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Is CWD a Health Risk for Humans?
As devastating as all prion diseases are, the good news for us is that most have proven notoriously difficult to transmit between unrelated animal groups. Take the much publicized mad cow disease outbreak in the UK during the 1990s.
"Experts at the time feared hundreds of thousands of human cases, but that just didn’t materialize," says the CDC's Dr. Ermias Belay, lead author of a recent paper in the journal Emerging Infectious Diseases on the potential for CWD jumping to the human population. To date, says Belay, the total number of human deaths from mad cow disease (approximately one for every 10,000 infected beef carcasses that entered the food chain in Great Britain) was in no way proportional to the panic generated by media coverage. "There seems to be a substantial species barrier," he says, "that prevents the agent from jumping from cows to humans."
If anything, the interspecies barrier with CWD appears as strong, if not more so. Despite intensive epidemiological and laboratory studies, no human cases (or cervid-to-cattle transmission) have yet been documented. Several highly publicized prion disease deaths in young hunters and/or consumers of venison, for instance, have been traced back to familial, genetic, or otherwise "normal" human prion disease. Indeed, the closest researchers have come to triggering CWD in a primate is by injecting diseased deer tissue directly into the brains of squirrel monkeys.
Unfortunately for the nation's deer herds, the high improbability of cervid-to-human transmission--and the complacency this has engendered--has proven something of a two-edged sword. "When CWD first appeared in Wisconsin, it triggered a huge panic," acknowledges Harry Campbell, co-owner of a Milwaukee-based marketing firm specializing in outdoor recreation. “Deer licenses and retail sales dropped precipitously, and the whole hunting industry seemed in peril. Today, that panic is gone completely. The basic reason: nobody died."
Clearly this "people are safe" message has spread through much of the hunting community nationwide. In the wake of the 2005 sportsmen's feast in Oneida County, for example (an instance in which 350 people were served steak, chili, stew, and sausage from a local game-farmed white-tail that subsequently tested positive for CWD), public health officials found themselves astonished by the indifference they saw in individuals who knew they'd eaten CWD positive venison. "We set up a hot line inviting people who'd attended the banquet to call us for more information," recalls Fanelli. "I anticipated a ton of calls from worried individuals, but I only got two. There just didn't seem to be a lot of concern out there." --Jim Thornton
Crutzfeld-Jakob Syndrome was first described among elk hunters in the 1970's. That's caused by a prion, just like CWD; if it's not human CWD itself, that is.
If anyone believes the various fish and game departments, that CWD is confined to the central nervous system of infected animals - I have a bridge I'd love to sell you.
The prions infect ALL nervous tissue. (When you wiggle your toes, NERVES are conducting the message - that's nervous tissue.)And they're not destroyed by heat (that means "cooking", geniuses).
C-J Syndrome is always misdiagnosed - ask your doc what the symptoms are: he or she won't have a clue...
When CWD hits central PA, where I live, I won't eat venison again. But go right ahead, it's really unlikely that the prion might be able to infect YOU - you're special.
Posted by: Dave | May 11, 2007 at 11:44 AM
Crutzfeld-Jakob Syndrome was first described among elk hunters in the 1970's. That's caused by a prion, just like CWD; if it's not human CWD itself, that is.
If anyone believes the various fish and game departments, that CWD is confined to the central nervous system of infected animals - I have a bridge I'd love to sell you.
The prions infect ALL nervous tissue. (When you wiggle your toes, NERVES are conducting the message - that's nervous tissue.)And they're not destroyed by heat (that means "cooking", geniuses).
C-J Syndrome is always misdiagnosed - ask your doc what the symptoms are: he or she won't have a clue...
When CWD hits central PA, where I live, I won't eat venison again. But go right ahead, it's really unlikely that the prion might be able to infect YOU - you're special.
