Theses and Dissertations (University of Pretoria)

Permanent URI for this collectionhttp://hdl.handle.net/2263/31741

Browse

Now showing 1 - 20 of 23995

The Missional calling of the church in post-genocidal societies in diaspora : the case of the descendants of Herero survivors in Botswana
Hambira, Rupert Tjitee Isaac (University of Pretoria, 2025)
This dissertation critically examines the missional calling of the church in post- genocidal societies, focusing on the descendants of the Herero people dispersed across the Southern African diaspora, particularly in Botswana, following the 1904– 1908 German genocide in present-day Namibia. It interrogates the enduring socioeconomic, cultural, and spiritual repercussions of this historical trauma, highlighting systemic marginalisation, cultural erosion, and the persistent struggle for justice and recognition. By synthesising focus group discussions, interviews, scholarly literature, newspapers, government archives, and missionary records, the study foregrounds the lived experiences of the Herero diaspora. An ethnographic lens—shaped by the researcher’s own heritage as a descendant of genocide survivors—provides a critical vantage point, deepening engagement with these narratives. Through the framework of biblical exilic accounts, such as the Israelites’ captivity, the research develops a theology of reconstruction that underscores the Herero’s resilience, their longing for ancestral lands, and their struggle for cultural preservation. It demonstrates that the church has a profound transformative role in post-genocidal settings, challenging conventional reconciliation models that often neglect the lived realities of affected communities. In critiquing contemporary reconciliation efforts— particularly the inadequacies of the Germany-Namibia negotiations—the study exposes the exclusion of Herero descendants from meaningful dialogue and the reduction of reparations to development aid. By integrating biblical theology, missional praxis, and ethnographic insights, this dissertation provides a contextualised framework for addressing the complexities of post-genocidal societies. It affirms that language, kinship structures, and access to ancestral land are fundamental to cultural identity and community resilience. Ultimately, the study meets its objectives by demonstrating that the church’s missional calling in post-genocide settings must prioritise anti-colonial, non-racial, and nonhierarchical paradigms. It calls for a renewed ecclesial engagement—one that actively fosters justice, healing, and systemic transformation in the wake of historical atrocity.
Context-specific pathways into adult female street-based sex work in Arcadia and Sunnyside, Pretoria
Myburgh, Gertruida Margaretha (University of Pretoria, 2019-01)
Researchers’ interest in the sex work phenomenon is not new and despite numerous studies alluding to the prevalence and nature thereof, the South African context of commercial sex work (CSW) entry remains poorly understood. Therefore, the aim of the study was to identify context-specific pathways into adult female street-based sex work in Arcadia and Sunnyside, Pretoria (Gauteng). In pursu1it of the aim of the study, the researcher endeavoured to compile a profile of sex workers, highlight possible risk factors which may shape an individual’s trajectory into CSW and describe the nature of adult female street-based sex work in Arcadia and Sunnyside, Pretoria (Gauteng). Due to the paucity of local studies regarding the research problem, objectives formulated for the study dictated the utilisation of a cross-sectional survey research design. Adult female street-based sex workers were approached in their area of work (Sunnyside and Arcadia), by means of non-probability sampling methods, where 60 face-to-face interviews were conducted utilising a structured questionnaire. Non-parametric procedures were used to determine significant relationships that could point to risk factors that play a meaningful role in shaping women’s pathways into CSW. The literature review elucidated various risk factors associated with CSW, which was subsequently supported by the current study’s findings. More than half of sex workers came from low socio-economic backgrounds (63.3%) and had poor educational levels (61.7%). Individuals who ran away from home were more likely to have experienced abuse prior to their involvement in sex work (r = - 0.3), as well as alluded to some substance use (r = - 0.3) and familial substance abuse (r = - 0.4). Sex workers who experienced abuse prior to their CSW involvement were less likely to have had previous employment (r = - 0.3). Furthermore, sex workers’ main motivation for their CSW involvement was related to financial need (93.3%) and unemployment (78.3%). Additionally, sex workers who were arrested were more likely to report experiences of police abuse. In light of the intersectionality of risk factors and the aim of the present study, the survey results alluded to four possible pathways for women into street-based CSW, which roughly comprise of economic circumstances, runaway behaviour, abuse and substance abuse. Therefore, the researcher recommends, amongst others, that the risk factors, which intersect in an across the different pathways, be considered by role-players in their service delivery to street-based sex workers.
Assessing the extent of and changes in the wildlife sector in Limpopo province, South Africa
Prinsloo , Cecilia (University of Pretoria, 2019-02)
The wildlife sector has grown rapidly over the past few decades and is considered a valuable asset for South African ecotourism, economy and conservation. However, there has been an increasing concern around its conservation efficacy, particularly with the industry becoming more intensive regarding its animal production. The growth of the wildlife sector, especially intensive breeding practices, has proliferated the use of fencing. Fences establish boundaries and protect wildlife, but may also cause mortality, inhibit animal movement, and can ultimately lead to landscape fragmentation which has been shown to have adverse effects on wildlife and the environment. To infer spatial changes in the wildlife sector across a ten year time frame, I used remote sensing procedures to manually map and quantify the changes in fences and camps (fenced areas) of wildlife properties based on satellite images of south-west Limpopo during 2007, 2012 and 2017. Results show an increase in intensive wildlife properties, total length of fences, and total number of camps from 2007 to 2017. The mean area of camps decreased over the ten year time period, accompanied by an overall increase in the number of smaller camps (≤200 ha) and a general decrease in larger camps (≥500 ha). Furthermore, the areas covered by smaller camps (≤200 ha) increased whilst the areas covered by larger camps decreased (≥500 ha) over the entire time period. The biggest changes in the wildlife sector occurred between 2012 and 2017, which suggest that the changes may be occurring progressively more and should therefore be urgently addressed. As fence maps would be very beneficial to wildlife researchers and managers, I pursued an alternative method to ‘automate’ the mapping of fences through image classification. Two image classification methods were used, namely Support Vector Machine (SVM) and Random Forest (RF), to classify the satellite images of the wildlife sector in south-west Limpopo. The fence area obtained from the classified images did not however correspond with the manual fence map, due to the high variability in accuracy values, specifically overall accuracy and kappa index. The SVM and RF methods were statistically identical in accuracy values. Furthermore, it was found that some landscape characteristics, such as percentage elevation and presence of water, correlated with the overall accuracy of certain classified images. Therefore, image classification methods have the potential to map fences of the wildlife sector, and needs to be improved for future use. The extent of increase in intensive wildlife production and the rise of fences are disconcerting trends that may have detrimental consequences to wildlife and their environment. It is vital to increase research efforts to assess the extent and effects of fencing, and inform landowners of fence impacts in South Africa so as to mitigate the ecological effects of fencing. Remote sensing and image classification methods can be used to map the full extent of fences in the wildlife sector. Ultimately, the reduction and regulation of intensive wildlife management practices and fencing may significantly aid in conserving South African wildlife.
