Detection of PrP^CWD in Postmortem Rectal Lymphoid Tissues in Rocky Mountain Elk (Cervus Elaphus Nelsoni) Infected with Chronic Wasting Disease

Abstract

Abstract. Preclinical diagnostic tests for transmissible spongiform encephalopathies have been described for mule deer (Odocoileus hemionus), using biopsy tissues of palatine tonsil, and for sheep, using lymphoid tissues from palatine tonsil, third eyelid, and rectal mucosa. The utility of examining the rectal mucosal lymphoid tissues to detect chronic wasting disease (CWD) was investigated in Rocky Mountain elk (Cervus elaphus nelsoni), a species for which there is not a live-animal diagnostic test. Postmortem rectal mucosal sections were examined from 308 elk from two privately owned herds that were depopulated. The results of the postmortem rectal mucosal sections were compared to immunohistochemical staining of the brainstem, retropharyngeal lymph nodes, and palatine tonsil. Seven elk were found positive using the brainstem (dorsal motor nucleus of the vagus nerve), retropharyngeal lymph nodes, and palatine tonsil. Six of these elk were also found positive using postmortem rectal mucosal sections. The remaining 301 elk in which CWD-associated abnormal isoform of the prion protein (PrP CWD ) was not detected in the brainstem and cranial lymphoid tissues were also found to be free of PrP CWD when postmortem rectal mucosal sections were examined. The use of rectal mucosal lymphoid tissues may be suitable for a live-animal diagnostic test as part of an integrated management strategy to limit CWD in elk.

A prion disease of cervids: Chronic wasting disease

“…In naturallyinfected mule deer, 45 of 50 subclinical and terminal CWD-infected deer, as determined by immunohistochemistry on tonsil or retropharyngeal lymph nodes, were also positive by rectal biopsy [95]. Rectal biopsies to diagnose CWD in elk may also be suitable, as one study showed a strong correlation between tonsil, rectal mucosa, and brain in CWD positive elk, although one of seven elk with early CWD was tonsil positive, but rectal mucosa negative [82].…”

Impact of Age and Sex of Rocky Mountain Elk (Cervus Elaphus Nelsoni) on Follicle Counts from Rectal Mucosal Biopsies for Preclinical Detection of Chronic Wasting Disease

“…A limitation of using lymphoid tissue from the rectal mucosal biopsy technique in elk appears to be a decrease in the number of follicles as elk age. 6,9 If the number of follicles decreases too much, then the test would decrease in sensitivity and be of limited use in older animals. As previously acknowledged, the minimum number of lymphoid follicles needed for an accurate diagnosis of CWD using rectal mucosal biopsies in elk is unknown but is estimated to be 10 follicles.…”

“…Preclinical diagnostic tests for CWD have been described for mule deer using biopsy tissues of palatine tonsil 10 and rectal mucosa. 13 A rectal mucosal biopsy technique has recently been described 6,9 for detecting CWD in Rocky Mountain elk. Examination of postmortem rectal mucosal tissue sections for evidence of the prion protein associated with CWD (PrP CWD ) has been reported 8 in elk for diagnosis of CWD, and data indicate that the technique may be useful in the diagnosis of preclinical cases of CWD.…”

Detection of prion protein in the cerebrospinal fluid of elk (Cervus canadensis nelsoni) with chronic wasting disease using protein misfolding cyclic amplification

“…18,21,24 However, IHC does not routinely detect very early cases of CWD in these tissues. 17,20 Various fluids, such as saliva, blood, urine, and cerebrospinal fluid (CSF) have been evaluated in animals for their use in preclinical antemortem detection of abnormal prions. 4,6,10,22 Due to the minute concentrations of infectious proteins in saliva, blood, and urine, detection of the misfolded infectious prion protein (PrP res ) has been limited or unsuccessful without the use of protein misfolding cyclic amplification (PMCA), which increases the concentration to a detectable level, and is orders of magnitude more sensitive for detecting PrP CWD than commonly used methods such as Western blotting and IHC, 7 enabling detection of minute amounts of infectious prions in animal tissues and environmental samples.…”