Submitted to: United States Animal Health Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/9/2003
Publication Date: 10/9/2003
Citation: Waters, W.R., Palmer, M.V., Stoffregen, W.C., Whipple, D.L., Slaughter, R., Jones, L.L., Pitzer, J.E., Minion, F.C. 2003. Experimental infection of reindeer (rangifer tarandus) with mycobacterium bovis: diagnostic implications. Proceedings of the United States Animal Health Association. p.569-576.
Technical Abstract: Reindeer (Rangifer tarandus) are routinely tested for tuberculosis by the comparative cervical test (CCT, a measure of delayed type hypersensitivity) as outlined in the USDA Uniform Methods and Rules for the eradication of bovine tuberculosis. The CCT, however, has an apparent lack of specificity for tuberculosis surveillance. Establishment of criteria for disposition of the CCT and other tests is hindered by a lack of confirmed Mycobacterium bovis-infected reindeer. Our objective was to evaluate and compare the CCT and an in vitro blood-based assay using experimentally infected reindeer. Treatment groups included: M. bovis-infected (n = 11, strain 95-1315 intratonsillarly), M. bovis BCG-vaccinated (n = 7, Pasteur strain subcutaneously), and naive reindeer (n = 12). CCT was performed 90 days after challenge or booster vaccination. Using USDA criteria, 11/11 infected reindeer were reactors; 4/7, 2/7, and 1/7 vaccinated reindeer and 1/12, 7/12, and 4/12 naïve reindeer were reactors, suspects, or considered negative, respectively. As early as 90 d postchallenge, mean mycobacteria-specific IFN-g responses by mononuclear cells from M. bovis-infected reindeer exceeded (P < 0.05) those of both BCG-vaccinated and naïve reindeer. As with the CCT, positive IFN-g responses [(i.e., no stimulation minus antigen stimulation > 0.1 optical density (D OD)] to crude mycobacterial antigens [i.e., M. bovis purified protein derivative (PPDb)] were also detected for a few naïve reindeer. ESAT-6 and CFP-10 are proteins expressed by tuberculosis complex Mycobacteria spp., but not by M. bovis BCG and most other non-tuberculous Mycobacteria spp. With a cutoff value of 0.1 D OD, 11/11 infected reindeer were determined positive using PPDb, recombinant CFP-10, and recombinant ESAT-6:CFP-10 whereas 3/4, 1/4, and 1/4 naïve reindeer were determined positive using PPDb, CFP-10 or recombinant ESAT-6:CFP-10 antigens, respectively. Concerning diagnosis of tuberculous reindeer, present findings indicate: (1) the current criteria for interpretation of the CCT results in numerous false positives, (2) a blood-based IFN-g assay may prove useful for tuberculosis diagnosis, and (3) use of recombinant CFP-10 or ESAT-6:CFP-10 antigens enhances the specificity of the IFN-g assay.