Prevalence and seasonal variations of rhinitis and associated factors in children in Gauteng and North-West province, South Africa
Rathogwa , Funzani (University of Pretoria, 2018-11)
BACKGROUND : Rhinitis is one of the most common global respiratory health problems. Despite its high prevalence, it is often undiagnosed and globally not much research in children has been conducted. The aim of the study was to investigate the prevalence, seasonal variations of rhinitis and associated factors in children living close to gold mine dumps in Gauteng and North West province, South Africa using previously collected data. METHODS : In a cross-sectional study of 3641 school children, we determined the prevalence and seasonal variations of rhinitis in communities living 1 to 2 km (exposed) and 5 km or more (unexposed) from five pre-selected mine dumps and assessed the associated risk factors with rhinitis in exposed and unexposed communities using STATA 14. RESULTS : The prevalence of rhinitis was reported to be 74.54% and 77.65% in exposed and unexposed communities respectively. The highest (39%) prevalence of rhinitis was observed in Autumn and the lowest (11%) was observed in Spring. Results from the multiple regression analysis indicated that living in exposed communities, tertiary level, being born in the same town, itchy eyes, increased truck frequency, cigarette smoke exposure in school increases the odds of rhinitis. CONCLUSION : To the best of our knowledge this study is the first of its kind in South Africa to investigate rhinitis and seasonal association. The results obtained in this study concur with those of studies done elsewhere in the world. The study found an alarmingly high prevalence of rhinitis in all communities and the highest prevalence in the Autumn season. More research is needed to better understand the trends of rhinitis thus it is worth investing resources into rhinitis research in South Africa.
Dismantling hegemonic conceptions of victimhood: German and peripheral narratives of wartime suffering in contemporary World War II fiction
Ruff, Tracey (University of Pretoria, 2018-08-05)
In recent years, scholars Michael Rothberg and Stef Craps have dedicated much of their work to the discussion and dismantling of competitive memory – a term that has featured prominently in Holocaust studies. In Multidirectional Memory: Remembering the Holocaust in the Age of Decolonization (2009), Rothberg emphasises how we can use the memory of the Holocaust as a platform to articulate other, lesser-known forms of trauma and suffering, such as historical sites of colonial violence and genocide. His theory is fundamentally concerned with the narrative of the marginalised Other (for example, Native Americans or African American slaves) and how we can contribute to the dismantling of hegemonic narratives of suffering through recognising the Other’s suffering. The central argument presented in this dissertation is that the selected fictional texts, Eva Weaver’s The Puppet Boy of Warsaw, Jim Shepard’s The Book of Aron, Anthony Doerr’s All the Light We Cannot See, and Markus Zusak’s The Book Thief, are multidirectional in nature because they are fundamentally concerned with discussing other, lesser-known World War II narratives of suffering (i.e. they dismantle the hegemony of the Holocaust narrative). While I also discuss French and Polish suffering, I mainly focus on German suffering during the wartime period. I analyse German suffering in each of the texts through the lens of Primo Levi’s concept of the gray zone and by discussing the figure of the ordinary German. By drawing on Levi’s concept of the gray zone and reading the characters in the selected texts in an empathetic manner, my study aims to contribute to a growing body of literature that has begun to rethink German and other peripheral World War II narratives of victimisation and suffering that were largely overshadowed by the memory of the Holocaust. This dissertation, therefore, contributes to broadening the field of Holocaust memory in memory studies, extending literature on multidirectional memory, and demonstrating how memories of the past can interact productively and thus enable us, in the contemporary moment, to think dialogically and help us recognise that not all memories are equally (and fairly) represented in both the public and scholarly sphere.
