List of Titles

Context-related drivers, occurrence and human exposure to antibiotic resistant Campylobacter in selected river systems in the Eastern Cape, South Africa

- Chibwe, Mary

Authors: Chibwe, Mary
Date: 2024-10-11
Subjects: Antibiotic resistance , Campylobacter , Health risk assessment , Drug resistance , Public health South Africa Eastern Cape , Polymerase chain reaction
Language: English
Type: Academic theses , Doctoral theses , text
Identifier: http://hdl.handle.net/10962/466644 , vital:76763 , DOI https://doi.org/10.21504/10962/466644
Description: The increasing prevalence of antibiotic-resistant Campylobacter species in river systems is a growing public health concern globally. This challenge presents the need to understand the drivers influencing the occurrence of these antibiotic-resistant strains to inform effective mitigation strategies. Identifying local anthropogenic pressures/activities will enable tailored intervention and ensure that management efforts are targeted and effective in mitigating actual risks faced by local water resources. In particular, the occurrence of antibiotic-resistant Campylobacter in river systems causes concerns regarding potential human exposure. Campylobacter species are regularly implicated in both animal and human diarrhoea, and have gained recognition as one of the main causes of waterborne diseases. This study investigated context-related drivers to the presence of antibiotic-resistant Campylobacter, its occurrence, and the risk of human exposure in the Bloukrans and Swartkops rivers in the Eastern Cape, South Africa. The study utilised a questionnaire survey and focus group discussions to identify context-related sources and drivers of antibiotic-resistant bacteria and genes in the Bloukrans and Swartkops rivers. Additionally, physico-chemical analysis of water samples was done, and polymerase chain reaction (PCR) was employed to investigate occurrences of Campylobacter in both rivers, as well as the presence of virulent and antibiotic-resistant genes. Two control sites, one for each river, and a total of nine other sampling sites were selected for this study, four along the Bloukrans River and five along the Swartkops River. Water samples were collected from all eleven sites over a period of one year, covering all the seasons (winter, spring, summer and autumn). Exposure assessment was investigated by conducting propidium monoazide-quantitative polymerase chain reaction (PMA-qPCR) to quantify the concentration of viable Campylobacter and its antibiotic-resistance genes (ARGs) in the river water. The calculated concentration of viable Campylobacter and ARGs was then used to estimate human exposure dose of antibiotic-resistant Campylobacter via unintentional ingestion during swimming in the Bloukrans or Swartkops rivers. The questionnaire surveys and focus group discussions identified the factors of socio-demographic characteristics of the study catchments, lack of knowledge regarding antibiotic resistance, inappropriate antibiotic and disposal practices as well as anthropogenic activities (improper solid waste management, discharge of poorly treated wastewater, poor animal husbandry practices, urban run-off and storm water, industrial effluent and agricultural run-off) as context-related sources and drivers contributing to the emergence and of continuing occurrence antibiotic-resistant bacteria and genes in the Bloukrans and Swartkops rivers. The results obtained in this study suggest that the physiochemical properties of the water in the Bloukrans and Swartkops rivers are conducive for Campylobacter survival. The prevalence of Campylobacter was high at sites that recorded high turbidity, low dissolved oxygen and high conductivity. This study also highlighted the widespread and continual presence of Campylobacter spp. in the Bloukrans and Swartkops rivers, which are potentially antibiotic-resistant. The prevalence of Campylobacter was 60% virulence genes were detected at 15% (cadF), 10% (htrB), 10% (clpP), 5% (ciaB) and 5% (ctdC) for water samples from the Bloukrans River. Campylobacter was detected in 58% of water samples from the Swartkops River, while cadF, htrB, ciaB, clpP and ctdB were detected at 24%, 0%, 9.5%, 14.8% and 4.8%, respectively. Of the Campylobacter-positive water samples, the virulence genes cmeA, cmeB and cmeC were detected in 20%, 65% and 10% of the water samples from Bloukrans River, respectively. Similarly, the genes cmeA, cmeB and cmeC were detected at 14.3%, 52% and 9.5%, respectively, for the Swartkops River. Tetracycline resistance genes (tetO) were detected in 70% and 76% of the water samples collected from the Bloukrans and Swartkops rivers, respectively. It was also observed that the sampling site had a significant effect on the detection of Campylobacter for both rivers (p < 0.05). The prevalence of Campylobacter was higher for sites impacted by anthropogenic activities. The results show that sampling season had no significant effect on the occurrence of Campylobacter for both rivers. The analysis through PMA-qPCR revealed that the mean concentrations of the Campylobacter 16S rRNA gene from viable cells ranged from 2.1 × 104 to 1.75 × 105 copies/ml for the Bloukrans River, and from 0 (no detection) to 1.11 × 104 copies/ml (viable concentration) for the Swartkops River. The concentration of tetO from viable cells ranged from 4.75 × 101 to 2.71 × 103 copies/ml and 115.96 to 325.12 copies/ml, for the Bloukrans and Swartkops Rivers, respectively. Similarly, the concentration of cmeB genes from viable cells ranged from 7.8 × 101 to 2.76 × 104 copies/ml for the Bloukrans River and from 1.71 × 101 to 7.39 × 103 copies/ml for the Swartkops River. We utilized the calculated concentrations of viable Campylobacter 16S rRNA genes and ARGs to estimate the human intake burden of viable Campylobacter 16S rRNA copies per one-hour of swimming to range from 9.9 × 101 – 3.7 × 106 copies/h across the two rivers. The human intake burden of Campylobacter ARGs ranged from 3.6 × 102 – 5.8 × 105 copies/h for cmeB, and 9.98 × 102 – 5.7 × 104 copies/h for tetO. This study highlighted the intricate interplay of socio-demographic characteristics in the study catchments, such as insufficient awareness of antibiotic resistance, inappropriate antibiotic disposal practices and anthropogenic activities, which all contribute to the prevalence of antibiotic-resistant Campylobacter in the Bloukrans and Swartkops rivers, emphasizing the need for targeted interventions to address these specific influences. There is a potential risk of Campylobacter infections associated with human exposure to the rivers. This work contributes towards the body of knowledge in closing the current research gap on possible human exposure to antibiotic-resistant Campylobacter, and in general, exposure to ARBs through freshwater sources. The findings have practical implications for designing targeted interventions to mitigate these risks, to enhance the overall environmental and public health management in the region. , Thesis (PhD) -- Faculty of Science, Institute for Water Research, 2024
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Date Issued: 2024-10-11

