Temporal Characterization of Prion Shedding in Secreta of White-Tailed Deer in Longitudinal Study of Chronic Wasting Disease, United States

Abstract

Chronic wasting disease (CWD) affects cervids in North America, Asia, and Scandinavia. CWD is unique in its efficient spread, partially because of contact with infectious prions shed in secreta. To assess temporal profiles of CWD prion shedding, we collected saliva, urine, and feces from white-tailed deer for 66 months after exposure to low oral doses of CWD-positive brain tissue or saliva. We analyzed prion seeding activity by using modified amyloid amplification assays incorporating iron oxide bead extraction, which improved CWD detection and reduced false positives. CWD prions were detected in feces, urine, and saliva as early as 6 months postinfection. More frequent and consistent shedding was observed in deer homozygous for glycine at prion protein gene codon 96 than in deer expressing alternate genotypes. Our findings demonstrate that improved amplification methods can be used to identify early antemortem CWD prion shedding, which might aid in disease surveillance of cervids.

Keywords: CWD; IPQ; RT-QuIC; United States; chronic wasting disease; excreta; feces; prions; prions and related diseases; real-time quaking induced conversion; saliva; secreta; urine; white-tailed deer.

Figure 1

Amyloid formation rates in fecal samples from white-tailed deer with chronic wasting disease in longitudinal study of temporal characterization of prion shedding in secreta, United States. A) Amyloid formation rates measured by using iron oxide bead capture and subsequent real-time quaking-induced conversion. Rates were measured for serial dilutions of fecal samples. B) Amyloid formation rates measured by using iron oxide bead capture, 4 rounds of serial protein misfolding amplification, and subsequent real-time quaking-induced conversion. Rates were measured for 1:100 dilutions of fecal samples from each round of amplification. Black indicates prion-negative feces; red indicates prion-positive feces. Horizontal lines in each grouping indicate median values. Rd, round.

Figure 2

Amyloid formation rates in urine and saliva samples from white-tailed deer with chronic wasting disease in longitudinal study of temporal characterization of prion shedding in secreta, United States. A) Amyloid formation rates measured by using iron oxide bead capture and subsequent real-time quaking-induced conversion. Black indicates prion-negative samples; red indicates prion-positive samples. B) Amyloid formation rates measured by using iron oxide bead capture, 4 rounds of serial protein misfolding amplification, and subsequent real-time quaking-induced conversion in the same samples as those in panel A. Rates were measured for samples after amplification rounds 2–4. Horizontal lines in each grouping indicate median values. Rd, round.

Figure 3

Percentage of prion-positive samples from white-tailed deer with chronic wasting disease that had the prion protein genotype 96GG in study of prion shedding in secreta, United States. Tissue samples and secreta were collected from deer after exposure to low oral doses of chronic wasting disease–positive brain tissue or saliva. RAMALT, recto-anal mucosa-associated lymphoid tissue.

Figure 4

Percentage of prion-positive samples from white-tailed deer with chronic wasting disease that had prion protein genotypes 96GS or 103NT in study of prion shedding in secreta, United States. Tissue samples and secreta were collected from deer after exposure to low oral doses of chronic wasting disease–positive brain tissue or saliva. RAMALT, recto-anal mucosa-associated lymphoid tissue.