Posted by: Dave | May 11, 2007 at 11:45 AM
Hi, Dave. I'm Jim Thornton, I wrote the CWD article, and I agree with you--I wouldn't personally eat CWD-infected meat unless the only alternative was starvation. One of the guys I interviewed for the story, Dr. Edward Hoover, said the CWD prions can be found in blood and hence throughout all the tissues of an infected animal, not just nerve cells (though they are more concentrated here.)
I also live in PA and dread the day the disease moves to our state, either on the hoof or from the back of a pickup truck.
If you talk to the folks at the CDC, they maintain there is a way to differentiate between various subtypes of prion diseases, and that the hunters that have come down with the C-J human variant had a different strain. You can find the paper in the journal Emerging Infectious Diseases, Vol. 10, No. 6, June, 2004.
Whether we can get sick from infected venison or not, the disease is horrific and I am convinced will change hunting and deer populations as we currently know them.
Posted by: James Thornton | May 21, 2007 at 01:50 PM
Hi Jim,
Like almost everything else relating to this family of diseases (TSEs or transmissible spongiform encephalopathies), the so-called "safety" issues are incredibly complex... and certainly much more so than you could possibly portray here. I would, however, have included a couple of fundamentals:
Begin with the axiom "absence of evidence is NOT evidence of absence." The British government repeatedly claimed that there was no danger to people from mad cow... all based on the "fact" that no cases had been documented. Then Ag minister John Gummer even had his 4 yr. old daughter on 'telly' eating a hamburger to reinforce his conviction. http://news.bbc.co.uk/2/hi/uk_news/369625.stm
Several factors (currently) indicate a smaller risk re CWD to people, but one ENORMOUS difference indicates much greater potential consequences if CWD ever manages the leap: BSE seemed not to move laterally between living animals; infection occured via feed (infected protein supplements-meat & bone from mad cows). About 200 people have died from eating infected beef... but the infection (hopefully) stops there.
The difference — as your article correcly points out — CWD moves readily between living deer... and saliva alone is sufficient.
Thus the big "if" re CWD to people is not just what if it jumps to a person, but what if it behaves in people as it does in deer... ? "If" it does, we could be in for a pandemic of an undetectable, untreatable, always-fatal disease that could be passed from person to person via any number of means, from kissing, to water bottles, or...!
That CWD is not yet showing transmissibility in transgenic mice gives us hope, but is offset by other evidence indicating potential detours, vectors, and alternatives that could provide eventual avenues to transmission.
Again, the TSE issues are very complex, but one thing is certain beyond any doubt: CWD and other diseases, parasites, and polluted genes have been translocated all over the world by the absurd practice of game farming, an industry without any legitimate purpose whatsoever (least of all economic).
Finally, it should be stated that none of this happened by accident: Authorities were repeatedly warned by top scientists that these consequences were inevitable if game farming were allowed (see Lanka et al, WY).
Thanks for the great article, and keep up the good work!
Darrel
Posted by: Darrel Rowledge | May 29, 2007 at 12:39 PM
P01.47
Quantifying the Species Barrier in Chronic Wasting Disease by a Novel in
vitro Conversion Assay
Li, L1; Coulthart, MB2; Balachandran, A3; Chakrabartty, A4; Cashman, NR1
1University of British Columbia, Brain Research Centre, Canada; 2Public
Health Agency
of Canada, National Microbiology Laboratory, Canada; 3Animal Diseases
Research Institute, Canada Food Inspection Agency, National Reference
Laboratory for
Scrapie and CWD, Canada; 4Ontario Cancer Institute and Department of Medical
Biophysics, University of Toronto, Canada
Background: Chronic wasting disease (CWD) is a transmissible spongiform
encephalopathy that can affect North American cervids (deer, elk, and
moose).
Although the risk of CWD crossing the species barrier and causing human
disease is still unknown, however, definite bovine spongiform encephalopathy
(BSE)
transmission to humans as variant CJD (vCJD), it would seem prudent to limit
the exposure of humans to CWD.
Aim: In view of the fact that BSE can be readily transmitted to non-bovid
species, it is important to establish the species susceptibility range of
CWD.