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Decolonizing the curriculum: a case study of the Humanities Faculty at Rhodes University

- Machiha, Nigel

Authors: Machiha, Nigel
Date: 2024-10-11
Subjects: Africanization , Curriculum change South Africa Makhanda , Decolonization , Rhodes University , Indigenization , Language barrier
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/466005 , vital:76676
Description: This thesis explores students’ experiences in the Faculty of Humanities at Rhodes University, specifically focusing on their perspectives on decolonization. The thesis has two central aims: first, to investigate the students’ general understanding of decolonizing the curriculum and second, to examine their experiences within the Humanities Faculty and their perception of how decolonized the faculty is. Through in-depth interviews with students in the faculty, the study aimed to answer questions regarding students’ thoughts on the decolonization of university curricula and their experiences within the Faculty of Humanities at Rhodes University. The findings reveal diverse student views on decolonization, with definitions of decolonization provided by students touching on topics such as the Africanization or Indigenization of the curriculum, systemic transformation, the importance of unlearning colonial ideologies and the relationship between language and decolonization. The students’ perceptions of the level of decolonization they witness in the faculty are categorized along three lines: the views of those who believe the departments they interact with are decolonized, the views of those who think efforts are being made but more progress is needed, and those who see no evidence of decolonization. The thesis highlights that while some students believe that positive steps towards decolonization are being taken, others express scepticism and call for a more diverse representation of scholars and scholarship and a departure from traditional Eurocentric approaches. , Thesis (MA) -- Faculty of Humanities, Political and International Studies, 2024
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Date Issued: 2024-10-11

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Determining the relationship between perceptions of HIV susceptibility and HIV status of women who have sex with women

