Detection and Decontamination of Chronic Wasting Disease Prions during Venison Processing

Volume 31, Number 4—April 2025

Research

Detection and Decontamination of Chronic Wasting Disease Prions during Venison Processing

Marissa Milstein, Sarah C. Gresch, Marc D. Schwabenlander, Manci Li, Jason C. Bartz, Damani N. Bryant, Peter R. Christenson, Laramie L. Lindsey, Nicole Lurndahl, Sang-Hyun Oh, Gage R. Rowden, Rachel L. Shoemaker, Tiffany M. Wolf, Peter A. Larsen, and Stuart S. Lichtenberg

Author affiliation: University of Minnesota, St. Paul, Minnesota, USA (M. Milstein, S.C. Gresch, M.D. Schwabenlander, M. Li, D.N. Bryant, L.L. Lindsey, N. Lurndahl, G.R. Rowden, R.L. Shoemaker, T.M. Wolf, P.A. Larsen, S.S. Lichtenberg); University of Minnesota, Minneapolis, Minnesota, USA (M. Li, P.R. Christenson, S.-H. Oh); Creighton University, Omaha, Nebraska, USA (J.C. Bartz)

Abstract

Prion diseases, including chronic wasting disease (CWD), are caused by prions, which are misfolded aggregates of normal cellular prion protein. Prions possess many characteristics that distinguish them from conventional pathogens, in particular, an extraordinary recalcitrance to inactivation and a propensity to avidly bind to surfaces. In middle to late stages of CWD, prions begin accumulating in cervid muscle tissues. Those features collectively create scenarios in which occupational hazards arise for workers processing venison and pose risks to consumers through direct prion exposure through ingestion and cross-contamination of food products. In this study, we demonstrate that steel and plastic surfaces used in venison processing can be directly contaminated with CWD prions and that cross-contamination of CWD-negative venison can occur from equipment that had previously been used with CWD-positive venison. We also show that several decontaminant solutions (commercial bleach and potassium peroxymonosulfate) are efficacious for prion inactivation on those same surfaces.

Chronic wasting disease (CWD) is a fatal prion disease affecting cervids caused by a self-templating, misfolded, and infectious form of the prion protein (PrPSc) (1). Since its discovery in the United States in the 1960s (2,3), CWD has been detected in free-ranging and captive cervid populations in 34 US states and 5 provinces in Canada, as well as Nordic countries and South Korea (4). CWD continues to spread in white-tailed deer (Odocoileus virginanus), mule deer (Odocoileus hemionus), moose (Alces alces), and elk (Cervus canadensis) populations across the United States and Canada. In the United States alone, >6 million white-tailed deer are harvested annually, many of which are consumed and represent a major source of protein for communities across the country (5). A 2017 estimate suggests that as many as 15,000 CWD-positive white-tailed deer are consumed in the United States annually (6). This number, however, is likely underestimated given the limitations of existing CWD surveillance programs and venison food donation efforts within CWD-endemic regions.

CWD prions accumulate in tissues during disease pathogenesis and can be detected in the muscle tissue of white-tailed deer (7); thus, consuming meat from CWD-positive cervids might expose humans to CWD prions. Scientific and public health communities are concerned about the potential transmission of CWD to humans, particularly through ingestion. The Centers for Disease Control and Prevention acknowledges this risk and recommends reducing risk by testing cervids before consuming meat, processing each animal individually to avoid cross-contamination, and not consuming CWD-positive meat (8). No cases of CWD in humans have been confirmed (9); however, as new CWD strains are identified (10) and more organisms are exposed to PrPSc (11), concerns are growing that the species barrier might be crossed.

When PrPSc prions are introduced into the environment through natural shedding (12,13) or carcass decomposition (14), they can adsorb to surfaces where they can be detected long after deposition (15–17). Surface swabbing is an effective CWD detection method for both laboratory settings (18) and natural, environmentally exposed surfaces (19). Yuan et al. (18) highlighted the importance of surface structure for prion recovery, noting that porous surfaces, such as wood, were ineffective for swab-based detection, as opposed to nonporous surfaces, such as glass and stainless steel. Those attributes (e.g., environmental stability, swab detection, surface adsorption) also factor into surface decontamination, because chemical decontaminants must physically contact PrPSc aggregates for disintegration or other forms of inactivation (20–22).

Venison processing for human consumption, both in-home and commercial, is an area of potential PrPSc cross-contamination and direct human exposure. Surfaces, tools, and equipment used for venison processing can be contaminated with PrPSc from CWD-positive venison (23,24). Cleaning strategies used during venison processing can vary widely and might not be effective in removing or destroying PrPSc, particularly in unregulated facilities or scenarios (e.g., home butchery, seasonal pop-up processors). Thus, understanding the potential of PrPSc to more widely enter the food supply through surface contamination and the efficacy of chemical decontamination are clearly needed.

In this study, we examined prion contamination of commonly used meat-processing equipment, including knives, cutting boards, and household-style meat grinders, and the efficacy of decontaminants commonly used in home or commercial processing. In addition, we investigated the cross-contamination of CWD-negative meat after contact with CWD-contaminated processing equipment.

Methods

Experimental design of knife and cutting board testing in study of detection and decontamination of chronic wasting disease prions during venison processing. 

A) For negative control, surfaces were swabbed before use. 

B) Step 1: chronic wasting disease–negative or chronic wasting disease–positive muscle was cut and surfaces were swabbed. 

Step 2: surfaces were cleaned. 

Step 3: surfaces were swabbed again and swabs were tested by real-time quaking-induced conversion.

Figure 1. Experimental design of knife and cutting board testing in study of detection and decontamination of chronic wasting disease prions during venison processing. 

A) For negative control, surfaces were swabbed before...

https://wwwnc.cdc.gov/eid/article/31/4/24-1176-t1

https://wwwnc.cdc.gov/eid/article/31/4/24-1176-f1

https://wwwnc.cdc.gov/eid/article/31/4/24-1176-app1.pdf

This work consisted of 5 distinct phases. The 5 phases were pilot study, study controls, knife and cutting board, meat cross-contamination, and meat grinder (Table 1, Figure 1; Appendix).

Pilot Study

We conducted a pilot study to determine whether we could recover, detect, and decontaminate prions on common meat-processing surfaces with known CWD-positive samples with different prion loads from white-tailed deer: cerebellum (high prion load) and muscle (low prion load). We conducted control experiments to determine whether the decontaminants could induce or suppress seeding activity during real-time quaking-induced conversion (RT-QuIC) (Appendix).

https://wwwnc.cdc.gov/eid/article/31/4/24-1176-app1.pdf

Study Controls

We performed experiments to test whether 5 chosen decontaminants would interfere with the RT-QuIC assay and whether those decontaminants would inhibit prion seeding activity on both stainless steel and cast iron surfaces. Chosen decontaminants were dish soap (Dawn brand; Procter and Gamble, https://dawn-dish.comExternal Link), Briotech (0.02% hypochlorous acid solution; https://briotechusa.shop), Virkon-S (2% potassium peroxymonosulfate solution; Lanxess AG, https://lanxess.comExternal Link), and 10% vol/vol (7,500 ppm) and 40% vol/vol (30,000 ppm) commercial bleach solution (7.5% sodium hypochlorite; The Clorox Company, https://www.clorox.comExternal Link). In addition, we conducted experiments to assess the recovery and detection of CWD prions from stainless steel and cast iron surfaces.

Knife and Cutting Board

We sought to determine whether prion seeding activity could be detected before and after decontamination on stainless steel knives and polyethylene cutting boards, 2 standard pieces of equipment used in home and commercial meat processing. We designated a knife and cutting board for each of the 5 chosen decontaminants. We collected negative controls by swabbing the knife and cutting board before contact with any muscle samples.

To test the efficacy of dish soap for prion decontamination, we made 2 cuts through CWD-negative muscle on the cutting board. We immediately swabbed the knife and cutting board after the first cut and left them to dry at room temperature for 30 minutes after the second cut. We filled a tray with dish soap and water according to manufacturer recommendations, scrubbed the knife and cutting board with a sponge (3M, https://www.scotch-brite.comExternal Link), and then rinsed with low-pressure municipal cold water. We then swabbed the surfaces again. We repeated the experiment using CWD-positive muscle and new materials. We stored all swabs at −80°C until use.

