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Resistance of Soil-Bound Prions to Rumen Digestion

Posted Sep 01 2012 5:19pm
Resistance of Soil-Bound Prions to Rumen Digestion



Samuel E. Saunders1¤, Shannon L. Bartelt-Hunt1*, Jason C. Bartz2



1 Department of Civil Engineering, University of Nebraska-Lincoln, Peter Kiewit Institute, Omaha, Nebraska, United States of America, 2 Department of Medical Microbiology and Immunology, Creighton University, Omaha, Nebraska, United States of America



Abstract



Before prion uptake and infection can occur in the lower gastrointestinal system, ingested prions are subjected to anaerobic digestion in the rumen of cervids and bovids. The susceptibility of soil-bound prions to rumen digestion has not been evaluated previously. In this study, prions from infectious brain homogenates as well as prions bound to a range of soils and soil minerals were subjected to in vitro rumen digestion, and changes in PrP levels were measured via western blot. Binding to clay appeared to protect noninfectious hamster PrPc from complete digestion, while both unbound and soil-bound infectious PrPSc proved highly resistant to rumen digestion. In addition, no change in intracerebral incubation period was observed following active rumen digestion of unbound hamster HY TME prions and HY TME prions bound to a silty clay loam soil. These results demonstrate that both unbound and soil-bound prions readily survive rumen digestion without a reduction in infectivity, further supporting the potential for soil-mediated transmission of chronic wasting disease (CWD) and scrapie in the environment.



Citation: Saunders SE, Bartelt-Hunt SL, Bartz JC (2012) Resistance of Soil-Bound Prions to Rumen Digestion. PLoS ONE 7(8): e44051. doi:10.1371/journal.pone.0044051



Editor: Jiyan Ma, Ohio State University, United States of America



Received: June 7, 2012; Accepted: July 27, 2012; Published: August 24, 2012



Copyright: © 2012 Saunders et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.



Funding: This work was supported by National Science Foundation (CBET-1149242) and the National Center for Research Resources (P20 RR0115635-6, C06 RR17417-01 and G200RR024001). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.



Competing interests: The authors have declared that no competing interests exist.






¤Current address: Stanford Law School, Stanford, California, United States of America




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Implications for Environmental Prion Transmission To initiate infection via absorption across the lower gastrointestinal epithelium, orally ingested prions must survive passage through the rumen [8]–[10]. Previous studies have observed varied PrPSc resistance to in vitro rumen digestion [9], [18], [20]. We observed that active in vitro rumen digestion did not reduce PrPSc abundance (Figure 1), and consistent with the previous work of Scherbel et al. [19], unbound prion infectivity was not reduced following rumen digestion (Table 2). Moreover, our results demonstrate that PrPSc sorption to soil does not reduce prion resistance to rumen digestion. However, since both unbound and soil-bound prions were resistant to rumen digestion, we cannot conclude that soil sorption increases prion resistance to gut degradation, only that it does not decrease it. Nevertheless, the resistance of soil-bound prions to rumen digestion supports the efficacy of soil-mediated prion transmission (prion-soil sorption and subsequent ingestion or inhalation by a naïve host) [21] as a natural mechanism of CWD and scrapie transmission.



We did observe variance in PrPSc resistance to digestion with respect to soil type, where, in contrast to the other soils and minerals, PrPSc levels bound to sand and sandy loam soil were reduced following digestion (Figure 1D and 1E). Variance in prion-soil interactions of this kind could lead to spatial variance in prion disease incidence based on local soil-type [21]. However, preliminary protein misfolding cyclic amplification (PMCA) experiments [27] indicate the replication efficiency of prions subjected to active digestion while bound to sand or SiO2 is not significantly different than unbound prions (data not shown). Based on the established relationship between PMCA replication efficiency and infectious titer [24], [27], these results suggest the SCL soil bioassay results are typical of the other soils and soil minerals used. Still, bioassay of other soils is needed to definitively evaluate soil-type variance in digestion resistance.



