Browsing by Author "Hofmeyr, Jennifer"

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    Genetic diversity, genetic structure, and scale of dispersal in Kruger National Park Lions (Panthera leo); implications for management and conservation.
    (2022-04) Hofmeyr, Jennifer; Hoal, Eileen; Matthee, Conrad A.; van Coeverden de Groot, Peter; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Molecular Biology and Human Genetics.
    ENGLISH ABSTRACT: The African lion is currently classified as vulnerable in the IUCN Red List of Threatened species (Bauer et al. 2016). The KNP lion population is by far the largest free-ranging South African lion population and therefore it is of great importance for lion conservation and management to describe the processes that maintain their genetic diversity patterns. General diversity is important to maintain the ability of a population to respond to changing climate ensuring their survival. With this work, I contribute new quantitative genetic data allowing novel demographic inferences for the Kruger National Park (KNP) lion (Panthera leo) population which can be used in their ongoing management. Analysis was done on 158 lion samples using 11 dinucleotide microsatellite markers for the full data set and then for comparison between geographic regions within the park (north and south), sexes, and temporal sampling (one year with large sample size). Results were compared to two other studies, (Miller et al. 2014; van Hooft et al. 2018) conducted using samples from KNP and lion studies done on other large lion populations in Tanzania, Zimbabwe, and Namibia (Spong et al. 2002; Morandin et al. 2014; Lyke et al. 2013; Tensen et al. 2018). The KNP lion population showed moderate variability and weak to moderate genetic structure with low to moderate levels of gene flow across the park, with an FST of 0.055 (P≤0.05), inbreeding coefficient (FIS) of 0.488 (P≤0.05) (heterozygote deficiency), and overall inbreeding coefficient of individual relative to the total population (FIT) of 0.516 (P≤0.05). The mean expected heterozygosity (He) (0.619) and mean observed heterozygosity (Ho) (0.409), for the KNP lion population show moderate to low diversity levels with a fixation index of 0.299. Spatially explicit analysis was done using TESS version 2.3 (Durand et al. 2009), resulting in two genetic groups I complete the first comprehensive study of scale of dispersal within KNP lions via spatial autocorrelation and compare the full dataset, large sampling year (2010 set), and males to females. The results indicate that individuals 100 to 150km apart are not closely related. For the 2010 samples, a higher positive autocorrelation coefficient (r) was found for individuals within 100km. The full data set for males show no strong spatial autocorrelation but when sampling in 2010 only a positive spatial autocorrelation was detected between individuals at 100km. Female autocorrelation is strong <50km at zero autocorrelation persisted beyond +/- 90km in all analyses with the 2010 set indicating stronger positive autocorrelation in the <50km class. Recommendations include maintaining connectivity and corridors with neighbouring countries, ensuring habitat expansion efforts are continued and allowing for dispersal. Non-invasive sampling and genotyping could facilitate extensive near-simultaneous sampling of KNP leading to more precise and accurate genetic structuring and dispersal estimates of KNP lions. The advent of these non-invasive technologies means one can relatively easily characterise the recolonisation dynamic of other Great Limpopo Transfrontier Park (GLTP) areas.
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    The kinetics of the humoral and interferon-gamma immune responses to experimental Mycobacterium bovis infection in the white rhinoceros (Ceratotherium simum)
    (Frontiers, 2017-12) Parsons, Sven D. C.; Morar-Leather, Darshana; Buss, Peter E.; Hofmeyr, Jennifer; McFadyen, Ross; Rutten, Victor P. M. G.; Van Helden, Paul D.; Miller, Michele Ann; Michel, Anita Luise
    ENGLISH ABSTRACT: Mycobacterium bovis is the cause of tuberculosis (TB) in a wide range of species, including white rhinoceroses (Ceratotherium simum). Control of the disease relies on the indirect detection of infection by measuring pathogen-specific responses of the host. These are poorly described in the white rhinoceros and this study aimed to characterize the kinetics of immune responses to M. bovis infection in this species. Three white rhinoceroses were infected with M. bovis and their immune sensitization to this pathogen was measured monthly for 20 months. Cell-mediated immunity was characterized in whole blood samples as the differential release of interferon-gamma in response to bovine purified protein derivative (PPDb) and avian PPD (PPDa) as well as the release of this cytokine in response to the M. bovis proteins 6 kDa early secretory antigenic target (ESAT-6)/10 kDa culture filtrate protein (CFP-10). Humoral immunity was quantified as the occurrence or the magnitude of antibody responses to the proteins ESAT-6/CFP-10, MPB83, MPB83/MPB70, and PPDb. The magnitude and duration of immune reactivity varied between individuals; however, peak responses to these antigens were detected in all animals circa 5–9 months postinfection. Hereafter, they gradually declined to low or undetectable levels. This pattern was associated with limited TB-like pathology at postmortem examination and appeared to reflect the control of M. bovis infection following the development of the adaptive immune response. Measurement of these markers could prove useful for assessing the disease status or treatment of naturally infected animals. Moreover, immune responses identified in this study might be used to detect infection; however, further studies are required to confirm their diagnostic utility.