Prevalence of cysticercosis in cattle and pigs slaughtered in Gauteng abattoirs, South Africa
Mabogoane, Nomsa Felecia (University of Pretoria, 2018-11)
Taenia saginata and Taenia solium are cestodes causing cysticercosis in cattle and pigs respectively. These zoonotic cestodes are of high medical and veterinary importance due to their impact on public health particularly in developing countries. Abattoirs are currently being used for surveillance of animal diseases through meat inspection in South Africa. Although this method has low sensitivity and is subjective, it is currently the standard method used for diagnosis of cysticercosis. The aim of this study was therefore to determine the prevalence of bovine and porcine cysticercosis in Gauteng abattoirs through both retrospective (review of records) and cross-sectional (sampling of animals at selected abattoirs) methods between 2017 and 2018, using serological assay (AgELISA) and molecular assay (conventional PCR) performed on pooled tissues collected from predilection sites (the masseter muscles, tongue, heart and diaphragm). A review of the 5-year (2013 – 2017) archived records on the occurrence of cysticercosis, based meat inspection in Gauteng abattoirs, revealed prevalence 0.0037% and 0.0008% for bovine and porcine cysticercosis, respectively. The prevalence of cysticercosis in cattle and pigs in the cross-sectional study by meat inspection was 0.0% in both cattle (0/351) and pigs (0/107). The apDIA AgELISA, determined the sero-prevalence of bovine and porcine cysticercosis to be 3.40% and 2.80% respectively. The difference was not statistically significant (P=0.778). Of the four risk factors (sex, breed, throughput and district) for cysticercosis investigated, statistically significant differences were detected for only sex and breed of animals. The seroprevalence of bovine cysticercosis was significantly (P=0.02) higher in heifers, 7.3% (6/82) than in bulls, 2.0% (5/249); however, the seroprevalence of porcine cysticercosis was not statistically significantly (P=0.421) different between sows, 4.3% (2/47) and boars, 1.7 (1/60). Nguni breed of cattle had a statistically significantly (P=0.003) higher seroprevalence of cysticercosis, 11.3% (5/44) than either the Jersey breed, 4.4% (2/45) or Bonsmara breed, 1.7% (4/241). All 458 pooled tissues from predilection sites of cattle and pigs did not contain cysts and therefore tested negative on T. saginata and T. solium DNA. The low prevalence detected from the review of 5-year records, and the very low seroprevalence of bovine and porcine cystiscercosis indicate that the risk of cysticercosis to consumers of beef and pork products from the abattoirs sampled in Gauteng province is low. Furthermore, the failure of conventional PCR to detect the DNA of the pathogens from predilection sites of slaughter cattle and pigs confirms that PCR can only be used as a confirmatory tool not a diagnostic tool for taeniid species identification in cattle and pigs.
Characterization of Bacillus anthracis from anthrax outbreaks in Kruger National Park (2014-2016) and the role of vultures in dissemination
Makwarela , Tsireledzo Goodwill (University of Pretoria, 2018-12)
Background: Bacillus anthracis is the causal agent of anthrax. Dissemination aspects of this well-known zoonotic diseases are poorly understood. In South Africa, anthrax is endemic in the Ghaap Plateau and Northern Kruger National Park (KNP). The aim of this study was to use multiloci variable number of tandem repeat (VNTR) analysis (MLVA) to determine genetic diversity and track the distribution of B. anthracis isolated during the 2014 - 2018 outbreaks. In addition to the genotyping; camera traps and GPS collars were used on vultures to investigate their dissemination role in the, environment. Material and Methods: Bacillus anthracis isolates (n=62) were sampled from carcasses and the environment (n=38) during outbreaks in the Pafuri and Singita regions of KNP and from 24 vultures. DNA profiles of each B. anthracis strain were established using 31 VNTR markers (MLVA-31). Amplicons were used to generate Minimum Spanning Trees (MST) and unweighted pair group method with arithmetic mean (UPGMA) phylogenetic data using Bionumeric v6.6.5. The genotyping data was coupled with observed activity at carcass sites from camera images and video, preexisting isolates (n=107), as well as GPS movement maps for the vultures. Results: MST and UPGMA cluster analysis of MLVA-31 revealed 3 dominant clonal genotypes with a further 29 unique genotypes out of 169 isolates (i.e. 32 genotypes out of 169 isolates). With regards to the role of vultures, , a spore diluting role was observed from the data as at carcass sites that vultures fed on, low soil spore counts were observed. In contrast untouched carcass sites demonstrated higher soil spore contamination. For vultures B. anthracis was isolated from beaks, talons, feathers and cloacal swabs. Bacterial genotyping could link vultures to anthrax outbreaks. Beaks and feathers had clonal genotype suggesting that vultures fed during clonal outbreaks and the unique genotypes were from cloacal swabs (digested meals) representing diverse isolates from carcass sites not sampled during this study. MLVA has proven to be a useful tool to distinguish and determine genetic diversity of B. anthracis strains in KNP and vultures played the role of diminishing the pathogen load in the environment.
Evaluating the effectiveness of ISo 14001-environmental management system (EMS) in improving key environmental performance indicators of Eskom distribution : a case study of Mpumalanga operating unit
Manake , Adeline (University of Pretoria, 2019-01)
The purpose of this research is to evaluate the effectiveness of Environmental Management System (EMS) (based on ISO 14001 Standard) in improving environmental Key Performance Indicators (KPIs). The identified KPIs are waste management, environmental training and environmental incidents. In order to achieve the aim, the methodology employed was mixed research methodology, which included quantitative approach in terms of survey questionnaires and qualitative approach in terms of interviews and observations at identified sites. The key findings reveal that ISO 14001 is effective in identifying the environmental aspects associated with waste management, environmental goals are achieved and key personnel dealing with waste management have been trained. The key contribution of this research is by creating an increased knowledge in literature with regard to EMS as a tool for improving environmental performance. Practically this research provides organisations planning to develop and implement EMS with knowledge on the critical areas to assess, in order to ensure effective implementation of EMS.
Molecular characterisation of Bacillus anthracis involved in outbreaks in the Zambezi basin
Mwamba (University of Pretoria, 2018-12)
Outbreaks of anthrax in livestock and wildlife have become a seasonal occurrence in Zambia. Consequently, the disease caused by Bacillus anthracis, has also been shown to be a classical zoonoses as almost with every outbreak, there is human involvement, where they get infected through contact and ingestion of contaminated meat/products. Accordingly, the disease has a direct effect on the livelihoods of the people living in the known endemic areas through which the socio-anthropogenic as well as socioeconomic determinants of the disease are observed. This scenario has been observed to occur almost annually in two ecosystems along the Zambezi basin, that is the Upper and Lower Zambezi basins. Thus, the aim of this study was to characterize and determine the genetic diversity of B. anthracis causing these mortalities in animals and humans in the two different sites of the Zambezi basin through molecular characterization. The first samples were collected from four (4) districts, located in the Upper Zambezi Basin, of Western Province of Zambia where livestock, particularly cattle, and human beings were infected following outbreaks in 2000, 2013 through to 2016. The second collection was from outbreaks in the Lower Zambezi basin during 2012, where predominantly wildlife was infected with concurrent outbreaks in human populations. Using the agarose gel methodology, multiple-locus variable-number of tandem repeat analysis (MLVA) based on 11 markers indicated 3 genotypes amongst 28 B. anthracis strains from Zambia in this study with one dominant genotype i.e. the Ancient A (Aβ) sublineage of the A -clade (consisting of 85.7% (24/28)). This indicate clonality of B. anthracis strains in this study from Zambia circulating in livestock, wildlife, humans and surrounding environments in the two regions.
