CWD TSE prion, plants, vegetables, and the potential for environmental contamination
AD.82: Prion-contaminated plants can transmit prion disease
Sandra J. Pritzkow, Rodrigo Morales, Fabio Moda and Claudio Soto
University of Texas Medical School at Houston; Houston. TX USA
Chronic Wasting Disease (CWD) is a prion disorder affecting deer and elk.
The efficient propagation of this disease in captive and free-ranging animals
suggest that it may involve horizontal transmission through contaminated
environment. It has been shown, that infectious prions can enter the environment
through saliva, feces, urine, blood or placenta tissue from infected animals, as
well as by carcasses from diseased animals. Various studies have demonstrated
that infectious prions bind tightly to soil and remain infectious after years in
this material.
We hypothesize that plants, which get in contact with infectious prions,
can also play a role on the horizontal transmission of prion diseases. To study
whether plants can interact with prions, we analyzed wheat grass roots and
leaves incubated with 263K-infected brain homogenate in vitro using the PMCA
technique and in vivo in Syrian hamsters. For in vitro analyses, the plant
tissue was incubated in serial dilutions of 263K-brain homogenate, washed
thoroughly and analyzed for the presence of Prpsc by PMCA. The results show that
even highly diluted Prpsc can bind to roots and leaves and sustain the
conversion of normal prion protein. Similar experiments are currently ongoing
using CWD infected material. In vivo, hamsters were orally infected with leaves
or roots incubated in 10% 263K-infected brain homogenate, which were thoroughly
washed as well. Hamsters, inoculated with 263K-contaminated roots or leaves,
developed typical signs of prion disease, whereas control animals inoculated
with non-contaminated plants did not. Prion disease was confirmed by
immunohistological and biochemical analyses.
These findings suggest that plants (leaves and roots) can efficiently bind
infectious prions and act as carrier of infectivity and may play an important
role in horizontal transmission by oral intake of the prion agent.
=====
AD.83: Are plants a potential transmission route for infectious prions?
Jay D. Rasmussen,1,3 Brandon H. Gilroyed,2 Tim Reuter,4 Sandor Dudas,5
Catherine Graham,5 Norman F. Neumann.6 Aru Balachandran,7 Stefanie Czub,5 Nat N.
Kav1 and Tim A. McAllister3
'Department of Agricultural; Food and Nutritional Sciences; University of
Alberta; Edmonton, AB Canada; 2School of Environmental Sciences; University of
Guelph Ridgetown Campus; Ridgetown, ON Canada; 3Agriculture and Aqri-Food
Canada; Lethbridge Research Centre; Lethbridge, AB Canada; 4Alberta Agriculture
and Rural Development; Agriculture Centre; Lethbridge. AB Canada; 5National and
OIE Reference Laboratories of BSE; National Centres for Animal Disease
Lethbridge Laboratory; Canadian Food Inspection Agency; Lethbridge. AB Canada;
School of Public Health; University of Alberta; Edmonton, AB Canada; 'National
and OIE Reference Laboratory for scrapie and CWD; Canadian Food Inspection
Agency; Ottawa ON Canada
Plants are capable of absorbing large organic materials such as proteins
and microorganisms through their roots. This phenomenon introduces the potential
for the uptake of infectious prions from the environment and is a possible route
for the distribution of prion diseases in natural habitats. Wheat (Triticum
aestivum), a major agricultural crop, was used as a model in our experiments to
examine prion uptake by plants. In preliminary experiments, model proteins of
similar size (Q prions were used (fluorescently-tagged ovalbumin, FT-OV;
recombinant cellular PrP, recPrPC). Plants were grown in sterile media
(Murashige and Skoog) for 30-45 d before roots were exposed to a model protein
solution for 24 h. Foreign target proteins were detected by fluorescent
microscopy (FT-OV) and western blotting (FT-OV and recPrPC). FT-OV was found to
enter the root system and translocate to the stem. For recPrPc, no detectable
uptake or translocation was found, but instead, a strong binding of recPrPc to
the outer root surface was observed. These results suggest that uptake by wheat,
although possible, might not be universal for all proteins. The consideration of
how different plants may respond and how natural root damage may affect protein
transport is important. The model described above was used to determine how
infectious prions interact with wheat plants. Wheat roots were exposed for 24 h
to Chronic Wasting Disease positive and negative elk brain homogenates that were
either digested with proteinase K (PK) or left undigested. Plant extracts were
analyzed by western blotting to determine the presence of prion proteins, Bands
corresponding to PK-sensitive prions were detected in root extracts, but not in
other regions of the plant. These results suggest that, similar to model work
with recPrPc, PrPc may bind to the outside of the root, without translocation to
other areas of the plant. Current work is investigating the implications of
exposure of wheat roots to purified PrPCWD on uptake. Future studies will
consider the impact of soil on absorption of PrPCWD by roots. Binding of PrPCWD
to the surface of wheat roots as shown for PrPc, would open a new discussion on
the distribution of infectious prions in the environment.