- Zuccarini, Aimee Frances

Authors: Zuccarini, Aimee Frances
Date: 2024-10-11
Subjects: Teenage girls Attitudes , Young women Attitudes , Women who have sex with women , Stigma (Social psychology) , Informed consent (Medical law) , HIV infections Susceptibility
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/465859 , vital:76660
Description: Background: Adolescent girls and young women (AGYW) who have sex with women (WSW) are at potential risk for HIV, contradicting the common belief that WSW have low HIV susceptibility, a misperception persists despite evidence to refute it. Objective: This study examined the relationship between perceived HIV susceptibility and actual HIV status among South African AGYW WSW, focusing on those reporting at least one same-sex sexual experience, using data from the DREAMS Evaluation survey. Methods/Design: An archival study employing the Expanded Health Beliefs Model (EHBM) analysed secondary de-identified data from the DREAMS Evaluation Survey with a multistage stratified cluster sampling design. The sample comprised 18,296 AGYW aged 12-24 across four districts in South Africa, including 1,362 identified as WSW. ANOVA was conducted using SPSS 28 to explore the relationship between perceived HIV susceptibility and actual HIV status. Results: WSW’s perceived HIV susceptibility was low (38.5%) to very low (25%), while HIV prevalence in this sample/group was 15.9%. No significant relationship was found between perceived HIV susceptibility and actual HIV status (p = 0.126). Conclusions: WSW do not perceive themselves as being susceptible to contracting HIV despite the high prevalence of the virus in this group. Public health interventions should focus on raising awareness about risk factors, such as low use of barrier protection, substance use, and other behaviours highlighted in the literature, to better inform and protect this population. , Thesis (MA) -- Faculty of Humanities, Psychology, 2024
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Date Issued: 2024-10-11

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Developing transformative community-university partnerships: a participatory assessment of Rhodes University community engagement monitoring and evaluation system

- Nkwinti, Nosipho

Authors: Nkwinti, Nosipho
Date: 2024-10-11
Subjects: Community engagement , Community and college South Africa Eastern Cape , Rhodes University , Collaboration , Social change
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/463592 , vital:76423
Description: This thesis comprehensively explores transformative community engagement (CE) in higher education, focusing on the context of collaborative community-university partnerships (CUPs) in Makhanda, South Africa. The study aimed to assess and revise the monitoring and evaluation (M&E) system of the Rhodes University Community Engagement division to foster a transformation in CUPs. The research employs an exploratory design to understand the complexities of CUPs and improve the M&E systems by generating new concepts and ideas. A variety of qualitative methods, including focus groups, interviews, and document analysis, were utilized to engage community partners, student leaders, and Rhodes University Community Engagement staff. The participatory approach to research was critical, involving stakeholders in finalizing the M&E framework to ensure it met the shared objective. Data analysis was conducted inductively, with themes emerging from the data to facilitate a bottom-up understanding of the research questions. The study found that diverse community engagement projects at Rhodes University enhanced partnerships between the university and the local community in Makhanda. Participants shared varied understandings and experiences of Community Engagement. They saw CE as crucial for bridging the university-community divide and aiding local development. Furthermore, the research identified the need for a Monitoring and Evaluation system that supports collaborative Community-University Partnerships. Participants collaboratively developed and refined this M&E system, ensuring it aligns with community needs and promotes sustained development in Makhanda. Challenges such as diverse perspectives, logistical issues in focus groups, and power dynamics were also highlighted and addressed through an inclusive and participatory approach. This research highlights the elaborate distinctions of community engagement and the importance of such partnerships in fostering sustainable societal development. The framework developed has practical implications for shaping policies, fostering inclusivity, and promoting responsive university-community engagement that is aligned with community needs. The research concludes by suggesting the value of inclusivity, communication, and a flexible adaptation of practices to maximize the benefits of such partnerships. Future research could explore the longitudinal impacts of university-community partnerships, examine the scalability of the current framework to other universities, and evaluate the long-term socio-economic outcomes of the engaged citizen program on the community. , Thesis (MEd) -- Faculty of Education, Secondary and Post-School Education, 2024
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Date Issued: 2024-10-11

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Disability and sexuality in Makhanda, in the Eastern Cape: a comparative exploration of how black queer physically disabled individuals vs heterosexual physically disabled individuals negotiate their sexualities

