Naturally occurring tuberculosis in white-tailed deer

Objective-To determine the distribution of lesions and extent of tissues in fected with Mycobacterium bovis in a captive population of white-tailed dee r. Design-Cross-sectional study. Animals-116 captive white-tailed deer. Procedure-Deer were euthanatized, and postmortem examinations were performe d. Tissues with gross lesions suggestive of tuberculosis were collected for microscopic analysis and bacteriologic culture. Tissues from the head, tho rax, and abdomen of deer with no gross lesions were pooled for bacteriologi c culture. Tonsillar, nasal, oral, and rectal swab specimens, fecal samples , and samples of hay and pelleted feed, soil around feeding sites, and wate r from 2 natural ponds were collected for bacteriologic culture. Results-Mycobacterium bovis was isolated from 14 of 116 (12%) deer; however , only 9 of 14 had lesions consistent with tuberculosis. Most commonly affe cted tissues included the medial retropharyngeal lymph node and lung. Five of 14 tuberculous deer had no gross lesions; however, M bovis was isolated from pooled tissue specimens from the heads of each of these deer. Bacterio logic culture of tonsillar swab specimens from 2 of the infected deer yield ed M bovis. Mean (+/- SEM) age of tuberculous deer was 2.5 +/- 0.3 years (r ange, 0.5 to 6 years). Mycobacterium bovis was not isolated from feed, soil , water, or fecal samples. Conclusions and Clinical Relevance-Examination of hunter-killed white-taile d deer for tuberculosis commonly includes only the lymph nodes of the head. Results of such examinations may underestimate disease prevalence by as mu ch as 57%. Such discrepancy should be considered when estimating disease pr evalence.