Browsing by Author "Smith, Katrin"

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    The evaluation and validation of cell-mediated immunological responses for the improved detection of Mycobacterium bovis infection in African buffaloes (Syncerus caffer)
    (Stellenbosch : Stellenbosch University, 2020-12) Smith, Katrin; Miller, Michele; Goosen, Wynand; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences.
    ENGLISH ABSTRACT: Mycobacterium bovis infection and the resulting bovine tuberculosis (bTB) disease affects a broad range of mammals including domestic animals, wildlife and humans. The presence of global wildlife maintenance hosts impedes efforts to control M. bovis transmission and bTB. African buffaloes (Syncerus caffer) are reservoir hosts of M. bovis in South Africa and thus pose a threat to multiple other wildlife species, adjacent livestock and their respective communities. Therefore, the efficient and early detection of M. bovis-infected buffaloes can help to minimize the spread of M. bovis and bTB disease. Considering that current standard bTB screening tools for buffaloes remain suboptimal, and in-field application presents several limitations, the validation of more optimal and approved diagnostic tools for M. bovis and bTB testing is required. This project investigated three such approaches to enhancing M. bovis detection in buffaloes. Firstly, the tuberculin skin test (TST), the primary ante mortem diagnostic tool for M. bovis detection in South Africa, was investigated for species-specific use. Buffalo specific cut-off values were calculated for the first time and TST test performance parameters evaluated, using a well-defined negative cohort and a gold standard positive cohort. The results present evidence for current South African guidelines for TST interpretation in buffaloes, in addition to providing alternative recommendations as required for different bTB testing scenarios. Moreover, the high specificity (Sp) yet suboptimal sensitivity (Se) of the TST was demonstrated, reiterating the necessity for additional tests to increase detection of infected animals. The most widely used ancillary test to the TST is the interferon-gamma (IFN-γ) release assay (IGRA). The second section of this project validated the new commercial Mabtech ELISAPRO bovine IFN-γ enzyme-linked immunosorbent assay (ELISA) that demonstrated promising test performance, with buffalo-specific cut-off values, in an IGRA using the QuantiFERON® TB-Gold Plus (QFT-Plus) stimulation platform and cohorts as described above. Furthermore, the QFT-Plus/Cattletype® IGRA, previously validated for buffalo use, was compared with the Mabtech IGRA after calculating species specific cut-off values to replace the manufacturer’s cattle threshold value. This served to significantly enhance Se. Finally, as a novel approach to in vitro measurement of cell-mediated immune responses to M. bovis, a MILLIPLEX® bovine cytokine/chemokine multiplex assay was investigated for use in buffaloes. The results demonstrated the detection of all fifteen target biomarkers with significant differences observed between mitogen-stimulated and/or antigen-stimulated, and unstimulated plasma samples in M. bovis-infected buffaloes. Overall, the results from this project reveal the importance of species-specific validation of diagnostic tests intended for field use. For wildlife species this is particularly challenging, and relevant positive and negative reference samples are not always readily available. Furthermore, the optimisation of current (and candidate) tests, as demonstrated in this project for the TST and IGRAs, should be performed in line with official validation standards (when possible). This will better enable the recognition and in-field application of enhanced and promising diagnostic tools for improved detection of M. bovis infection in African buffaloes.
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    Novel molecular transport medium used in combination with Xpert MTB/RIF ultra provides rapid detection of Mycobacterium bovis in African buffaloes
    (Nature Research (part of Springer Nature), 2021) Clarke, Charlene; Smith, Katrin; Goldswain, Samantha J.; Helm, Christopher; Cooper, David V.; Kerr, Tanya J.; Kleynhans, Leanie; Van Helden, Paul D.; Warren, Robin M.; Miller, Michele A.; Goosen, Wynand J.
    ENGLISH ABSTRACT: Mycobacterium bovis is the causative agent of bovine tuberculosis (bTB) in wildlife. Confirmation of M. bovis infection relies on mycobacterial culture, which is time-consuming. Collection and transportation of infectious material also pose a human health risk. PrimeStore Molecular Transport Medium (MTM) has been shown to effectively inactivate infectious organisms, making it a safe method for handling infectious samples. This study investigated an in-field sampling technique for rapid, safe detection of M. bovis in buffalo tissues. Potentially infected tissues from bTB test-positive buffaloes were swabbed at post-mortem examination and stored in PrimeStore MTM at ambient temperature until Xpert MTB/RIF Ultra testing was performed. Additionally, tissue samples were frozen and transported before homogenisation for culture and Ultra testing. Oral swabs were collected from M. bovis-unexposed buffaloes as a negative control cohort. Mycobacterium tuberculosis complex (MTBC) DNA was detected by Ultra in 13/16 tissue swabs and 9/16 matched tissue homogenates from culture-confirmed M. bovis-positive buffalo tissues. MTBC DNA was not detected in swabs from M. bovis-unexposed animals, showing the potentially high specificity of Ultra with PrimeStore swabs. PrimeStore MTM sample processing, in combination with the Ultra assay, has the potential to provide a safe, rapid post-mortem screening test for M. bovis in buffaloes.
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    Review of diagnostic tests for detection of mycobacterium bovis infection in South African wildlife
    (Frontiers Media S.A, 2021-01) Bernitz, Netanya; Kerr, Tanya J.; Goosen, Wynand J.; Chileshe, Josephine; Higgitt, Roxanne L.; Roos, Eduard O.; Meiring, Christina; Gumbo, Rachiel; De Waal, Candice; Clarke, Charlene; Smith, Katrin; Goldswain, Samantha; Sylvester, Taschnica T.; Kleynhans, Léanie; Dippenaar, Anzaan; Buss, Peter E.; Cooper, David V.; Lyashchenko, Konstantin P.; Warren, Robin M.; Van Helden, Paul D.; Parsons, Sven D. C.; Miller, Michele A.
    Wildlife tuberculosis is a major economic and conservation concern globally. Bovine tuberculosis (bTB), caused byMycobacteriumbovis (M. bovis), is themost common form of wildlife tuberculosis. In South Africa, to date, M. bovis infection has been detected in 24 mammalian wildlife species. The identification of M. bovis infection in wildlife species is essential to limit the spread and to control the disease in these populations, sympatric wildlife species and neighboring livestock. The detection of M. bovis-infected individuals is challenging as only severely diseased animals show clinical disease manifestations and diagnostic tools to identify infection are limited. The emergence of novel reagents and technologies to identify M. bovis infection in wildlife species are instrumental in improving the diagnosis and control of bTB. This review provides an update on the diagnostic tools to detect M. bovis infection in South African wildlife but may be a useful guide for other wildlife species.