- Mzondo, Sinokuhle

Authors: Mzondo, Sinokuhle
Date: 2024-10-11
Subjects: Sexual minorities South Africa Makhanda , College students with disabilities Sexual behavior , People with disabilities , Race discrimination , College students with disabilities Social conditions , Discrimination against people with disabilities
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/466240 , vital:76710
Description: The study aimed to comparatively explore the sexualities of queer disabled people and heterosexual disabled people. The objectives of the study were to comparatively explore their negotiation of romantic and sexual lives, comparatively explore the construction of sexual identities that intersect with disability, and offer an understanding of how both groups experience other people’s perceptions of their identities. The social model of disability and queer theory were used to guide the study. The study was qualitative in nature. In-depth, semi-structured interviews were used to collect data. Three queer disabled and five heterosexual disabled individuals were interviewed. Thematic analysis methods were used to analyse the data. The findings of the study revealed how disability affected the romantic and sexual lives of the participants – both queer and heterosexual; their experience of others’ perceptions of their identities, how they grew up with disabilities, how they adapted to their acquired disabilities, and the construction of their sexual identities. , Thesis (MSocSci) -- Faculty of Humanities, Sociology, 2024
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Date Issued: 2024-10-11

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Double jeopardy: reflections of accessing and navigating public spaces during COVID-19 by blind and visually impaired (BVI) people in Gqeberha

- Sysaar, Nicay Courtlynn

Authors: Sysaar, Nicay Courtlynn
Date: 2024-10-11
Subjects: People with visual disabilities South Africa , Blind South Africa , COVID-19 Pandemic, 2020-2023 Influence , Barrier-free design , Epidemics Social aspects , Blind Social conditions
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/466306 , vital:76716
Description: Disability only exists in reference to ability, denoting that people are only disabled if considered and treated as disabled. The inherent social conditions and features of society significantly shape disability. The impact of the COVID-19 pandemic was significant in the lives of blind and visually impaired individuals (BVI) since these individuals “access the world” through tactile contact, a behaviour strongly opposed during the pandemic. Therefore, this study explored how BVI individuals struggled to access and navigate public spaces in Gqeberha and how their risk of contracting COVID-19 increased when accessing these spaces. The study was qualitative ethnographic research. It was conducted in Gqeberha and embedded within a non-governmental organisation (NGO). A heterogeneous purposive sampling method was used to recruit ten BVI individuals and four trainers. Data was generated through semi-structured interviews and participant observation and analysed thematically. The study's key findings demonstrate that the COVID-19 countermeasures implicated the lives of BVI individuals, as some felt the need to avoid public spaces not by choice but by obligation to protect themselves from the possible risk of infection. The research findings reveal the barriers encountered through social encounters, physical navigation of the built environment, and information access, thus making the social, digital, and physical spheres inaccessible. COVID-19 exacerbated these barriers while simultaneously revealing the perpetual debilitating barriers in the lives of BVI people before the pandemic, during the pandemic, and presently. The recommendations explored the implementation of awareness-based programmes, integration and inclusion in physical spheres, and inclusionary disaster communication during disasters. Ultimately, as a society, we have a lot to do to achieve accessibility and, fundamentally, social integration. It is recommended that when developing health safety policies in times of crisis, it is crucial to consider populations with unique challenges rather than having a blasé approach. , Thesis (MSocSci) -- Faculty of Humanities, Anthropology, 2024
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Date Issued: 2024-10-11

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Eastern Cape jazz heritage: the jazz tradition and veteran musicians of East London and Zwelitsha

- Giyose, Thandikile Qhawekazi

Authors: Giyose, Thandikile Qhawekazi
Date: 2024-10-11
Subjects: Jazz musicians South Africa Eastern Cape , Jazz South Africa Eastern Cape , International Library of African Music , Popular-music archives , Collective memory in music , South African jazz
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/465964 , vital:76672
Description: This thesis explores the memories of musicians and music collectors as evident in the performance of traditional jazz songs in East London and Zwelitsha. I ask, how may research on musicians and their songs develop new knowledge about the aesthetics of jazz in the Eastern Cape and contribute to transforming notions of memories and archives? I argue that these songs are repositories of collective memory about the musical pasts of Eastern Cape modernity. We commemorate cities such as Johannesburg and Cape Town for nurturing South African jazz but what is known of the jazz musicians who remained in the country, and those musicians whose musicality was nurtured in the Eastern Cape? Where are the stories of their musical journeys and compositions located? How did these musicians contribute to the development of a form of South African jazz, which now represents and forms a large part of our heritage and our various identities as musicians, fans and performers in South Africa? In-depth and semi-structured interviews were conducted with veteran jazz musicians, jazz music collectors and members of the younger generation of jazz musicians who are originally from or reside in East London and Zwelitsha, Eastern Cape. The research follows a qualitative methodology, using an exploratory case study with a focused ethnographic approach, to understand how these musicians’ songs have retained memories of their lived experiences. The research is derived from oral histories of musicians to understand how the songs survive in the collective memory of musicians and their fans, contributing to the preservation of Eastern Cape’s jazz heritage. , Thesis (MA) -- Faculty of Humanities, Music and Musicology, 2024
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Date Issued: 2024-10-11

