ranging felids scavenge cervid carcasses, including
those in CWD affected areas, we evaluated the susceptibility of domestic cats to
CWD infection experimentally. Groups of n = 5 cats each were inoculated either
intracerebrally (IC) or orally (PO) with CWD deer brain homogenate. Between
40–43 months following IC inoculation, two cats developed mild but progressive
symptoms including weight loss, anorexia, polydipsia, patterned motor behaviors
and ataxia—ultimately mandating euthanasia. Magnetic resonance imaging (MRI) on
the brain of one of these animals (vs. two age-matched controls) performed just
before euthanasia revealed increased ventricular system volume, more prominent
sulci, and T2 hyperintensity deep in the white matter of the frontal hemisphere
and in cortical grey distributed through the brain, likely representing
inflammation or gliosis. PrPRES and widely distributed peri-neuronal vacuoles
were demonstrated in the brains of both animals by immunodetection assays. No
clinical signs of TSE have been detected in the remaining primary passage cats
after 80 months pi. Feline-adapted CWD was sub-passaged into groups (n=4 or 5)
of cats by IC, PO, and IP/SQ routes. Currently, at 22 months pi, all five IC
inoculated cats are demonstrating abnormal behavior including increasing
aggressiveness, pacing, and hyper responsiveness.
*** Two of these cats have developed rear limb ataxia. Although the limited
data from this ongoing study must be considered preliminary, they raise the
potential for cervid-to-feline transmission in nature.
AD.63:
Susceptibility of domestic cats to chronic wasting disease
Amy V.Nalls,1 Candace Mathiason,1 Davis Seelig,2 Susan Kraft,1 Kevin
Carnes,1 Kelly Anderson,1 Jeanette Hayes-Klug1 and Edward A. Hoover1 1Colorado
State University; Fort Collins, CO USA; 2University of Minnesota; Saint Paul, MN
USA
Domestic and nondomestic cats have been shown to be susceptible to feline
spongiform encephalopathy (FSE), almost certainly caused by consumption of
bovine spongiform encephalopathy (BSE)-contaminated meat. Because domestic and
free-ranging nondomestic felids scavenge cervid carcasses, including those in
areas affected by chronic wasting disease (CWD), we evaluated the susceptibility
of the domestic cat (Felis catus) to CWD infection experimentally. Cohorts of 5
cats each were inoculated either intracerebrally (IC) or orally (PO) with
CWD-infected deer brain. At 40 and 42 mo post-inoculation, two IC-inoculated
cats developed signs consistent with prion disease, including a stilted gait,
weight loss, anorexia, polydipsia, patterned motor behaviors, head and tail
tremors, and ataxia, and progressed to terminal disease within 5 mo. Brains from
these two cats were pooled and inoculated into cohorts of cats by IC, PO, and
intraperitoneal and subcutaneous (IP/SC) routes. Upon subpassage, feline-adapted
CWD (FelCWD) was transmitted to all IC-inoculated cats with a decreased
incubation period of 23 to 27 mo. FelCWD was detected in the brains of all the
symptomatic cats by western blotting and immunohistochemistry and abnormalities
were seen in magnetic resonance imaging, including multifocal T2 fluid
attenuated inversion recovery (FLAIR) signal hyper-intensities, ventricular size
increases, prominent sulci, and white matter tract cavitation. Currently, 3 of 4
IP/SQ and 2 of 4 PO inoculared cats have developed abnormal behavior patterns
consistent with the early stage of feline CWD.
*** These results demonstrate that CWD can be transmitted and adapted to
the domestic cat, thus raising the issue of potential cervid-to- feline
transmission in nature.
www.landesbioscience.com
PO-081: Chronic wasting disease in the cat— Similarities to feline
spongiform encephalopathy (FSE)
FELINE SPONGIFORM ENCEPHALOPATHY FSE
IBNC Tauopathy or TSE Prion disease, it appears, no one is sure
Posted by flounder on 03 Jul 2015 at 16:53 GMT
Wednesday, July 15, 2015
Additional BSE TSE prion testing detects pathologic lesion in unusual brain
location and PrPsc by PMCA only, how many cases have we missed?
HOUND STUDY
*** AS implied in the Inset 25 we must not _ASSUME_ that transmission of
BSE to other species will invariably present pathology typical of a scrapie-like
disease. ***
snip...
