Chronic Wasting Disease A Time Bomb For Agriculture?
Chris Bennett, Farm Journal Media
January 30, 2018 11:25 AM
“Everyone at least needs to wake up to the potential of CWD to move in crops because it would shake up agriculture as we know it,” says David Clausen. ( © Herbert Lange, WDNR )
Is chronic wasting disease (CWD) a potential time bomb for the agriculture industry? A silent killer stalking deer and elk, CWD continues to move quietly across the U.S., with 22 states currently reporting CWD presence in free-ranging cervids.
CWD is a neural malady with devastating final-stage symptoms akin to mad cow disease. There is no direct proof of transmission via contaminated grain or feedstuffs, but researchers say accumulating evidence warrants a closer look at the possibility for potential disruption of multiple facets of the agriculture industry.
CWD is a guarantee of protracted death. Without exception, host deer slowly enter a zombie-like state characterized by extreme thirst, lack of mobility, loss of balance and near-total disorientation. CWD plays by a unique set of disease rules and does not spread by the common modes of infection (bacteria or virus), but is transmitted by a corrupted prion, essentially a misfolded protein. The corrupted prions multiply until the infection reaches the brain, destroying cells and attacking the central nervous system. Brain cells die in response to the presence of prions, creating holes in the brain.
“It’s a bad way to die. The animals are emaciated and waste away, and ultimately die from aspiration pneumonia because the swallowing reflex is affected and saliva gets into the lungs, or they freeze to death because they have no more body fat,” says Tracy Nichols, a molecular biologist and staff officer with USDA’s Veterinary Services Cervid Health Program in Fort Collins, Co.
On average whitetail deer have an approximate two-year CWD incubation period from infection to death. Although deer appear and act healthy for the vast majority of the disease duration, they can transmit CWD during nearly the entire span. (It is detectable in bodily fluids from infected animals as early as three months.) Deer directly contract CWD through infectious saliva, feces and urine, or indirectly via soil ingestion, foraging or a water source contaminated with prion proteins.
After initial detection in 1967 at a Colorado captive mule deer facility, CWD spread with a slow, but sure pace. Fifty years later, CWD has infected cervid populations in 181 counties across 22 states, according to the Centers for Disease Control and Prevention (CDC).
The geographic footprint of CWD continues to swell, likely through two different functions. One, slow diffusion from deer to deer in the wild. Two, faster movement through human-assisted spread by captive cervid farms or hunter-transported carcasses.
There are no known cases of natural transmission of CWD to domestic livestock. However, in laboratory conditions, CWD has been reproduced experimentally in cattle and swine, and research studies continue to examine crossover possibilities. There is no evidence of human crossover of CWD, although a 2017 studydocumented oral transmission of CWD to macaque monkeys. (Conducted in Canada, the study awaits peer review and publication.) Since 1997, the World Health Organization (WHO) has called for the exclusion of all prion disease material from the human and animal food chains.“Mad cow disease crossed the species barrier to humans, but we haven’t seen evidence of CWD crossover. We can’t say crossover won’t happen in time, and as a precautionary measure WHO doesn’t want infected prions in the human or animal food chains,” says Bryan Richards, chronic wasting disease project leader for the U.S. Geological Survey (USGS) National Wildlife Health Center in Madison, Wis.
The possibility of CWD transmission beyond cervid populations remains an unanswered question, partly because different strains of CWD behave distinctly. “There is so much about CWD transmission we don’t know and so much yet to be studied. There are so many CWD unknowns related to brain matter, infectivity, prion stage, lymph nodes and more,” says David Clausen, a retired Wisconsin veterinarian, farmer, and former chair of the Wisconsin Natural Resources Board. Clausen presently serves as board president of Midwest Environmental Advocates.
The infectivity range of CWD is another significant unknown. When one species door is closed, another may serve as a Trojan horse. Hamsters were originally thought to be immune to CWD, while ferrets were easily infected. “Take deer CWD and infect the ferret. Take the ferret CWD and infect the hamster. Boom. The hamster can’t be infected by the deer, but is susceptible to the ferret. These prions are constantly evolving and changing,” Clausen explains.