A number of factors must be considered in extending the present results. First, the results were obtained using in vitro digestion, which is a simulation of in vivo processes with limitations [30], [35]. We used standard in vitro methods, consistent with previous prion digestion studies, although the limited amount of prion-infected brain homogenate available necessitated using small (0.2 ml) tubes, which may have contributed to the observed variance. Second, prion resistance to digestion may vary with prion strain and species [23], [33]. As noted above, our preliminary work with other prion strains and species suggests broad prion resistance to rumen digestion, but these results would need to be confirmed with additional studies. Third, rumen digestion can vary with host species and diet, with the latter appearing more significant than the former [38]. Studies have reported similar in vitro digestion (as measured by parameters such as gas production and substrate utilization) when using rumen fluid contents from sheep and cows [39], [40], sheep and goats [41], and sheep and red deer [42] when animals were fed the same diet. Variance in the diet of the cows used to collect rumen fluid (23–66% grain) did not observably affect the immunoblot results of this study (data not shown), suggesting that diet is not a significant factor and that our results are applicable across a wide range of diets and species (cervids, sheep, goats, and cattle). However, an extensive study of the effect of diet was not conducted. Moreover, dairy cow diets are notably different than free-ranging deer diets, and deer diets vary seasonally as well as geographically, which can affect rumen digestion [43].



Finally, unbound and soil-bound prions surviving rumen passage will be exposed to stomach and intestinal digestion before uptake. These two processes are less complex than rumen digestion, and previous results indicate unbound prions are resistant to both [8], [9], [44]. Still, the effect of soil sorption on prion resistance to lower gastrointestinal digestion has yet to be investigated. Moreover, while passage through the rumen and lower gastrointestinal tract may not digest PrPSc, it may alter PrPSc uptake efficiency, which would not be detected by immunoblot or intracerebral bioassay. Thus, study of soil-bound prions in, for example, the gut-loop system employed by Dagleish and Jeffery [8], [9] would be of interest in further evaluating the efficacy of soil-mediated prion transmission.









April/May/June 2012; © 2012 Landes Bioscience



PO-033: Replication efficiency of soil-bound prions varies with soil type



Shannon Bartelt-Hunt,1 Samuel Saunders,1 Ronald Shikiya,2 Katie Langenfeld,2 Jason Bartz2 1University of Nebraska-Lincoln; Omaha, NE USA; 2Creighton University; Omaha, NE USA



Prion sorption to soil is thought to play an important role in the transmission of scrapie and chronic wasting disease (CWD) via the environment. Sorption of PrP to soil and soil minerals is influenced by the strain and species of PrPSc and by soil characteristics. However, the ability of soil-bound prions to convert PrPc to PrPSc under these wide-ranging conditions remains poorly understood. We developed a semiquantitative protein misfolding cyclic amplification (PMCA) protocol to evaluate replication efficiency of soil-bound prions. Binding of the hyper (HY) strain of transmissible mink encephalopathy (TME) (hamster) prions to a silty clay loam soil yielded a greater-than-1-log decrease in PMCA replication efficiency with a corresponding 1.3-log reduction in titer. The increased binding of PrPSc to soil over time corresponded with a decrease in PMCA replication efficiency. The PMCA efficiency of bound prions varied with soil type, where prions bound to clay and organic surfaces exhibited significantly lower replication efficiencies while prions bound to sand exhibited no apparent difference in replication efficiency compared to unbound controls. PMCA results from hamster and CWD agent-infected elk prions yielded similar findings. Given that PrPSc adsorption affinity varies with soil type, the overall balance between prion adsorption affinity and replication efficiency for the dominant soil types of an area may be a significant determinant in the environmental transmission of prion diseases.




PO-248: TSE infectivity survives burial for five years with little reduction in titer



Allister Smith, Robert Somerville, Karen Fernie The Roslin Institute and R(D)SVS; University of Edinburgh; Edinburgh, UK



BSE infected animals, BSE-contaminated materials and other sources of TSE (prion) infection, such as carcasses from scrapie infected sheep, CWD infected deer and cadavers of individuals infected with CJD may all end up in the environment through burial or other methods of disposal. They may continue to act as a reservoir of TSE infectivity if cattle or other susceptible animals were to be exposed to these sources in the future. In order to address these concerns, we performed two large scale demonstration experiments under field conditions which were designed to mimic some of the ways by which TSE infected materials may have been disposed of. The project examined the fate of TSE infectivity over a period of five years in two scenarios; when the infectivity was contained within bovine heads and when the infectivity was buried without any containment. Two soil types were compared: a sandy loam and a clay loam. We used the 301V TSE strain which was derived by serial passage of BSE in VM mice.



