Detection of Mycobacterium bovis infection in African buffaloes (Syncerus caffer) using QuantiFERON-TB Gold (QFT) tubes and the Qiagen cattletype IFN-gamma ELISA.

African buffaloes (Syncerus caffer) are wildlife maintenance hosts of Mycobacterium bovis, the cause of bovine tuberculosis. Consequently, M. bovis infected buffaloes pose a transmission risk for cattle and other wildlife species. Previously, a modification to the Qiagen QuantiFERON-TB Gold (QFT) system, using QFT tubes and an in-house bovine interferon-gamma (IFN-γ) ELISA, was evaluated for the detection of M. bovis infection in buffaloes. Subsequently, Qiagen has developed a commercially available cattletype IFN-gamma ELISA for the detection of antigen-specific IFN-γ release in ruminants. The aim of this study was to investigate the use of QFT tubes and the cattletype IFN-gamma ELISA, in a cattletype IFN-γ release assay (IGRA), to detect M. bovis infection in African buffaloes. The test agreements between the cattletype IGRA, single comparative intradermal skin test (SCITT) and Bovigam 1G IGRA in two M. bovis-exposed buffalo populations (n = 134 and n = 92) were calculated and κ coefficients ranged from 0.65 (95% CI 0.48-0.82) to 0.86 (95% CI 0.72-0.99). Increasing the QFT incubation time in one M. bovis-exposed buffalo cohort (n = 92), from 20 to 40 h, had no effect on the cattletype IGRA test results. Inter-assay and intra-assay reproducibility determination for the cattletype IGRA produced coefficient of variations (CV) <9.1% and <1.7%, respectively. A total of 21/21 known M. bovis-unexposed buffaloes tested negative in the cattletype IGRA. Moreover, the cattletype IGRA test result values were significantly greater for 13 M. bovis culture-positive buffaloes compared with 14 M. bovis-exposed culture-negative (P < .01) and 21 M. bovis-unexposed (P < .001) buffaloes, respectively. These findings suggest that the combination of QFT tubes and the cattletype IFN-gamma ELISA is a promising new diagnostic assay for the detection of M. bovis infection in African buffaloes. However, further research is needed to evaluate the sensitivity and specificity of the assay in larger African buffalo populations.