Use of the intradermal tuberculin test in a herd of captive elk (Cervus elaphus nelsoni) naturally infected with Mycobacterium bovis.

ABSTRACT

In the United States, tuberculosis of captive cervids, caused by Mycobacterium bovis, attracted attention in 1991 when investigations, prompted by the identification of a tuberculous elk (Cervus elaphus nelsoni) of U.S. origin exported to Canada, revealed tuberculosis in 10 different elk herds in 8 different states. Based on methods used in cattle, official regulations pertaining to testing and eradication of tuberculosis in captive cervids were added to the U.S. Department of Agriculture bovine tuberculosis eradication effort in 1994. However, little published information exists on the accuracy of intradermal tuberculin testing in naturally infected cervids. Evaluation of a captive herd of 71 animals in Wisconsin included postmortem examination and tissue sample collection from both tuberculin test responders and nonresponders. Within this captive herd, of admittedly small size, results showed the single cervical test to have a sensitivity of 88% and a specificity of 69%. Evaluation of diagnostic tests in the species of interest is important, as extrapolation of data obtained from other species may not be appropriate.