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Encroaching species are stronger anisohydric “water spenders” under elevated CO2 conditions: implications for savanna seedling establishment rates

- Reynolds, Liam Macleod

Authors: Reynolds, Liam Macleod
Date: 2024-10-11
Subjects: Xylem , Scrub encroachment , Isotopes , Photosynthesis , Plants Effect of atmospheric carbon dioxide on
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/465091 , vital:76572
Description: Plant water transport systems play a fundamental role in the productivity and survival of terrestrial plants due to the vascular architecture placing a physical limit on metabolic function. Savannas have high variability in rainfall, leading multiple studies to suggest that plant water-use strategies are key mechanisms affecting seedling establishment rates. Many savannas are seeing a directional shift towards an increase in the abundance of certain woody species through a process known as bush encroachment, which has been largely attributed to the fertilising effect of rising atmospheric [CO2] on C3 trees. These species are classified as encroachers. While there have been multiple studies investigating changes in the physiology of savanna species under elevated CO2 (eCO2), few have examined how climate and eCO2 affects the fundamental water-use strategies in the seedling stage, a crucial demographic bottleneck. Here, this research provides valuable insights into the mechanisms behind bush encroachment in the context of eCO2 using results from a pot experiment at the Rhodes University Elevated CO2 facility and a field experiment. All species showed water use strategies characteristic of anisohydric “water-spenders”, however, the vulnerability to embolism and rates of water-use were different between encroachers and non-encroachers. Encroachers are better at taking advantage of water pulses, particularly under eCO2 and grass competition. This comes at the cost of higher xylem vulnerability during drought, leading to reductions in conductance when exposed to heavy water stress. The response of the photosynthetic parameters mirrored this, with encroaching species had higher rates of photosynthesis and photosystem II quantum yield than non-encroachers under the well-watered treatments. Field experiments revealed that small trees are particularly vulnerable to drought stress, when compared to medium and large trees. The outcomes of this complex response will largely depend on the extent of changes to biotic and abiotic factors across spatial and temporal zones caused by climate change. This research highlights potential hydraulic mechanisms contributing to the increase in bush encroachment, as well as providing important insights into the determinant factors that make a savanna species capable of encroachment. , Thesis (MSc) -- Faculty of Science, Botany, 2024
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Date Issued: 2024-10-11

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Enhancing licence plate recognition for a robust vehicle re-identification system

- Boby, Alden Zachary

Authors: Boby, Alden Zachary
Date: 2024-10-11
Subjects: Automobile theft South Africa , Deep learning (Machine learning) , Object detection , YOLOv7 , YOLO , Pattern recognition systems , Image processing Digital techniques , Automobile license plates
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/464322 , vital:76501
Description: Vehicle security is a growing concern for citizens of South Africa. Law enforcement relies on reports and security camera footage for vehicle identification but struggles to match the increasing number of carjacking incidents and low vehicle recovery rates. Security camera footage offers an accessible means to identify stolen vehicles, yet it often poses hurdles like anamorphic plates and low resolution. Furthermore, depending on human operators proves inefficient, requiring faster processes to improve vehicle recovery rates and trust in law enforcement. The integration of deep learning has revolutionised object detection algorithms, increasing the popularity of vehicle tracking for security purposes. This thesis investigates advanced deep-learning methods for a comprehensive vehicle search and re-identification system. It enhances YOLOv7’s algorithmic capabilities and employs preprocessing techniques like super-resolution and perspective correction via the Improved Warped Planar Object Detection network for more effective licence plate optical character recognition. Key contributions include a specifically annotated dataset for training object detection models, an optical character recognition model based on YOLOv7, and a method for identifying vehicles in unrestricted data. The system detected rectangular and square licence plates without prior shape knowledge, achieving a 98.7% character recognition rate compared to 95.31% in related work. Moreover, it outperformed traditional optical character recognition by 28.25% and deep-learning EasyOCR by 14.18%. Its potential applications in law enforcement, traffic management, and parking systems can improve surveillance and security through automation. , Thesis (MSc) -- Faculty of Science, Computer Science, 2024
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Date Issued: 2024-10-11