Neurobiology of Disease
Bovine Spongiform Encephalopathy Induces Misfolding of Alleged
Prion-Resistant Species Cellular Prion Protein without Altering Its
Pathobiological Features
Enric Vidal3, Natalia Fernández-Borges1, Belén Pintado4, Montserrat
Ordóñez3, Mercedes Márquez6, Dolors Fondevila5,6, Juan María Torres7, Martí
Pumarola5,6, and Joaquín Castilla1,2 + Author Affiliations
1CIC bioGUNE, 48160 Derio, Bizkaia, Spain,
2IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Bizkaia, Spain,
3Centre de Recerca en Sanitat Animal, Campus de la Universitat Autònoma de
Barcelona (UAB)-IRTA, 08193 Bellaterra, Barcelona, Spain,
4Centro Nacional de Biotecnología, Campus de Cantoblanco, 28049
Cantoblanco, Madrid, Spain,
5Department of Animal Medicine and Surgery, Veterinary Faculty, UAB, 08193
Bellaterra (Cerdanyola del Vallès), Barcelona, Spain,
6Murine Pathology Unit, Centre de Biotecnologia Animal i Teràpia Gènica,
UAB, 08193 Bellaterra (Cerdanyola del Vallès), Barcelona, Spain, and
7Centro de Investigación en Sanidad Animal-Instituto Nacional de
Investigación y Tecnología Agraria y Alimentaria, 28130 Valdeolmos, Madrid,
Spain
Author contributions: E.V., N.F.-B., and J.C. designed research; E.V.,
N.F.-B., B.P., M.O., M.M., D.F., and J.C. performed research; E.V., N.F.-B.,
B.P., and J.C. contributed unpublished reagents/analytic tools; E.V., N.F.-B.,
B.P., M.O., M.M., D.F., J.M.T., M.P., and J.C. analyzed data; E.V. and J.C.
wrote the paper.
Abstract
Bovine spongiform encephalopathy (BSE) prions were responsible for an
unforeseen epizootic in cattle which had a vast social, economic, and public
health impact. This was primarily because BSE prions were found to be
transmissible to humans. Other species were also susceptible to BSE either by
natural infection (e.g., felids, caprids) or in experimental settings (e.g.,
sheep, mice). However, certain species closely related to humans, such as canids
and leporids, were apparently resistant to BSE. In vitro prion amplification
techniques (saPMCA) were used to successfully misfold the cellular prion protein
(PrPc) of these allegedly resistant species into a BSE-type prion protein. The
biochemical and biological properties of the new prions generated in vitro after
seeding rabbit and dog brain homogenates with classical BSE were studied.
Pathobiological features of the resultant prion strains were determined after
their inoculation into transgenic mice expressing bovine and human PrPC. Strain
characteristics of the in vitro-adapted rabbit and dog BSE agent remained
invariable with respect to the original cattle BSE prion, suggesting that the
naturally low susceptibility of rabbits and dogs to prion infections should not
alter their zoonotic potential if these animals became infected with BSE. This
study provides a sound basis for risk assessment regarding prion diseases in
purportedly resistant species.
Received January 18, 2013. Revision received March 7, 2013. Accepted March
23, 2013. Copyright © 2013 the authors 0270-6474/13/337778-09$15.00/0
2005
DEFRA Department for Environment, Food & Rural Affairs
Area 307, London, SW1P 4PQ Telephone: 0207 904 6000 Direct line: 0207 904
6287 E-mail: h.mcdonagh.defra.gsi.gov.uk
GTN: FAX:
Mr T S Singeltary P.O. Box 42 Bacliff Texas USA 77518
21 November 2001
Dear Mr Singeltary
TSE IN HOUNDS
Thank you for e-mail regarding the hounds survey. I am sorry for the long
delay in responding.
As you note, the hound survey remains unpublished. However the Spongiform
Encephalopathy Advisory Committee (SEAC), the UK Government's independent
Advisory Committee on all aspects related to BSE-like disease, gave the hound
study detailed consideration at their meeting in January 1994. As a summary of
this meeting published in the BSE inquiry noted, the Committee were clearly
concerned about the work that had been carried out, concluding that there had
clearly been problems with it, particularly the control on the histology, and
that it was more or less inconclusive. However was agreed that there should be a
re-evaluation of the pathological material in the study.
Later, at their meeting in June 95, The Committee re-evaluated the hound
study to see if any useful results could be gained from it. The Chairman
concluded that there were varying opinions within the Committee on further work.
It did not suggest any further transmission studies and thought that the lack of
clinical data was a major weakness.
Overall, it is clear that SEAC had major concerns about the survey as
conducted. As a result it is likely that the authors felt that it would not
stand up to r~eer review and hence it was never published. As noted above, and
in the detailed minutes of the SEAC meeting in June 95, SEAC considered whether
additional work should be performed to examine dogs for evidence of TSE
infection. Although the Committee had mixed views about the merits of conducting
further work, the Chairman noted that when the Southwood Committee made their
recommendation to complete an assessment of possible spongiform disease in dogs,
no TSEs had been identified in other species and hence dogs were perceived as a
high risk population and worthy of study. However subsequent to the original
recommendation, made in 1990, a number of other species had been identified with
TSE ( e.g. cats) so a study in hounds was less
critical. For more details see- http://www.bseinquiry,
gov.uk/files/yb/1995/06/21005001 .pdf
As this study remains unpublished, my understanding is that the ownership
of the data essentially remains with the original researchers. Thus
unfortunately, I am unable to help with your request to supply information on
the hound survey directly. My only suggestion is that you contact one of the
researchers originally involved in the project, such as Gerald Wells. He can be
contacted at the following address.
Dr Gerald Wells, Veterinary Laboratories Agency, New Haw, Addlestone,
Surrey, KT 15 3NB, UK
You may also wish to be aware that since November 1994 all suspected cases
of spongiform encephalopathy in animals and poultry were made notifiable. Hence
since that date there has been a requirement for vets to report any suspect SE
in dogs for further investigation. To date there has never been positive
identification of a TSE in a dog.