To test the efficacy of Briotech, 2% Virkon-S, 10% vol/vol (7,500 ppm) bleach solution and 40% vol/vol (30,000 ppm) bleach solution, we followed the same procedure as described but did not perform the sponge step. Instead, after drying the polyethylene cutting board and knife for 30 minutes, we soaked the items in the decontaminant solution for 5 minutes. Then, we rinsed the knife and cutting board with water and swabbed them again (Figure 1).

Meat Cross-Contamination

We passed CWD-positive muscle samples through a meat grinder several times to produce a homogenized pool of CWD-positive muscle, which we then subsampled. We used that pool of CWD-positive material for the meat grinder experiments. We disassembled the grinder, removed the gross material, and swabbed the parts. We then reassembled the grinder, passed CWD-negative muscle through the grinder, and subsampled.

We performed an endpoint titration on the homogenized CWD-positive muscle pool to determine prion load relative to our positive lymph node control. We tested the muscle pool at dilutions from 10–1 to 10–9. We observed statistically significant seeding activity at 10–1 and 10–2 dilution and nonsignificant seeding activity at 10–3 dilution. We observed no seeding activity in the pool at dilutions 10–4 through 10–9. Comparatively, our positive lymph node control has historically shown seeding activity through a dilution of 10–6.

Meat Grinder

On the basis of preliminary results demonstrating the efficacy of the decontaminants used in the knife and polyethylene cutting board study, we chose the following 4 decontaminants to be used in experiments using meat grinders: dish soap, Virkon-S, 10% (7,500 ppm) bleach solution, and 40% (30,000 ppm) bleach solution. We used stainless steel (CHOLISM) and cast iron (CucinaPro, https://cucinapro.comExternalLink) meat grinders with each decontaminant. We disassembled each grinder and swabbed the worm spindle, plate cutter holes, and screw ring threads before contact with CWD-positive muscle. The experiments were designed to mimic home or small-scale commercial meat processing.

Cleaning of Grinder after CWD-Positive Homogenate

Experimental setup of the meat grinder testing in study of detection and decontamination of chronic wasting disease prions during venison processing. A) For negative control, surfaces were swabbed before use. B) Step 1: chronic wasting disease–negative or–positive muscle was passed through the grinder and surfaces swabbed. Step 2: grinders were disassembled and surfaces were cleaned/decontaminated. Step 3: grinder surfaces were swabbed again, and swabs were tested by real-time quaking-induced conversion.

Figure 2. Experimental setup of the meat grinder testing in study of detection and decontamination of chronic wasting disease prions during venison processing. A) For negative control, surfaces were swabbed before use....

After each grinder was assembled, we passed through CWD-positive homogenate and then allowed the grinder to air dry for 30 minutes. We then disassembled the grinders, removed gross material, and swabbed the grinder parts again. We then placed the parts in a tray with diluted dish soap, used a sponge to wash them, and rinsed them with water. We sampled the sponge and swabbed the grinder parts. For the remaining 3 decontaminants (Virkon-S, 10% [7,500 ppm] bleach, and 40% [30,000 ppm] bleach), we left the grinder parts to soak for 5 minutes (instead of washing with a sponge), rinsed them with low-pressure cold water, and swabbed in the same locations (Figure 2). Swab extraction and processing followed the procedure of Yuan et al. (19) with some modifications (Appendix).

Analysis

Fluorescence readout from the RT-QuIC assay captures the kinetics of amyloid formation in vitro (25). Three metrics can be used to describe data generated by RT-QuIC: rate of amyloid formation (RAF) for nucleation, maximum slope (MS) for elongation (26,27), and maxpoint ratio (MPR) for equilibrium (28). We calculated RAF per well as the reciprocal of the time required for fluorescence to reach a threshold of twice the background fluorescence. If a well did not reach the threshold, we assigned a value of zero. We calculated background fluorescence as the average fluorescent reading per well at cycles 2 and 3 to control for any variability in relative fluorescence units (RFU) among wells and to compensate for the greater ThT fluorescence typically found in the first cycle because of viscosity effects. We calculated the slope as the difference between the RFU at the current time position plus 6 cycles (3.75 hours) divided by the time. MPR was calculated as the maximum RFU divided by the background RFU. Using all 3 metrics, genuine amyloid formation of PrPSc induced by CWD prions in RT-QuIC reactions should generate responses that are significantly different from reactions with no seeding activities.

A member of the research team (M.L.), blinded to sample identity and treatment, analyzed the data generated from the pilot study. Using a 1-tailed Wilcoxon Rank Sum test, with an ɑ-level of 0.05, we compared RAF, MPR, and MS against the negative plate controls. M.L. and unblinded team members (M.M., S.G.) reviewed the results from the pilot data and set the following swab inclusion criteria for the remainder of the study: all 3 metrics (RAF, MPR, MS) must be statistically significantly higher than the negative plate controls to be considered positive, and regardless of dilution level, if a sample meets the first criterion, the sample will be considered positive. We performed all statistical analysis for swab samples in R version 4.3.2 (The R Project for Statistical Computing, https://www.r-project.orgExternal Link).

For all muscle sample analyses, we used an uncorrected Fisher LSD test with a single pooled variance (α level of 0.05). We compared RAF, MPR, and MS against the negative plate controls. All 3 metrics (RAF, MPR, MS) must be statistically significantly higher than the negative plate controls to be considered positive. If a sample met those criteria, it was considered positive regardless of the dilution level. We performed all statistical analyses of muscle samples using GraphPad Prism version 10.0.2 (https://www.graphpad.comExternal Link).

Results

Pilot Study

Multiple swabs demonstrated significant seeding activity in the RT-QuIC assay: knife blade swabs and polyethylene cutting board swabs from cutting CWD-positive muscle and knife blade swabs and cutting board swabs from cutting CWD-positive brain. After soaking the knife and cutting board with 3 dilutions of household bleach (10%, 40%, 100%), all posttreatment swabs (n = 30; 2 or 3 knife swabs and 3 cutting board swabs per dilution, per sample type) were negative by RT-QuIC.

Study Controls

All negative controls (both knife and polyethylene cutting board) were negative by RT-QuIC for each of the 5 decontaminants after treatment (Tables 2,3). For each of the 5 decontaminants (dish soap, Briotech, Virkon-S, 10% [7,500 ppm] bleach, 40% [30,000 ppm] bleach), all samples had no significant seeding activity when CWD-negative muscle tissue was used during knife and cutting board experiments (Tables 2,3).

Knife and Cutting Board

Dish Soap

Results from knife and cutting board experiments after CWD-positive muscle cutting and after cleaning with 5 decontaminants in study of detection and decontamination of CWD prions during venison processing. Dish soap, Dawn brand (Procter & Gamble, https://dawn-dish.com); Briotech, 0.02% hypochlorous acid (https://briotechusa.shop); Virkon-S, 2% potassium peroxymonosulfate (Lanxess AG, https://lanxess.com); bleach, 10% vol/vol (7,500 ppm) and 40% vol/vol (30,000 ppm) commercial bleach solutions (7.5% sodium hypochlorite; The Clorox Company, https://www.clorox.com). CB, cutting board; CWD, chronic wasting disease.

Figure 3. Results from knife and cutting board experiments after CWD-positive muscle cutting and after cleaning with 5 decontaminants in study of detection and decontamination of CWD prions during venison processing. Dish...

We detected significant seeding activity on the stainless steel knife and polyethylene cutting board after cutting CWD-positive muscle (Figure 3). We also detected significant seeding activity on the cutting board after cleaning with dish soap but not on the knife or sponge after cleaning with dish soap (Figure 3; sponge data not shown).

Briotech, 2% Virkon-S, 10% Bleach, 40% Bleach

After cleaning the CWD-contaminated polyethylene cutting board with Briotech, we detected significant seeding activity in 1 sample (Figure 3). We detected no significant seeding activity on CWD-contaminated knives after cleaning with any of the decontaminants (Figure 3) or on CWD-contaminated cutting boards after decontamination with Virkon-S, 10% (7,500 ppm) bleach, or 40% (30,000 ppm) bleach (Figure 3).