“The question is sitting there: If CWD is able to get into livestock or swine, could it be transmitted in feedstuffs?” he adds.
Echoing Clausen’s query, is CWD passed along in agricultural plant matter exposed to urine, feces or carcass material? Prions form a chemical bond with plant surfaces and also bind to some soil particles, according to Richards. “After dipping plant leaves in prion proteins, researchers haven’t been able to wash off the prions. There isn’t enough science yet, but it’s been shown that plants can pick up proteins in the soil matrix through their roots and deposit those proteins in shoots and leaves, likely in flowers as well,” he explains. “Is the infectivity still there and is the concentration enough to transmit disease?”
![[IMG]](https://www.agweb.com/assets/1/6/MainFCKEditorDimension/660d4f6ad8884258b2d563af68716d241.jpg)
CWD has infected cervid populations in 181 counties across 22 states, according to the Centers for Disease Control and Prevention.
© USGS
Uptake in a laboratory isn’t real-world confirmation, but Richards finds the implications disturbing. In addition, CWD expansion across the U.S. compounds the infectivity issue. “With the geographic footprint of CWD greatly expanded, we have to ask if plant material really moves infectious material. We have to contemplate the question because agriculture would be such a huge mechanism for disease movement,” he says.
In theory, take a county with a 40% CWD rate in a whitetail population. If 20 whitetail typically feed in-and-out of a given wheat field, eight of those deer are CWD-positive. An adult deer defecates roughly 12 times per day and urinates at a higher frequency. After harvest, if the wheat straw is rolled, statistical probability places a good deal of fecal material in the bales. “It’s not a far-fetched idea for infectious material to move in agricultural commodities,” Richards says. “This is not really on the ag industry radar, but it comes up regularly in conversations among scientists. We don’t know if transmission happens, but it must be kept on the radar screen.”
“There was once a time when people said mad cow disease could never cross the species barrier. Almost 300 human deaths and an industry disaster later, it’s pretty simple to see why we keep on conducting the science and relying strictly on what the evidence shows,” he adds.
Nichols cites several studies where plant roots grown in hydroponic or spiked soil solutions were exposed to CWD material. The stem and leaf tissue subsequently tested positive for infected prions, despite no contact with the CWD material. However, high levels of laboratory exposure don’t necessarily equate with field environments. “The results are disconcerting, but what really matters is what happens in the real world. The next level of inquiry is to find out if there is any threat via agriculture crops,” Nichols says.
“There is no scientific conclusion, but the questions raised could impact international trade. Right now, we don’t know what, if any, threat exists,” she continues.
Clausen takes a dim view of CWD containment and believes the disease will continue to creep into additional states: “I’m a country boy. Basic epidemiology of disease control is to contain and quarantine. Deer farm or deer carcass, we have to prevent the movement of all CWD material, dead or alive.”
![[IMG]](https://www.agweb.com/assets/1/6/MainFCKEditorDimension/343f03f6323e4ba3915262859ab519711.jpg)
“With the geographic footprint of CWD greatly expanded, we have to ask if plant material really moves infectious material. We have to contemplate the question because agriculture would be such a huge mechanism for disease movement,” says Bryan Richards, USGS.© HERBERT LANGE, WDNR
It is incumbent on the agriculture industry to consider the ramifications of CWD spread through agricultural commodities, according to Clausen. “Sometimes we just seem to bounce from crisis to crisis without enough preparation or foresight. Corn or alfalfa, CWD uptake has been demonstrated in plants. Whether the uptake is infectious, that research hasn’t been done.”
