Browsing by Author "Gumbo, Rachiel"

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    Adaptation and diagnostic potential of a commercial cat interferon gamma release assay for the detection of Mycobacterium bovis infection in African lions (Panthera leo)
    (MDPI, 2022-07) Gumbo, Rachiel; Sylvester, Tashnica T.; Goosen, Wynand J.; Buss, Peter E.; De Klerk-Lorist, Lin-Mari; Van Schalkwyk, O. Louis; McCall, Alicia; Warren, Robin M.; Van Helden, Paul D.; Miller, Michele A.; Kerr, Tanya J.
    Mycobacterium bovis (M. bovis) infection in wildlife, including lions (Panthera leo), has implications for individual and population health. Tools for the detection of infected lions are needed for diagnosis and disease surveillance. This study aimed to evaluate the Mabtech Cat interferon gamma (IFN-γ) ELISABasic kit for detection of native lion IFN-γ in whole blood samples stimulated using the QuantiFERON® TB Gold Plus (QFT) platform as a potential diagnostic assay. The ELISA was able to detect lion IFN-γ in mitogen-stimulated samples, with good parallelism, linearity, and a working range of 15.6–500 pg/mL. Minimal matrix interference was observed in the recovery of domestic cat rIFN-γ in lion plasma. Both intra- and inter-assay reproducibility had a coefficient of variation less than 10%, while the limit of detection and quantification were 7.8 pg/mL and 31.2 pg/mL, respectively. The diagnostic performance of the QFT Mabtech Cat interferon gamma release assay (IGRA) was determined using mycobacterial antigen-stimulated samples from M. bovis culture-confirmed infected (n = 8) and uninfected (n = 4) lions. A lion-specific cut-off value (33 pg/mL) was calculated, and the sensitivity and specificity were determined to be 87.5% and 100%, respectively. Although additional samples should be tested, the QFT Mabtech Cat IGRA could identify M. bovisinfected African lions.
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    Detection of host and pathogen biomarkers for Mycobacterium bovis infection in African big cats (lions (Panthera leo), leopards (Panthera pardus), cheetahs (Acinonyx jubatus))
    (Stellenbosch : Stellenbosch University, 2023-12) Gumbo, Rachiel; Miller, Michele Ann; Kerr, Tanya Jane; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Molecular Biology and Human Genetics.
    ENGLISH ABSTRACT: Animal tuberculosis (animal TB) is a chronic disease caused by infection with Mycobacterium bovis (M. bovis). In South Africa, animal TB affects many of the country’s most iconic wildlife species including leopards (Panthera pardus), African lions (Panthera leo), and cheetahs (Acinonyx jubatus), and therefore poses a risk to both ecotourism and conservation. Although the overall impact on wildlife populations is unknown, this disease has resulted in historic and recent deaths of cheetahs, lions, and leopards in South Africa. The development of speciesspecific immunological tests for diagnosis of animal TB in wild felids has so far been relatively limited. Therefore, the development of accurate antemortem tests for TB screening and diagnosis of M. bovis infection in African big cat populations is urgently required. The overall goal of this study was to identify host and pathogen biomarkers that can be used to detect M. bovis infection in cheetahs, African lions, and leopards. This was achieved by 1) using conventional mycobacterial culture and GeneXpert® MTB/RIF Ultra (GXU) qPCR for confirmation of M. bovis infection, 2) identification of potential cytokines associated with cellmediated immune (CMI) activation and detection of M. bovis sensitization using cheetah, lion, and leopard stimulated whole blood, and 3) evaluation of serological assays for M. bovis detection. Mycobacterium bovis-infected cheetahs, lions, and leopards were identified using conventional mycobacterial culture and compared with rapid results for Mycobacterium tuberculosis complex (MTBC) diagnosis that were obtained using GXU® qPCR assay. A cytokine release assay (CRA) that can distinguish between M. bovis-infected and uninfected cheetahs, leopards, and lions, using commercially available feline cytokine ELISAs with QuantiFERON® -TB Gold Plus (QFT) stimulated plasma, was developed, and partially validated in African lions. Provisional specific interferon gamma release assay (IGRA) cut-off values, for M. bovis detection in lions and cheetahs, were calculated. The findings in this study suggested that a chemokine C-X-C motif ligand 9 (CXCL9) gene expression assay (GEA), previously designed for use in African lions, showed promise as a tool for detection of both general immune activation and M. bovis immune sensitization in leopards. Although a serological test (DPP® ) used for measurement of humoral response in this study was not sensitive, CMI response-based tests, including the tuberculin skin test (TST), showed potential as antemortem screening tests for wild felids and should be further explored. The incorporation of diagnostic tools into surveillance and routine screening of wild felids for health assessment or as translocation candidates will improve TB detection and prompt management changes to prevent spread of infection and enhance disease control, especially in vulnerable populations.
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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.