Xanthomonas campestris pv. musacearum : population diversity and the identification of potential sources of resistance from banana accessions representing the Musa diversity worldwide
Valentine, Nakato Gloria (University of Pretoria, 2018-08)
Banana, plantain and enset are economically important crops worldwide, contributing to income and food security. Production of Musa spp. and enset is constrained by several pests and diseases, including Xanthomonas wilt (XW), caused by the bacterium Xanthomonas campestris pv. musacearum (Xcm). The pathogen is transmitted through infected planting materials, contaminated tools and insects visiting the inflorescence. Significant disease management measures include malebud removal to reduce insect transmitted infections, decontaminating farm tools, and using disease-free planting material. As Xcm infects both banana and enset, understanding relationships between the bacterial genotype and the plant host species is important as it might reveal genetic factors that drive host specialization, thus guiding the management options. A clear understanding of the genetic variation existing within and between the Xcm population is essential for tracking the movement of the pathogen through time and space and uncover routes of geographical spread, as well as rate of evolution (emergence of new strains) and patterns of adaptation. Correct identification and differentiation of pathogenic strains and closely related species is essential for development and dissemination of suitable and sustainable disease control measures. Although numerous studies have been performed on the pathogenicity of Xcm on banana and enset, information gaps still exist. No detailed studies have been conducted to understand the population structure or determine the genetic differences among Xcm strains from different countries. Similarly, no study has been conducted to understand why there is differential varietal response among Musa spp. and enset to Xcm. Previous studies to understand the population genetics of Xcm were conducted on a limited (small) number of strains. An analysis of a larger pathogen population could potentially reveal whether or not there is differentiation structured by host specificity or preference, as well as potential routes of pathogen spread from the point of origin and emergence of new strains. Chapter 1 of this thesis reviews literature on the importance of banana and enset, constraints to production with a focus on Xanthomonas campestris pv. musacearum (Xcm), Xcm taxonomy, pathology and pathogenesis, ecology, epidemiology and management options. This review further focuses on pathogenicity and virulence factors present in Xcm, molecular techniques that have been used to explore diversity and concludes by focusing on future prospects, including the need for more comprehensive studies to understand genetic variation using more discriminative molecular and epidemiological tools to better understand patterns of dissemination and adaptation. SNP-based molecular markers have been developed for phylogeographic studies of epidemiology and spread of Xcm. Chapter Two sought to understand levels of genetic diversity within Xcm using SNP-based molecular markers previously developed by Wasukira et al. (2012) in a large Xcm population collected from several East Africa countries. Restriction fragment length polymorphism (RFLP) of fragments derived from single nucleotide polymorphisms (SNP) based markers were used to validate Xcm diversity based on studies previously described by Wasukira et al. (2012). Chapter Three describes the development of new genotyping markers based on multiplelocus variable number of tandem repeat analysis (MLVA) and their use to genotype a collection of Xcm strains. The aim was to produce a highly discriminatory identification scheme suitable for distinguishing between closely related Xcm strains, and to update the knowledge about diversity and structure of African Xcm populations. Chapter Four focused on evaluating banana varieties constituting the entire IITA collection for response to Xcm and identification of potential sources of resistance. Banana varieties representing the major groups within the IITA collection were screened for response to a known virulent Xcm strain to identify potential sources of resistance. Cluster analysis was used to test the hypothesis of whether resistance to Xcm is clustered, that is, restricted to certain areas and banana varieties or is random. This information will be used to identify banana varieties to target for further screening and use in breeding programs. Chapter Five summarises the conclusions and prospects from the different chapters.
An assessment of alien terrestrial invertebrate species in the pet trade in South Africa
Nelufule, Takalani (University of Pretoria, 2018-10-01)
Many species have been introduced throughout the globe for the pet trade and some have escaped or been released from captivity and become invasive. In South Africa, different terrestrial invertebrate species are offered for sale in pet stores, on websites and by breeders. It is not known which alien terrestrial invertebrate species are traded, if the names used are correctly applied or whether these species could pose the risk of becoming invasive should they be released or escape. To determine which species are in the South African pet trade, species names were collected from pet stores, websites and via private breeders. Twenty-seven specimens from 11 species were purchased from different pet stores for DNA barcoding to determine if the species were correctly labelled. To determine if any parts of South Africa would be climatically suitable, climate match (13 species) and species distribution models (23 species) were developed for 36 terrestrial invertebrate species. The Socio-Economic Impact Classification of Alien Taxa (SEICAT) and Environmental Impact Classification for Alien Taxa (EICAT) were used to assess the recorded impacts of terrestrial invertebrate species. A total of 53 (36 recognized and 17 unrecognized) terrestrial invertebrate species were recorded as being for sale in South Africa. The most popular species were mealworms (Tenebrio molitor) (89 availability index score), superworms (Zophobas morio) (78 availability index score) and dubia roach (Blaptica dubia) (49 availability index score). Terrestrial invertebrate species are used for various purposes such as pets, food for pets, cleaners of cages and soil improvement. Out of the 11 species that were sequenced, nine species were correctly identified. The phylogenetic tree indicated that nine species clustered with reference sequences of the same species with high nodal support values while two species clustered with the same genus but not the same species names. Nine species assessed following the climate match method had suitable climate in South Africa. The model performance indicated that models were successful in predicting areas that are climatically suitable for 15 species. Impact records were available for only 18 species. The recorded socio-economic impacts were generally higher than the recorded environmental impacts. We did not find any species that had large areas that were climatically suitable and high availability and that also had high environmental or socioeconomic impacts. Overall, the risk of invasion from terrestrial invertebrate species in the pet trade appears to be low based on the species considered in this study. However, the trade is dynamic which could mean that species availability could change in future or new species could be introduced. Therefore, long term sampling is necessary to obtain a more complete list as the market appears to be dynamic.