Meat Cross-Contamination

Results of real-time quaking-induced conversion in study of detection and decontamination of chronic wasting disease prions during venison processing. Results are shown for the CWD-positive muscle homogenate (positive pool), CWD-negative muscle homogenate before passing through a contaminated grinder (negative pool), and the CWD-negative muscle homogenate after passing through a contaminated meat grinder (contaminated pool). A) Rate of amyloid formation; B) maxpoint ratio (ratio of the maximum value to the initial reading) (28); C) maximum slope. NS, not statistically significant. 

Figure 4. Results of real-time quaking-induced conversion in study of detection and decontamination of chronic wasting disease prions during venison processing. Results are shown for the CWD-positive muscle homogenate (positive pool), CWD-negative...

We detected an 88% significant seeding rate in the CWD-positive muscle homogenate pool (7/8 biological replicates) (Figure 4). When we passed CWD-positive muscle homogenate through a grinder, we detected significant seeding activity on the plate cutter (2/3 biological replicates, 66.7%) and screw ring thread (1/3 biological replicates, 33.3%). We detected no seeding activity on the worm spindle of the grinder. When we passed CWD-negative muscle through the grinder after the CWD-positive muscle homogenate, we found a 63% seeding activity rate (5/8 biological replicates) (Figure 4).

Meat Grinder

Results of real-time quaking-induced conversion conducted on meat grinder swab samples in study of detection and decontamination of chronic wasting disease prions during venison processing. A) Rate of amyloid formation; B) maxpoint ratio (ratio of the maximum value to the initial reading); C) maximum slope. Results are shown for negative controls (before meat grinder was used; top row) and after homogenate (after chronic wasting disease–positive muscle was passed through; bottom row). Each dot is an average of a single biologic replicate (consisting of 8 technical replicates). Each set of paired samples (e.g., cast iron worm spindles) resulted in a statistically significant difference post homogenate compared with the negative samples (p<0.05; data not shown). Dashed lines indicate the cutoff for significance using the maxpoint ratio (28). PC, plate cutter; SRT, screw ring threads; WS, worm spindle.

Figure 5. Results of real-time quaking-induced conversion conducted on meat grinder swab samples in study of detection and decontamination of chronic wasting disease prions during venison processing. A) Rate of amyloid formation;...

Results from stainless steel and cast iron meat grinder experiments in study of detection and decontamination of chronic wasting disease prions during venison processing. Samples were taken after chronic wasting disease–positive muscle homogenate passed through each grinder and after cleaning with each of 4 decontaminants: dish soap, Dawn brand (Procter & Gamble, https://dawn-dish.com); Virkon-S, 2% potassium peroxymonosulfate (Lanxess AG, https://lanxess.com); and bleach, 10% vol/vol (7,500 ppm) and 40% vol/vol (30,000 ppm) commercial bleach solutions (7.5% sodium hypochlorite; The Clorox Company, https://www.clorox.com).). PC, plate cutter; SRT, screw ring threads; WS, worm spindle.

Figure 6. Results from stainless steel and cast iron meat grinder experiments in study of detection and decontamination of chronic wasting disease prions during venison processing. Samples were taken after chronic wasting...

Results of real-time quaking-induced conversion assays conducted on meat grinder swab samples in study of detection and decontamination of chronic wasting disease prions during venison processing. Swab samples were taken after grinder parts were soaked in 1 of 4 decontaminants (after chronic wasting disease–positive muscle was passed through each): dish soap (top row), Dawn brand (Procter & Gamble, https://dawn-dish.com); Virkon-S (second row), 2% potassium peroxymonosulfate (Lanxess AG, https://lanxess.com); and bleach, 10% vol/vol (7,500 ppm) (third row) and 40% vol/vol (30,000 ppm) (bottom row) commercial bleach solutions (7.5% sodium hypochlorite; The Clorox Company, https://www.clorox.com). A) Rate of amyloid formation; B) maxpoint ratio (ratio of the maximum value to the initial reading); C) maximum slope. Each dot is an average of a single biological replicate (consisting of 8 technical replicates). PC, plate cutter; SRT, screw ring threads; WS, worm spindle.

Figure 7. Results of real-time quaking-induced conversion assays conducted on meat grinder swab samples in study of detection and decontamination of chronic wasting disease prions during venison processing. Swab samples were taken...

All negative controls of the stainless steel and cast iron grinder parts were negative by RT-QuIC (Figure 5). Significant seeding activity was demonstrated from swabs from all stainless steel and cast iron grinder parts after passage of CWD-positive muscle homogenate (Figures 5, 6). Significant seeding activity was demonstrated from multiple swabs after decontamination of the stainless steel and cast iron grinder parts with dish soap and Virkon-S, whereas no significant seeding activity was demonstrated from swabs after decontamination with 10% (7,500 ppm) and 40% (30,000 ppm) bleach (Figures 6, 7).

Discussion

In this study, we examined the contamination of commonly used meat-processing equipment with CWD prions from CWD-positive muscle and the efficacy of decontaminants commonly used in homes or previously shown to have variable levels of efficacy for prion decontamination (20–22). In addition, we investigated the cross-contamination of meat in CWD prion–contaminated meat-processing equipment. Using a conservative approach in determining whether samples were positive (by requiring positivity using all 3 RT-QuIC metrics), we found that CWD prion seeding activity can be detected on common meat-processing surfaces after coming into contact with CWD-positive white-tailed deer muscle; CWD prion seeding activity can be transferred to CWD-negative meat after passing through a contaminated meat grinder; Virkon S, 10% bleach, and 40% bleach were effective for CWD prion decontamination on surfaces, as shown by removal of seeding activity; and surface composition might play a role in CWD prion detection and decontamination on meat-processing equipment.

On the basis of our results, CWD prion seeding activity is clearly detectable on common meat-processing equipment, such as knives, polyethylene cutting boards, and multiple parts of meat grinders. We would note that the presence of seeding activity does not directly imply infectivity, and the relationship between seeding activity and infectivity can be complicated. However, given that seeding activity is correlated with infectivity (29), and we are using materials that have verification of PrPSc presence by other means, the presence or absence of seeding activity in our study can be reasonably be concluded to correlate with the presence or absence of infectivity. Further investigation is warranted into the contamination regimes and decontaminants described using animal bioassays.

Of note, seeding activity was demonstrated not only in tissues containing high levels of prions (i.e., brain from a CWD-positive animal) but also in muscles with progressively lower levels of prions from a clinical deer and 2 hunter-harvested deer. We also detected seeding activity in the CWD-negative muscle homogenate after it passed through the contaminated meat grinder. Those findings exemplify real-life scenarios with implications for the food supply in which surfaces and tools are reused between deer and meat is mixed from multiple deer, potentially with nonclinical, untested deer.

Except for dish soap, all of the decontamination agents used in this study have been shown to inactivate prions (20–22); the active ingredient in Briotech is hypochlorous acid (22) and the active ingredient in Virkon-S is peroxymonosulfate (20). We found that 10% bleach and 40% bleach were highly effective at decontaminating the meat-processing surfaces tested in this study; Virkon-S was slightly less effective. Briotech was less effective and inconsistent in decontamination. Although the overall findings are promising, further investigation is warranted, especially given the lower relative prion load in our CWD-positive muscle pool used in the meat grinder studies. Decontamination efficacy on grinder parts could be further investigated by using tissues with prion loads higher than that typical in muscle. Reduced concentrations of bleach and contact times could still result in effective decontamination, but we did not test the lowest effective duration or concentration of decontaminants, nor did we test how repeated disinfection with the solutions affects surface integrity and ongoing disinfection efficacy. This factor is noteworthy because the chemicals can compromise the integrity of surfaces such as stainless steel, leading to unknown consequences of prion adsorption and decontamination. In addition, although we observed a few negative control swabs of grinder parts that were positive on initial test but negative upon retest, we hypothesize that those interferences arose from grease or metallic debris from the machining of parts. From a cleaning protocol perspective, the scrubbing of tools, parts, and surfaces is a key step, because tissue debris tends to remain on some surfaces after a decontamination soak. As demonstrated by others (21), decontaminants are ineffective at penetrating tissue, so removal of the tissue remnants will lead to more effective decontamination and reduce cross-contamination. This factor is one plausible explanation for the reduced efficacy (i.e., retained seeding activity) of Virkon-S in one of the treatments. Containing and disposing of the predecontamination cleaning wash is also a consideration for environmental prion contamination.

