Browsing by Author "Roos, Eduard Otto"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Detection and Characterization of Mycobacterial Infections Occurring in Phacochoerus africanus (Gmelin, 1788) (Common Warthog)
    (Stellenbosch : Stellenbosch University, 2018-12) Roos, Eduard Otto; Miller, Michele Ann; Parsons, Sven David Charles; Olea-Popelka, Francisco; Stellenbosch University. Faculty of Medicine and Health Science. Dept. of Biomedical Sciences: Molecular Biology and Human Genetics.
    ENGLISH ABSTRACT: Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex and the cause of bovine tuberculosis (bTB), has an extensive host range that includes livestock and wildlife. While warthogs are considered spill-over hosts for bTB, they could potentially become reservoir hosts, if conditions are favourable, i.e. increased population densities. With limited knowledge on the infection status of warthogs in South Africa and their epidemiological significance for other species, it is imperative to have readily available diagnostic tests for warthogs. Therefore, this study aimed to (i) establish reference cohorts of M. bovis-infected and uninfected warthogs; (ii) utilize these for the development and evaluation of diagnostic tools that can distinguish between infected and uninfected individuals; (iii) determine the seroprevalence of bTB in warthogs using the newly developed diagnostic tools; and (iv) characterize the genetic diversity of M. bovis isolates from warthogs. Three serological assays, i.e. the indirect PPD ELISA, the TB ELISA-VK® and the DPP® VetTB Assay, could distinguish between M. bovis-infected and uninfected warthogs with high sensitivity (75-88%) and specificity (79-89%). The overall seroprevalence from four M. bovis-endemic locations was high, i.e. 38%. Furthermore, three tests measuring the cellmediated immune responses of warthogs were developed. A cytokine release assay measuring interferon gamma induced protein 10 was able to distinguish between M. bovisinfected and uninfected warthog with a sensitivity of 68% and a specificity of 84%. The comparative intradermal tuberculin test classified 100% of culture-negative warthogs as test negative and 81% of culture-positive warthogs as test positive. Lastly, CXCL9, 10, 11, IFNG and TNFA gene expression were significantly increased in whole blood from M. bovis-infected warthogs in response to antigen stimulation, with CXCL10 showing the greatest mean fold increase. High genetic diversity of M. bovis isolates from warthogs was confirmed through spoligotyping and whole genome sequencing. Two distinct clades of M. bovis were identified by WGS, even though they shared the same spoligotype patterns This study has demonstrated that warthogs develop measurable and specific immune responses to M. bovis infection, which can be used to identify infected individuals ante-mortem. Furthermore, these tests will facilitate epidemiological studies of bTB in warthogs. With a high culture prevalence in warthogs from bTB endemic areas such as uMhkuze Nature Reserve and the Greater Kruger National Park, and high seroprevalence, warthogs seem to be highly susceptible to M. bovis infection. This suggests that warthogs may be an ideal sentinel species and strengthens the case that, under certain circumstances, they could be maintenance hosts. The genetic diversity of M. bovis isolates and the identification of two distinct clades challenges the current hypothesis that a single dominant strain circulates within a specific geographical location. Warthogs as a species should receive greater attention as potential disease maintenance hosts or as sentinels for bTB disease surveillance.