The influence of wildlife and livestock herbivore assemblages on grazing lawn flora
Voysey , Michael Darryl (University of Pretoria, 2018-09-18)
Large swathes of savannas in Africa have witnessed the replacement of indigenous herbivore assemblages by domestic livestock, the consequences of which remain poorly understood for savanna plant communities. Grazing lawns, which are important floristic features of African savannas, are characterised by intensely grazed, short-grass patches with grass species uniquely adapted to tolerate high grazing intensity. In turn, lawn-grass ecosystems provide a nutrient-rich forage resource to large mammal grazers. However, heavy grazing sometimes results in woody expansion, which threatens to diminish the productivity of lawn-grass ecosystems. The aim of this study was to determine the consequences of replacing wild herbivore assemblages by domestic livestock for grazing lawn flora. The first part of this study set out to determine the prevalence of grazing lawns created by livestock, and then to contrast species composition, structure and function of grazing lawn flora between wildlife and livestock herbivore areas. Transects were surveyed in wildlife and livestock areas in and around Orpen, Kruger National Park, South Africa. Grass and forb species composition, growth form, cover and height were recorded. So too was tree density and tree height. Thereafter, the effect of wildlife vs. livestock areas on these was tested. Livestock areas were characterised by denser and taller tree communities, suggesting that browser absence facilitates tree establishment and growth. Grass and forb species composition differed between the two herbivore communities. Livestock areas uniformly possessed short grass, whereas wildlife areas were heterogeneous, possessing both short and tall grass patches. Furthermore, the strong positive effect of tree density on grass height in wildlife, but not in livestock areas, suggests predator-avoidance behaviour as a distinctive feature of wildlife systems. In summary, replacement of wildlife by livestock (at higher densities) results in very different ecosystem function, driven by differences in the functional composition of the two herbivore assemblage types, and also by contrasting management practices. The second part of this study set out to determine the role of wildlife browsers in maintaining the open physiognomy of lawn-grass ecosystems, to better understand why heavily grazed wildlife areas tend to experience woody suppression while heavily grazed livestock areas mostly experience woody expansion. The effect of grass height on browser species presence was tested in a short- and tall-grass mosaic in Satara, Kruger National Park. In the same mosaic, an exclosure experiment was set-up to test the effect of grass height habitat (short vs. tall) and herbivory (exclosed vs. non-exclosed) on seedling survival and sapling growth. The effect of grazing intensity and herbivory were also tested on long-term growth rates of woody plants in Hluhluwe-iMfolozi Park (HiP). Preference for short grass habitats scaled negatively with interspecific herbivore body mass, indicating that predator avoidance might be a key factor driving smaller bodied herbivores to utilize grazing lawns. At intraspecific level, impala was the only species to significantly select short- over tall-grass as preferred foraging sites, while large browsers, elephant and giraffe, preferred tall grass. The exclosure experiments revealed that seedling survival and sapling growth are indeed limited by herbivory in short grass, though evidence for this was stronger in the long-term exclosure experiment in HiP than at Satara. Combined, these results support the hypothesis that browsers, specifically impala and small-bodied mixed feeders elsewhere, are necessary for maintaining grazing lawn open physiognomy. Overall, this study demonstrated that the replacement of wildlife by domestic livestock (at higher densities) has important consequences for grazing lawn flora, and savanna plant communities in general, by altering the structure, function and species composition of savanna grass, forb and woody plant communities.
Assessing the invasive status of cryptostegia grandiflora and C. madagascariensis in southern Africa and predicting potential risk areas
Kern, Ludi (University of Pretoria, 2018)
Biological invasions are a major threat to global biodiversity. The complexity and high cost associated with management of invasions emphasizes the need for a strategic approach that can predict and prioritise potential invasive species. Risk assessments are commonly used tools that evaluate a species potential to become invasive. While risk assessments can be based on a variety of species characteristics, accurate estimates of a species contemporary distribution and the species potential future range, provide key information to prioritise management decisions. Understanding the factors driving the distribution of invasive species at different spatial scales can provide insight into the full range of environmental variables that influence its distribution. At broad-scales climate variables are expected to be the dominant factors determining where a species occurs and at finer scales, biotic interactions, disturbance, soil type and microclimatic conditions are predicted to become more important. In consequence, coarser scales are usually more suitable for directing management strategies (i.e. where to focus monitoring or control efforts), while finer scales are better to examine environmental features that influence distribution patterns within a single habitat. In this study, a multi-scale approached was used to assess the risk and predict the potential distribution of two Cryptostegia species identified as emerging invaders in southern Africa. Occurrence surveys were conducted across Botswana, Namibia and South Africa to determine the current extent and invasive status of Cryptostegia grandiflora and Cryptostegia madagascariensis. The potential broad-scale distribution of both species was predicted using species distribution models. By incorporating climate data and the current global distribution of both species habitat suitability maps were created using maximum entropy (MaxEnt; Chapter 2). At local scale, an invasive C. grandiflora population occurring along the Mogalakwena River in northern South Africa was used to determine the variables influencing fine-scale spatial variation in occurrence and cover (Chapter 3). Occurrence surveys confirmed both species are present in southern Africa. Cryptostegia grandiflora is widespread occurring as cultivated, naturalised and invasive populations in many semi-arid regions of southern Africa. In contrast, few C. madagascariensis occurrences were observed and none found outside of cultivation. Habitat suitability maps predicted large areas beyond current distribution highly suitable for both species. The mean temperature during the coldest quarter is the key restricting factor and predicted areas with temperatures below 15 °C to be unsuitable. The results from fine-scale surveys revealed that the drivers influencing C. grandiflora occurrence differed from those most strongly correlated with the cover of the species. Erosion and bare soil had weaker influences on C. grandiflora cover than on species occurrence, suggesting that this species can occur in moist disturbed areas but possibly achieves optimal growth under conditions of high leaf litter, low non-woody plant cover and deep soils with high moisture to initially establish. Given the widespread distribution, existing invasive populations and large uninvaded suitable range, C. grandiflora is a high risk species with the potential to severely impact riparian areas in semi-arid regions of southern Africa. Cryptostegia grandiflora’s current extent, high seed production and large dispersal range excludes eradication as a feasible management option. Monitoring and control efforts should instead focus on high priority areas already invaded or likely to be within the suitable ranges. In particular riparian areas in or adjacent to economically and ecological valuable areas (i.e. protected areas), should be targeted to prevent spread. In contrast, C. madagascariensis’s limited cultivated occurrences and restricted suitable range shows this species is not high risk and is not an imminent threat to southern Africa and is an ideal candidate for eradication.