I hope this is helpful
Yours sincerely 4
HUGH MCDONAGH BSE CORRESPONDENCE SECTION
======================================
HOUND SURVEY
I am sorry, but I really could have been a co-signatory of Gerald's
minute.
I do NOT think that we can justify devoting any resources to this study,
especially as larger and more important projects such as the pathogenesis study
will be quite demanding.
If there is a POLITICAL need to continue with the examination of hound
brains then it should be passed entirely to the VI Service.
J W WILESMITH Epidemiology Unit 18 October 1991
Mr. R Bradley
cc: Mr. G A H Wells
3.3. Mr R J Higgins in conjunction with Mr G A Wells and Mr A C Scott would
by the end of the year, indentify the three brains that were from the
''POSITIVE'' end of the lesion spectrum.
TSE in dogs have not been documented simply because OF THE ONLY STUDY,
those brain tissue samples were screwed up too. see my investigation of this
here, and to follow, later follow up, a letter from defra, AND SEE SUSPICIOUS
BRAIN TISSUE SAF's. ...TSS
Saturday, July 18, 2015
CHARLES "SAM" JAMES, Columbia, Missouri, was charged in a one-count federal
indictment for violations of the Lacey Act involved the sale of white-tailed
deer transported in violation of Missouri and Florida law
98 | Veterinary Record | January 24, 2015
EDITORIAL
Scrapie: a particularly persistent pathogen
Cristina Acín
Resistant prions in the environment have been the sword of Damocles for
scrapie control and eradication. Attempts to establish which physical and
chemical agents could be applied to inactivate or moderate scrapie infectivity
were initiated in the 1960s and 1970s,with the first study of this type focusing
on the effect of heat treatment in reducing prion infectivity (Hunter and
Millson 1964). Nowadays, most of the chemical procedures that aim to inactivate
the prion protein are based on the method developed by Kimberlin and
collaborators (1983). This procedure consists of treatment with 20,000 parts per
million free chlorine solution, for a minimum of one hour, of all surfaces that
need to be sterilised (in laboratories, lambing pens, slaughterhouses, and so
on). Despite this, veterinarians and farmers may still ask a range of questions,
such as ‘Is there an official procedure published somewhere?’ and ‘Is there an
international organisation which recommends and defines the exact method of
scrapie decontamination that must be applied?’
From a European perspective, it is difficult to find a treatment that could
be applied, especially in relation to the disinfection of surfaces in lambing
pens of affected flocks. A 999/2001 EU regulation on controlling spongiform
encephalopathies (European Parliament and Council 2001) did not specify a
particular decontamination measure to be used when an outbreak of scrapie is
diagnosed. There is only a brief recommendation in Annex VII concerning the
control and eradication of transmissible spongiform encephalopathies (TSE
s).
Chapter B of the regulation explains the measures that must be applied if
new caprine animals are to be introduced to a holding where a scrapie outbreak
has previously been diagnosed. In that case, the statement indicates that
caprine animals can be introduced ‘provided that a cleaning and disinfection of
all animal housing on the premises has been carried out following
destocking’.
Issues around cleaning and disinfection are common in prion prevention
recommendations, but relevant authorities, veterinarians and farmers may have
difficulties in finding the specific protocol which applies. The European Food
and Safety Authority (EFSA ) published a detailed report about the efficacy of
certain biocides, such as sodium hydroxide, sodium hypochlorite, guanidine and
even a formulation of copper or iron metal ions in combination with hydrogen
peroxide, against prions (EFSA 2009). The report was based on scientific
evidence (Fichet and others 2004, Lemmer and others 2004, Gao and others 2006,
Solassol and others 2006) but unfortunately the decontamination measures were
not assessed under outbreak conditions.
The EFSA Panel on Biological Hazards recently published its conclusions on
the scrapie situation in the EU after 10 years of monitoring and control of the
disease in sheep and goats (EFSA 2014), and one of the most interesting findings
was the Icelandic experience regarding the effect of disinfection in scrapie
control. The Icelandic plan consisted of: culling scrapie-affected sheep or the
whole flock in newly diagnosed outbreaks; deep cleaning and disinfection of
stables, sheds, barns and equipment with high pressure washing followed by
cleaning with 500 parts per million of hypochlorite; drying and treatment with
300 ppm of iodophor; and restocking was not permitted for at least two years.
Even when all of these measures were implemented, scrapie recurred on several
farms, indicating that the infectious agent survived for years in the
environment, even as many as 16 years after restocking (Georgsson and others
2006).
In the rest of the countries considered in the EFSA (2014) report,
recommendations for disinfection measures were not specifically defined at the
government level. In the report, the only recommendation that is made for sheep
is repopulation with sheep with scrapie-resistant genotypes. This reduces the
risk of scrapie recurrence but it is difficult to know its effect on the
infection.