“Everyone at least needs to wake up to the potential of CWD to move in crops because it would shake up agriculture as we know it,” Clausen says. “We’re all responsible to take a precautionary approach and consider what could happen.”
https://www.porkbusiness.com/article/chronic-wasting-disease-time-bomb-agriculture
CWD TO PIGS
Research Project: TRANSMISSION, DIFFERENTIATION, AND PATHOBIOLOGY OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES
Location: Virus and Prion Research
Title: Disease-associated prion protein detected in lymphoid tissues from pigs challenged with the agent of chronic wasting disease
Author item Moore, Sarah item Kunkle, Robert item Kondru, Naveen item Manne, Sireesha item Smith, Jodi item Kanthasamy, Anumantha item West Greenlee, M item Greenlee, Justin
Submitted to: Prion Publication Type: Abstract Only Publication Acceptance Date: 3/15/2017 Publication Date: N/A Citation: N/A Interpretive Summary:
Technical Abstract: Aims: Chronic wasting disease (CWD) is a naturally-occurring, fatal neurodegenerative disease of cervids. We previously demonstrated that disease-associated prion protein (PrPSc) can be detected in the brain and retina from pigs challenged intracranially or orally with the CWD agent. In that study, neurological signs consistent with prion disease were observed only in one pig: an intracranially challenged pig that was euthanized at 64 months post-challenge. The purpose of this study was to use an antigen-capture immunoassay (EIA) and real-time quaking-induced conversion (QuIC) to determine whether PrPSc is present in lymphoid tissues from pigs challenged with the CWD agent.
Methods: At two months of age, crossbred pigs were challenged by the intracranial route (n=20), oral route (n=19), or were left unchallenged (n=9). At approximately 6 months of age, the time at which commercial pigs reach market weight, half of the pigs in each group were culled (<6 challenge="" groups="" month="" pigs="" remaining="" the="">6 month challenge groups) were allowed to incubate for up to 73 months post challenge (mpc). The retropharyngeal lymph node (RPLN) was screened for the presence of PrPSc by EIA and immunohistochemistry (IHC). The RPLN, palatine tonsil, and mesenteric lymph node (MLN) from 6-7 pigs per challenge group were also tested using EIA and QuIC.
Results: PrPSc was not detected by EIA and IHC in any RPLNs. All tonsils and MLNs were negative by IHC, though the MLN from one pig in the oral <6 5="" 6="" at="" by="" detected="" eia.="" examined="" group="" in="" intracranial="" least="" lymphoid="" month="" months="" of="" one="" pigs="" positive="" prpsc="" quic="" the="" tissues="" was="">6 months group, 5/6 pigs in the oral <6 4="" and="" group="" months="" oral="">6 months group. Overall, the MLN was positive in 14/19 (74%) of samples examined, the RPLN in 8/18 (44%), and the tonsil in 10/25 (40%). Conclusions:
This study demonstrates that PrPSc accumulates in lymphoid tissues from pigs challenged intracranially or orally with the CWD agent, and can be detected as early as 4 months after challenge.
CWD-infected pigs rarely develop clinical disease and if they do, they do so after a long incubation period. This raises the possibility that CWD-infected pigs could shed prions into their environment long before they develop clinical disease.
Furthermore, lymphoid tissues from CWD-infected pigs could present a potential source of CWD infectivity in the animal and human food chains.
CONFIDENTIAL
EXPERIMENTAL PORCINE SPONGIFORM ENCEPHALOPATHY
While this clearly is a cause for concern we should not jump to the conclusion that this means that pigs will necessarily be infected by bone and meat meal fed by the oral route as is the case with cattle. ...
we cannot rule out the possibility that unrecognised subclinical spongiform encephalopathy could be present in British pigs though there is no evidence for this: only with parenteral/implantable pharmaceuticals/devices is the theoretical risk to humans of sufficient concern to consider any action.
Our records show that while some use is made of porcine materials in medicinal products, the only products which would appear to be in a hypothetically ''higher risk'' area are the adrenocorticotrophic hormone for which the source material comes from outside the United Kingdom, namely America China Sweden France and Germany. The products are manufactured by Ferring and Armour. A further product, ''Zenoderm Corium implant'' manufactured by Ethicon, makes use of porcine skin - which is not considered to be a ''high risk'' tissue, but one of its uses is described in the data sheet as ''in dural replacement''. This product is sourced from the United Kingdom.....
