Research Articles (University of Pretoria)

Permanent URI for this collectionhttp://hdl.handle.net/2263/121

This collection offers open access to the full text of research articles published by staff, students and affiliates of the University of Pretoria. These items are identical in content to their published counterparts. It is linked to the Research Information System and complements the Annual Research Report.

Access to the full text of UP theses and dissertations is available at UP Electronic Theses and Dissertations.

Information and guidelines for authors/ submitters available at http://www.ais.up.ac.za/openup/index.htm.

For inquiries regarding this collection or items in the collection, please contact : Hendriette Jansen van Vuuren
Tel.: +27 12 420 4712

Browse

Now showing 1 - 20 of 41177

First Sagittarius A* Event Horizon Telescope results. VIII. Physical interpretation of the polarized ring
(American Astronomical Society, 2024-04-01) Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Algaba, Juan Carlos; Anantua, Richard; Asada, Keiichi; Azulay, Rebecca; Bach, Uwe; Baczko, Anne-Kathrin; Ball, David; Baloković, Mislav; Bandyopadhyay, Bidisha; Barrett, John; Bauböck, Michi; Benson, Bradford A.; Bintley, Dan; Blackburn, Lindy; Blundell, Raymond; Bouman, Katherine L.; Bower, Geoffrey C.; Boyce, Hope; Bremer, Michael; Brinkerink, Christiaan D.; Brissenden, Roger; Britzen, Silke; Broderick, Avery E.; Broguiere, Dominique; Bronzwaer, Thomas; Bustamante, Sandra; Byun, Do-Young; Carlstrom, John E.; Ceccobello, Chiara; Chael, Andrew; Chan, Chi-kwan; Chang, Dominic O.; Chatterjee, Koushik; Chatterjee, Shami; Chen, Ming-Tang; Chen, Yongjun; Cheng, Xiaopeng; Cho, Ilje; Christian, Pierre; Conroy, Nicholas S.; Conway, John E.; Cordes, James M.; Crawford, Thomas M.; Crew, Geoffrey B.; Cruz-Osorio, Alejandro; Cui, Yuzhu; Dahale, Rohan; Davelaar, Jordy; De Laurentis, Mariafelicia; Deane, Roger; Dempsey, Jessica; Desvignes, Gregory; Dexter, Jason; Dhruv, Vedant; Dihingia, Indu K.; Doeleman, Sheperd S.; Dougall, Sean; Dzib, Sergio A.; Eatough, Ralph P.; Emami, Razieh; Falcke, Heino; Farah, Joseph; Fish, Vincent L.; Fomalont, Edward; Ford, H. Alyson; Foschi, Marianna; Fraga-Encinas, Raquel; Freeman, William T.; Friberg, Per; Fromm, Christian M.; Fuentes, Antonio; Galison, Peter; Gammie, Charles F.; García, Roberto; Gentaz, Olivier; Georgiev, Boris; Goddi, Ciriaco; Gold, Roman; Gómez-Ruiz, Arturo I.; Gómez, José L.; Gu, Minfeng; Gurwell, Mark; Hada, Kazuhiro; Haggard, Daryl; Haworth, Kari; Hecht, Michael H.; Hesper, Ronald; Heumann, Dirk; Ho, Luis C.; Ho, Paul; Honma, Mareki; Huang, Chih-Wei L.; Huang, Lei; Hughes, David H.; Ikeda, Shiro; Impellizzeri, C.M. Violette; Inoue, Makoto; Issaoun, Sara; James, David J.; Jannuzi, Buell T.; Janssen, Michael; Jeter, Britton; Jiang, Wu; Jiménez-Rosales, Alejandra; Johnson, Michael D.; Jorstad, Svetlana; Joshi, Abhishek V.; Jung, Taehyun; Karami, Mansour; Karuppusamy, Ramesh; Kawashima, Tomohisa; Keating, Garrett K.; Kettenis, Mark; Kim, Dong-Jin; Kim, Jae-Young; Kim, Jongsoo; Kim, Junhan; Kino, Motoki; Koay, Jun Yi; Kocherlakota, Prashant; Kofuji, Yutaro; Koch, Patrick M.; Koyama, Shoko; Kramer, Carsten; Kramer, Joana A.; Kramer, Michael; Krichbaum, Thomas P.; Kuo, Cheng-Yu; La Bella, Noemi; Lauer, Tod R.; Lee, Daeyoung; Lee, Sang-Sung; Leung, Po Kin; Levis, Aviad; Li, Zhiyuan; Lico, Rocco; Lindahl, Greg; Lindqvist, Michael; Lisakov, Mikhail; Liu, Jun; Liu, Kuo; Liuzzo, Elisabetta; Lo, Wen-Ping; Lobanov, Andrei P.; Loinard, Laurent; Lonsdale, Colin J.; Lowitz, Amy