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Title: Antemortem detection of chronic wasting disease prions in nasal brush collections and rectal biopsies from white-tailed deer by real time quaking-induced conversion

item HALEY, NICHOLAS - Kansas State University
item SIEPKER, CHRIS - Kansas State University
item WALTER, W. DAVID - Us Geological Survey (USGS)
item THOMSEN, BRUCE - Animal And Plant Health Inspection Service (APHIS)
item Greenlee, Justin
item LEHMKUHL, AARON - Animal And Plant Health Inspection Service (APHIS)
item RICHT, JÜRGEN - Kansas State University

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2015
Publication Date: 2/10/2016
Citation: Haley, N.J., Siepker, C., Walter, W.D., Thomsen, B.V., Greenlee, J.J., Lehmkuhl, A.D., Richt, J.A. 2016. 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. Journal of Clinical Microbiology. 54(4):1108-1116.

Interpretive Summary: Chronic Wasting Disease (CWD), a fatal neurodegenerative disease that occurs in farmed and wild cervids (deer and elk) of North America, is a transmissible spongiform encephalopathy (TSE). TSEs are caused by infectious proteins called prions that are resistant to various methods of decontamination and environmental degradation. Early diagnosis of CWD in wild and captive herds would be very helpful to controlling the spread of CWD, for which there are not yet any preventative or treatment measures available. The purpose of this study was to test a laboratory method of prion detection (real-time Quaking Induced Conversion; RT-QuIC) that has the potential to detect very low levels of infectious prions in samples collected from live animals against the gold standard diagnostic where abnormal prion in tissues is stained on a microscope slide. This study reports that RT-QuIC detects more cases of CWD than standard methods, but also can identify a small number of animals without CWD as being positive. In the case of CWD, where it is likely that large numbers of animals within a herd may be positive, misidentifying a negative as a positive may have less of an impact than in the case of other prion diseases such as bovine spongiform encephalopathy considering that this test allows testing much larger numbers of samples with a faster turn around time than traditional methods. This information could have an impact on regulatory and wildlife officials developing plans to reduce or eliminate CWD and cervid farmers that want to ensure that their herd remains CWD-free.

Technical Abstract: Chronic wasting disease (CWD), a transmissible spongiform encephalopathy of cervids, was first documented nearly fifty years ago in Colorado and Wyoming and has since spread to cervids in 23 states, 2 Canadian provinces, and the Republic of Korea. The increasing expansion of this disease makes the development of sensitive diagnostic assays and antemortem sampling techniques crucial for the mitigation of spread; this is especially true in cases of relocation/reintroduction of farmed or free-ranging deer and elk, or surveillance studies in private or protected herds where depopulation may be contraindicated. This study sought to evaluate the sensitivity of the real-time quaking-induced conversion (RT-QuIC) assay in samples collected antemortem. Antemortem findings were then compared to results from ante- and postmortem samples evaluated using the current gold standard diagnostic assay, immunohistochemistry (IHC). Recto-anal mucosal associated lymphoid tissue (RAMALT) biopsies and nasal brush collections from three separate herds of farmed white-tailed deer (n=409) were evaluated, along with standard postmortem microscopic analysis of brainstem at the level of the obex and retropharyngeal lymph nodes. We hypothesized the sensitivity of RT-QuIC would be comparable to IHC in antemortem tissues, and would correlate with both genotype and stage of clinical disease. Our results showed that RAMALT testing by RT-QuIC had the highest sensitivity (69.8%) when compared to postmortem testing. This data suggests that RT-QuIC, like IHC, is a fairly sensitive assay for detection of CWD prions in rectal biopsies and other antemortem samples, and with further investigation has potential for large scale and rapid automated testing for CWD diagnosis.