Of note, we saw differences in the detection of prion seeding activity between the knife and cutting board; after decontamination with dish soap, we were able to detect prion seeding on the surface of the cutting board but not on the surface of the knife. Curiously, we did not detect prion seeding activity in any of the sponge samples. We cannot discount the possibility that prions were removed from the knife surface by dish soap and simply remained in the decontaminant solution, speaking back to our point regarding containment and disposal of the cleaning solution itself. The principal components of dish soap are surfactants (30), which can remove adsorbed prions from surfaces, resulting in a lack of detection on the steel surface while also diluting prions to the point that they are undetectable by RT-QuIC. Those factors must all be considered when planning and implementing cleaning and decontamination of environmental prions.

In conclusion, our results show that processing of CWD-positive cervids for consumption has the potential to contaminate meat-processing equipment and cross-contaminate downstream meat products. Further, our data and previous studies (20,21) indicate that Virkon-S and bleach solutions with appropriate contact times (as little as 5 minutes) can effectively decontaminate nonporous surfaces of CWD prions. After the bovine spongiform encephalopathy outbreak in Europe in the early 1990s, processing practices became mandatory to remove and avoid specified risk materials (e.g., spinal cord, brain) and incorporate downstream molecular testing procedures to identify contamination in meat products (31). Our findings indicate similar practices may be necessary to reduce CWD exposure in humans through meat processing. However, given the unique features of CWD prions, contamination of equipment and surfaces is more challenging to control. This concern further highlights the importance of testing cervids before processing, in addition to the need for compliance with effective meat processing, environmental screening, waste management, and cleaning and decontamination protocols.

This article was published as a preprint at https://www.biorxiv.org/content/10.1101/2024.07.23.604851v1 External Link.

Dr. Milstein is a wildlife veterinary researcher at the University of Minnesota in St. Paul. Her primary research interests involve studying zoonotic disease transmission from the hunting, butchery, and consumption of wildlife.

https://wwwnc.cdc.gov/eid/article/31/4/24-1176_article

Volume 31, Number 4—April 2025

Research

Detection and Decontamination of Chronic Wasting Disease Prions during Venison Processing

https://wwwnc.cdc.gov/eid/article/31/4/24-1176_article

CDC CWD TSE Prion Update 2025

KEY POINTS

Chronic wasting disease affects deer, elk and similar animals in the United States and a few other countries.

The disease hasn't been shown to infect people.

However, it might be a risk to people if they have contact with or eat meat from animals infected with CWD.

https://www.cdc.gov/chronic-wasting/about/index.html

Prions in Muscles of Cervids with Chronic Wasting Disease, Norway

Volume 31, Number 2—February 2025

Research

Prions in Muscles of Cervids with Chronic Wasting Disease, Norway

Snip…

In summary, the results of our study indicate that prions are widely distributed in peripheral and edible tissues of cervids in Norway, including muscles. This finding highlights the risk of human exposure to small amounts of prions through handling and consuming infected cervids. Nevertheless, we note that this study did not investigate the zoonotic potential of the Norway CWD prions. In North America, humans have historically consumed meat from CWD-infected animals, which has been documented to harbor prions (35,44–47). Despite the potential exposure to prions, no epidemiologic evidence indicates a correlation between the occurrence of CWD cases in animals and the prevalence of human prion diseases (48). A recent bioassay study reported no transmissions from 3 Nordic isolates into transgenic mice expressing human PrP (49). Therefore, our findings should be interpreted with caution in terms of human health implications, and further research is required to determine the zoonotic potential of these CWD strains.

The presence of prions in peripheral tissues indicates that CWD may have a systemic nature in all Norwegian cervid species, challenging the view that prions are exclusively localized in the CNS in sporadic CWD of moose and red deer. Our findings expand the notion of just how widely distributed prions can be in cervids affected with CWD and call into question the capability of emerging CWD strains in terms of infectivity to other species, including humans.

Appendix

https://wwwnc.cdc.gov/eid/article/31/2/24-0903-app1.pdf

https://wwwnc.cdc.gov/eid/article/31/2/24-0903_article

Volume 31, Number 2—February 2025

Dispatch

Detection of Chronic Wasting Disease Prions in Raw, Processed, and Cooked Elk Meat, Texas, USA

Rebeca Benavente, Fraser Brydon, Francisca Bravo-Risi, Paulina Soto, J. Hunter Reed, Mitch Lockwood, Glenn Telling, Marcelo A. Barria, and Rodrigo MoralesComments to Author

Snip…

CWD prions have been detected in the muscle of both farmed and wild deer (10), and at concentrations relevant to sustain disease transmission (11). CWD prions have also been identified across several cervid species and in multiple tissues, including lymph nodes, spleen, tongue, intestines, adrenal gland, eyes, reproductive tissues, ears, lungs, and liver, among others (12–14). Those findings raise concerns about the safety of ingesting processed meats that contain tissues other than skeletal muscle (15) (Appendix). https://wwwnc.cdc.gov/eid/article/31/2/24-0906-app1.pdf .

In addition, those findings highlight the need for continued vigilance and research on the transmission risks of prion diseases and for development of new preventative and detection measures to ensure the safety of the human food supply.

Snip…

Overall, our study results confirm previous reports describing the presence of CWD prions in elk muscles (13). The data also demonstrated CWD prion persistence in food products even after processing through different procedures, including the addition of salts, spices, and other edible elements. Of note, our data show that exposure to high temperatures used to cook the meat increased the availability of prions for in vitro amplification. Considering the potential implications in food safety and public health, we believe that the findings described in this study warrant further research. Our results suggest that although the elk meat used in this study resisted different manipulations involved in subsequent consumption by humans, their zoonotic potential was limited. Nevertheless, even though no cases of CWD transmission to human have been reported, the potential for human infection is still unclear and continued monitoring for zoonotic potential is warranted.

https://wwwnc.cdc.gov/eid/article/31/2/24-0906_article

Volume 31, Number 1—January 2025

Dispatch

Detection of Prions in Wild Pigs (Sus scrofa) from Areas with Reported Chronic Wasting Disease Cases, United States

Abstract

Using a prion amplification assay, we identified prions in tissues from wild pigs (Sus scrofa) living in areas of the United States with variable chronic wasting disease (CWD) epidemiology. Our findings indicate that scavenging swine could play a role in disseminating CWD and could therefore influence its epidemiology, geographic distribution, and interspecies spread.

Snip…

Conclusions In summary, results from this study showed that wild pigs are exposed to cervid prions, although the pigs seem to display some resistance to infection via natural exposure. Future studies should address the susceptibility of this invasive animal species to the multiple prion strains circulating in the environment. Nonetheless, identification of CWD prions in wild pig tissues indicated the potential for pigs to move prions across the landscape, which may, in turn, influence the epidemiology and geographic spread of CWD.

https://wwwnc.cdc.gov/eid/article/%2031/1/24-0401_article

***> Price of TSE Prion Poker goes up substantially, all you cattle ranchers and such, better pay close attention here...terry <***

Transmission of the chronic wasting disease agent from elk to cattle after oronasal exposure

Justin Greenlee, Jifeng Bian, Zoe Lambert, Alexis Frese, and Eric Cassmann Virus and Prion Research Unit, National Animal Disease Center, USDA-ARS, Ames, IA, USA 

Aims: The purpose of this study was to determine the susceptibility of cattle to chronic wasting disease agent from elk. 

Materials and Methods: Initial studies were conducted in bovinized mice using inoculum derived from elk with various genotypes at codon 132 (MM, LM, LL). Based upon attack rates, inoculum (10% w/v brain homogenate) from an LM132 elk was selected for transmission studies in cattle. At approximately 2 weeks of age, one wild type steer (EE211) and one steer with the E211K polymorphism (EK211) were fed 1 mL of brain homogenate in a quart of milk replacer while another 1 mL was instilled intranasally. The cattle were examined daily for clinical signs for the duration of the experiment. One steer is still under observation at 71 months post-inoculation (mpi). 

