Antemortem Detection of Chronic Wasting Disease Prions in Nasal Brush Collections and Rectal Biopsy Specimens from White-Tailed Deer by Real-Time Quaking-Induced Conversion

Abstract

dChronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, was first documented nearly 50 years ago in Colorado and Wyoming and has since spread to cervids in 23 states, two Canadian provinces, and the Republic of Korea. The expansion of this disease makes the development of sensitive diagnostic assays and antemortem sampling techniques crucial for the mitigation of its spread; this is especially true in cases of relocation/reintroduction of farmed or free-ranging deer and elk or surveillance studies of private or protected herds, where depopulation is contraindicated. This study sought to evaluate the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay by using recto-anal mucosa-associated lymphoid tissue (RAMALT) biopsy specimens and nasal brush samples collected antemortem from farmed white-tailed deer (n ‫؍‬ 409). Antemortem findings were then compared to results from ante-and postmortem samples (RAMALT, brainstem, and medial retropharyngeal lymph nodes) evaluated by using the current gold standard in vitro assay, immunohistochemistry (IHC) analysis. We hypothesized that the sensitivity of RT-QuIC would be comparable to IHC analysis in antemortem tissues and would correlate with both the genotype and the stage of clinical disease. Our results showed that RAMALT testing by RT-QuIC assay had the highest sensitivity (69.8%) compared to that of postmortem testing, with a specificity of >93.9%. These data suggest that RT-QuIC, like IHC analysis, is an effective assay for detection of PrP CWD in rectal biopsy specimens and other antemortem samples and, with further research to identify more sensitive tissues, bodily fluids, or experimental conditions, has potential for large-scale and rapid automated testing for CWD diagnosis. C hronic wasting disease (CWD) is an efficiently transmitted spongiform encephalopathy of cervids (e.g., deer, elk, and moose) and is the only known prion disease affecting both farmed and free-ranging, nondomestic animals. It is the only prion disease of animals the control and eradication of which, through movement restrictions, genotypic breeding schemes, or herd reduction/depopulation efforts, for example, are problematic (1, 2). While the origins of CWD are uncertain, the disease has been present in cervid populations of northern Colorado and southern Wyoming for nearly 50 years (3, 4) and has now been identified in both captive and free-ranging cervids in 23 states, two Canadian provinces, and the Republic of Korea (5, 6). With intensified national and international surveillance efforts, CWD continues to be identified in areas previously considered free of infection, including recent discoveries in Iowa, Texas, Pennsylvania, and Ohio (7, 8, 9, 10). The prevalence of CWD varies from 0 to 30% among free-ranging populations (11, 12) but may approach 80% in cervid farm operations under quarantine (13).The expanding distribution of CWD across North America can be considered to have followed two nearly distinct pathways: (i) gradual proliferatio...

Pathways of Prion Spread during Early Chronic Wasting Disease in Deer

“…Here, we demonstrate that both RTQuIC and TSA-IHC can enhance PrP CWD detection, with RT-QuIC being more sensitive during early infection. This finding is consistent with recent studies reporting RT-QuIC has sensitivity at least equal to that of IHC in detecting PrP CWD in RAMALT biopsy specimens from WTD and elk (35,36); however, a larger sample size is necessary to evaluate RT-QuIC as a diagnostic tool for subclinical infection.…”

“…The vomeronasal organ is a collection of accessory olfactory cells located in the anterior nasal mucosa that functions in pheromone detection in cervids (34). RT-QuIC analysis of nasal brushings have recently been shown to be a useful preclinical prion diagnostic tool for CJD in humans and CWD in cervids (35)(36)(37). The early PrP CWD accumulation in the nasal cavity, not only in 96GG deer but also during the prolonged subclinical phase in 96SS deer, may provide an additional pathway contributing to indirect environmental transmission in cervids.…”

Are Brazilian cervids at risk of prion diseases?

“…One M. gouazoubira individual, and one O. bezoarticus individual showed the 226LL and 226QQ genotypes, respectively, whereas all the other sampled individuals of the 3 species showed the 226EE genotype. 13 These results suggest a potential susceptibility to CWD in Brazilian deer. 22 However, no cases of CWD have been reported in Brazil.…”

“…10,11,14,17 In addition, we examined codons 116 and 226, where putative CWD-resistant polymorphisms (116G and 226K) have recently been identified. 13 …”

“…12 In addition, in white-tailed deer, alleles encoding Glycine in codon 116, and alleles encoding Lysine in codon 226 have been identified as putatively CWD-resistant. 13 O'Rourke et al 14 reported a new single nucleotide polymorphism in elks at the codon 132 (M132L) associated with CWD susceptibility. In the following year, the sequence of PRNP in CWD-positive and CWD-negative animals was determined to identify any correlation with CWD susceptibility.…”