Until the EFSA was established (in May 2003), scientific opinions about TSE
s were provided by the Scientific Steering Committee (SSC) of the EC, whose
advice regarding inactivation procedures focused on treating animal waste at
high temperatures (150°C for three hours) and high pressure alkaline hydrolysis
(SSC 2003). At the same time, the TSE Risk Management Subgroup of the Advisory
Committee on Dangerous Pathogens (ACDP) in the UK published guidance on safe
working and the prevention of TSE infection. Annex C of the ACDP report
established that sodium hypochlorite was considered to be effective, but only if
20,000 ppm of available chlorine was present for at least one hour, which has
practical limitations such as the release of chlorine gas, corrosion,
incompatibility with formaldehyde, alcohols and acids, rapid inactivation of its
active chemicals and the stability of dilutions (ACDP 2009).
In an international context, the World Organisation for Animal Health (OIE)
does not recommend a specific disinfection protocol for prion agents in its
Terrestrial Code or Manual. Chapter 4.13 of the Terrestrial Code, General
recommendations on disinfection and disinsection (OIE 2014), focuses on
foot-and-mouth disease virus, mycobacteria and Bacillus anthracis, but not on
prion disinfection. Nevertheless, the last update published by the OIE on bovine
spongiform encephalopathy (OIE 2012) indicates that few effective
decontamination techniques are available to inactivate the agent on surfaces,
and recommends the removal of all organic material and the use of sodium
hydroxide, or a sodium hypochlorite solution containing 2 per cent available
chlorine, for more than one hour at 20ºC.
The World Health Organization outlines guidelines for the control of TSE s,
and also emphasises the importance of mechanically cleaning surfaces before
disinfection with sodium hydroxide or sodium hypochlorite for one hour (WHO
1999).
Finally, the relevant agencies in both Canada and the USA suggest that the
best treatments for surfaces potentially contaminated with prions are sodium
hydroxide or sodium hypochlorite at 20,000 ppm. This is a 2 per cent solution,
while most commercial household bleaches contain 5.25 per cent sodium
hypochlorite. It is therefore recommended to dilute one part 5.25 per cent
bleach with 1.5 parts water (CDC 2009, Canadian Food Inspection Agency
2013).
So what should we do about disinfection against prions? First, it is
suggested that a single protocol be created by international authorities to
homogenise inactivation procedures and enable their application in all
scrapie-affected countries. Sodium hypochlorite with 20,000 ppm of available
chlorine seems to be the procedure used in most countries, as noted in a paper
summarised on p 99 of this issue of Veterinary Record (Hawkins and others 2015).
But are we totally sure of its effectiveness as a preventive measure in a
scrapie outbreak? Would an in-depth study of the recurrence of scrapie disease
be needed?
What we can conclude is that, if we want to fight prion diseases, and
specifically classical scrapie, we must focus on the accuracy of diagnosis,
monitoring and surveillance; appropriate animal identification and control of
movements; and, in the end, have homogeneous and suitable protocols to
decontaminate and disinfect lambing barns, sheds and equipment available to
veterinarians and farmers. Finally, further investigations into the resistance
of prion proteins in the diversity of environmental surfaces are required.
References
snip...
98 | Veterinary Record | January 24, 2015
Persistence of ovine scrapie infectivity in a farm environment following
cleaning and decontamination
Steve A. C. Hawkins, MIBiol, Pathology Department1, Hugh A. Simmons, BVSc
MRCVS, MBA, MA Animal Services Unit1, Kevin C. Gough, BSc, PhD2 and Ben C.
Maddison, BSc, PhD3 + Author Affiliations
1Animal and Plant Health Agency, Woodham Lane, New Haw, Addlestone, Surrey
KT15 3NB, UK 2School of Veterinary Medicine and Science, The University of
Nottingham, Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK 3ADAS
UK, School of Veterinary Medicine and Science, The University of Nottingham,
Sutton Bonington, Loughborough, Leicestershire LE12 5RD, UK E-mail for
correspondence: ben.maddison@adas.co.uk Abstract Scrapie of sheep/goats and
chronic wasting disease of deer/elk are contagious prion diseases where
environmental reservoirs are directly implicated in the transmission of disease.
In this study, the effectiveness of recommended scrapie farm decontamination
regimens was evaluated by a sheep bioassay using buildings naturally
contaminated with scrapie. Pens within a farm building were treated with either
20,000 parts per million free chorine solution for one hour or were treated with
the same but were followed by painting and full re-galvanisation or replacement
of metalwork within the pen. Scrapie susceptible lambs of the PRNP genotype
VRQ/VRQ were reared within these pens and their scrapie status was monitored by
recto-anal mucosa-associated lymphoid tissue. All animals became infected over
an 18-month period, even in the pen that had been subject to the most stringent
decontamination process. These data suggest that recommended current guidelines
for the decontamination of farm buildings following outbreaks of scrapie do
little to reduce the titre of infectious scrapie material and that environmental
recontamination could also be an issue associated with these premises.
SNIP...