Methods: In vitro conversion system was performed by incubation of prions
with normal brain homogenates as described before, and protease K (PK)
resistant
PrP was determined by immunoblotting with 6H4 monoclonal prion antibody.
Results: Our results demonstrate that PrPC from cervids (including moose)
can be efficiently converted to a protease-resistant form by incubation with
elk
CWD prions, presumably due to sequence and structural similarities between
these
species. Interestingly, hamster shows a high conversion ratio by PrPCWD.
Moreover,
partial denaturation of substrate PrPC can apparently overcome the
structural
barriers between more distant species.
Conclusions: Our work correctly predicted the transmission of CWD to a wild
moose.
We find a species barrier for prion protein conversion between cervids and
other species, however, this barrier might be overcome if the PrPC substrate
has
been partially denatured in a cellular environment. Such an environment
might
also promote CWD transmission to non-cervid species, *** including humans.
Acid/GdnHCl-treated brain PrPC was a superior substrate for the in vitro
conversion than PrPC treated at physiological pH. This has implications for
the process
by which the prion protein is converted in disease.
http://www.prion2007.com/pdf/Prion%20Book%20of%20Abstracts.pdf
TSS
Posted by: Terry S. Singeltary Sr. | October 03, 2007 at 12:04 PM
Subject: Species barriers for chronic wasting disease by in vitro conversion
of prion protein
Date: November 3, 2007 at 10:57 am PST
Species barriers for chronic wasting disease by in vitro conversion of prion
protein
Li Li a, Michael B. Coulthart b, Aru Balachandran c, Avi Chakrabartty d,
Neil R. Cashman a,*
a Brain Research Centre, Division of Neurology, Department of Medicine,
University of British Columbia and Vancouver Coastal Health,
UBC Hospital, 2211 Wesbrook Mall, Vancouver, BC, Canada V6T 2B5
b Prion Diseases Program, National Microbiology Laboratory, Public Health
Agency of Canada, Winnipeg, Man., Canada R3E 3R2 Q1
c National Reference Laboratory for Scrapie and CWD, Animal Diseases
Research Institute, Canadian Food Inspection Agency,
3851 Fallowfield Road, Nepean, Ont., Canada K2H 8P9
d University Health Network, Department of Medical Biophysics, University of
Toronto, Toronto, Ont., Canada M5G 1L7
Received 6 October 2007
Abstract
Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy
that can affect North American cervids (deer, elk, and
moose). Using a novel in vitro conversion system based on incubation of
prions with normal brain homogenates, we now report that
PrPCWD of elk can readily induce the conversion of normal cervid PrP (PrPC)
molecules to a protease-resistant form, but is less efficient
in converting the PrPC of other species, such as human, bovine, hamster, and
mouse. However, when substrate brain homogenates are
partially denatured by acidic conditions (pH 3.5), PrPCWD-induced conversion
can be greatly enhanced in all species. Our results dem-
onstrate that PrPC from cervids (including moose) can be efficiently
converted to a protease-resistant form by incubation with elk CWD
prions, presumably due to sequence and structural similarities between these
species. Moreover, partial denaturation of substrate PrPC
can apparently overcome the structural barriers between more distant
species.
snip...
Although Syrian hamsters were initially deemed resistant to CWD [19], a
recent publication demonstrates that CWD can be transmitted
and adapted to hamster [20].
snip...
Substrate denaturation and human health
We confirm with multiple species that acid/GdnHCl-
treated brain PrPC is a superior substrate for in vitro con-
version than untreated PrPC, possibly by overcoming con-
formational barriers in partial denaturation of substrate
PrPC. PrP conversion in scrapie-infected neuroblastoma
cells is believed to occur in endosomes, a low-pH and
reducing environment [26]. The non-ruminant stomach
possesses a low pH lumen, and PrPC is expressed in this
organ [27]. Such acidic (denaturing) organ or cellular
organellar environments might also promote CWD trans-
mission to non-cervid species, including humans.
