Comparison of Chronic Wasting Disease Detection Methods and Procedures: Implications for Free-Ranging White-Tailed Deer (Odocoileus Virginianus) Surveillance and Management

Abstract

Throughout North America, chronic wasting disease (CWD) has emerged as perhaps the greatest threat to wild cervid populations, including white-tailed deer (Odocoileus virginianus). Whitetailed deer are the most sought after big game species across North America with populations of various subspecies in nearly all Canadian provinces, the contiguous USA, and Mexico. Documented CWD cases have dramatically increased across the white-tailed deer range since the mid-1990s, including in Minnesota. CWD surveillance in free-ranging white-tailed deer and other cervid populations mainly depends upon immunodetection methods (e.g., immunohistochemistry [IHC] and enzyme-linked immunosorbent assay [ELISA]) on medial retropharyngeal lymph nodes and obex. More recent technologies centered on prion protein amplification methods of detection have shown promise as more sensitive and rapid CWD diagnostic tools. Here, we used blinded samples to test the efficacy of real time quaking-induced conversion (RT-QuIC) in comparison to ELISA and IHC for screening tissues, blood, and feces collected in 2019 from white-tailed deer in southeastern Minnesota, where CWD has been routinely detected since 2016. Our results support previous findings that RT-QuIC is a more sensitive tool for CWD detection than current antibody-based methods. Additionally, a CWD testing protocol that includes multiple lymphoid tissues (medial retropharyngeal lymph node, parotid lymph node, and palatine tonsil) per animal may effectively identify a greater number of CWD detections in a white-tailed deer population than a single sample type (i.e., medial retropharyngeal lymph nodes). These results reveal that the variability of CWD pathogenesis, sampling protocol, and testing platform must be considered for the effective detection and management of CWD throughout North America.

A Field-Deployable Diagnostic Assay for the Visual Detection of Misfolded Prions

“…RPLN and palatine tonsils collected from WTD were the basis for the laboratory-based analyses conducted herein because these tissues are ideal for early and accurate identification of CWD infection, with tonsils additionally having antemortem applications. 27,63 Future analyses will focus on leveraging MN-QuIC for CWD diagnostics using a variety of antemortem biological samples (e.g., blood, saliva, and feces).…”

“…3a). 27 In light of our previous results, we anticipated that AuNPs could be utilized to facilitate direct visualization of QuIC-amplified misfolded rPrP solutions that were seeded with CWD positive tissue using a standard bench-top thermomixer. Thermomixers have been used previously in conjunction with end-point ThT readings (i.e., EP-QuIC) to determine the presence of CJD prion seeding activity.…”

“…Twenty-eight WTD tissues (14 CWD-negative and 14 CWD-positive) were selected for laboratory-based RT-QuIC and MN-QuIC analyses. These samples were collected from WTD through collaboration with the Minnesota DNR (Schwabenlander et al 27 2021; Tables S1 and S3), and their CWD status was independently identified utilizing the Bio-Rad TeSeE Short Assay Protocol (SAP) Combo Kit (BioRad Laboratories Inc., Hercules, CA, USA). Positive RPLNs were confirmed by IHC at the Colorado State University Veterinary Diagnostic Laboratory).…”

“…These samples are referred to as 10% homogenates. All CWD positive and negative samples were selected based on independent ELISA, IHC, and/or RT-QuIC results and were subsampled using methods as reported in Schwabenlander et al 27…”

“…The detection of prion seeding activity was recently enhanced by various assays involving the amplification of protein misfolding in vitro, including protein misfolding cyclic amplification (PMCA), 6,21 end-point quaking-induced conversion (EP-QuIC) 22,23 and real-time quaking-induced conversion (RT-QuIC). 6,[24][25][26][27] Of these prion amplification methods both EP-QuIC and RT-QuIC (Fig. 1b) utilize a recombinant mammalian PrP substrate (rPrP) that is incubated and shaken with the diagnostic samples.…”