AUTHOR=Gumbo Rachiel , Goosen Wynand J. , Buss Peter E. , de Klerk-Lorist Lin-Mari , Lyashchenko Konstantin , Warren Robin M. , van Helden Paul D. , Miller Michele A. , Kerr Tanya J. 

TITLE=“Spotting” Mycobacterium bovis infection in leopards (Panthera pardus) – novel application of diagnostic tools

JOURNAL=Frontiers in Immunology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1216262

DOI=10.3389/fimmu.2023.1216262

ISSN=1664-3224

ABSTRACT=<sec><title>Background</title><p><italic>Mycobacterium bovis</italic> (<italic>M. bovis</italic>) is the causative agent of animal tuberculosis (TB) which poses a threat to many of South Africa’s most iconic wildlife species, including leopards (<italic>Panthera pardus</italic>). 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 <italic>M. bovis</italic> infection in leopards.</p></sec><sec><title>Methods</title><p>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<sup>®</sup> MTB/RIF Ultra (GXU<sup>®</sup>) qPCR assay, mycobacterial culture, and speciation by genomic regions of difference PCR, was used to confirm <italic>M. bovis</italic> infection in leopards.</p></sec><sec><title>Results</title><p><italic>Mycobacterium bovis</italic> infection was confirmed in six leopards and individuals that were tuberculin skin test (TST) negative were used for comparison. The GXU<sup>®</sup> assay was positive using all available tissue homogenates (n=5) from <italic>M. bovis</italic> culture positive animals. <italic>Mycobacterium bovis</italic> culture-confirmed leopards had greater antigen-specific responses, in the QFT interferon gamma release assay, <italic>CXCL9</italic> and <italic>CXCL10</italic> gene expression assays, compared to TST-negative individuals. One <italic>M. bovis</italic> culture-confirmed leopard had detectable antibodies using the DPP<sup>®</sup> Vet TB assay.</p></sec><sec><title>Conclusion</title><p>Preliminary results demonstrated that immunoassays and TST may be potential tools to identify <italic>M. bovis</italic>-infected leopards. The GXU<sup>®</sup> 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.</p></sec>