Comparison of postmortem techniques for the detection of Mycobacterium bovis in white-tailed deer (Odocoileus virginianus)

A retrospective study of various diagnostic postmortem techniques used in a 4-year surveillance program for detection of Mycobacterium bovis infection in wild white-tailed deer (Odocoileus virginianus) was conducted. The test s evaluated were routine histopathology, acid-fast staining, detection of a cid-fast bacilli in culture, and an M. tuberculosis group-specific genetic probe applied to pure cultures. Each of these techniques were compared with a reference or "gold standard" of mycobacterial culture and identification . Histopathology, the most rapid form of testing for M. bovis infection in white-tailed deer samples, had a sensitivity of 98% and a specificity of 87 %, resulting in a positive predictive value of 94%. The detection of acid-f ast bacilli by staining was less sensitive than histopathology (90%), but i ts higher specificity (97%) resulted in a positive predictive value of 99%. The detection of acid-fast bacilli on culture was both highly specific (93 %) and sensitive (100%). The group-specific genetic probe had the highest s ensitivity and specificity and produced results in complete agreement with those of mycobacterial culture, suggesting that this technique could be use d as the new "gold standard" for this particular wildlife tuberculosis surv eillance program.