Detection and Decontamination of Chronic Wasting Disease Prions during Venison Processing

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.

Keywords: RT-QuIC; United States; chronic wasting disease; food safety; prions; seeded amplification assay; transmissible spongiform encephalopathy; white-tailed deer.

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 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 created using BioRender (https://www.biorender.com).

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. 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 created using BioRender (https://www.biorender.com).

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 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 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 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 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; 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 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 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 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 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.