TSE infectivity was recovered from all the heads exhumed annually for five years from both types of soil, with little reduction in the amount of infectivity throughout the period of the experiment. Small amounts of infectivity were found in the soil immediately surrounding the heads, but not in samples remote from them. Similarly there was no evidence of significant lateral movement of infectivity from the buried bolus. However large amounts of TSE infectivity were recovered at the site of burial of both boluses. There was limited vertical upward movement of infectivity from the bolus buried in clay soil and downward movement from the bolus buried in sandy soil.



Now that these experiments are completed we conclude that TSE infectivity is likely to survive burial for long periods of time with minimal loss of infectivity and restricted movement from the site of burial. These experiments emphasize that the environment is a viable reservoir for retaining large quantities of TSE infectivity, and reinforce the importance of risk assessment when disposing of this type of infectious material.









PRION 2011



Envt.16: Soil Properties as a Factor in CWD Spread in Western Canada



Alsu Kuznetsova,† Tariq Siddique and Judd Aiken



University of Alberta; Edmonton, AB Canada†Presenting author; Email: alsu@ualberta.ca



Soil can serve as a stable reservoir for infectious prion proteins (PrPSc). Soils are diverse and complex, varying in clay, silt, sand and organic components. We have shown that PrPSc binds clay minerals avidly, an interaction that considerably enhances prion infectivity. Conversely quartz sand bound PrPSc less avidly. These studies would suggest that soils with lower clay and higher sand content bind prions less avidly and do not enhance infectivity to the same level as clay-rich soils. We hypothesize that clay content of a soil plays an integral role in the spread of CWD. In this study, we present the soil properties in the western Canada. Soils of the CWD-region generally are similar in texture, clay mineralogy and soil organic matter content. In total these soils can be characterized as clay loamy, montmorillonite (smectite) with 6–10 % organic carbon. The major soils in the CWD-region are Chernozems, present in 60% of total area. These soils have a humic horizon in which organic matter has accumulated (1–17% organic C). Solonetzic soils are also common to Alberta and Saskatchewan. We suggest that the greatest risk of CWD spread in western Canada is restricted to clay loamy, montmorillonite soils with humus horizon. Such soils are predominant in the southern region of Alberta, Saskatchewan and Manitoba, but are less common in northern regions of the provinces.




Envt.28:



High Survival Rates of TSE Infectivity Buried in Two Soil



Types Allister J. Smith The Roslin Insitute; Roslin, UK Email: allister.smith@roslin.ed.ac.uk



Two field experiments nearing completion are investigating the migration and/or persistence of TSE infectivity in the soil environment, either buried within bovine heads or buried without containment. In the first experiment five pairs of bovine heads, spiked with mouse-passaged BSE (301V) macerate, were buried within lysimeters containing either clay or sandy soil. A pair of unspiked bovine heads was also buried to act as controls. Pairs of heads have been exhumed annually during which a corer is used to take soil samples above, surrounding and below the head. Any brain material within the head is recovered during dissection. The soil samples have undergone protein extraction, and the extracts along with the brain material have been assayed for infectivity by bioassay in VM mice. Bioassay results from the first experiment show that for all four years most of the intracranial brain samples have been positive for TSE infectivity in both the clay and sandy soil. There is little change in the survival curves between years 1 and 4 indicating little reduction in the amounts of infectivity over time. There has been very limited infectivity found in samples surrounding the heads buried in the sandy soil, but infectivity has been found in the soil samples surrounding the clay heads and the levels increase slightly from years one to four, presumably as the heads have decomposed. In a parallel experiment a bolus of infectivity (301V) was placed in the centre of two large lysimeters, containing either clay or sandy soil. Over the course of four years, core samples have been taken at eight time points, on the vertical and at 3 distances from the centre. These samples have been assayed for infectivity and to date only one sample from the sandy soil has produced pathological evidence of TSE disease in one mouse. In order to ascertain whether any of the bolus remained at the end of the experiment, we collected a much larger central core (d = 16 cm) and extracted samples for bioassay, concentrating on the core portions that correlated to the original bolus location. The samples from these core portions caused disease in a high proportion of mice (bioassay still in progress), with apparently higher infectivity levels in the clay soil, so far. This result indicates that there has been very little migration of TSE infectivity without containment in either clay or sandy soil and that there has been little reduction in titre with time.




