Abstract:
Mycobacterium bovis is the main cause of tuberculosis in wildlife. In South Africa, African
buffaloes (Syncerus caffer) are a wildlife maintenance host while a number of other species are
considered spillover hosts. Nyala (Tragelaphus angasii), a large antelope species from Southern
Africa, is frequently traded and can be infected with M. bovis. Interferon gamma (IFN-γ) release
assays that detect cell-mediated immune (CMI) responses to M. bovis infection have shown
promise in elephants, rhinoceroses and buffaloes. The BOVIGAM® assay is a commercial
IFN-γ release assay designed to detect tuberculosis in cattle and has been validated in buffaloes.
We tested the suitability of the BOVIGAM® assay to detect native IFN-γ release in nyala. Blood
samples collected from 17 nyalas were stimulated with different mitogens and IFN-γ release
measured. We found that incubating whole blood with phorbol 12-myristate 13-acetate and
calcium ionophore (PMA/CaI) resulted in the highest levels of IFN-y release. Samples
stimulated with tuberculin purified protein derivatives of M. bovis (PPDb) and M. avium
(PPDa) did not show significant IFN-γ production. An intradermal tuberculin test (IDT) and
culture of tissues from 15 of the 17 culled nyala were also performed, which supported the
findings of the BOVIGAM® assay, suggesting the potential value of this assay for the diagnosis
of tuberculosis in nyala.
