Comparison of Retropharyngeal Lymph Node and Obex Region of the Brainstem in Detection of Chronic Wasting Disease in White-Tailed Deer (Odocoileus Virginianus)

Abstract

Chronic wasting disease (CWD) in Wisconsin was first identified in February 2002. By April 2005, medial retropharyngeal lymph node (RLN) tissues had been examined from over 75,000 white-tailed deer for the presence of CWD by either immunohistochemical (IHC) staining for the prion protein associated with CWD (PrP(res)) or by using enzyme-linked immunosorbent assays with confirmation of positives by IHC staining and had been detected in 469 animals. Obex tissue was also available from 438 of the CWD-positive animals and was CWD positive by IHC staining in 355 (81%). To verify whether false-negative results were possible examining only RLN, both obex and RLN samples were examined for CWD by IHC staining from 4,430 of the white-tailed deer harvested from an area in Wisconsin where the overall deer CWD prevalence was approximately 6.2%. Two hundred and fourteen of the 269 positive deer (79.6%) had deposits of PrP(res) in both obex and lymphoid tissues, 55 (20.4%) had deposits only in lymphoid tissue, and there were no deer that had deposits only in obex.

Effects of Chronic Wasting Disease on Reproduction and Fawn Harvest Vulnerability in Wisconsin White-Tailed Deer

“…Based on this progression, the approximate stage of infection at harvest was determined for each CWDinfected animal as follows: 1) accumulation of PrP CWD in lymph node tissue only (henceforth referred to as lymph only); 2) accumulation of PrP CWD in lymph node tissue and the dorsal motor nucleus of the vagal nerve, but not in surrounding tissue (henceforth referred to as obex +); or 3) accumulation of PrP CWD in lymph node and throughout the obex (henceforth referred to as obex ++). Obex + is equivalent to obex scores 1 and 2; obex ++ is equivalent to obex scores 3 and 4 of Keane et al (2008a). To our knowledge, none of the CWD-positive deer in our study exhibited clinical signs of disease.…”

“…Retropharyngeal lymph nodes and the obex portion of the brainstem for all adults were sent to the Wisconsin Veterinary Diagnostic Laboratory, where CWD-infection status was determined using immunohistochemistry (Johnson et al, 2006;Keane et al, 2008a). A deer was determined to be CWD-positive at harvest if abnormal prions (PrP CWD ) were detected in lymph nodes or obex.…”

“…A deer was determined to be CWD-positive at harvest if abnormal prions (PrP CWD ) were detected in lymph nodes or obex. In whitetailed deer, PrP CWD accumulates in retropharyngeal lymph nodes prior to invasion and accumulation in the central nervous system (Keane et al, 2008b). Based on this progression, the approximate stage of infection at harvest was determined for each CWDinfected animal as follows: 1) accumulation of PrP CWD in lymph node tissue only (henceforth referred to as lymph only); 2) accumulation of PrP CWD in lymph node tissue and the dorsal motor nucleus of the vagal nerve, but not in surrounding tissue (henceforth referred to as obex +); or 3) accumulation of PrP CWD in lymph node and throughout the obex (henceforth referred to as obex ++).…”

“…We conducted analyses separately for candidate female parents and candidate male parents. Because retrospective determination of CWD status is partly subjective and Prnp genotype or dose may be related to the rate of disease accumulation in the obex (Johnson et al, 2006;Keane et al, 2008a), we also conducted these analyses using only candidate parents and fawns harvested during the 2002 season. We were most confident in our classifications of infection status of these deer at breeding (i.…”

Metals in obex and retropharyngeal lymph nodes of Illinois white-tailed deer and their variations associated with CWD status

“…3,4 Obex and retropharyngeal lymph nodes (RLN) are important tissues for CWD diagnosis, as PrP Sc is detectable in both tissues even at sub-clinical stages of CWD. 5 PrP C can be found throughout the body with higher concentrations at presynaptic membranes in the central nervous system (CNS). The exact physiological roles of PrP C are still under investigation, but many studies have suggested its participation in the metabolism of metals and its role as antioxidant (superoxide dismutase (SOD)-like activity).…”