Results: Inoculum derived from MM132 elk resulted in similar attack rates and incubation periods in mice expressing wild type or K211 bovine PRNP, 35% at 531 days post inoculation (dpi) and 27% at 448 dpi, respectively. Inoculum from LM132 elk had a slightly higher attack rates in mice: 45% (693 dpi) in wild type cattle PRNP and 33% (468) in K211 mice. Inoculum from LL132 elk resulted in the highest attack rate in wild type bovinized mice (53% at 625 dpi), but no K211 mice were affected at >700 days. At approximately 70 mpi, the EK211 genotype steer developed clinical signs suggestive of prion disease, depression, low head carriage, hypersalivation, and ataxia, and was necropsied. Enzyme immunoassay (IDEXX) was positive in brainstem (OD=4.00, but non-detect in retropharyngeal lymph nodes and palatine tonsil. Immunoreactivity was largely limited to the brainstem, midbrain, and cervical spinal cord with a pattern that was primarily glia-associated. 

Conclusions: Cattle with the E211K polymorphism are susceptible to the CWD agent after oronasal exposure of 0.2 g of infectious material. 

Funded by: This research was funded in its entirety by congressionally appropriated funds to the United States Department of Agriculture, Agricultural Research Service. The funders of the work did not influence study design, data collection and analysis, decision to publish, or preparation of the manuscript.

"Cattle with the E211K polymorphism are susceptible to the CWD agent after oronasal exposure of 0.2 g of infectious material."

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Strain characterization of chronic wasting disease in bovine-PrP transgenic mice 

Nuria Jerez-Garrido1, Sara Canoyra1, Natalia Fernández-Borges1, Alba Marín Moreno1, Sylvie L. Benestad2, Olivier Andreoletti3, Gordon Mitchell4, Aru Balachandran4, Juan María Torres1 and Juan Carlos Espinosa1. 1 Centro de Investigación en Sanidad Animal, CISA-INIA-CSIC, Madrid, Spain. 2 Norwegian Veterinary Institute, Ås, Norway. 3 UMR Institut National de la Recherche Agronomique (INRA)/École Nationale Vétérinaire de Toulouse (ENVT), Interactions Hôtes Agents Pathogènes, Toulouse, France. 4 Canadian Food Inspection Agency, Ottawa, Canada. 

Aims: Chronic wasting disease (CWD) is an infectious prion disease that affects cervids. Various CWD prion strains have been identified in different cervid species from North America and Europe. The properties of the infectious prion strains are influenced by amino acid changes and polymorphisms in the PrP sequences of different cervid species. This study, aimed to assess the ability of a panel of CWD prion isolates from diverse cervid species from North America and Europe to infect bovine species, as well as to investigate the properties of the prion strains following the adaptation to the bovine-PrP context. 

Materials and Methods: BoPrP-Tg110 mice overexpressing the bovine-PrP sequence were inoculated by intracranial route with a panel of CWD prion isolates from both North America (two white-tailed deer and two elk) and Europe (one reindeer, one moose and one red deer). 

Results: Our results show distinct behaviours in the transmission of the CWD isolates to the BoPrP-Tg110 mouse model. Some of these isolates did not transmit even after the second passage. Those able to transmit displayed differences in terms of attack rate, survival times, biochemical properties of brain PrPres, and histopathology. 

Conclusions: Altogether, these results exhibit the diversity of CWD strains present in the panel of CWD isolates and the ability of at least some CWD isolates to infect bovine species. Cattle being one of the most important farming species, this ability represents a potential threat to both animal and human health, and consequently deserves further study. 

Funded by: MCIN/AEI /10.13039/501100011033 and by European Union NextGeneration EU/PRTR 

Grant number: PCI2020-120680-2 ICRAD

"Altogether, these results exhibit the diversity of CWD strains present in the panel of CWD isolates and the ability of at least some CWD isolates to infect bovine species. Cattle being one of the most important farming species, this ability represents a potential threat to both animal and human health, and consequently deserves further study."

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https://prion2023.org/wp-content/uploads/2023/10/Meeting-book-final-version2.pdf

MONDAY, OCTOBER 16, 2023 

Transmission of the chronic wasting disease agent from elk to cattle after oronasal exposure 

Price of TSE Prion Poker goes up substantially, all you cattle ranchers and such, better pay close attention here...

https://chronic-wasting-disease.blogspot.com/2023/10/transmission-of-chronic-wasting-disease.html

PRION 2023 CONTINUED;  

https://prion2023.org/wp-content/uploads/2023/10/Meeting-book-final-version2.pdf

Detection of chronic wasting disease prions in processed meats

Rebeca Benavente1 , Francisca Bravo1,2, J. Hunter Reed3 , Mitch Lockwood3 , Glenn Telling4 , Rodrigo Morales1,2 1 Department of Neurology, McGovern Medical School, University of Texas Health Science Center at Houston, Texas, USA; 2 Universidad Bernardo O’Higgins. Santiago, Chile; 3 Texas Parks and Wildlife Department, Texas, USA. 4 Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO, USA

Aims: identify the presence of CWD prions in processed meats derived from elk.

Materials and Methods: In this study, we analyzed different processed meats derived from a CWD-positive (pre-clinical) free-ranging elk. Products tested included filets, sausages, boneless steaks, burgers, seasoned chili meats, and spiced meats. The presence of CWD-prions in these samples were assessed by PMCA using deer and elk substrates. The same analyses were performed in grilled and boiled meats to evaluate the resistance of the infectious agent to these procedures.

Results: Our results show positive prion detection in all the samples analyzed using deer and elk substrates. Surprisingly, cooked meats displayed increased seeding activities. This data suggests that CWD-prions are available to people even after meats are processed and cooked.

Conclusions: These results suggest CWD prions are accessible to humans through meats, even after processing and cooking. Considering the fact that these samples were collected from already processed specimens, the availability of CWD prions to humans is probably underestimated.

Funded by: NIH and USDA

Grant number: 1R01AI132695 and APP-20115 to RM

Acknowledgement: We would like to thank TPWD personnel for providing us with valuable samples

"Our results show positive prion detection in all the samples analyzed using deer and elk substrates. Surprisingly, cooked meats displayed increased seeding activities."

end...

PRION 2023 CONTINUED;

https://prion2023.org/wp-content/uploads/2023/10/Meeting-book-final-version2.pdf

The detection and decontamination of chronic wasting disease prions during venison processing

Aims: There is a growing concern that chronic wasting disease (CWD) prions in venison pose a risk to human health. CWD prions accumulate in infected deer tissues that commonly enter the human food chain through meat processing and consumption. The United States (US) Food and Drug Administration and US Department of Agriculture now formally consider CWD-positive venison unfit for human and animal consumption. Yet, the degree to which prion contamination occurs during routine venison processing is unknown. Here, we use environmental surface swab methods to:

a) experimentally test meat processing equipment (i.e., stainless steel knives and polyethylene cutting boards) before and after processing CWD-positive venison and

b) test the efficacy of five different disinfectant types (i.e., Dawn dish soap, Virkon-S, Briotech, 10% bleach, and 40% bleach) to determine prion decontamination efficacy.

Materials and Methods: We used a real-time quaking-induced conversion (RT-QuIC) assay to determine CWD infection status of venison and to detect CWD prions in the swabs. We collected three swabs per surface and ran eight technical replicates on RT-QuIC.

Results: CWD prions were detected on all cutting boards (n= 3; replicates= 8/8, 8/8, 8/8 and knives (n= 3; replicates= 8/8, 8/8, 8/8) used in processing CWD-positive venison, but not on those used for CWD-negative venison. After processing CWD-positive venison, allowing the surfaces to dry, and washing the cutting board with Dawn dish soap, we detected CWD prions on the cutting board surface (n= 3; replicates= 8/8, 8/8, 8/8) but not on the knife (n= 3, replicates = 0/8, 0/8, 0/8). Similar patterns were observed with Briotech (cutting board: n= 3; replicates= 7/8, 1/8, 0/8; knife: n= 3; replicates = 0/8, 0/8, 0/8). We did not detect CWD prions on the knives or cutting boards after disinfecting with Virkon-S, 10% bleach, and 40% bleach.