=====
AD.81: Detection of prion protein associated with cervid chronic wasting
disease in environmental samples
Chad J. Johnson, Christen B. Smith, Michael D. Samuel and Joel A. Pedersen
University of Wisconsin; Madison. WI USA
Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy
(TSE) or prion disease affecting North American members of the deer family
(cervids). The disease agent may enter the environment through decomposition of
carcasses and shedding in feces, saliva, and urine. Once in the environment
disease associated prion protein (PrPTSE) can bind to soil components and remain
bioavailable for extended time periods. Assessment of the environmental load of
the disease agent is difficult because relevant levels are below the detection
limits of immunochemical methods and bioassay is prohibitively expensive to use
as a surveillance technique. Here, we report that a combination of detergent
extraction and protein misfolding cyclic amplification with beads (PMCAb)
substantially improves the sensitivity of PrPTSE detection in environmental
samples. Using this technique we are able to achieve detection limits
substantially lower than animal bioassay. Working with amended soils we are able
to extract and amplify PrPTSE to detectable levels. We have investigated factors
contributing to PMCAb inhibition and methods to circumvent those inhibitions.
This technique holds promise for helping to clarify the relative importance of
direct and indirect transmission of CWD, assess the effectiveness of
environmental remediation, and determine environmental loads of infectious
agent.
=====
AD.80: Kinetics of chronic wasting disease prion shedding in cervid saliva
and urine
Nicholas J. Haley, Davin Henderson, Glenn C. Telling and Edward A. Hoover
Colorado State University; Fort Collins. CO USA
Efficient horizontal transmission is a unique hallmark of chronic wasting
disease (CWD) of deer, elk, and moose. Saliva trans- fer, for example via
grazing or mutual grooming, is thought to be the primary mechanism of horizontal
transmission, although urine and feces are also thought ro play an important
role. It is not known how shortly after exposure an animal may begin shedding
PrPCWD, though it has been reported that both clinical and pre-clinical animals
may successfully transmit CWD to naive deer. We hypothesized that transmission
would occur primarily in end-stage disease, though the purpose of this study was
to identify earlier time points during the course of CWD infection in which
saliva and urine may carry infectivity. Using both transgenic mouse bioassay and
real-rime quaking-induced conversion (RT-QuIC), we evaluated saliva and urine
from two experimentally infected white tail deer for which samples were
available from multiple time points post-inoculation (p.i.) (e.g., 3, 6 and 12
mo p.i., as well as immediately prior to euthanasia at 24-27 mos). We found that
while saliva collected during clinical disease was infectious in mouse bioassay,
saliva collected 12 mo p.i., prior to the onset of clinical signs was also
variably infectious. Saliva from time points earlier than 12 mo p.i. failed to
transmit infection, while urine collected from clinically affected deer had very
low potential to transmit infection, as has been reported previously. These
findings extend our understanding of CWD shedding in the natural host, and may
improve control of CWD transmission in captive and free-ranging settings.
PRION UPDATE VIA VEGETABLE PLANTS FROM THE SOIL
56. Members considered that there is no evidence that crops grown on the
land which received composted excreta from BSE-challenged animals pose a TSE
risk to humans or animals. One member suggested that, as some of these animals
are orally challenged with high doses of BSE-infected materials, and the
distribution of infectivity in the digestive system is not completely
understood, it might be premature to conclude that there is no infective agent
in the manure.
Furthermore, an unpublished study had indicated low level absorption of PrP
from soil by tomato plants although it should be noted that this study had not
been repeated. Details of this work would be sent to the SEAC Secretary. Dr
Matthews explained that most of the manure from animals challenged with high
doses of BSE had already been composted and used for coppicing. Members agreed
that the risks from disposal of residual manure from experimental animals would
be much less than historic risks of on farm contamination from naturally
infected animals at the height of the BSE epidemic. ...SNIP...END
SRM are certain cattle tissues capable of transmitting BSE. There is no
human health risk assessment to indicate the absence of human health concerns
associated with use of composted SRM domestically. To date, scientific evidence
has not been able to demonstrate that composting destroys prions. Although
domestic use would pose a negligible risk to livestock, there is a potential
risk to humans via direct ingestion of the compost or of compost particles
adhered to skin or plant material (e.g. carrots). Another potential route of
exposure is by ingestion of prions that have been taken up by plants. It has
been proven that bacteria are readily taken up by some plants (e.g. E. coli in
lettuce) thus the uptake of prions by plants cannot be precluded or dismissed at
this time. As a science-based regulator, the CFIA cannot change the policy on
this issue without a risk assessment demonstrating that the use of composted SRM
poses an acceptable risk to humans.
