Epidemiology and Diagnostic Testing of Tuberculosis (Mycobacterium bovis) Infection in Ungulates in a Texas Zoo

Tuberculosis infection among ungulates with Mycobacterium bovis (M. bovis) in a Texas zoo resulted in epidemiological assessment and testing of 161ungulates because of concerns about the validity of tuberculosis infection in the zoo. Three intradermal tests and one serological test were used to assess M.bovis infection : 1)the comparative cervical tuberculin test (CCT) consisting of biologically balanced bovine purified protein derivative (PPD) and avian PPD; 2) the single cervical bovine PPD tuberculin (BPDD); 3) the Tuberculin-Mammalian (MOT) intradermal tuberculin; and 4) the serological blood tuberculosis test (BTB). All four tests were evaluated. Validity (i.e. sensitivity and specificity), positive predictive value (PPV), and negative predictive value (NPV) were measured. The MOT followed by the BPPD were the most sensitive tests, correctly identifying 100% and 67%, respectively of tuberculosis infected/exposed ungulates. The BTB test was the third order of recommendation followed by the combined CCT and BTB (CCT+BTB) tests, where a positive result in either test denoted a positive response. The CCT test ranked last, as this test had the lowest sensitivity and would have allowed tuberculosis infection to remain in the zoo.