Envt.29:



Time-Dependent Decline in PrPTSE Desorption from Soil



Particles Christen B. Smith,1,† Clarissa J. Booth,2 Kartik Kumar2 and Joel A. Pedersen1–3 1Environmental Chemistry and Technology Program; 2Molecular and Environmental Toxicology Center; 3Department of Soil Science, University of Wisconsin; Madison, WI USA †Presenting author, Email: cmbell@wisc.edu



Environmental routes of transmission are implicated in epizootics of sheep scrapie and chronic wasting disease in deer, elk, and moose. Strong evidence suggests that soil may serve as an environmental reservoir of prions, which can persist in the environment for years. The disease-associated form of the prion protein (PrPTSE) readily attaches to soil particle surfaces. Prior studies reported reduced PrPTSE recovery from experimentally spiked soils after longer contact times, which in some cases has been interpreted as degradation of PrPTSE. Here, we investigate PrPTSE desorption from sterilized and untreated soil particles as a function of protein-soil contact time. Soil particles were sterilized by autoclaving or g-irradiation. Desorption of PrPTSE from whole soils, montmorillonite clay, and quartz sand was analyzed by immunoblotting following 1-, 7-, and 14-day contact times. We found that PrPTSE recovery from both sterile and untreated soil samples declined significantly with contact time suggesting the strengthening of protein-particle interactions over time. Recovery of PrPTSE from whole soils declined to a larger extent than did that from montmorillonite and quartz sand possibly reflecting t he contribution of particle-associated natural organic matter to the mechanisms of PrPTSE attachment. The influence of PrPTSE-soil particle attachment on oral disease transmission warrants investigation.



www.landesbioscience.com PRION









PO-031: Aerosol transmission of chronic wasting disease to white-tailed deer



Nathaniel Denkers,1 Jeanette Hayes-Klug,1 Kelly Anderson,1 Sally Dahmes,2 David Osborn,3 Karl Miller,3 Robert Warren,3 Candace Mathiason,1 Edward Hoover1



1Colorado State University; Fort Collins, CO USA; 2WASCO Inc.; Monroe, GA USA; 3Warnell School of Forestry and Natural Resources, University of Georgia; Athens, GA USA



Purpose. A signature feature of chronic wasting disease (CWD) is its efficient lateral transmission in nature, almost surely by mucosal exposure. Our previous studies employing Tg(cerPrP) mice determined that CWD can be transmitted to a susceptible host by aerosol exposure, a route with relatively little investigation. The present study was designed to determine whether CWD is transmissible by aerosol to a native cervid host, white-tailed deer.



Materials and Methods. Nine white-tailed deer were exposed to two (2) aerosol doses of a 5% w/v CWD+ (n = 6) or CWD- (n = 3) brain homogenate, delivered via the nasal passages using a customized aerosol apparatus. At 3-month intervals post inoculation (mpi), tonsil and recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsies were collected and assayed for CWD infection by protein misfolding cyclic amplification (PMCA), western blotting (WB), and immunohistochemistry (IHC).



Results. At 3 mpi and 6 mpi, tonsil and RAMALT biopsies were collected from 5 of the 6 CWD + aerosol-exposed deer. Three of the 5 (60%) tested positive for CWD by PMCA but not IHC or western blot analysis at 3 mpi. By 6 mpi, 5 of 5 (100%) were tonsil and/or RAMALT biopsy positive by at least two of the three assays. Biopsies were collected from all CWD+ aerosol-exposed deer at 9 mpi, with 6 of 6 (100%) tonsil and/ or RAMALT positive by western blot or IHC. At 10 mpi 3 of the 6 prion-exposed deer have developed early clinical signs of CWD infection (hyperphagia, polydypsia, wide leg stance and head/neck dorsi-flexion). All sham-inoculated deer are showing no clinical signs and have remained CWD negative as assessed by all three assays. Interestingly, the prion dose delivered to the deer by aerosol-exposure is estimated to be 20-fold lower than the historical oral dose that has resulted in detectable CWD infection at 6 or 12 mpi.



Conclusions. This study documents the first aerosol transmission of CWD in deer. These results further infer that aerosolized prions facilitate CWD transmission with greater efficiency than does oral exposure to a larger prion dose. Thus exposure via the respiratory mucosa may be significant in the facile spread of CWD in deer and perhaps in prion transmission overall.