Conclusions: These preliminary results suggest that Dawn dish soap and Briotech do not reliably decontaminate CWD prions from these surfaces. Our data suggest that Virkon-S and various bleach concentrations are more effective in reducing prion contamination of meat processing surfaces; however, surface type may also influence the ability of prions to adsorb to surfaces, preventing complete decontamination. Our results will directly inform best practices to prevent the introduction of CWD prions into the human food chain during venison processing.

Prion 2023 Abstracts

https://prion2023.org/wp-content/uploads/2023/10/Meeting-book-final-version2.pdf

DETECTION OF CHRONIC WASTING DISEASE PRIONS IN PROCESSED MEATS.

Abstract

The zoonotic potential of chronic wasting disease (CWD) remains unknown. Currently, there are no known natural cases of CWD transmission to humans but increasing evidence suggests that the host range of CWD is not confined only to cervid species. Alarmingly, recent experimental evidence suggests that certain CWD isolates can induce disease in non-human primates. While the CDC strongly recommends determining CWD status in animals prior to consumption, this practice is voluntary. Consequently, it is plausible that a proportion of the cervid meat entering the human food chain may be contaminated with CWD. Of additional concern is that traditional diagnostic techniques used to detect CWD have relatively low sensitivity and are only approved for use in tissues other than those typically ingested by humans. In this study, we analyzed different processed meats derived from a pre-clinical, CWD-positive free-ranging elk. Products tested included filets, sausages, boneless steaks, burgers, ham steaks, seasoned chili meats, and spiced meats. CWD-prion presence in these products were assessed by PMCA using deer and elk substrates. Our results show positive prion detection in all products. To confirm the resilience of CWD-prions to traditional cooking methods, we grilled and boiled the meat products and evaluated them for any remnant PMCA seeding activity. Results confirmed the presence of CWD-prions in these meat products suggesting that infectious particles may still be available to people even after cooking. Our results strongly suggest ongoing human exposure to CWD-prions and raise significant concerns of zoonotic transmission through ingestion of CWD contaminated meat products.

***> Products tested included filets, sausages, boneless steaks, burgers, ham steaks, seasoned chili meats, and spiced meats.

***> CWD-prion presence in these products were assessed by PMCA using deer and elk substrates.

***> Our results show positive prion detection in all products.

***> Results confirmed the presence of CWD-prions in these meat products suggesting that infectious particles may still be available to people even after cooking.

***> Our results strongly suggest ongoing human exposure to CWD-prions and raise significant concerns of zoonotic transmission through ingestion of CWD contaminated meat products.

https://intcwdsympo.files.wordpress.com/2023/06/final-agenda-with-abstracts.pdf?force_download=true

Transmission of prion infectivity from CWD-infected macaque tissues to rodent models demonstrates the zoonotic potential of chronic wasting disease.

Samia Hannaoui1,2, Ginny Cheng1,2, Wiebke Wemheuer3, Walter Schulz-Schaeffer3, Sabine Gilch1,2, Hermann Schatzl1,2 1University of Calgary, Calgary, Canada. 2Calgary Prion Research Unit, Calgary, Canada. 3Institute of Neuropathology, Medical Faculty, Saarland University, Homburg/Saar, Germany

Snip…

***> Further passage to cervidized mice revealed transmission with a 100% attack rate.

***> Our findings demonstrate that macaques, considered the best model for the zoonotic potential of prions, were infected upon CWD challenge, including the oral one.

****> The disease manifested as atypical in macaques and initial transgenic mouse transmissions, but with infectivity present at all times, as unveiled in the bank vole model with an unusual tissue tropism.

***> Epidemiologic surveillance of prion disease among cervid hunters and people likely to have consumed venison contaminated with chronic wasting disease

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https://intcwdsympo.files.wordpress.com/2023/06/final-agenda-with-abstracts.pdf?force_download=true

Transmission of Cervid Prions to Humanized Mice Demonstrates the Zoonotic Potential of CWD

Samia Hannaouia, Irina Zemlyankinaa, Sheng Chun Changa, Maria Immaculata Arifina, Vincent Béringueb, Debbie McKenziec, Hermann M. Schatzla, and Sabine Gilcha

Results: Here, we provide the strongest evidence supporting the zoonotic potential of CWD prions, and their possible phenotype in humans. Inoculation of mice expressing human PrPCwith deer CWD isolates (strains Wisc-1 and 116AG) resulted in atypical clinical manifestations in > 75% of the mice, with myoclonus as leading clinical sign. Most of tg650brain homogenates were positive for seeding activity in RT-QuIC. Clinical disease and presentation was transmissible to tg650 mice and bank voles. Intriguingly, protease-resistant PrP in the brain of tg650 mice resembled that found in a familial human prion disease and was transmissible upon passage. Abnormal PrP aggregates upon infection with Wisc-1 were detectable in thalamus, hypothalamus, and midbrain/pons regions.

Unprecedented in human prion disease, feces of CWD-inoculated tg650 mice harbored prion seeding activity and infectious prions, as shown by inoculation of bank voles and tg650 with fecal homogenates.

Conclusions: This is the first evidence that CWD can infect humans and cause disease with a distinctive clinical presentation, signature, and tropism, which might be transmissible between humans while current diagnostic assays might fail to detect it. These findings have major implications for public health and CWD-management.

https://www.tandfonline.com/doi/full/10.1080/19336896.2022.2091286

The finding that infectious PrPSc was shed in fecal material of CWD-infected humanized mice and induced clinical disease, different tropism, and typical three banding pattern-PrPres in bank voles that is transmissible upon second passage is highly concerning for public health. The fact that this biochemical signature in bank voles resembles that of the Wisc-1 original deer isolate and is different from that of bvWisc-1, in the migration profile and the glyco-form-ratio, is valid evidence that these results are not a product of contamination in our study. If CWD in humans is found to be contagious and transmissible among humans, as it is in cervids [57], the spread of the disease within humans might become endemic.

Transmission of cervid prions to humanized mice demonstrates the zoonotic potential of CWD

Acta Neuropathol 144, 767–784 (2022). https://doi.org/10.1007/s00401-022-02482-9

Published

22 August 2022

https://link.springer.com/article/10.1007/s00401-022-02482-9

Fortuitous generation of a zoonotic cervid prion strain

Aims: Whether CWD prions can infect humans remains unclear despite the very substantial scale and long history of human exposure of CWD in many states or provinces of USA and Canada. Multiple in vitro conversion experiments and in vivo animal studies indicate that the CWD-to-human transmission barrier is not unbreakable. A major long-term public health concern on CWD zoonosis is the emergence of highly zoonotic CWD strains. We aim to address the question of whether highly zoonotic CWD strains are possible.

Materials and Methods: We inoculated several sCJD brain samples into cervidized transgenic mice (Tg12), which were intended as negative controls for bioassays of brain tissues from sCJD cases who had potentially been exposed to CWD. Some of the Tg12 mice became infected and their brain tissues were further examined by Western blot as well as serial passages in humanized or cervidized mice.

Results: Passage of sCJDMM1 in transgenic mice expressing elk PrP (Tg12) resulted in a “cervidized” CJD strain that we termed CJDElkPrP. We observed 100% transmission of the original CJDElkPrP in transgenic mice expressing human PrP. We passaged CJDElkPrP two more times in the Tg12 mice. We found that such second and third passage CJDElkPrP prions retained 100% transmission rate in the humanized mice, despite that the natural elk CWD isolates and CJDElkPrP share the same elk PrP sequence. In contrast, we and others found zero or poor transmission of natural elk CWD isolates in humanized mice.