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Evaluating baculovirus mixtures against false codling moth Thaumatotibia leucotreta Meyrick. (Lepidoptera: Tortricidae)

- Tole, Siviwe

Authors: Tole, Siviwe
Date: 2024-10-11
Subjects: False codling moth Biological control , Baculoviruses , Integrated pest management , Natural pesticides , Granulovirus
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/463996 , vital:76464
Description: False codling moth (FCM), Thaumatotibia leucotreta, is an important pest of citrus, stone fruit, avocados, peppers, and other important agricultural crops in southern Africa. Baculovirus-based biopesticides are components in an integrated pest management (IPM) programme to manage the pest in the field. Cryptogran™ and Cryptex™ which are CrleGV-SA based-biopesticides have been effective in the control of T. leucotreta for the past 15 years. Recently, CrpeNPV-based Multimax™ and Codlmax™ have been commercialised to control T. leucotreta and other important agricultural pests. Despite these viruses being relatively host-specific and safe to humans and animals in comparison to chemical insecticides, their application is hindered by their slow speed of kill, sensitivity to UV light, and the potential for insect resistance. Research investigating the effects of mixed baculoviral interactions against target pests has been a growing field of interest due to their potential to overcome such shortcomings. Previous studies using a combination of CrleGV-SA and CrpeNPV against T. leucotreta observed a reduction in lethal concentration in laboratory bioassays, indicating that such mixtures may have the potential for application in the field. This has led to the motivation to investigate further interactions between CrleGV-SA in combination with CrpeNPV, CpGV-M, and HearNPV-Au to understand better how these viruses interact and to determine whether synergistic, additive, or antagonistic interactions can occur against T. leucotreta. The outcome of these interactions will inform researchers and farmers about best practices concerning these viruses should they be combined against T. leucotreta in the future. Prior to performing mixed baculovirus infections in laboratory bioassays, oligonucleotides targeting unique regions in the viral genomes of CrleGV-SA, CrpeNPV, CpGV-M, and HearNPV-Au were designed using Primer-BLAST. The specificity of these oligonucleotides was further tested in silico using Geneious R11 software (11.1.5). The stocks of CrpeNPV, CpGV-M, and HearNPV-Au were purified using crude OB extraction from diseased C. peltastica, C. pomonella, and H. armigera larval cadavers provided by River Bioscience (Pty) Ltd (Gqeberha, South Africa). The stock of CrleGV-SA was purified using crude OB extraction from infected T. leucotreta cadavers. Subsequently, the unique oligonucleotides were used in PCR assays to detect if the samples contained the baculoviruses of interest. Amplicons of the expected sizes were generated indicating the presence of CrleGV-SA, CrpeNPV, CpGV-M, and HearNPV-Au in each of the samples. The OBs were counted using darkfield microscopy and a counting chamber before the single and mixed infections were initiated against T. leucotreta neonate larvae. Surface-dose biological assays were used to evaluate the relative virulence in terms of lethal concentration of CrleGV-SA, CrpeNPV, and CpGV-M, alone against T. leucotreta. After 7 days, the dose mortality data was analysed using “drc” in R studio and the LC50 and LC90 were compared amongst each virus. The CrleGV-SA treatment was estimated to be the most virulent in comparison to CrpeNPV and CpGV-M. A dose discriminate assay confirmed that HearNPV does not cause mortality in T. leucotreta. Similarly, the relative virulence in terms of lethal concentration of CrleGV-SA in various ratios in combination with CrpeNPV, CpGV-M, and HearNPV-Au was determined using 7-day surface dose biological assays. The CrleGV/CrpeNPV was the most virulent mixture with lower LC50 and LC90 values measured in comparison to CrleGV/CpGV and CrleGV/HearNPV, respectively. The Tammes Bakuniak graphic method confirmed the CrleGV/CrpeNPV, CrleGV/CpGV, and CrleGV/HearNPV mixtures to be antagonistic against T. leucotreta neonate larvae in terms of lethal concentration. The last aspect of the study was to determine the probable cause of larval death. A modified CTAB protocol was used to extract genomic DNA from neonate-sized T. leucotreta cadavers collected in single and mixed infection assays. The gDNA served as templates in PCR assays using the unique oligonucleotides. In single infections, the presence of CrleGV-SA in CrpeNPV and HearNPV inoculated larvae was observed. The results suggest possible covert infections of CrleGV-SA in the T. leucotreta colony which may be caused by virus infection or an unknown stress factor. The results from the mixed infections showed the presence of each virus in all replicates except for the CrleGV/CpGV and CrleGV/HearNPV mixtures. In the CrleGV/CpGV mixture, only CrleGV-SA was present in the last replicate, suggesting a possible competition for host resources. In the CrleGV/HearNPV mixture, only CrleGV-SA was detected in all 3 replicates, suggesting that HearNPV did not have any effect and the larvae died of the CrleGV-SA infection. This is the first study to report mixtures of CrleGV-SA in combination with CpGV-M and HearNPV-Au against T. leucotreta neonate larvae. Despite the antagonistic interactions observed in the evaluated mixtures, this study has laid a foundation to further investigate how these viruses interact in dual infections for the improved control of T. leucotreta. This may be done by evaluating different ratios and combinations of baculoviruses to those used in this study. , Thesis (MSc) -- Faculty of Science, Biochemistry, Microbiology & Bioinformatics, 2024
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Date Issued: 2024-10-11