PO-073: Multiple routes of prion transepithelial transport in the nasal cavity following inhalation



Anthony Kincaid, Shawn Feilmann, Melissa Clouse, Albert Lorenzo, Jason Bartz



Creighton University; Omaha, NE USA



Introduction. Inhalation of either prion-infected brain homogenate or aerosolized prions has been shown to cause disease, and in the case of inhalation of infected brain homogenate, the nasal route of infection has been shown to be 10–100 times more efficient than the oral route. The cell types involved in the in vivo transport of prions across the nasal cavity epithelium have not been determined. M cells in the follicular associated epithelium have been shown to mediate transcellular transport of prions in vitro and in the gut of experimentally infected mice. We tested the hypothesis that M-cell mediated transport was responsible for prion entry across nasal cavity epithelium following inhalation. Materials and Methods. Hamsters were inoculated extranasally with 50 or 100ul of infected (n = 31) or mock-infected (n = 13) brain homogenate. Control animals were inoculated with buffer (n = 4) or were untreated (n = 5). Following survival periods ranging from 15 to 180 min, animals were perfused, skulls were decalcified and nasal cavities were embedded in paraffin. Tissue sections were cut and processed immunohistochemically for glial fibrillary acidic protein to identify brain homogenate, or for the disease-associated form of the prion protein. Tissue sections not further than 112 um apart through the entire extent of the nasal cavity were analyzed using light microscopy; photomicrographs were obtained wherever inoculum was observed on the surface of, within, or deep to the nasal mucosa for each animal. Results. Infected or uninfected brain homogenate was identified within the nasal cavities of animals at all time points and was seen crossing the nasal cavity epithelium within minutes of inoculation; the transepithelial transport of brain homogenate continued for up to 3 h after inoculation. Infected or uninfected brain homogenate was seen adhering to, or located within, M cells at all time points. However, larger volumes of infected or uninfected brain homogenate were identified crossing between cells of the olfactory and respiratory epithelia in multiple locations. In addition, infected or uninfected brain homogenate was identified within the lumen of lymphatic vessels in the lamina propria beneath the nasal mucosa at all time points. Conclusion. Transepithelial transport of prions across nasal cavity mucosa begins within minutes of inhalation and can continue for up to 3 h. While M cells appear to transport prions across the follicular associated epithelium, larger amounts of prions are transported between the cells of the respiratory and olfactory epithelia, where they immediately enter the lymphatic vessels in the lamina propria. Thus, inhaled prions can be spread via lymph draining the nasal cavity and have access to somatic and autonomic nerves in the lamina propria of the nasal cavity. The increased efficiency of the nasal cavity route of infection compared with the oral route may be due to the rapid and prolonged transport of prions between cells of the respiratory and olfactory epithelia.











Saturday, June 09, 2012


USDA Establishes a Herd Certification Program for Chronic Wasting Disease in the United States











Thursday, May 31, 2012



CHRONIC WASTING DISEASE CWD PRION2012 Aerosol, Inhalation transmission, Scrapie, cats, species barrier, burial, and more









Soil clay content underlies prion infection odds



W. David Walter 1 , * , Daniel P. Walsh 2 , * , Matthew L. Farnsworth 3 , Dana L. Winkelman 1 & Michael W. Miller 2



1 United States Department of the Interior, United States Geological Survey, Colorado Cooperative Fish and Wildlife Research Unit , Fort Collins , Colorado



80523-1484, USA. 2 Colorado Division of Wildlife, Wildlife Research Center, Fort Collins, Colorado 80526-2097, USA. 3 United States Department



of Agriculture, Animal and Plant Health Inspection Services, Veterinary Services, Centers for Epidemiology and Animal Health , Fort Collins , Colorado



80526-8117 , USA . * These authors contributed equally to this work. Correspondence and requests for materials should be addressed to M.W.M.



(email: mike.miller@state.co.us ) .