snip...see much more here ;
WEDNESDAY, APRIL 05, 2017
Disease-associated prion protein detected in lymphoid tissues from pigs challenged with the agent of chronic wasting disease
WEDNESDAY, APRIL 05, 2017
*** Disease-associated prion protein detected in lymphoid tissues from pigs challenged with the agent of chronic wasting disease ***
cattle are highly susceptible to white-tailed deer CWD and mule deer CWD
***In contrast, cattle are highly susceptible to white-tailed deer CWD and mule deer CWD in experimental conditions but no natural CWD infections in cattle have been reported (Sigurdson, 2008; Hamir et al., 2006). It is not known how susceptible humans are to CWD but given that the prion can be present in muscle, it is likely that humans have been exposed to the agent via consumption of venison (Sigurdson, 2008). Initial experimental research, however, suggests that human susceptibility to CWD is low and there may be a robust species barrier for CWD transmission to humans (Sigurdson, 2008). It is apparent, though, that CWD is affecting wild and farmed cervid populations in endemic areas with some deer populations decreasing as a result.
SNIP...
price of prion poker goes up for cwd to cattle;
Monday, April 04, 2016
*** Limited amplification of chronic wasting disease prions in the peripheral tissues of intracerebrally inoculated cattle ***
*** The potential impact of prion diseases on human health was greatly magnified by the recognition that interspecies transfer of BSE to humans by beef ingestion resulted in vCJD. While changes in animal feed constituents and slaughter practices appear to have curtailed vCJD, there is concern that CWD of free-ranging deer and elk in the U.S. might also cross the species barrier. Thus, consuming venison could be a source of human prion disease. Whether BSE and CWD represent interspecies scrapie transfer or are newly arisen prion diseases is unknown. Therefore, the possibility of transmission of prion disease through other food animals cannot be ruled out. There is evidence that vCJD can be transmitted through blood transfusion. There is likely a pool of unknown size of asymptomatic individuals infected with vCJD, and there may be asymptomatic individuals infected with the CWD equivalent. These circumstances represent a potential threat to blood, blood products, and plasma supplies.
TUESDAY, JANUARY 30, 2018
Colorado Chronic Wasting Disease CWD TSE Prion 7/2015-6/2016 Results (2017?)
Volume 23, Number 9—September 2017
Research Letter Chronic Wasting Disease Prion Strain Emergence and Host Range Expansion
***Thus, emergent CWD prion strains may have higher zoonotic potential than common strains.
2017
Subject: ***CDC Now Recommends Strongly consider having the deer or elk tested for CWD before you eat the meat
CDC Now Recommends Strongly consider having the deer or elk tested for CWD before you eat the meat
Chronic Wasting Disease (CWD)
Prevention
* Strongly consider having the deer or elk tested for CWD before you eat the meat.
* If you have your deer or elk commercially processed, consider asking that your animal be processed individually to avoid mixing meat from multiple animals.
* If your animal tests positive for CWD, do not eat meat from that animal.
> However, to date, no CWD infections have been reported in people.
key word here is 'reported'. science has shown that CWD in humans will look like sporadic CJD. SO, how can one assume that CWD has not already transmitted to humans? they can't, and it's as simple as that. from all recorded science to date, CWD has already transmitted to humans, and it's being misdiagnosed as sporadic CJD. ...terry
LOOKING FOR CWD IN HUMANS AS nvCJD or as an ATYPICAL CJD, LOOKING IN ALL THE WRONG PLACES $$$
*** These results would seem to suggest that CWD does indeed have zoonotic potential, at least as judged by the compatibility of CWD prions and their human PrPC target. Furthermore, extrapolation from this simple in vitro assay suggests that if zoonotic CWD occurred, it would most likely effect those of the PRNP codon 129-MM genotype and that the PrPres type would be similar to that found in the most common subtype of sCJD (MM1).***
TUESDAY, SEPTEMBER 12, 2017
CDC Now Recommends Strongly consider having the deer or elk tested for CWD before you eat the meat
SATURDAY, JANUARY 27, 2018
CDC CHRONIC WASTING DISEASE CWD TSE PRION UPDATE REPORT USA JANUARY 2018
Terry S. Singeltary Sr.
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