ARS | Publication request: Evaluation and interpretation of rectal mucosa biopsy testing for chronic wasting disease within four white-tailed deer (Odocoileus virginianus) herds in North America

Submitted to: J Vet Diagn Invest
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 26, 2012
Publication Date: September 1, 2012
Citation: Thomsen, B.V., Schneider, D.A., Orourke, K.I., Gidlewski, T., Mclane, J., Allen, R.W., Mcisaac, A.A., Mitchell, G.B., Keane, D.P., Spraker, T., Balachandran, A. 2012. Evaluation and interpretation of rectal mucosa biopsy testing for chronic wasting disease within four white-tailed deer (Odocoileus virginianus) herds in North America. J Vet Diagn Invest. 24(5):878-87.

Interpretive Summary: Control of prion diseases such as scrapie disease and chronic wasting disease (CWD) relies upon the use of accurate diagnostic testing methods. Biopsy of the rectal mucosa has proven to be an acceptable method of obtaining samples from live animals for the accurate diagnosis of scrapie in sheep and CWD in elk, and has shown promise for similar use in deer. The present study was a multi-national inter-agency effort to determine the diagnostic accuracy of testing based on samples obtained through biopsy of the rectal mucosa of deer and includes evaluation of over 600 white-tailed deer from 4 North American herds that were experiencing natural, subclinical CWD infection. Despite some limitation on sensitivity associated with early stage infection and with certain prion protein genotypes, it is concluded that selective use will provide regulatory veterinarians a useful live-animal method for investigating herds suspected of having subclinical CWD and with the potential of reducing the investigative costs based on current protocols.

Technical Abstract: A diagnostically accurate live-animal test is needed to assist in the control of chronic wasting disease (CWD). This study compared the diagnostic results for CWD obtained from postmortem biopsy samples of the rectal mucosa to those from conventional tissue samples (brainstem at the level of the obex, medial retropharyngeal lymph node, palatine tonsil). The study included paired tissue samples from over 600 white-tailed deer from 4 genotypically and geographically diverse herds. The diagnostic specificity for biopsy samples of the rectal mucosa was 99.8% while the overall diagnostic sensitivity between herds ranged from 63% to 100%, giving a pooled estimate of sensitivity equal to 68%. Investigation on the potential influence of deer-related factors (age, sex, genotype at PRNP codon 96) showed a negative influence of G96S polymorphism on the diagnostic sensitivity of rectal biopsy samples such that sensitivity was 76% for 96GG deer but only 42% for 96GS deer. In addition, early stage of disease progression (estimated by grading the obex for PrP-CWD accumulation) also had a negative impact on diagnostic sensitivity such that sensitivity was essentially 100% for deer with the greatest hindbrain accumulations of PrP-CWD (obex grades 3 and 4) but only ~36% for deer in which no obex accumulation of PrP-CWD was detected in the hindbrain. Thus, the selective use of live-animal biopsy of the rectal mucosa should be a valuable adjunct diagnostic method for use by regulatory veterinarians during disease investigations of CWD suspect deer herds.