Population biology and impact of Austropuccinia psidii in South Africa
Du Plessis, Esna (University of Pretoria, 2018-10)
The myrtle rust fungus, Austropuccinia psidii (Sphaerophragmiaceae, Pucciniales), has a wide global distribution, having been recorded from five continents. It has a known host range of over 500 species within the family Myrtaceae and causes disease of young leaves, shoots and flowers. In its most severe manifestation, it leads to tree stunting and mortality. Austropuccinia psidii is one of the most economically important pathogens of species of Eucalyptus commercially planted in Brazil, and has been described as the biggest threat to native Myrtaceae in Australia. Austropuccinia psidii was first discovered on the African continent in 2013 in KwaZulu-Natal, South Africa, on a non-native host, Myrtus communis. It has since been reported from two additional provinces and five host species in the country. A recent study showed that the genotype of A. psidii in South Africa is different from the pandemic genotype which has spread internationally. The aims of this dissertation were to: (i) expand studies on the host range and distribution of A. psidii in South Africa, (ii) investigate the population genetic diversity of A. psidii within the country and the potential presence of other genotypes of the pathogen in South Africa, (iii) determine the threat of A. psidii to the commercial eucalypt industry in the country. Samples of A. psidii from New Zealand and Singapore were received by the Forestry and Agricultural Biotechnology Institute (FABI) between 2016 and 2017, which were included in the research studies presented in this dissertation. Chapter one is a literature review that provides a general background to the research presented in this dissertation. It elaborates on the distribution, host range and population diversity of A. psidii globally. Furthermore, a complete list of known strains of A. psidii and their hosts is included to assist in elucidating the complex global population diversity of this pathogen. Chapter two of this dissertation investigated the current distribution and host range of A. psidii in South Africa as well as the population genetic diversity of the pathogen in New Zealand, Singapore and South Africa. Extensive surveys were done in South Africa in 2016 across natural ecosystems, nurseries and gardens. A large number of samples were collected from seedlings, shrubs and trees exhibiting myrtle rust symptoms in South Africa. Samples from New Zealand and Singapore were included in the study and the genotypic identity of the samples from the three countries described. In Chapter three we determined the potential threat of A. psidii to the commercial eucalypt industry. We screened hybrid clones of Eucalyptus currently grown by South African forestry companies for susceptibility to A. psidii. A total of 13 genotypes of E. grandis × E. urophylla (GU), E. urophylla × E. grandis (UG), and E. grandis × E. nitens (GN) were screened for susceptibility to A. psidii in a controlled environment. In addition to the above research questions, I authored and co-authored three publications that overlapped between the research presented in this dissertation and work at the TPCP disease clinic. These ancillary publications include a new disease report from Singapore, a paper that provides new knowledge on sexual reproduction by A. psidii, and a manuscript currently under review that identifies the strain of A. psidii in New Zealand. These publications and submitted manuscript are included at the end of the dissertation. The information presented in this dissertation provides new insights into the host and geographic distribution of an invasive pathogen in South Africa. It highlights the possible future threats of the pathogen to both native and non-native species of Myrtaceae in the country, raising concerns regarding the limited attention given to the pathogen. We emphasise the need for quarantine, which can prevent the introduction potentially more aggressive strains of A. psidii into South Africa. Through this work, we hope that more attention will be given to plant quarantine and that preventative actions will be improved to reduce the impact of such pathogens in South Africa.
Invasional meltdown in Sagina procumbens facilitates the establishment of some invasive taxa on sub-Antarctic Island
Twala , Mthokozisi Nkosingiphile (University of Pretoria, 2018-08)
Invasional meltdown occurs when one invasive species facilitates the establishment, spread and increase of other invasive species, and subsequently increases their impacts. Most studies on invasional meltdown have assessed facilitation of a single invasive species by another invader, but few have assessed meltdowns across different taxa. Therefore, the aim of this study was to evaluate whether an invasive plant, Sagina procumbens L. (procumbent pearlwort, Caryophyllaceae), causes an invasional meltdown in two different taxa (vascular plants and Collembola) on sub-Antarctic Marion Island. Additionally, some direct impacts of S. procumbens on native taxa were assessed. Sagina procumbens is an invasive cushion or mat-forming vascular plant that has spread extensively in the sub-Antarctic. While little is known about the species’ ecological impacts, it is thought to negatively impact biodiversity on Marion Island. Invasional meltdown was tested by comparing the richness of plants growing epiphytically on S. procumbens to those growing on two indigenous plant species (Azorella selago and Clasmatocolea humilis) that are being locally outcompeted by S. procumbens. Additionally, the richness, abundance, and biomass of native and of invasive Collembola extracted from these three focal plant species were compared between S. procumbens and the two indigenous plant species. The direct impacts of S. procumbens on native species were assessed by comparing the composition of plants growing epiphytically and of Collembola associated with S. procumbens to those of the two indigenous plant species. Additionally, native and invasive Collembola richness and abundance in S. procumbens were compared. Hardly any invasive plants grew on any of the three focal plant species. The richness of native plants did not differ between S. procumbens and the indigenous focal species. Invasive Collembola had a higher abundance, richness and biomass in S. procumbens than in both A. selago and C. humilis. However, native Collembola were also more abundant in S. procumbens than in the two native focal plant species. In contrast, the richness of native Collembola was not significantly different between the focal species, and the biomass of native Collembola did not differ significantly between S. procumbens and A. selago, although it was higher in S. procumbens than C. humilis. The composition of plants growing on S. procumbens did not differ significantly from those of plants growing on the two native focal species, though native Collembola assemblages did differ somewhat between the three focal species. Additionally, there was no significant difference between the richness of native and invasive Collembola assemblages in S. procumbens, although the abundance of native Collembola was significantly higher than that of invasive Collembola. Therefore, while I found no evidence for invasional meltdown in plants brought about by S. procumbens, some evidence for invasional meltdown in Collembola exists: S. procumbens leads to an increase in the species richness and biomass of invasive Collembola, but not native Collembola. Therefore, S. procumbens impacts Collembola community structure and composition, and may affect ecosystem processes, like decomposition, which are strongly linked to Collembola.