Received 6 Sep 2010 | Accepted 19 Jan 2011 | Published 15 Feb 2011 DOI: 10.1038/ncomms1203



Environmental factors — especially soil properties — have been suggested as potentially important in the transmission of infectious prion diseases. Because binding to montmorillonite (an aluminosilicate clay mineral) or clay-enriched soils had been shown to enhance experimental prion transmissibility, we hypothesized that prion transmission among mule deer might also be enhanced in ranges with relatively high soil clay content. In this study, we report apparent influences of soil clay content on the odds of prion infection in free-ranging deer. Analysis of data from prion-infected deer herds in northern Colorado, USA, revealed that a 1 % increase in the clay-sized particle content in soils within the approximate home range of an individual deer increased its odds of infection by up to 8.9 % . Our findings suggest that soil clay content and related environmental properties deserve greater attention in assessing risks of prion disease outbreaks and prospects for their control in both natural and production settings.



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The capacity of clay minerals and clay-laden soils to capture and enhance infectivity of shed or deposited prions 19,20,25 – 27 and the common tendency of ruminants to ingest soil both deliberately and incidentally in the course of foraging and grooming 12,44,45 provide an elegantly simple hypothetical mechanism for indirect prion transmission, as follows: infected individuals propagate infectious prions in mucosa-associated lymphoid tissues and shed prions into ingesta and saliva; ingested and environmental soil microparticles with a high phyllosilicate (especially smectite) content bind to, sequester and enhance infectivity of prions both before and after leaving the host; microparticle-bound prions are incorporated into surface soil; susceptible individuals consume contaminated soil and some become infected. (Also see Supplementary Figure S1 .) This mechanism may underlie the apparent importance of indirect transmission in explaining observed patterns of prion infection among captive mule deer 10,11 , and perhaps among sheep 3,4,6,7 . In light of these and others ’ findings, soil clay content and related environmental properties deserve greater attention in assessing local and regional risks of prion disease outbreaks and prospects for their control in natural and production settings.







Friday, February 25, 2011



Soil clay content underlies prion infection odds







Thursday, February 17, 2011


Environmental Sources of Scrapie Prions







PRION 2010



International Prion Congress: From agent to disease September 8–11, 2010 Salzburg, Austria



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PPo4-4:



Survival and Limited Spread of TSE Infectivity after Burial



Karen Fernie, Allister Smith and Robert A. Somerville The Roslin Institute and R(D)SVS; University of Edinburgh; Roslin, Scotland UK



Scrapie and chronic wasting disease probably spread via environmental routes, and there are also concerns about BSE infection remaining in the environment after carcass burial or waste 3disposal. In two demonstration experiments we are determining survival and migration of TSE infectivity when buried for up to five years, as an uncontained point source or within bovine heads. Firstly boluses of TSE infected mouse brain were buried in lysimeters containing either sandy or clay soil. Migration from the boluses is being assessed from soil cores taken over time. With the exception of a very small amount of infectivity found 25 cm from the bolus in sandy soil after 12 months, no other infectivity has been detected up to three years. Secondly, ten bovine heads were spiked with TSE infected mouse brain and buried in the two soil types. Pairs of heads have been exhumed annually and assessed for infectivity within and around them. After one year and after two years, infectivity was detected in most intracranial samples and in some of the soil samples taken from immediately surrounding the heads. The infectivity assays for the samples in and around the heads exhumed at years three and four are underway. These data show that TSE infectivity can survive burial for long periods but migrates slowly. Risk assessments should take into account the likely long survival rate when infected material has been buried.




The authors gratefully acknowledge funding from DEFRA.








Wednesday, September 08, 2010



CWD PRION CONGRESS SEPTEMBER 8-11 2010








2009 CWD SYMPOSIUM UTAH







Detection of Protease-Resistant Prion Protein in Water from a CWD-Endemic Area




Tracy A. Nichols*1,2, Bruce Pulford1, Christy Wyckoff1,2, Crystal Meyerett1, Brady Michel1, Kevin Gertig3, Jean E. Jewell4, Glenn C. Telling5 and M.D. Zabel1 1Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA 2National Wildlife Research Center, Wildlife Services, United States Department of Agriculture, Fort Collins, Colorado, 80521, USA 3Fort Collins Water and Treatment Operations, Fort Collins, Colorado, 80521, USA 4 Department of Veterinary Sciences, Wyoming State Veterinary Laboratory, University of Wyoming, Laramie, Wyoming, 82070, USA 5Department of Microbiology, Immunology, Molecular Genetics and Neurology, Sanders Brown Center on Aging, University of Kentucky, Lexington, Kentucky, 40536, USA * Corresponding author- tracy.a.nichols@aphis.usda.gov



