Tonsillar biopsy test for chronic wasting disease: Two sampling approaches in mule deer and white-tailed deer

Preclinical antemortem testing of deer (Odocoileus spp.) for chronic wasting disease (CWD) can be important for determining prevalence rates and removing infected individuals from wild populations. Because samples with high numbers of tonsillar follicles are likely to provide earlier detection of CWD than samples with fewer follicles, the method of obtaining follicular samples may be critical when investigating disease prevalence. Between January 2003 and January 2005, white-tailed deer (O. virginianus) in southeast and southwest Minnesota and white-tailed and mule deer (O. hemionus) in Wind Cave National Park, South Dakota, were sampled using dorso-lateral and ventral-medial approaches for collecting tonsillar follicles. We obtained significantly more follicles using a dorso-lateral (median number of follicles = 19) rather than a ventral-medial (median number of follicles = 5.5) approach. No differences were observed in collection of tonsillar follicles that were related to sex, age class, or species of deer. We recommend the dorso-lateral approach for assessing CWD prevalence in deer populations.