Discussion
Thorough pressure washing of a pen had no effect on the amount of
bioavailable scrapie infectivity (pen B). The routine removal of prions from
surfaces within a laboratory setting is treatment for a minimum of one hour with
20,000 ppm free chlorine, a method originally based on the use of brain
macerates from infected rodents to evaluate the effectiveness of decontamination
(Kimberlin and others 1983). Further studies have also investigated the
effectiveness of hypochlorite disinfection of metal surfaces to simulate the
decontamination of surgical devices within a hospital setting. Such treatments
with hypochlorite solution were able to reduce infectivity by 5.5 logs to lower
than the sensitivity of the bioassay used (Lemmer and others 2004). Analogous
treatment of the pen surfaces did not effectively remove the levels of scrapie
infectivity over that of the control pens, indicating that this method of
decontamination is not effective within a farm setting. This may be due to the
high level of biological matrix that is present upon surfaces within the farm
environment, which may reduce the amount of free chlorine available to
inactivate any infectious prion. Remarkably 1/5 sheep introduced into pen D had
also became scrapie positive within nine months, with all animals in this pen
being RAMALT positive by 18 months of age. Pen D was no further away from the
control pen (pen A) than any of the other pens within this barn. Localised hot
spots of infectivity may be present within scrapie-contaminated environments,
but it is unlikely that pen D area had an amount of scrapie contamination that
was significantly different than the other areas within this building.
Similarly, there were no differences in how the biosecurity of pen D was
maintained, or how this pen was ventilated compared with the other pens. This
observation, perhaps, indicates the slower kinetics of disease uptake within
this pen and is consistent with a more thorough prion removal and
recontamination. These observations may also account for the presence of
inadvertent scrapie cases within other studies, where despite stringent
biosecurity, control animals have become scrapie positive during challenge
studies using barns that also housed scrapie-affected animals (Ryder and others
2009). The bioassay data indicate that the exposure of the sheep to a farm
environment after decontamination efforts thought to be effective in removing
scrapie is sufficient for the animals to become infected with scrapie. The main
exposure routes within this scenario are likely to be via the oral route, during
feeding and drinking, and respiratory and conjunctival routes. It has been
demonstrated that scrapie infectivity can be efficiently transmitted via the
nasal route in sheep (Hamir and others 2008), as is the case for CWD in both
murine models and in white-tailed deer (Denkers and others 2010, 2013).
Recently, it has also been demonstrated that CWD prions presented as dust when
bound to the soil mineral montmorillonite can be infectious via the nasal route
(Nichols and others 2013). When considering pens C and D, the actual source of
the infectious agent in the pens is not known, it is possible that biologically
relevant levels of prion survive on surfaces during the decontamination regimen
(pen C). With the use of galvanising and painting (pen D) covering and sealing
the surface of the pen, it is possible that scrapie material recontaminated the
pens by the movement of infectious prions contained within dusts originating
from other parts of the barn that were not decontaminated or from other areas of
the farm.
Given that scrapie prions are widespread on the surfaces of affected farms
(Maddison and others 2010a), irrespective of the source of the infectious prions
in the pens, this study clearly highlights the difficulties that are faced with
the effective removal of environmentally associated scrapie infectivity. This is
likely to be paralleled in CWD which shows strong similarities to scrapie in
terms of both the dissemination of prions into the environment and the facile
mode of disease transmission. These data further contribute to the understanding
that prion diseases can be highly transmissible between susceptible individuals
not just by direct contact but through highly stable environmental reservoirs
that are refractory to decontamination.
The presence of these environmentally associated prions in farm buildings
make the control of these diseases a considerable challenge, especially in
animal species such as goats where there is lack of genetic resistance to
scrapie and, therefore, no scope to re-stock farms with animals that are
resistant to scrapie.
Scrapie Sheep Goats Transmissible spongiform encephalopathies (TSE)
Accepted October 12, 2014. Published Online First 31 October 2014
Monday, November 3, 2014
Persistence of ovine scrapie infectivity in a farm environment following
cleaning and decontamination
PPo3-22:
Detection of Environmentally Associated PrPSc on a Farm with Endemic
Scrapie
Ben C. Maddison,1 Claire A. Baker,1 Helen C. Rees,1 Linda A. Terry,2 Leigh
Thorne,2 Susan J. Belworthy2 and Kevin C. Gough3 1ADAS-UK LTD; Department of
Biology; University of Leicester; Leicester, UK; 2Veterinary Laboratories
Agency; Surry, KT UK; 3Department of Veterinary Medicine and Science; University
of Nottingham; Sutton Bonington, Loughborough UK
Key words: scrapie, evironmental persistence, sPMCA
Ovine scrapie shows considerable horizontal transmission, yet the routes of
transmission and specifically the role of fomites in transmission remain poorly
defined. Here we present biochemical data demonstrating that on a
scrapie-affected sheep farm, scrapie prion contamination is widespread. It was
anticipated at the outset that if prions contaminate the environment that they
would be there at extremely low levels, as such the most sensitive method
available for the detection of PrPSc, serial Protein Misfolding Cyclic
Amplification (sPMCA), was used in this study. We investigated the distribution
of environmental scrapie prions by applying ovine sPMCA to samples taken from a
range of surfaces that were accessible to animals and could be collected by use
of a wetted foam swab. Prion was amplified by sPMCA from a number of these
environmental swab samples including those taken from metal, plastic and wooden
surfaces, both in the indoor and outdoor environment. At the time of sampling
there had been no sheep contact with these areas for at least 20 days prior to
sampling indicating that prions persist for at least this duration in the
environment. These data implicate inanimate objects as environmental reservoirs
of prion infectivity which are likely to contribute to disease transmission.