Chronic wasting disease (CWD) is the only known transmissible spongiform encephalopathy affecting free-ranging wildlife. Experimental and epidemiological data indicate that CWD can be transmitted horizontally and via blood and saliva, although the exact mode of natural transmission remains unknown. Substantial evidence suggests that prions can persist in the environment, implicating it as a potential prion reservoir and transmission vehicle. CWD- positive animals can contribute to environmental prion load via biological materials including saliva, blood, urine and feces, shedding several times their body weight in possibly infectious excreta in their lifetime, as well as through decomposing carcasses. Sensitivity limitations of conventional assays hamper evaluation of environmental prion loads in water. Here we show the ability of serial protein misfolding cyclic amplification (sPMCA) to amplify minute amounts of CWD prions in spiked water samples at a 1:1 x106 , and protease-resistant prions in environmental and municipal-processing water samples from a CWD endemic area. Detection of CWD prions correlated with increased total organic carbon in water runoff from melting winter snowpack. These data suggest prolonged persistence and accumulation of prions in the environment that may promote CWD transmission.



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The data presented here demonstrate that sPMCA can detect low levels of PrPCWD in the environment, corroborate previous biological and experimental data suggesting long term persistence of prions in the environment2,3 and imply that PrPCWD accumulation over time may contribute to transmission of CWD in areas where it has been endemic for decades. This work demonstrates the utility of sPMCA to evaluate other environmental water sources for PrPCWD, including smaller bodies of water such as vernal pools and wallows, where large numbers of cervids congregate and into which prions from infected animals may be shed and concentrated to infectious levels.


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Volume 18, Number 3—March 2012



Synopsis



Occurrence, Transmission, and Zoonotic Potential of Chronic Wasting Disease



Samuel E. Saunders1, Shannon L. Bartelt-Hunt, and Jason C. Bartz Author affiliations: University of Nebraska-Lincoln, Omaha, Nebraska, USA (S.E. Saunders, S.L. Bartelt-Hunt); Creighton University, Omaha (J.C. Bartz)



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CWD has been identified in free-ranging cervids in 15 US states and 2 Canadian provinces and in ≈100 captive herds in 15 states and provinces and in South Korea (Figure 1, panel B). Except in South Korea, CWD has not been detected outside North America. In most locations reporting CWD cases in free-ranging animals, the disease continues to emerge in wider geographic areas, and prevalence appears to be increasing in many disease-endemic areas. Areas of Wyoming now have an apparent CWD prevalence of near 50% in mule deer, and prevalence in areas of Colorado and Wisconsin is <15 0="0" 10="10" 5="5" according="according" adult="adult" age="age" agencies.="agencies." and="and" appear="appear" areas="areas" between="between" but="but" cwd="cwd" data="data" deer.="deer." deer="deer" div="div" elk="elk" factors="factors" for="for" from="from" gene="gene" genetic="genetic" highest="highest" however="however" in="in" include="include" influence="influence" influences="influences" is="is" known="known" less="less" lower="lower" male="male" many="many" obtained="obtained" of="of" parts="parts" polymorphisms="polymorphisms" prevalence="prevalence" provincial="provincial" prp="prp" reaches="reaches" remain="remain" remains="remains" reports="reports" risk="risk" scrapie.="scrapie." sex="sex" show="show" state="state" strong="strong" susceptibility="susceptibility" than="than" the="the" to="to" understood="understood" wildlife="wildlife" wyoming.="wyoming.">


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Long-term effects of CWD on cervid populations and ecosystems remain unclear as the disease continues to spread and prevalence increases. In captive herds, CWD might persist at high levels and lead to complete herd destruction in the absence of human culling. Epidemiologic modeling suggests the disease could have severe effects on free-ranging deer populations, depending on hunting policies and environmental persistence (8,9). CWD has been associated with large decreases in free-ranging mule deer populations in an area of high CWD prevalence (Boulder, Colorado, USA) (5). In addition, CWD-infected deer are selectively preyed upon by mountain lions (5), and may also be more vulnerable to vehicle collisions (10).



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Conclusions



Much remains unknown about prion diseases and CWD in particular, especially about CWD strains (which may have varied zoonotic potentials) and the long-term effects of CWD on cervid ecosystems. CWD prevalence and geographic range appear likely to continue to increase. Moreover, the disease is inevitably fatal, and no effective therapeutic measures are presently available. As such, it would seem wise to continue research and surveillance of CWD to elucidate the details of its transmission, pathogenesis, and continued emergence in cervid populations in hopes that strategies for mitigating its negative effects on humans and cervid ecosystems can be identified.









