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Assessment of Chronic Wasting Disease Prion Shedding in Deer Saliva with Occupancy Modeling
Kristen A Davenport1, Brittany A Mosher2, Brian M Brost3
1Prion Research Center, Microbiology, Immunology and Pathology Department, Colorado State University, Fort Collins, Colorado, USA.
Abstract:
The detection of prions is difficult due to the peculiarity of the pathogen, which is a misfolded form of a normal protein. The specificity and sensitivity of detection methods are imperfect in complex samples, including in excreta. Here, we combined optimized prion amplification procedures with a statistical method that accounts for false-positive and false-negative errors to test deer saliva for chronic wasting disease (CWD) prions. This approach enabled us to discriminate the shedding of prions in saliva and the detection of prions in saliva-a distinction crucial to understanding the role of prion shedding in disease transmission and for diagnosis. We found that assay sensitivity and specificity were indeed imperfect, and we were able to draw several conclusions pertinent to CWD biology from our analyses: (i) the shedding of prions in saliva increases with time postinoculation, but is common throughout the preclinical phase of disease; (ii) the shedding propensity is influenced neither by sex nor by prion protein genotype at codon 96; and (iii) the source of prion-containing inoculum used to infect deer affects the likelihood of prion shedding in saliva; oral inoculation of deer with CWD-positive saliva resulted in 2.77 times the likelihood of prion shedding in saliva compared to that from inoculation with CWD-positive brain. These results are pertinent to horizontal CWD transmission in wild cervids. Moreover, the approach described is applicable to other diagnostic assays with imperfect detection.
Insights
Detecting chronic wasting disease (CWD) prions in deer saliva is challenging. This study developed a new method to accurately identify prion shedding, crucial for understanding CWD transmission and diagnosis.
Area of Science:
- Veterinary Medicine
- Neuroscience
- Biochemistry
Background:
- Prion detection is challenging due to misfolded protein structures.
- Current diagnostic methods for prions in complex samples like excreta lack perfect sensitivity and specificity.
- Chronic Wasting Disease (CWD) prions pose a threat to cervid populations.
Purpose of the Study:
- To develop and validate a sensitive method for detecting CWD prions in deer saliva.
- To differentiate between prion shedding and prion detection in saliva.
- To understand the dynamics and factors influencing prion shedding in CWD-affected deer.
Main Methods:
- Combined optimized prion amplification techniques with a statistical error-correction model.
- Tested deer saliva samples for the presence of CWD prions.
- Analyzed the relationship between prion shedding, disease progression, host factors, and inoculum type.
Main Results:
- The developed assay demonstrated imperfect but quantifiable sensitivity and specificity.
- Prion shedding in saliva increases with time post-inoculation and is prevalent during the preclinical phase.
- Prion shedding was not influenced by deer sex or prion protein genotype (Codon 96).
- Oral inoculation with CWD-positive saliva led to a 2.77-fold higher likelihood of prion shedding compared to brain inoculum.
Conclusions:
- The study successfully discriminated prion shedding from detection in deer saliva.
- Findings provide critical insights into horizontal CWD transmission dynamics in wild cervids.
- The methodology is adaptable for improving other diagnostic assays with imperfect detection capabilities.
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