Conclusions: Our data indicate that highly zoonotic cervid prion strains are not only possible but also can retain zoonotic potential after serial passages in cervids, suggesting a very significant and serious long-term risk of CWD zoonosis given that the broad and continuing spread of CWD prions will provide fertile grounds for the emergence of zoonotic CWD strains over time.

https://prion2023.org/wp-content/uploads/2023/10/Meeting-book-final-version2.pdf

The finding that infectious PrPSc was shed in fecal material of CWD-infected humanized mice and induced clinical disease, different tropism, and typical three banding pattern-PrPres in bank voles that is transmissible upon second passage is highly concerning for public health. The fact that this biochemical signature in bank voles resembles that of the Wisc-1 original deer isolate and is different from that of bvWisc-1, in the migration profile and the glyco-form-ratio, is valid evidence that these results are not a product of contamination in our study. If CWD in humans is found to be contagious and transmissible among humans, as it is in cervids [57], the spread of the disease within humans might become endemic.

Transmission of cervid prions to humanized mice demonstrates the zoonotic potential of CWD

Acta Neuropathol 144, 767–784 (2022). https://doi.org/10.1007/s00401-022-02482-9

Published

22 August 2022

https://link.springer.com/article/10.1007/s00401-022-02482-9

Transmission of cervid prions to humanized mice demonstrates the zoonotic potential of CWD

Samia Hannaoui1 · Irina Zemlyankina1 · Sheng Chun Chang1 · Maria Immaculata Arifn1 · Vincent Béringue2 · Debbie McKenzie3 · Hermann M. Schatzl1 · Sabine Gilch1

Received: 24 May 2022 / Revised: 5 August 2022 / Accepted: 7 August 2022

© The Author(s) 2022

Abstract

Prions cause infectious and fatal neurodegenerative diseases in mammals. Chronic wasting disease (CWD), a prion disease of cervids, spreads efficiently among wild and farmed animals. Potential transmission to humans of CWD is a growing concern due to its increasing prevalence. Here, we provide evidence for a zoonotic potential of CWD prions, and its probable signature using mice expressing human prion protein (PrP) as an infection model. Inoculation of these mice with deer CWD isolates resulted in atypical clinical manifestation with prion seeding activity and efficient transmissible infectivity in the brain and, remarkably, in feces, but without classical neuropathological or Western blot appearances of prion diseases. Intriguingly, the protease-resistant PrP in the brain resembled that found in a familial human prion disease and was transmissible upon second passage. Our results suggest that CWD might infect humans, although the transmission barrier is likely higher compared to zoonotic transmission of cattle prions. Notably, our data suggest a different clinical presentation, prion signature, and tissue tropism, which causes challenges for detection by current diagnostic assays. Furthermore, the presence of infectious prions in feces is concerning because if this occurs in humans, it is a source for human-to-human transmission. These findings have strong implications for public health and CWD management.

Keywords Chronic wasting disease · CWD · Zoonotic potential · Prion strains · Zoonotic prions

HIGHLIGHTS OF THIS STUDY

================================

Our results suggest that CWD might infect humans, although the transmission barrier is likely higher compared to zoonotic transmission of cattle prions. Notably, our data suggest a different clinical presentation, prion signature, and tissue tropism, which causes challenges for detection by current diagnostic assays. Furthermore, the presence of infectious prions in feces is concerning because if this occurs in humans, it is a source for human-to-human transmission. These findings have strong implications for public health and CWD management.

In this study, we evaluated the zoonotic potential of CWD using a transgenic mouse model overexpressing human M129-PrPC (tg650 [12]). We inoculated tg650 mice intracerebrally with two deer CWD isolates, Wisc-1 and 116AG [22, 23, 27, 29]. We demonstrate that this transgenic line was susceptible to infection with CWD prions and displayed a distinct leading clinical sign, an atypical PrPSc signature and unusual fecal shedding of infectious prions. Importantly, these prions generated by the human PrP transgenic mice were transmissible upon passage. Our results are the first evidence of a zoonotic risk of CWD when using one of the most common CWD strains, Wisc-1/CWD1 for infection. We demonstrated in a human transgenic mouse model that the species barrier for transmission of CWD to humans is not absolute. The fact that its signature was not typical raises the questions whether CWD would manifest in humans as a subclinical infection, whether it would arise through direct or indirect transmission including an intermediate host, or a silent to uncovered human-to-human transmission, and whether current detection techniques will be suffcient to unveil its presence.

Our findings strongly suggest that CWD should be regarded as an actual public health risk. Here, we use humanized mice to show that CWD prions can cross the species barrier to humans, and remarkably, infectious prions can be excreted in feces.

Our results indicate that if CWD crosses the species-barrier to humans, it is unlikely to resemble the most common forms of human prion diseases with respect to clinical signs, tissue tropism and PrPSc signature. For instance, PrPSc in variable protease-sensitive prionopathy (VPSPr), a sporadic form of human prion disease, and in the genetic form Gerstmann-Sträussler-Scheinker syndrome (GSS) is defined by an atypical PK-resistant PrPSc fragment that is non-glycosylated and truncated at both C- and N-termini, with a molecular weight between 6 and 8 kDa [24, 44–46]. These biochemical features are unique and distinctive from PrPSc (PrP27-30) found in most other human or animal prion disease. The atypical PrPSc signature detected in brain homogenate of tg650 mice #321 (1st passage) and #3063 (2nd passage), and the 7–8 kDa fragment (Figs. 2, 4) are very similar to that of GSS, both in terms of migration profile and the N-terminal cleavage site.

CWD in humans might remain subclinical but with PrPSc deposits in the brain with an unusual morphology that does not resemble the patterns usually seen in different prion diseases (e.g., mouse #328; Fig. 3), clinical with untraceable abnormal PrP (e.g., mouse #327) but still transmissible and uncovered upon subsequent passage (e.g., mouse #3063; Fig. 4), or prions have other reservoirs than the usual ones, hence the presence of infectivity in feces (e.g., mouse #327) suggesting a potential for human-to-human transmission and a real iatrogenic risk that might be unrecognizable.

“suggesting a potential for human-to-human transmission and a real iatrogenic risk that might be unrecognizable.”

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Supplementary Information The online version contains supplementary material available at

https://doi.org/10.1007/s00401-022-02482-9

snip...see full text;

https://link.springer.com/article/10.1007/s00401-022-02482-9

https://link.springer.com/content/pdf/10.1007/s00401-022-02482-9.pdf

EFSA Panel on Biological Hazards (BIOHAZ) Antonia Ricci Ana Allende Declan Bolton Marianne Chemaly Robert Davies Pablo Salvador Fernández Escámez ...

First published: 17 January 2018 https://doi.org/10.2903/j.efsa.2018.5132

also, see;

8. Even though human TSE‐exposure risk through consumption of game from European cervids can be assumed to be minor, if at all existing, no final conclusion can be drawn due to the overall lack of scientific data.

***> In particular the US data do not clearly exclude the possibility of human (sporadic or familial) TSE development due to consumption of venison.

The Working Group thus recognizes a potential risk to consumers if a TSE would be present in European cervids. It might be prudent considering appropriate measures to reduce such a risk, e.g. excluding tissues such as CNS and lymphoid tissues from the human food chain, which would greatly reduce any potential risk for consumers.. However, it is stressed that currently, no data regarding a risk of TSE infections from cervid products are available.

https://efsa.onlinelibrary.wiley.com/doi/full/10.2903/j.efsa.2018.5132

''The association between venison eating and risk of CJD shows similar pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK OF CJD (p = 0.04).''

CREUTZFELDT JAKOB DISEASE SURVEILLANCE IN THE UNITED KINGDOM THIRD ANNUAL REPORT AUGUST 1994

Consumption of venison and veal was much less widespread among both cases and controls. For both of these meats there was evidence of a trend with increasing frequency of consumption being associated with increasing risk of CJD. (not nvCJD, but sporadic CJD...tss) These associations were largely unchanged when attention was restricted to pairs with data obtained from relatives. ...

Table 9 presents the results of an analysis of these data.

There is STRONG evidence of an association between ‘’regular’’ veal eating and risk of CJD (p = .0.01).

Individuals reported to eat veal on average at least once a year appear to be at 13 TIMES THE RISK of individuals who have never eaten veal.

There is, however, a very wide confidence interval around this estimate. There is no strong evidence that eating veal less than once per year is associated with increased risk of CJD (p = 0.51).

