"Spotting" infection in leopards () - novel application of diagnostic tools.

Background: () is the causative agent of animal tuberculosis (TB) which poses a threat to many of South Africa's most iconic wildlife species, including leopards (). Due to limited tests for wildlife, the development of accurate ante-mortem tests for TB diagnosis in African big cat populations is urgently required. The aim of this study was to evaluate currently available immunological assays for their ability to detect infection in leopards.

Methods: Leopard whole blood (n=19) was stimulated using the QuantiFERON Gold Plus In-Tube System (QFT) to evaluate cytokine gene expression and protein production, along with serological assays. The GeneXpert MTB/RIF Ultra (GXU) qPCR assay, mycobacterial culture, and speciation by genomic regions of difference PCR, was used to confirm infection in leopards.

Results: infection was confirmed in six leopards and individuals that were tuberculin skin test (TST) negative were used for comparison. The GXU assay was positive using all available tissue homogenates (n=5) from culture positive animals. culture-confirmed leopards had greater antigen-specific responses, in the QFT interferon gamma release assay, and gene expression assays, compared to TST-negative individuals. One culture-confirmed leopard had detectable antibodies using the DPP Vet TB assay.

Conclusion: Preliminary results demonstrated that immunoassays and TST may be potential tools to identify -infected leopards. The GXU assay provided rapid direct detection of infected leopards. Further studies should aim to improve TB diagnosis in wild felids, which will facilitate disease surveillance and screening.