Optimisation of the tuberculin skin test for detection of Mycobacterium bovis in African buffaloes (Syncerus caffer)

• Published in: Preventive veterinary medicine 2021-03, Vol.188, p.105254-105254, Article 105254
• Main Authors: Smith, Katrin, Bernitz, Netanya, Cooper, David, Kerr, Tanya J., de Waal, Candice R., Clarke, Charlene, Goldswain, Samantha, McCall, Warren, McCall, Alicia, Cooke, Debbie, Rambert, Emma, Kleynhans, Léanie, Warren, Robin M., van Helden, Paul, Parsons, Sven D.C., Goosen, Wynand J., Miller, Michele A.
• Format: Article
• Language: English
• Subjects: African buffaloes; Bovine tuberculosis; Cut-off values; Mycobacterium bovis; Single intradermal comparative tuberculin test; Single intradermal tuberculin test
• ISSN: 0167-5877; 1873-1716
• DOI: 10.1016/j.prevetmed.2020.105254

•Species-specific 3 mm cut-off for TST best identifies M. bovis-infected buffaloes.•Confirms suitability of current buffalo recommendation (3 mm) in South Africa.•The comparative TST performs better than the single intradermal tuberculin test.•Species-specific cut-off values improve TST performance.•Despite high specificity (86–97 %), sensitivity of TST remains suboptimal (69–76 %). Effective screening methods are critical for preventing the spread of bovine tuberculosis (bTB) among livestock and wildlife species. The tuberculin skin test (TST) remains the primary test for bTB globally, although performance is suboptimal. African buffaloes (Syncerus caffer) are a maintenance host of Mycobacterium bovis in South Africa, tested using the single intradermal tuberculin test (SITT) or comparative test (SICTT). The interpretation of these tests has been based on cattle thresholds due to the lack of species-specific cut-off values for African buffaloes. Therefore, the aims of this study were to calculate buffalo-specific thresholds for different TST criteria (SITT, SICTT, and SICTT72h that calculates the differential change at 72 h only) and compare performance using these cut-off values. The results confirm that 3 mm best discriminates M. bovis-infected from unexposed control buffaloes with sensitivities of 69 % (95 % CI 60–78; SITT and SICTT) and 76 % (95 % CI 65–83; SICTT72h), and specificities of 86 % (95 % CI 80–90; SITT), 96 % (95 % CI 92–98; SICTT72h) and 97 % (95 % CI 93–99; SICTT), respectively. A comparison between TST criteria using buffalo-specific thresholds demonstrates that the comparative TST performs better than the SITT, although sensitivity remains suboptimal. Therefore, further research and the addition of ancillary tests, such as cytokine release assays, are necessary to improve M. bovis detection in African buffaloes.