Friday, May 22, 2015
Chronic Wasting Disease and Program Updates - 2014 NEUSAHA Annual Meeting
12-14 May 2014
Friday, May 15, 2015
Grass Plants Bind, Retain, Uptake, and Transport Infectious Prions
Report
CWD TO HUMANS, AND RISK FACTORS THERE FROM (see latest science)
Monday, March 09, 2015
*** Chronic Wasting Disease CWD TSE prion and human animal risk factor
there from ***
Tuesday, May 26, 2015
Minimise transmission risk of CJD and vCJD in healthcare settings Last
updated 15 May 2015
Tuesday, May 26, 2015
Michigan confirms state's first case of chronic wasting disease in
free-ranging white-tailed deer
Friday, July 17, 2015
TPW Commission Holds Special Meeting on Chronic Wasting Disease
Wednesday, July 01, 2015
TEXAS Chronic Wasting Disease Detected in Medina County Captive Deer
Thursday, July 09, 2015
TEXAS Chronic Wasting Disease (CWD) Herd Plan for Trace-Forward Exposed
Herd with Testing of Exposed Animals
Tuesday, July 14, 2015
Texas Parks and Wildlife Commission Special Meeting Thursday on Chronic
Wasting Disease CWD
Rare report of deer disease in Texas causes stir
Houston Chronicle
Rare report of deer disease in Texas causes stir, especially since it’s the
8 case of CWD documented in Texas, and the first case of CWD in Captive deer.
here is how I would have titled this article, and why.
Shannon Tompkins Finally Breaks Silence on Texas First Captive CWD Case and
Starts Off Spreading False Information About Risk Factors. ...
Thursday, July 16, 2015
Wednesday, March 18, 2015
Chronic Wasting Disease CWD Confirmed Texas Trans Pecos March 18,
2015
Wednesday, March 25, 2015
Chronic Wasting Disease CWD Cases Confirmed In New Mexico 2013 and 2014
UPDATE 2015
Thursday, May 02, 2013
*** Chronic Wasting Disease (CWD) Texas Important Update on OBEX ONLY
TEXTING
Monday, February 11, 2013
TEXAS CHRONIC WASTING DISEASE CWD Four New Positives Found in Trans Pecos
Tuesday, July 10, 2012
Chronic Wasting Disease Detected in Far West Texas
Monday, March 26, 2012
Texas Prepares for Chronic Wasting Disease CWD Possibility in Far West
Texas
***for anyone interested, here is some history of CWD along the Texas, New
Mexico border, and my attempt to keep up with it...terry
snip...
see history CWD Texas, New Mexico Border ;
Monday, March 26, 2012
3 CASES OF CWD FOUND NEW MEXICO MULE DEER SEVERAL MILES FROM TEXAS BORDER
Sunday, October 04, 2009
CWD NEW MEXICO SPREADING SOUTH TO TEXAS 2009 2009 Summary of Chronic
Wasting Disease in New Mexico New Mexico Department of Game and Fish
Friday, May 22, 2015
*** Chronic Wasting Disease and Program Updates - 2014 NEUSAHA Annual
Meeting 12-14 May 2014
Sunday, July 12, 2015
*** Insights into CWD and BSE species barriers using real-time conversion
Wednesday, July 15, 2015
Kansas Ten Deer Test Positive for CWD in 2014-2015 7-16-15 News
Wednesday, July 01, 2015
DRAFT Virginia Deer Management Plan 2015-2024 (bans urine scents do to CWD
2015)
Tuesday, July 14, 2015
*** TWO Escaped Captive Deer on the loose in Eau Claire County Wisconsin
CWD postive farm Yellow ear tag
Thursday, June 25, 2015
Wisconsin CWD-positive white-tailed deer found on Eau Claire County farm
Friday, July 17, 2015
Michigan confirms CWD in second free-ranging white-tailed deer
The initial discovery at Wilderness Whitetails was the first in five years.
In trying to explain the sudden appearance, McGraw cited several possibilities
for transmission, including the chance it occurred spontaneously.
That drew attention of Clausen and wildlife staff at the DNR. Clausen said
he knew of no peer-reviewed research showing the disease turned up that way.
Tami Ryan, wildlife health section chief with the DNR, asked the
agriculture department to back up the claim.
Richard Bourie, a veterinarian, pointed to a paper by Nobel Laureate
Stanley Prusiner of the University of California, San Francisco, who discussed
spontaneous occurrence in TSEs.
Ryan wrote back and said, "to the best of our collective knowledge,
spontaneous CWD in wild deer has not been substantiated," although she said the
DNR wasn't trying to pick a fight.
Friday, April 04, 2014
Wisconsin State officials kept silent on CWD discovery at game farm
However, a BSE expert said that consumption of infected material is the
only known way that cattle get the disease under natural conditons.