Acknowledgments
This work was supported by the Canadian Institutes of
Health Research (Institute of Infection and Immunity, Safe
Food and Water program) and PrioNet Canada.
[20] G.J. Raymond, L.D. Raymond, K.D. Meade-White, A.G. Hughson,
C. Favara, D. Gardner, E.S. Williams, M.W. Miller, R.E. Race, B.
Caughey, Transmission and adaptation of chronic wasting disease to
hamsters and transgenic mice: evidence for strains, J. Virol. 81 (2007)
4305–4314.
http://jvi.asm.org/cgi/content/abstract/81/8/4305
2007 Elsevier Inc. All rights reserved.
Please cite this article in press as: L. Li et al., Species barriers for
chronic wasting disease by in vitro...,
Biochem. Biophys. Res. Commun. (2007), doi:10.1016/j.bbrc.2007.10.087
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WBK-4R04PFW-3&_user=10&_coverDate=10%2F25%2F2007&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=d2eb8cb35fa637a9a1245df2ecc170d1#bcor1
Transmission and adaptation of chronic wasting disease to hamsters and
transgenic mice: evidence for strains
Gregory J. Raymond1, Lynne D. Raymond1, Kimberly D. Meade-White1, Andrew G.
Hughson1, Cynthia Favara1, Donald Gardner2, Elizabeth S. Williams3§, Michael
W.
Miller4, Richard E. Race1*, and Byron Caughey1*
Running title: CWD transmission to rodent species
Laboratory of Persistent Viral Diseases1, and Rocky Mountain Veterinary
Branch2, NIAID, NIH, Rocky Mountain Laboratories, Hamilton, MT 59840;
Department of Veterinary Sciences, University of Wyoming, Laramie, WY
820703; Colorado Division of Wildlife, Wildlife Research Center, Fort
Collins, CO
80526-20974.
§deceased
*corresponding authors:
Byron Caughey, Rocky Mountain Labs, 903 S. 4th St, Hamilton, MT 59840, USA;
[email protected]; Tel: (406) 363-9264; FAX: (406) 363-9286
Richard Race, Rocky Mountain Labs, 903 S. 4th St, Hamilton, MT 59840, USA;
[email protected]; Tel: (406) 363-9358; FAX: (406) 363-9286
In vitro screening using the cell-free prion protein conversion system
indicated
that certain rodents may be susceptible to chronic wasting disease (CWD).
Therefore,
CWD isolates from mule deer, white-tailed deer and elk were inoculated
intracerebrally
into various rodent species to assess their susceptibility and to develop
new rodent
models of CWD. The species inoculated were Syrian golden, Djungarian,
Chinese,
Siberian, and Armenian hamsters; transgenic mice expressing the Syrian
golden
hamster prion protein; and, RML Swiss and C57 BL10 wild-type mice. The
transgenic
mice and the Syrian golden, Chinese, Siberian and Armenian hamsters had
limited
susceptibility to certain of the CWD inocula as evidenced by incomplete
attack rates and
long incubation periods. With serial passages of CWD isolates in Syrian
golden
hamsters, incubation periods rapidly stabilized as isolates with either
short (85-89 days)
or long (408-544 days) mean incubation periods and distinct
neuropathological patterns.
In contrast, wild-type mouse strains and Djungarian hamsters were not
susceptible to
CWD. These results show that CWD can be transmitted and adapted to some
species
of rodents and suggest that the cervid-derived CWD inocula may have
contained, or
diverged into, at least two distinct transmissible spongiform encephalopathy
strains.
snip...