The effectiveness of the Albertina Sisulu Executive Leadership Programme in enhancing leadership competencies of public health service managers in South Africa
Van der Berg-Cloete , Sophy (University of Pretoria, 2019-02)
The purpose of this study was to assess whether the part-time modular Albertina Sisulu Executive Leadership Programme in Health (ASELPH) Fellowship training, based on competencies and using case studies as a core methodology, successfully enhanced the leadership performance of public health service managers in South Africa (SA). The problem statement was that organisations spend on leadership training and development, but seldom assess their impact. This research adds to the scarce literature on the subject. A mixed-method quasi-experimental study determining pre-post changes in competence and performance of the ASELPH Fellows, was undertaken. The sample was public health sector managers in the second cohort of the ASELPH Fellowship, drawn from eight of the nine provinces in South Africa. ASELPH had determined 14 competencies that it sought to develop and the researcher developed four indicators of performance for each competency. The Fellows’ self-assessments and a 360° assessment by their supervisors, peers and subordinates (assessors) were used to determine changes in the Fellows competence and performance. Information on the standard of the course, the Fellows’ learning journey and the factors affecting their performance in the workplace were obtained from a survey that accompanied the 3600 assessment, as well as from Fellows’ reflective essays and evaluations of course modules. The methodology was tested and the sample size was found to be sufficient, the questionnaires reliable and the training intervention applicable. There was no significant difference in the Fellows’ assessments of their own competence and performance and that of their 360° assessors, indicating that the self-assessments were consistent. In spite of the small sample, statistically significant improvements were found in 11 of the 14 competencies and 44 of the 56 performance indicators. The improvement was corroborated by the retrospective assessments of the 360° assessors. Therefore, the study provides evidence that the training was effective in enhancing the leadership competencies and the performance of the ASELPH Fellows. This was despite human and financial resource shortages and a poor governance environment impacting negatively on their ability to implement their learning. All Fellows and assessors affirmed the difference that leadership training and development could make to the healthcare environment in SA. The unique strengths of the ASELPH Fellowship were its case-based method, eLearning, reflective assignments, round-table conference-style classrooms, group-work, networking, mentorship and focused assessments. The facilities and the quality of lecturers enhanced interactive learning. Aspects to be improved included the balance between class and online learning, the number of SA case studies, greater involvement of Fellows’ senior management and improved mentorship in the workplace. The study confirms the effectiveness of the ASELPH Fellowship and the value of investing in leadership development to influence the performance of public health sector managers in South Africa.
Bacterial pathogens of tomato plants and fruit: identification population diversity and control
Shutt, Vou Moses (University of Pretoria, 2018-11)
Tomato (Solanum lycopersicon) is the world’s most important vegetable after potato (Panthee & Chen, 2010). The tomato fruit are rich in carotene, carotenoid and lycopene which are antioxidants (Agarwal & Rao, 2000). Lycopene has been shown to protect human cells from oxygen damage which has been related to its ability to reduce the risk of heart diseases (Agarwal & Rao, 2000; Stoyanova et al., 2014). The fruits are nutritious, rich in vitamins A and C, have high potassium phosphates, calcium and magnesium (Miller, 2002). They can be eaten raw, boiled or fried as stews, sundried and processed to powder (Devi et al., 2008). Tomato fruits are also the most canned vegetable in the world, used for purees, pickle and ketchup (tomato sauce) which are used regularly in most households (Panthee & Chen, 2010).