The association between venison eating and risk of CJD shows similar pattern, with regular venison eating associated with a 9 FOLD INCREASE IN RISK OF CJD (p = 0.04).

There is some evidence that risk of CJD INCREASES WITH INCREASING FREQUENCY OF LAMB EATING (p = 0.02).

The evidence for such an association between beef eating and CJD is weaker (p = 0.14). When only controls for whom a relative was interviewed are included, this evidence becomes a little STRONGER (p = 0.08).

snip...

It was found that when veal was included in the model with another exposure, the association between veal and CJD remained statistically significant (p = < 0.05 for all exposures), while the other exposures ceased to be statistically significant (p = > 0.05).

snip...

In conclusion, an analysis of dietary histories revealed statistical associations between various meats/animal products and INCREASED RISK OF CJD. When some account was taken of possible confounding, the association between VEAL EATING AND RISK OF CJD EMERGED AS THE STRONGEST OF THESE ASSOCIATIONS STATISTICALLY. ...

snip...

In the study in the USA, a range of foodstuffs were associated with an increased risk of CJD, including liver consumption which was associated with an apparent SIX-FOLD INCREASE IN THE RISK OF CJD. By comparing the data from 3 studies in relation to this particular dietary factor, the risk of liver consumption became non-significant with an odds ratio of 1.2 (PERSONAL COMMUNICATION, PROFESSOR A. HOFMAN. ERASMUS UNIVERSITY, ROTTERDAM). (???...TSS)

snip...see full report ;

http://web.archive.org/web/20090506050043/http://www.bseinquiry.gov.uk/files/yb/1994/08/00004001.pdf

http://web.archive.org/web/20090506050007/http://www.bseinquiry.gov.uk/files/yb/1994/10/00003001.pdf

http://web.archive.org/web/20090506050244/http://www.bseinquiry.gov.uk/files/yb/1994/07/00001001.pdf

Transmission of scrapie prions to primate after an extended silent incubation period

*** In complement to the recent demonstration that humanized mice are susceptible to scrapie, we report here the first observation of direct transmission of a natural classical scrapie isolate to a macaque after a 10-year incubation period. Neuropathologic examination revealed all of the features of a prion disease: spongiform change, neuronal loss, and accumulation of PrPres throughout the CNS.

*** This observation strengthens the questioning of the harmlessness of scrapie to humans, at a time when protective measures for human and animal health are being dismantled and reduced as c-BSE is considered controlled and being eradicated.

*** Our results underscore the importance of precautionary and protective measures and the necessity for long-term experimental transmission studies to assess the zoonotic potential of other animal prion strains.

http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=313160

***Transmission data also revealed that several scrapie prions propagate in HuPrP-Tg mice with efficiency comparable to that of cattle BSE. While the efficiency of transmission at primary passage was low, subsequent passages resulted in a highly virulent prion disease in both Met129 and Val129 mice.

***Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion.

***These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.

http://www.tandfonline.com/doi/abs/10.1080/19336896.2016.1163048?journalCode=kprn20

***Moreover, sporadic disease has never been observed in breeding colonies or primate research laboratories, most notably among hundreds of animals over several decades of study at the National Institutes of Health25, and in nearly twenty older animals continuously housed in our own facility.***

Even if the prevailing view is that sporadic CJD is due to the spontaneous formation of CJD prions, it remains possible that its apparent sporadic nature may, at least in part, result from our limited capacity to identify an environmental origin.

https://www.nature.com/articles/srep11573

https://www.ars.usda.gov/research/publications/publication/?seqNo115=361032

O.05: Transmission of prions to primates after extended silent incubation periods: Implications for BSE and scrapie risk assessment in human populations

*** We recently observed the direct transmission of a natural classical scrapie isolate to macaque after a 10-year silent incubation period,

***with features similar to some reported for human cases of sporadic CJD, albeit requiring fourfold long incubation than BSE. Scrapie, as recently evoked in humanized mice (Cassard, 2014),

***is the third potentially zoonotic PD (with BSE and L-type BSE),

***thus questioning the origin of human sporadic cases.

==============

PRION 2015 CONFERENCE

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5019500/

PRION 2016 TOKYO

Saturday, April 23, 2016

SCRAPIE WS-01: Prion diseases in animals and zoonotic potential 2016

Prion. 10:S15-S21. 2016 ISSN: 1933-6896 1933-690X

WS-01: Prion diseases in animals and zoonotic potential

Transmission of the different scrapie isolates in these mice leads to the emergence of prion strain phenotypes that showed similar characteristics to those displayed by MM1 or VV2 sCJD prion.

These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.

http://www.tandfonline.com/doi/abs/10.1080/19336896.2016.1163048?journalCode=kprn20

Tuesday, December 16, 2014

Evidence for zoonotic potential of ovine scrapie prions

Hervé Cassard,1, n1 Juan-Maria Torres,2, n1 Caroline Lacroux,1, Jean-Yves Douet,1, Sylvie L. Benestad,3, Frédéric Lantier,4, Séverine Lugan,1, Isabelle Lantier,4, Pierrette Costes,1, Naima Aron,1, Fabienne Reine,5, Laetitia Herzog,5, Juan-Carlos Espinosa,2, Vincent Beringue5, & Olivier Andréoletti1, Affiliations Contributions Corresponding author Journal name: Nature Communications

Volume: 5, Article number: 5821 DOI: doi:10.1038/ncomms6821 Received 07 August 2014 Accepted 10 November 2014 Published 16 December 2014

Abstract

Although Bovine Spongiform Encephalopathy (BSE) is the cause of variant Creutzfeldt Jakob disease (vCJD) in humans, the zoonotic potential of scrapie prions remains unknown. Mice genetically engineered to overexpress the human prion protein (tgHu) have emerged as highly relevant models for gauging the capacity of prions to transmit to humans. These models can propagate human prions without any apparent transmission barrier and have been used used to confirm the zoonotic ability of BSE. Here we show that a panel of sheep scrapie prions transmit to several tgHu mice models with an efficiency comparable to that of cattle BSE.

***The serial transmission of different scrapie isolates in these mice led to the propagation of prions that are phenotypically identical to those causing sporadic CJD (sCJD) in humans.

***These results demonstrate that scrapie prions have a zoonotic potential and raise new questions about the possible link between animal and human prions.

Subject terms: Biological sciences• Medical research At a glance

http://www.nature.com/ncomms/2014/141216/ncomms6821/full/ncomms6821.html

This old study always fascinates me, iatrogenic TSE Transmission is a real threat…

1: J Neurol Neurosurg Psychiatry 1994 Jun;57(6):757-8

Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery.

Gibbs CJ Jr, Asher DM, Kobrine A, Amyx HL, Sulima MP, Gajdusek DC.

Laboratory of Central Nervous System Studies, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892.

Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8006664&dopt=Abstract

iatrogenic TSE Prion Transmission

https://itseprion.blogspot.com/ 

Friday, February 21, 2025 

CWD, BAITING, AND MINERAL LICKS, WHAT IF? 

https://chronic-wasting-disease.blogspot.com/2025/02/cwd-baiting-and-mineral-licks-what-if.html

Friday, February 21, 2025

Deer don’t die from CWD, it’s the insurance companies, or it's a Government conspiracy?

https://chronic-wasting-disease.blogspot.com/2025/02/deer-dont-die-from-cwd-its-insurance.html

Friday, February 21, 2025

LEGISLATING CWD TSE Prion, Bills to release Genetically Modified Cervid into the wild, what could go wrong?

https://chronic-wasting-disease.blogspot.com/2025/02/legislating-cwd-tse-prion-bills-to.html

Friday, February 21, 2025 

Distribution of Chronic Wasting Disease in North America February 2025 

https://chronic-wasting-disease.blogspot.com/2025/02/distribution-of-chronic-wasting-disease.html

***> Creutzfeldt Jakob Disease CJD, BSE, CWD, TSE, Prion, December 14, 2024 Annual Update

https://creutzfeldt-jakob-disease.blogspot.com/2024/12/creutzfeldt-jacob-disease-cjd-bse-cwd.html

Terry S. Singeltary Sr. Flounder9@verizon.net Bacliff, Texas 77518