To: BSE-L@uni-karlsruhe.de
CWD SYPMPOSIUM PROGRAM AND ABSTRACTS
snip...
Is Chronic Wasting Disease Transmissible to Humans?
Ermias Belay, Center for Disease Control
The transmission of bovine spongiform encephalopathy to humans causing
variant CreutzfeldtJakob disease (CJD) in Europe has created a concern
about the possible zoonotic transmission of other animal transmissible
spongiform encephalopathies prevalent in the United States such as
chronic wasting disease (CWD) of deer and elk. This concern was
heightened by the recent detection of CWD in free-ranging deer outside
of the known CWD-endemic areas and the occurrence of unusually young CJD
patients who were reported to have regularly consumed venison. However,
investigation of these unusually young CJD patients found no strong
evidence for a causal link between CWD and the CJD illness in the
patients. Ongoing CJD surveillance as well as epidemiologic and
laboratory investigations remain critical for continuing to assess the
risk, if any, of CWD transmission to humans. to top
Occurrence of Creutzfeldt-Jakob Disease in Colorado and Wyoming
John Pape, Colorado Department of Public Health and Environment
Surveillance for human transmissible spongiform encephalopathies was
initiated in Colorado in 1997 when the Colorado Board of Health made
human TSE, in persons less than fifty-five years of age, a reportable
condition. The age parameter was removed in 2000. In the four years with
complete data (1998-2001), eighteen cases of human TSE in Colorado
residents were reported. Three additional cases, including a case of
GSS, were identified in residents from other states (NE, KS, NC). Ten
patients were female. Mean age was 64.8 years (range 40-79). One
patient, a 61 year-old woman, was determined to have a history of
venison consumption from Colorado's CWD endemic area. Pathological
examination was consistent with sporadic CJD. to top
SESSION VI
Public Hunter Perspectives on Hunting in CWD Areas: Should Hunters be
Concerned?
Gary J. Wolfe, Chronic Wasting Disease Alliance, Missoula, MT
With the growing media attention given to Chronic Wasting Disease, many
hunters are asking if they should continue to hunt in areas where CWD
has been identified, and to eat the deer and elk they harvest from those
areas.
In areas where CWD occurs, only a relatively small number of animals are
infected. Even in the parts of Wyoming and Colorado where chronic
wasting disease has existed for at least 30 years, an average of less
than six percent of deer are infected. CWD is far less prevalent in elk
than deer. Less than 1 percent of elk found in areas where the disease
occurs in northeastern Colorado are infected.
There is currently no scientific evidence that CWD can spread to humans,
either through contact with infected animals or by eating meat of
infected animals. The Center of Disease Control has thoroughly
investigated any connection between CWD and the human forms of TSEs and
stated: "Although it is generally prudent to avoid consuming food
derived from any animal with evidence of a TSE, to date, there is no
evidence that CWD has been transmitted or can be transmitted to humans
under natural conditions. However, there is not yet strong evidence that
such transmissions could not occur."
Hunters should take the following commonsense precautions when field
dressing and processing deer or elk taken in areas where CWD is found:
· Do not shoot, handle or consume any animal that is acting abnormally
or appears to be sick.
· Wear latex or rubber gloves when field dressing deer or elk.
· Bone out the meat. Don't saw through bone, and avoid cutting through
the brain or spinal cord (backbone).
· Minimize the handling of brain and spinal tissues.
· Wash hands and instruments thoroughly after field dressing is completed.
· Avoid consuming brain, spinal cord, eyes, spleen, tonsils and lymph
nodes of harvested animals.
· Avoid consuming the meat from any animal that tests positive for the
disease.
· If the deer or elk is commercially processed, it should be processed
individually, without meat from other animals being mixed together.
State and provincial wildlife agencies are stepping up their
surveillance for CWD, so be alert to their advisories and follow the
recommended safety precautions. Concerns over CWD shouldn't stop you
from enjoying this hunting season. to top
Why Hunters Should Not Be Required to Consume Deer or Elk Harvested in
CWD Endemic
Areas
Dick Steele, Western Colorado Sportsmen's Council
1. This is not an individual health issue. The chances of a hunter
contracting CJD from his deer or elk after testing negative for CWD and
handling the meat properly is remote.
2. This is a human health threat with very serious potential
consequences. Unlike BSE, CWD is spread by animal-to-animal contact.
This is by ingestion or inhalation of saliva, feces, or possibly urine.
