Detection of native interferon-&gamma; in nyala (Tragelaphus angasii): Towards diagnosing tuberculosis

Roux, Lezaan; McCall, Alicia J.; Michel, Anita L.

Detection of native interferon-γ in nyala (Tragelaphus angasii): Towards diagnosing tuberculosis

2019

Roux, Lezaan(University of Pretoria Faculty of Veterinary Science Department of Veterinary Tropical Diseases, Bovine Tuberculosis and Brucellosis Research Programme) | McCall, Alicia J.(Veterinary Services Department of Agriculture and Rural Development) | Michel, Anita L.(University of Pretoria Faculty of Veterinary Science Department of Veterinary Tropical Diseases, Bovine Tuberculosis and Brucellosis Research Programme)

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.

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