The role of cysteine residues on the bioactivity of the antimicrobial peptide Os derived from the tick ornithodoros savignyi
Stanley, René (University of Pretoria, 2018-07)
Antimicrobial peptides (AMPs), small cationic molecules possessing a broad spectrum of bioactivities, have for long been considered promising multi-therapeutic candidates and antibiotic alternatives. High production costs and stability issues have however, limited the application of these molecules, emphasising the need for smaller, more stable, peptide analogues. Such synthetic analogues require structural and functional evaluation prior to their development and use. Previously, the anti-endotoxin and anti-inflammatory potential of synthetic peptides, Os and its cysteine (Cys)-deficient analogue, Os-C, shown to exhibit more potent bactericidal activity than that of their parent peptide, tick defensin OsDef2, had been evaluated. Interestingly, Os demonstrated significantly greater anti-inflammatory activity compared with Os-C. To determine whether the Cys residues or a modified amino acid sequence was responsible for the differences observed between Os and Os-C, current research aimed to determine the cellular, antioxidant, and anti-inflammatory activity of the serine (Ser)-substituted Os analogue, Os(C→S). Selection of Ser was based on structural and chemical similarities between Ser and Cys residues. Neither Os nor Os(C→S) elicited any significant toxic effect against mammalian L929 cells, human erythrocytes or human leukocytes. The cell-penetrating capacity of Os, compared with Os(C→S), although limited appeared to be associated with the presence of Cys residues, shown to be implicated in the overall hydrophobicity of the peptide. In chemico, Os and Os(C→S) were capable of inhibiting free radical production using both electron transfer (ET)- and hydrogen atom transfer (HAT)-based reactions. In vitro, however, the protective effect of Os(C→S) against 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH)-induced oxidative damage was largely negligible, implying some functional contribution of Cys residues to the antioxidant activity of Os. The in chemico nitric oxide (NO) scavenging potential of Os was significantly greater than that of Os(C→S), while ex vivo, extensive platelet activation was observed in whole blood (WB) exposed The absence of significant antioxidant and anti-inflammatory activity by Os(C→S) correlates with the peptide's low hydrophobicity and associated limitation in it’s ability to translocate across the cell membrane, reducing its intracellular availability and subsequent exertion of its protective effects. The thiol groups of sulphur-containing Cys residues present in Os therefore, play a significant role in the cell-penetrating and antioxidant activity of the peptide. Despite this, Os(C→S) may still be considered as an effective AMP owing to its potent antibacterial activity and lack of cytotoxicity in mammalian cells - emphasising the peptide's specificity towards bacterial cells. to both Os and Os(C→S), in the presence and absence of lipopolysaccharide (LPS), consistent with the inability of peptide to bind LPS. The absence of significant antioxidant and anti-inflammatory activity by Os(C→S) correlates with the peptide's low hydrophobicity and associated limitation in it’s ability to translocate across the cell membrane, reducing its intracellular availability and subsequent exertion of its protective effects. The thiol groups of sulphur-containing Cys residues present in Os therefore, play a significant role in the cell-penetrating and antioxidant activity of the peptide. Despite this, Os(C→S) may still be considered as an effective AMP owing to its potent antibacterial activity and lack of cytotoxicity in mammalian cells - emphasising the peptide's specificity towards bacterial cells.
Theoretical and experimental studies on PIBSA-based surfactants
Van der Merwe, Marina Mikhailovna (University of Pretoria, 2018-06)
The polyisobutylene succinic anhydride (PIBSA) surfactants have been used for decades to attain kinetic stability in ammonium nitrate (AN) based emulsions. There are a number of studies concerned with the structure activity relationship and mechanism of surfactant rendered stability. However, the reported surfactant structures are inconsistent and a relation of structure to emulsion stability is yet to be established. This defined two main objectives of this thesis: to confirm the structure of PIBSA surfactants (the experimental study), and to establish a direct link between the structure and efficiency (the theoretical part). Experimentally, based on the detailed analysis of the precursors and by chromatographic separation, the structure of the most effective surfactant in the series, the monoethanolamine (MEA) adduct of PIBSA (PIBSA-MEA), was resolved in this study. The proposed structure is consistent with the products of the classic Alder-ene thermal maleation step, followed by the regioselective ring fission of succinic anhydride. By analogy, structures were assigned to surfactants branded as PIBSA-IMIDE and PIBSA-UREA. Based on the nuclear magnetic resonance structural assignments, a novel semi-quantitative method was developed; and the estimated content of the surfactants, relative to the unreacted materials in the industrial concentrates, was found to be below 27 mole percent. The theoretical study focused on the surfactant series with known efficacy: PIBSA-MEA, PIBSA-UREA, PIBSA-IMIDE and PIBSA-DEA. With practical application in mind, and based on our experimental results, model surfactants with a partly truncated side chain were used to study electronic structures with density functional theory (DFT), and to predict likely ionization states of the surfactants in the gas phase. The order of the calculated dipole moment, which was the highest in the amide-bearing surfactants (e.g. PIBSA-MEA and PIBSA-UREA), followed the experimental surface activity trend. Surface affinity of the untruncated surfactants with the simulated surfaces of aqueous ammonium nitrate, water, and growth faces of ammonium nitrate was then probed with Molecular Dynamics using condensed phase optimised Compass force-field. Surface adsorption energies were used to compare the efficacy. Discrimination between water and ammonium nitrate ions and the electrostatic interactions were found to be the key factors driving the values of the interaction energy within the surfactant-oxidizer system.
Perspectives of rehabilitation professionals on assistive technology provision for young children with disabilities in South Africa
Van Niekerk, Karin (University of Pretoria, 2019-02)
When assistive technology is selected for young children within a context with limited resources such as South Africa, research is needed to determine the factors influencing the recommendation and provision process. This is necessary as these factors could either facilitate or hinder the accessibility and availability of assistive technology that is adaptable, affordable, acceptable and high quality. The aim of this study was to identify the factors perceived by rehabilitation professionals to influence the recommendation and provision of assistive technology to young children within the South African context and to determine the extent to which these factors are perceived as influential. The study followed a sequential exploratory mixed methods design. The qualitative phase of the study consisted of a systematic review of studies identifying factors influencing assistive technology provision to children, as well as two online focus groups with South African rehabilitation professionals experienced in recommending and providing assistive technology to young children. The qualitative phase enabled the researcher to adapt an existing assistive technology selection framework for use with young children within the South African context. The adapted theoretical framework was utilised to construct a best-worst questionnaire, where participants were asked to select the items (corresponding to factors of the adapted theoretical framework) that were most and least influential on their assistive technology provision. The survey was distributed electronically and completed by 451 rehabilitation professionals throughout South Africa. Analysis of the results enabled the researcher to confirm the inclusion of the identified factors in the adapted theoretical framework and identify a rank order of factors that influence the recommendation and provision of assistive technology in South Africa, as perceived by rehabilitation professionals. Differences between the perceptions of professionals with various years of experience were explored to illustrate the influence of experience on reasoning regarding assistive technology provision.

Browse

Recent Submissions