The BSE Inquiry / Statement No 19B (supplementary) Dr Alan Colchester
Issued 06/08/1999 (not scheduled to give oral evidence) SECOND STATEMENT TO THE
BSE INQUIRY Dr A Colchester BA BM BCh PhD FRCP Reader in Neurosciences &
Computing, University of Kent at Canterbury; Consultant Neurologist, Guy’s
Hospital London and William Harvey Hospital Ashford April 1999
snip...
88. Natural decay: Infectivity persists for a long time in the environment.
A study by Palsson in 1979 showed how scrapie was contracted by healthy sheep,
after they had grazed on land which had previously been grazed by
scrapie-infected sheep, even though the land had lain fallow for three years
before the healthy sheep were introduced. Brown also quoted an early experiment
of his own (1991), where he had buried scrapie-infected hamster brain and found
that he could still detect substantial infectivity three years later near where
the material had been placed. 89. Potential environmental routes of infection:
Brown discusses the various possible scenarios, including surface or subsurface
deposits of TSE-contaminated material, which would lead to a build-up of
long-lasting infectivity. Birds feeding on animal remains (such as gulls
visiting landfill sites) could disperse infectivity. Other animals could become
vectors if they later grazed on contaminated land. "A further question concerns
the risk of contamination of the surrounding water table or even surface water
channels, by effluents and discarded solid wastes from treatment plants. A
reasonable conclusion is that there is a potential for human infection to result
from environmental contamination by BSE-infected tissue residues. The potential
cannot be quantified because of the huge numbers of uncertainties and
assumptions that attend each stage of the disposal process". These comments,
from a long established authority on TSEs, closely echo my own statements which
were based on a recent examination of all the evidence. 90. Susceptibility: It
is likely that transmissibility of the disease to humans in vivo is probably
low, because sheep that die from scrapie and cattle that die from BSE are
probably a small fraction of the exposed population. However, no definitive data
are available.
91. Recommendations for disposal procedures: Brown recommends that material
which is actually or potentially contaminated by BSE should be: 1) exposed to
caustic soda; 2) thoroughly incinerated under carefully inspected conditions;
and 3) that any residue should be buried in landfill, to a depth which would
minimise any subsequent animal or human exposure, in areas that would not
intersect with any potable water-table source.
92. This review and recommendations from Brown have particular importance.
Brown is one of the world's foremost authorities on TSEs and is a senior
researcher in the US National Institutes of Health (NIH). It is notable that
such a respected authority is forthright in acknowledging the existence of
potential risks, and in identifying the appropriate measures necessary to
safeguard public health. Paper by SM Cousens, L Linsell, PG Smith, Dr M
Chandrakumar, JW Wilesmith, RSG Knight, M Zeidler, G Stewart, RG Will,
"Geographical distribution of variant CJD in the UK (excluding Northern
Ireland)". Lancet 353:18-21, 2 nd January 1999 93. The above paper {Appendix 41
(02/01/99)} (J/L/353/18) examined the possibility that patients with vCJD
(variant CJD) might live closer to rendering factories than would be expected by
chance. All 26 cases of vCJD in the UK with onset up to 31 st August 1998 were
studied. The incubation period of vCJD is not known but by analogy with other
human TSEs could lie within the range 5-25 years. If vCJD had arisen by exposure
to rendering products, such exposure might plausibly have occurred 8-10 years
before the onset of symptoms. The authors were able to obtain the addresses of
all rendering plants in the UK which were in production in 1988. For each case
of vCJD, the distance from the place of residence on 1st January 1998 to the
nearest rendering plant was calculated
snip...
*** Behavior of Prions in the Environment: Implications for Prion Biology
http://chronic-wasting-disease.blogspot.com/2013/02/behavior-of-prions-in-environment.html
Saturday, March 10, 2012
CWD, GAME FARMS, urine, feces, soil, lichens, and banned mad cow protein
feed CUSTOM MADE for deer and elk
Monday, July 16, 2012
Persistence of the bovine spongiform encephalopathy infectious agent in
sewage
Thursday, August 08, 2013
Characterization of the first case of naturally occurring chronic wasting disease in a captive red deer (Cervus elaphus) in North America
http://chronic-wasting-disease.blogspot.com/2013/08/characterization-of-first-case-of.html
Characterization of the first case of naturally occurring chronic wasting disease in a captive red deer (Cervus elaphus) in North America
http://chronic-wasting-disease.blogspot.com/2013/08/characterization-of-first-case-of.html
Sunday, June 09, 2013
Missouri House forms 13-member Interim Committee on the Cause and Spread of
Chronic Wasting Disease CWD
Sunday, July 21, 2013
As Chronic Wasting Disease CWD rises in deer herd, what about risk for
humans?
TSS
posted by Terry S. Singeltary Sr. at
4:18 PM
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