“In view of what we know about BSE after almost 20 years experience,
contaminated feed has been the source of the epidemic,” said Paul Brown, a
scientist retired from the National Institute of Neurological Diseases and
Stroke.
BSE is not caused by a microbe. It is caused by the misfolding of the
so-called “prion protein” that is a normal constituent of brain and other
tissues. If a diseased version of the protein enters the brain somehow, it can
slowly cause all the normal versions to become misfolded. It is possible the
disease could arise spontaneously, though such an event has never been recorded,
Brown said.
Conclusion/Significance: Our results point to a possibly higher degree of
pathogenicity of BASE than classical BSE in primates and also raise a question
about a possible link to one uncommon subset of cases of apparently sporadic
CJD. Thus, despite the waning epidemic of classical BSE, the occurrence of
atypical strains should temper the urge to relax measures currently in place to
protect public health from accidental contamination by BSE-contaminated
products.
SPONTANEOUS TSE
Perspectives BIOMEDICINE: A Fresh Look at BSE Bruce Chesebro*
Mad cow disease, or bovine spongiform encephalopathy (BSE), is the cattle
form of a family of progressive brain diseases. These diseases include scrapie
in sheep, Creutzfeldt-Jakob disease (CJD) in humans, and chronic wasting disease
(CWD) in deer and elk. They are also known as either "prion diseases" because of
the association of a misfolded cellular prion protein in pathogenesis or
"transmissible spongiform encephalopathies" (TSEs) because of the spongelike
nature of the damaged brain tissue (1).
The recent discovery of two BSE-infected cows, one in Canada and one in the
United States, has dramatically increased concern in North America among meat
producers and consumers alike over the extent to which BSE poses a threat to
humans as well as to domestic and wild animals. The European BSE epidemic of the
late-1980s seems to have been initiated a decade earlier in the United Kingdom
by changes in the production of meat and bone meal (MBM) from rendered
livestock, which led to contamination of MBM with the BSE infectious agent.
Furthermore, the fact that UK farmers fed this rendered MBM to younger animals
and that this MBM was distributed to many countries may have contributed to the
ensuing BSE epidemic in the United Kingdom and internationally (2).
Despite extensive knowledge about the spread of BSE through contaminated
MBM, the source of BSE in Europe remains an unsolved mystery (2). It has been
proposed that BSE could be derived from a cross-species infection, perhaps
through contamination of MBM by scrapie-infected sheep tissues (see the figure).
Alternatively, BSE may have been an endemic disease in cattle that went
unnoticed because of its low level of horizontal transmission. Lastly, BSE might
have originated by "spontaneous" misfolding of the normal cellular prion protein
into the disease-associated abnormal isoform (3), which is postulated to be the
infectious agent or "prion."
Five possible sources of BSE in North American cattle. Sheep, deer, and elk
could spread prion diseases (TSEs) to cattle through direct animal contact or
contamination of pastures. Endemic BSE has not been proven to exist anywhere in
the world, but it is difficult to exclude this possibility because of the
inefficient spread of BSE infectivity between individual animals (2). BSE caused
by spontaneous misfolding of the prion protein has not been proven. CREDIT:
KATHARINE SUTLIFF/SCIENCE
snip...
Nevertheless, the idea that BSE might originate due to the spontaneous
misfolding of prion proteins has received renewed interest in the wake of
reports suggesting the occurrence of atypical BSE (9-11). These results imply
that new strains of cattle BSE might have originated separately from the main UK
outbreak. Where and how might such strains have originated? Although such rare
events cannot be studied directly, any number of sources of the original BSE
strain could also explain the discovery of additional BSE strains in cattle (see
the figure). However, it would be worrisome if spontaneous BSE were really a
valid etiology because such a mechanism would be impossible to prevent--unlike
other possible scenarios that could be controlled by large-scale eradication of
TSE-positive animals.
Another way to look at this problem is to examine evidence for possible
spontaneous TSE disease in other animals besides cattle. Spontaneous BSE would
be extremely difficult to detect in cattle, where horizontal spread is minimal.
However, in the case of the sheep TSE disease, scrapie, which spreads from ewes
to lambs at birth as well as between adults, spontaneous disease should be
detectable as new foci of clinical infection. In the early 1950s scrapie was
eradicated in both Australia and New Zealand, and the mainland of both these
countries has remained scrapie-free ever since. This scrapie-free status is not
the result of selection of sheep resistant to scrapie because sheep from New
Zealand are as susceptible as their UK counterparts to experimental scrapie
infection (12). These experiments of man and nature appear to indicate that
spontaneous clinical scrapie does not occur in sheep. Similarly, because CWD is
known to spread horizontally, the lack of CWD in the deer or elk of eastern
North America but its presence in western regions would also argue against a
spontaneous disease mechanism. This is particularly noteworthy in New Zealand,
where there are large numbers of deer and elk farms and yet no evidence of
spontaneous CWD. If spontaneous scrapie does not occur in sheep or deer, this
would suggest that spontaneous forms of BSE and sporadic Creutzfeldt-Jakob
disease (sCJD) are unlikely to be found in cattle or humans. The main caveat to
this notion is that spontaneous disease may arise in some animal species but not
others. In humans, sCJD--which is considered by some researchers to begin by
spontaneous misfolding of the prion protein--usually takes more than 50 years to
appear. Thus, in animals with a shorter life-span, such as sheep, deer, and
cattle, an analogous disease mechanism might not have time to develop.