Differences in PrP-res glycoform patterns analyzed from several CWD-
affected deer and elk have also suggested that CWD in mule deer may be more
heterogeneous than in elk (19). Curiously, however, this apparent strain
difference was not manifested when the identical mule deer CWD inoculum was
serially passaged through only one recipient species. Serial passage in Sg
hamsters yielded only the fast isolate (Table 1 and Figure 3), while passage
first
through the Tg (haPrP) mice then into Sg hamsters yielded only the slow
isolate
(Table 2 and Figure 3). With this in mind, it is important to consider other
possible explanations for these results. One possibility is that CWD might
be
able to undergo a stochastic change into a more rapid and aggressive strain
in
Sg hamsters, and that this happened to occur after the mule deer CWD
inoculations. A similar emergence of both fast and slow strains has been
observed upon inoculation of TME into Sg hamsters (5). These strains
developed even when a clonal isolate of the TME inoculum was used,
suggesting
that they arose in the recipient Sg hamsters rather than in the mink source
(1).
Finally, although extensive precautions were taken, we cannot formally
prove that inadvertent contamination of the mule deer CWD inoculum with
hamster-derived 263K strain did not occur which potentially could yield
short-
incubation-period passages in Sg hamsters (Table 1). However, the incubation
period observed with the CWD passages (85-89 d) were significantly longer
than
263K incubation periods observed in our lab (70-75 d) and no mock-infected
controls became sick during their lifespan. Also, we saw no 263K-like
infectivity
develop in the highly susceptible Tg (haPrP) mice even though we used the
identical primary inoculum for both recipient species. Interestingly, the
similarity
of the Sg hamster-adapted CWD fast isolate and 263K might be due to a
common origin since there is circumstantial evidence that CWD arose from
cervid exposure to sheep scrapie, which was also the origin of the 263K
strain in
hamsters (14). Furthermore, the Hyper strain derived from TME inoculations
has
263K-like strain characteristics in Sg hamsters (5). Thus, it would appear
that
both CWD and TME transmissions into Sg hamsters can result in divergent fast
and slow strains.
end...
http://jvi.asm.org/cgi/reprint/JVI.02474-06v1
http://jvi.asm.org/cgi/content/abstract/JVI.02474-06v1
Transmissible Mink Encephalopathy TME
http://transmissible-mink-encephalopathy.blogspot.com/
TME hyper/drowsy, INTER-SPECIES TRANSMISSION CWD and strain
properties
https://www.blogger.com/comment.g?blogID=37955408&postID=116577315153980667
Monitoring the occurrence of emerging forms of Creutzfeldt-Jakob disease in
the United States
http://cjdusa.blogspot.com/
i am reminded of a few things deep throat (high ranking official at usda)
told me years ago;
==========================================
The most frightening thing I have read all day is the
report of Gambetti's finding of a new strain of
sporadic cjd in young people.........Dear God,
https://www.blogger.com/comment.g?blogID=7842737484277562285&postID=5759550357128128100
BSE BASE MAD COW TESTING TEXAS, USA, AND CANADA, A REVIEW OF SORTS
http://madcowtesting.blogspot.com/
MADCOW USDA the untold story
http://madcowusda.blogspot.com/
MADCOW USDA the untold story continued
https://www.blogger.com/comment.g?blogID=6472149427883113751&postID=4829467681293855400
USA NOR-98 SCRAPIE UPDATE AUGUST 31, 2007 RISES TO 5 DOCUMENTED CASES
http://nor-98.blogspot.com/
Government Accountability Project
https://www.blogger.com/comment.g?blogID=3995372399492420922&postID=295754279213239559
PLEASE NOTE IN USA CJD UPDATE AS AT JUNE 2007, please note steady increase
in ''TYPE UNKNOWN''. ...TSS
1 Acquired in the United Kingdom; 2 Acquired in Saudi Arabia; 3 Includes 17
inconclusive and 9 pending (1 from 2006, 8
from 2007); 4 Includes 17 non-vCJD type unknown (2 from 1996, 2 from 1997, 1
from 2001, 1 from 2003, 4 from 2004, 3
from 2005, 4 from 2006) and 36 type pending (2 from 2005, 8 from 2006,
*** 26 from 2007)
http://www.cjdsurveillance.com/pdf/case-table.pdf
TSS
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