Submitted to: Journal of Veterinary Diagnostic Investigation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2008
Publication Date: 1/2/2009
Citation: Spraker, T.R., Vercauteren, K.C., Gidlewski, T., Schneider, D.A., Munger, R., Balanchandran, A., Orourke, K.I. 2009. Antemortem detection of PrP-CWD in preclinical, ranch-raised Rocky Mountain elk (Cervus elaphus nelsoni) by biopsy of the rectal mucosa. Journal of Veterinary Diagnostic Investigation. 21(1):15-24.
Interpretive Summary: Chronic wasting disease is a fatal disease of deer and elk. Infected animals are clinically normal for prolonged periods, eventually developing a degenerative disorder of the brain. The period of time during which infected elk are clinically normal but capable of transmitting the disease to herdmates is unknown. We have previously demonstrated that PrP-CWD, the protein marker for the disease, is present in the peripheral rectal mucosal tissue of CWD-infected free ranging Rocky Mountain elk. In this study, the feasibility of the rectal mucosal biopsy as a herd screening test was evaluated. Forty ranch raised elk in a facility with naturally acquired CWD were tested. PrP-CWD was detected in the rectal mucosal tissue of one elk with clinical signs of late stage CWD, one animal with signs suggestive of early CWD, and 2 elk with no clinical signs of disease. All animals were diagnosed with CWD following postmortem examination of brain and lymphoid tissues. The rectal biopsy procedure is easy and rapid to perform. The procedure may be suitable as a live animal test as part of an integrated strategy to manage CWD.
Technical Abstract: Chronic wasting disease is a transmissible spongiform encephalopathy or TSE of deer and elk in North America. All diseases in this family are characterized by long preclinical incubation periods following by a relatively short clinical course. The abnormal isoform of the normal cellular prion protein accumulates in the lymphoid tissues of most infected elk during the preclinical period. Biopsy sampling of peripheral lymphoid tissue has proven to be useful in identifying sheep in the preclinical stage of the ovine TSE scrapie and has shown potential in diagnosing chronic wasting disease in farmed white tailed deer. In this study, we evaluated the rectal mucosal lymphoid tissue biopsy procedure for early detection of chronic wasting disease in farmed Rocky Mountain elk, Cervus elaphus nelsoni. Forty elk from a quarantined infected herd were sampled; biopsy tissue was analyzed using monoclonal antibody based immunohistochemistry. Positive samples were identified in one clinical animal and two preclinical animals; chronic wasting disease was confirmed in these three animal following necropsy. The remaining elk will be sampled at intervals to estimate the sensitivity of the assay and to monitor the reduction in lymphoid follicle count in elk as they age. Rectal lymphoid tissue biopsy is relatively easy to perform on farmed elk and may be suitable as a live animal diagnostic test as part of an integrated strategy to manage chronic wasting disease in farmed herds.