Study on supplemental test to improve the detection of bovine tuberculosis in individual animals and herds.

Background: Bovine tuberculosis (bTB), is a worldwide disease caused by Mycobacterium bovis (M. bovis). The success of bTB eradication and control programs is based on early detection and the removal of reactors from a herd thus routine testing and cull strategy have been applied globally. Since the late nineteenth century, the Tuberculin Skin Test (TST) has been the primary antemortem test available to support bTB eradication campaigns. Due to the TST limitations in terms of Se and Sp, the credibility of the diagnosis is frequently questioned given the occurrence of false-positive and false-negative reactions, therefore, it is necessary to confirm reactive animals using other methods, ensuring the reliability of the diagnosis. The aim of this study was to evaluate the sensitivity and specificity of a multiplex enzyme-linked immunosorbent assay (ELISA) relative to the tuberculin test used for the diagnosis of tuberculosis in cattle in Brazil.

Results: Lack of agreement between comparative cervical tuberculin test and ELISA IDEXX TM was observed. The 2 animals positive on the comparative cervical tuberculin test did not react at the ELISA IDEXX TM and 22 negative reactors by comparative cervical tuberculin test were positive by the ELISA IDEXX TM. The ELISA IDEXX TM showed sensitivity that is significantly lower than the official screening test the single cervical tuberculin. ELISA IDEXX TM also detected infected animals and herds undetected by the comparative cervical tuberculin test. The parallel use of comparative cervical tuberculin test and ELISA IDEXX TM increased sensitivity and the feasibility bTB screening.

Conclusions: The results obtained here suggest that the ELISA IDEXX TM may be a supplemental test for the detection of Mycobacterium bovis infection in regions without routine testing and slaughter, where the disease generally progresses to more advanced stages and antibody responses are likely to be more prevalent. Evidence to support the validation of the ELISA IDEXX™ as a supplemental test for bTB eradication programs was provided.