50 GAME FARMS IN USA INFECTED WITH CHRONIC WASTING DISEASE CWD



2012




Tuesday, December 20, 2011



CHRONIC WASTING DISEASE CWD WISCONSIN Almond Deer (Buckhorn Flats) Farm Update DECEMBER 2011



The CWD infection rate was nearly 80%, the highest ever in a North American captive herd.



Despite the five year premise plan and site decontamination, The WI DNR has concerns over the bioavailability of infectious prions at this site to wild white-tail deer should these fences be removed. Current research indicates that prions can persist in soil for a minimum of 3 years.



However, Georgsson et al. (2006) concluded that prions that produced scrapie disease in sheep remained bioavailable and infectious for at least 16 years in natural Icelandic environments, most likely in contaminated soil.



Additionally, the authors reported that from 1978-2004, scrapie recurred on 33 sheep farms, of which 9 recurrences occurred 14-21 years after initial culling and subsequent restocking efforts; these findings further emphasize the effect of environmental contamination on sustaining TSE infectivity and that long-term persistence of prions in soils may be substantially greater than previously thought










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Thursday, February 09, 2012



50 GAME FARMS IN USA INFECTED WITH CHRONIC WASTING DISEASE








Friday, February 03, 2012



Wisconsin Farm-Raised Deer Farms and CWD there from 2012 report Singeltary et al








Saturday, February 04, 2012



Wisconsin 16 age limit on testing dead deer Game Farm CWD Testing Protocol Needs To Be Revised



 
 
 
 
 
 
 
 
Monday, June 11, 2012



OHIO Captive deer escapees and non-reporting







Friday, July 20, 2012



CWD found for first time in Iowa at hunting preserve








Friday, August 31, 2012



COMMITTEE ON CAPTIVE WILDLIFE AND ALTERNATIVE LIVESTOCK and CWD 2009-2012 a review








LANCET INFECTIOUS DISEASE JOURNAL




Volume 3, Number 8 01 August 2003



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Newsdesk



Tracking spongiform encephalopathies in North America



Xavier Bosch



My name is Terry S Singeltary Sr, and I live in Bacliff, Texas. I lost my mom to hvCJD (Heidenhain variant CJD) and have been searching for answers ever since. What I have found is that we have not been told the truth. CWD in deer and elk is a small portion of a much bigger problem.



49-year-old Singeltary is one of a number of people who have remained largely unsatisfied after being told that a close relative died from a rapidly progressive dementia compatible with spontaneous Creutzfeldt-Jakob disease (CJD). So he decided to gather hundreds of documents on transmissible spongiform encephalopathies (TSE) and realised that if Britons could get variant CJD from bovine spongiform encephalopathy (BSE), Americans might get a similar disorder from chronic wasting disease (CWD)the relative of mad cow disease seen among deer and elk in the USA. Although his feverish search did not lead him to the smoking gun linking CWD to a similar disease in North American people, it did uncover a largely disappointing situation.



Singeltary was greatly demoralised at the few attempts to monitor the occurrence of CJD and CWD in the USA. Only a few states have made CJD reportable. Human and animal TSEs should be reportable nationwide and internationally, he complained in a letter to the Journal of the American Medical Association (JAMA 2003; 285: 733). I hope that the CDC does not continue to expect us to still believe that the 85% plus of all CJD cases which are sporadic are all spontaneous, without route or source.



Until recently, CWD was thought to be confined to the wild in a small region in Colorado. But since early 2002, it has been reported in other areas, including Wisconsin, South Dakota, and the Canadian province of Saskatchewan. Indeed, the occurrence of CWD in states that were not endemic previously increased concern about a widespread outbreak and possible transmission to people and cattle.



To date, experimental studies have proven that the CWD agent can be transmitted to cattle by intracerebral inoculation and that it can cross the mucous membranes of the digestive tract to initiate infection in lymphoid tissue before invasion of the central nervous system. Yet the plausibility of CWD spreading to people has remained elusive.




Getting data on TSEs in the USA from the government is like pulling teeth, Singeltary argues. You get it when they want you to have it, and only what they want you to have.






SNIP...FULL TEXT ;
















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