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Evaluation of traditional and residual momentum strategies during the Covid period on the Johannesburg Stock Exchange

- Yengwa, Mphathi Lubabalo

Authors: Yengwa, Mphathi Lubabalo
Date: 2024-10-11
Subjects: Efficient market theory , Residual momentum , Economic crisis , Johannesburg Stock Exchange , COVID-19 Pandemic, 2020-2023 Influence
Language: English
Type: Academic theses , Master's theses , text
Identifier: http://hdl.handle.net/10962/462834 , vital:76339
Description: Traditional momentum is a concept which was first discovered by Jegadeesh and Titman (1993), defined as a tendency of stocks to experience a continuation in their relative performance. A stock that performed relatively well will continue to perform relatively well, and vice versa. It has been observed by other researchers that during market crises, traditional momentum tends to produce large negative returns for investors, defined as a momentum crash. To mitigate momentum crashes, many researchers have developed new momentum strategies which have better performance than traditional momentum during market crises; such strategies include residual momentum. While both residual and traditional momentum have been studied in international markets and locally, the performance of both the residual and traditional momentum strategies have not been examined in the most recent Covid-fuelled financial crisis on the Johannesburg Stock Exchange. The study compares the performance of hypothetical long-only winner traditional and residual momentum portfolios (from 2018–2022) using various risk metrics, which include the tracking error, Sharpe ratio, Jensen’s alpha and information ratio. To compare the statistical significance of the difference in mean returns of residual and traditional momentum strategies to the benchmark (FTSE/Johannesburg Stock Exchange (JSE) Top 40) the study uses Welch’s t-test. The study uses an Auto regressive distributed lag (ARDL) regression to examine the effect that various market conditions (bull market, bear market and extreme volatility) have on the returns of residual and traditional momentum strategies. Given the limited period examined in this study, the Monte Carlo simulation was used to extrapolate potential outcomes of how the momentum strategies might perform under different market conditions (as mentioned) in 1 000 iterations of each condition. The simple return analysis undertaken in this research revealed that traditional momentum outperformed residual momentum both before and throughout the COVID period. In the risk-adjusted performance measures, traditional momentum outperformed at all four risk indicators during the 2020 COVID year. The statistical significance tests, which compared the strategies' mean returns to the benchmark, demonstrated no statistically significant difference in returns over the COVID year. Furthermore, when evaluating the strategies over a five-year period (2018-2022), the difference in mean returns was shown to be statistically insignificant. However, statistical significance in returns was shown in some individual years. The ARDL regression findings show that bull, bear, and volatility factors explain relatively little of the returns for both momentum strategies, which is consistent with previous research. The Monte Carlo simulation, using the bear variable, forecasted that traditional momentum would result in negative returns during market declines, but residual momentum would provide positive returns and surpass traditional momentum with a probability of 26%. When using the bull variable, the simulation discovered that both traditional and residual momentum strategies resulted in positive returns. However, the residual momentum strategy outperformed in terms of returns and had an 84% likelihood of outperforming the traditional momentum strategy across 1,000 iterations. Nevertheless, when the simulation included the volatility variable, it projected negative returns for residual momentum and positive returns for traditional momentum. Additionally, it estimated a 14% probability of residual momentum surpassing traditional momentum under volatile market circumstances. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2024
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Date Issued: 2024-10-11

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