Excreta of one animal comes in contact with tonsils or the intestinal
tract of another animal. This is how many human diseases are transmitted
such as the common cold and salmonella. With BSE it was consuming
infected tissues. This is easy to circumvent by not eating infected
material.
3. If the CWD prion adapted to just one human it could potentially
instigate an epidemic. The really threatening aspect is we would not
know it existed until it had spread among the population for ten or more
years when the first person exhibited clinical symptoms. Therefore we
need to consider protecting the entire human population not just the
individual hunters safety.
4. Locker plant amplification of exposure is likely since the prion is
not inactivated by currently used cleaning methods of hot water. One
pound of sheep brain infected with scrapie contains 454 million
infective doses of prion. Very minute amounts of lymph node tissue from
a CWD deer could contaminate an entire locker plant and every carcass
that passes through it subsequently.
5. Field dressing situations are very difficult to control. First the
hunter is often tired from a long hunt. Or he may be charged with
adrenaline. It is easy to cut into spleen or mesenteric lymph nodes in
gutting the carcass. If several people are involved, one person may be
cutting the horns off exposing the brain tissue while others are cutting
up the meat. It is easy to share knives and saws in the process. If the
person removing the skullcap and horns completes his task first he may
assist the others bagging up the meat or even cutting up the meat.
6. CWD prions are much closer in structure to scrapie prions than are
BSE prions to scrapie prions. Ergo if BSE came from scrapie, CWD is more
likely to have originated from scrapie prions. According to Paul Brown
of the National Institutes of Health and others, once prions cross the
species barrier they are more likely to adapt to other species. This is
what we saw with BSE transmitting from scrapie to cattle to a multitude
of other species. Raymond et al. showed that in vitro human prions were
converted by CWD prions at approximately the same efficiency as they
were converted by BSE prions (7% verses 10%). This should ring in a
serious warning that cross species transmission is possible.
7. Human exposure to CWD has been so limited that statistically we are
unlikely to have seen one single case at this time. Comparing harvest
data to CWD prevalence rates would indicate that fewer than 300 CWD
infected elk and fewer than 3000 CWD infected deer have been harvested
from Colorado's endemic area in the last 30 years. If each hunter shared
his game meat with 10 people we would have a maximum of 33,000 people
exposed to CWD. At this point in time
120 people have died in Britain of nvCJD out of 60 million people
exposed. This equates to one case per 500,000 people exposed. We are
467,000 exposures to CWD short of having enough to develop one case. To
say there is no evidence that CWD cannot transmit to people is quite
premature.
8. CWD has been transmitted to a primate by intracerebral injection
(squirrel monkey). Another warning shot across our bow that should not
be ignored as it was with BSE.
9. The finding of scrapie prions in the hind leg muscles of scrapie
infected mice indicates we need to look for the CWD prion in different
muscle groups of deer and elk. If found, human exposure may be possible
with meat consumption. to top
snip...
http://www.cwd-info.org/index.php/fuseaction/resources.symposiumAbstracts/#28
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.
PMID: 6997404
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6997404&dopt=Abstract
Oral transmission and early lymphoid tropism of chronic wasting
disease PrPres in mule deer fawns (Odocoileus hemionus )
Christina J. Sigurdson1, Elizabeth S. Williams2, Michael W. Miller3,
Terry R. Spraker1,4, Katherine I. O'Rourke5 and Edward A. Hoover1
Department of Pathology, College of Veterinary Medicine and Biomedical
Sciences, Colorado State University, Fort Collins, CO 80523- 1671, USA1
Department of Veterinary Sciences, University of Wyoming, 1174 Snowy
Range Road, University of Wyoming, Laramie, WY 82070, USA 2
Colorado Division of Wildlife, Wildlife Research Center, 317 West
Prospect Road, Fort Collins, CO 80526-2097, USA3
Colorado State University Veterinary Diagnostic Laboratory, 300 West
Drake Road, Fort Collins, CO 80523-1671, USA4
Animal Disease Research Unit, Agricultural Research Service, US
Department of Agriculture, 337 Bustad Hall, Washington State University,
Pullman, WA 99164-7030, USA5
Author for correspondence: Edward Hoover.Fax +1 970 491 0523. e-mail