What can we conclude so far about BSE in North America? Is the BSE detected
in two North American cows sporadic or spontaneous or both? "Sporadic" pertains
to the rarity of disease occurrence. "Spontaneous" pertains to a possible
mechanism of origin of the disease. These are not equivalent terms. The rarity
of BSE in North America qualifies it as a sporadic disease, but this low
incidence does not provide information about cause. For the two reported North
American BSE cases, exposure to contaminated MBM remains the most likely
culprit. However, other mechanisms are still possible, including cross-infection
by sheep with scrapie or cervids with CWD, horizontal transmission from cattle
with endemic BSE, and spontaneous disease in individual cattle. Based on our
understanding of other TSEs, the spontaneous mechanism is probably the least
likely. Thus, "idiopathic" BSE--that is, BSE of unknown etiology--might be a
better term to describe the origin of this malady. ...
snip...full text ;
DR. DEHAVEN: “All right. I think we've got three different questions in
there, and I'll try to touch on each one of them.
“First of all, let me correct just a technical issue, and that is you
mentioned 1 in 10,000. And actually our surveillance system currently is
designed, the one that we have in place now is designed to detect 1 positive in
1 million cattle, and I gave some numbers between 200,000 and 268,000 that would
allow us to detect 1 in 10 million as opposed to 1 in 10,000.
“So we would, if we were able to collect in the ballpark of those numbers
of samples then we with increasing numbers of samples have an increasingly
statistically valid sample from which to determine, one, whether or not the
disease exists and, if so, at what prevalence level.
“So our real emphasis is to test as many of those animals as we can, ensure
that we get an appropriate geographical distribution, but not setting a specific
number as far as a target. Again, consistent with the recommendation from the
International Review Team, their recommendation was to test all of them.
“So that's consistent with where we're going is to test as many as we
possibly can.
*** “As far as spontaneous cases, that is a very difficult issue. There is
no evidence to prove that spontaneous BSE occurs in cattle; but here again it's
an issue of proving a negative. We do know that CJD, the human version of the
disease, does occur spontaneously in humans at the rate of about 1 in 1 million.
We don't have enough data to definitively say that spontaneous cases of BSE in
cattle occur or do not occur.
“Again, it's a very difficult situation to prove a negative.
“So a lot of research is ongoing. Certainly if we do come up with any
positive samples in the course of this surveillance we will be looking at that
question in evaluating those samples but no scientifically hard evidence to
confirm or refute whether or not spontaneous cases of BSE occur.
snip...
http://www.usda.gov/wps/portal/!ut/p/_s.7_0_A/7_0_1OB?contentidonly=true&contentid=2004/03/0106.html
The occurrence of the disease in a patient who had contact with cases of
familial C.J.D., but was not genetically related, has been described in Chile
(Galvez et al., 1980) and in France (Brown et al., 1979b). In Chile the patient
was related by marriage, but with no consanguinity, and had social contact with
subsequently affected family members for 13 years before developing the disease.
The contact case in France also married into a family in which C.J.D. was
prevalent and had close contact with an affected member. In neither instance did
the spouse of the non-familial case have the disease. The case described in this
report was similarly related to affected family members and social contact had
occurred for 20 years prior to developing C.J.D. If contact transmission had
occurred, the minimum transmission period would be 11 years. Contact between
sporadic cases has not been described and it is remarkable that possible contact
transmissions have all been with familial cases. No method of transmission by
casual social contact has been suggested.
***The occurrence of contact cases raises the possibility that transmission
in families may be effected by an unusually virulent strain of the agent.
snip...see full text here;
Thursday, June 04, 2015
Catholic Medical Center v. Civil No. 14-cv-180-JL Opinion No. 2015 DNH 110
Fireman’s Fund Insurance Company Creutzfeldt Jakob Disease TSE Prion tainted
medical instruments
UNITED STATES DISTRICT COURT DISTRICT OF NEW HAMPSHIRE
Tuesday, May 26, 2015
Minimise transmission risk of CJD and vCJD in healthcare settings Last
updated 15 May 2015
2015 PRION CONFERENCE
*** RE-P.164: Blood transmission of prion infectivity in the squirrel
monkey: The Baxter study
***suggest that blood donations from cases of GSS (and perhaps other
familial forms of TSE) carry more risk than from vCJD cases, and that little or
no risk is associated with sCJD. ***
ran across an old paper from 1984 ;
***The occurrence of contact cases raises the possibility that transmission
in families may be effected by an unusually virulent strain of the agent.
***
Saturday, December 13, 2014
Terry S. Singeltary Sr. Publications TSE prion disease
Diagnosis and Reporting of Creutzfeldt-Jakob Disease
Singeltary, Sr et al. JAMA.2001; 285: 733-734. Vol. 285 No. 6, February 14,
2001 JAMA
snip...
Terry S. Singeltary Sr.
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