ehoover@lamar.colostate.edu
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Mule deer fawns (Odocoileus hemionus) were inoculated orally with a
brain homogenate prepared from mule deer with naturally occurring
chronic wasting disease (CWD), a prion-induced transmissible spongiform
encephalopathy. Fawns were necropsied and examined for PrP res, the
abnormal prion protein isoform, at 10, 42, 53, 77, 78 and 80 days
post-inoculation (p.i.) using an immunohistochemistry assay modified to
enhance sensitivity. PrPres was detected in alimentary-tract-associated
lymphoid tissues (one or more of the following: retropharyngeal lymph
node, tonsil, Peyer's patch and ileocaecal lymph node) as early as 42
days p.i. and in all fawns examined thereafter (53 to 80 days p.i.). No
PrPres staining was detected in lymphoid tissue of three control fawns
receiving a control brain inoculum, nor was PrPres detectable in neural
tissue of any fawn. PrPres-specific staining was markedly enhanced by
sequential tissue treatment with formic acid, proteinase K and hydrated
autoclaving prior to immunohistochemical staining with monoclonal
antibody F89/160.1.5. These results indicate that CWD PrP res can be
detected in lymphoid tissues draining the alimentary tract within a few
weeks after oral exposure to infectious prions and may reflect the
initial pathway of CWD infection in deer. The rapid infection of deer
fawns following exposure by the most plausible natural route is
consistent with the efficient horizontal transmission of CWD in nature
and enables accelerated studies of transmission and pathogenesis in the
native species.
snip...
Oral exposure is the most plausible pathway by which the CWD prion may
be introduced to deer in nature. Consequently, we chose this means of
inoculation in an attempt to demonstrate the feasibility of CWD
transmission by this route and to study early lymphoid tissue tropism of
the PrPres in deer. Each deer was repeatedly exposed to a known
infectious CWD inoculum over a 5-day-period because recent results with
scrapie in hamsters indicate repeated oral exposure increases the
incidence of infection (Diringer et al., 1998
). Because mice are relatively resistant to CWD (M. Bruce, personal
communication) precluding bioassay, and because several studies have
shown that PrPres strongly correlates with disease (McKinley et al.,
1983
; Race et al. , 1998
), we employed an enhanced immunostaining method (formic acid,
proteinase K and hydrated autoclaving) to detect PrPres in situ. Formic
acid and hydrated autoclaving have been previously described for PrPres
epitope exposure prior to immunohistochemistry (IHC) (Miller et al.,
1994
; van Keulen et al., 1995
). Using these methods, we demonstrate PrPres in regional lymph nodes as
early as 6 weeks after oral exposure of deer fawns to the CWD agent.
snip...
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
These results indicate that mule deer fawns develop detectable PrP res
after oral exposure to an inoculum containing CWD prions. In the
earliest post-exposure period, CWD PrPres was traced to the lymphoid
tissues draining the oral and intestinal mucosa (i.e. the
retropharyngeal lymph nodes, tonsil, ileal Peyer's patches and
ileocaecal lymph nodes), which probably received the highest initial
exposure to the inoculum. Hadlow et al. (1982)
demonstrated scrapie agent in the tonsil, retropharyngeal and mesenteric
lymph nodes, ileum and spleen in a 10-month-old naturally infected lamb
by mouse bioassay. Eight of nine sheep had infectivity in the
retropharyngeal lymph node. He concluded that the tissue distribution
suggested primary infection via the gastrointestinal tract. The tissue
distribution of PrPres in the early stages of infection in the fawns is
strikingly similar to that seen in naturally infected sheep with
scrapie. These findings support oral exposure as a natural route of CWD
infection in deer and support oral inoculation as a reasonable exposure
route for experimental studies of CWD.
snip...
full text;
http://vir.sgmjournals.org/cgi/content/full/80/10/2757?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&titleabstract=Oral+Transmission+And+Early+Lymphoid+Tropism+Of+Chronic+Wasting+Disease&fulltext=Oral+Transmission+And+Early+Lymphoid+Tropism+Of+Chronic+Wasting+Disease&searchid=1056118413058_454&stored_search=&FIRSTINDEX=0&search_url=http%3A%2F%2Fvir.sgmjournals.org%2Fcgi%2Fsearch&journalcode=vir
Asante/Collinge et al, that BSE transmission to the 129-methionine
genotype can lead to an alternate phenotype that is indistinguishable
from type 2 PrPSc, the commonest _sporadic_ CJD;
http://www.fda.gov/ohrms/dockets/ac/03/slides/3923s1_OPH.htm
TSS