E.; Lu, Ru-Sen; MacDonald, Nicholas R.; Mao, Jirong; Marchili, Nicola; Markoff, Sera; Marrone, Daniel P.; Marscher, Alan P.; Martí-Vidal, Iván; Matsushita, Satoki; Matthews, Lynn D.; Medeiros, Lia; Menten, Karl M.; Michalik, Daniel; Mizuno, Izumi; Mizuno, Yosuke; Mora, James M.; Moriyama, Kotaro; Moscibrodzka, Monika; Mulaudzi, Wanga; Müller, Cornelia; Müller, Hendrik; Mus, Alejandro; Musoke, Gibwa; Myserlis, Ioannis; Nadolski, Andrew; Nagai, Hiroshi; Nagar, Neil M.; Nakamura, Masanori; Narayanan, Gopal; Natarajan, Iniyan; Nathanail, Antonios; Navarro Fuentes, Santiago; Neilsen, Joey; Neri, Roberto; Ni, Chunchong; Noutsos, Aristeidis; Nowak, Michael A.; Oh, Junghwan; Okino, Hiroki; Olivares, Héctor; Ortiz-León, Gisela N.; Oyama, Tomoaki; Özel, Feryal; Palumbo, Daniel C.M.; Paraschos, Georgios Filippos; Park, Jongho; Parsons, Harriet; Patel, Nimesh; Pen, Ue-Li; Pesce, Dominic W.; Piétu, Vincent; Plambeck, Richard; PopStefanija, Aleksandar; Porth, Oliver; Pötzl, Felix M.; Prather, Ben; Preciado-López, Jorge A.; Psaltis, Dimitrios; Pu, Hung-Yi; Ramakrishnan, Venkatessh; Rao, Ramprasad; Rawlings, Mark G.; Raymond, Alexander W.; Rezzolla, Luciano; Ricarte, Angelo; Ripperda, Bart; Roelofs, Freek; Rogers, Alan; Romero-Cañizales, Cristina; Ros, Eduardo; Roshanineshat, Arash; Rottmann, Helge; Roy, Alan L.; Ruiz, Ignacio; Ruszczyk, Chet; Rygl, Kazi L.J.; Sánchez, Salvador; Sánchez-Argüelles, David; Sánchez-Portal, Miguel; Sasada, Mahito; Satapathy, Kaushik; Savolainen, Tuomas; Schloerb, F. Peter; Schonfeld, Jonathan; Schuster, Karl-Friedrich; Shao, Lijing; Shen, Zhiqiang; Small, Des; Sohn, Bong Won; SooHoo, Jason; Sosapanta Salas, León David; Souccar, Kamal; Stanway, Joshua S.; Sun, He; Tazaki, Fumie; Tetarenko, Alexandra J.; Tiede, Paul; Tilanus, Remo P. J.; Titus, Michael; Torne, Pablo; Toscano, Teresa; Traianou, Efthalia; Trent, Tyler; Trippe, Sascha; Turk, Matthew; Van Bemmel, Ilse; Van Langevelde, Huib Jan; Van Rossum, Daniel R.; Vos, Jesse; Wagner, Jan; Ward-Thompson, Derek; Wardle, John; Washington, Jasmin E.; Weintroub, Jonathan; Wharton, Robert; Wielgus, Maciek; Wiik, Kaj; Witzel, Gunther; Wondrak, Michael F.; Wong, George N.; Wu, Qingwen; Yadlapalli, Nitika; Yamaguchi, Paul; Yfantis, Aristomenis; Yoon, Doosoo; Young, André; Young, Ken; Younsi, Ziri; Yu, Wei; Yuan, Feng; Yuan, Ye-Fei; Zensus, J. Anton; Zhang, Shuo; Zhao, Guang-Yao; Zhao, Shan-Shan; Najafi-Ziyazi, Mahdi
In a companion paper, we present the first spatially resolved polarized image of Sagittarius A* on event horizon scales, captured using the Event Horizon Telescope, a global very long baseline interferometric array operating at a wavelength of 1.3mm. Here we interpret this image using both simple analytic models and numerical general relativistic magnetohydrodynamic (GRMHD) simulations. The large spatially resolved linear polarization fraction (24%–28%, peaking at ∼40%) is the most stringent constraint on parameter space, disfavoring models that are too Faraday depolarized. Similar to our studies of M87*, polarimetric constraints reinforce a preference for GRMHD models with dynamically important magnetic fields. Although the spiral morphology of the polarization pattern is known to constrain the spin and inclination angle, the time-variable rotation measure (RM) of SgrA* (equivalent to ≈46°±12° rotation at 228 GHz) limits its present utility as a constraint. If we attribute the RM to internal Faraday rotation, then the motion of accreting material is inferred to be counterclockwise, contrary to inferences based on historical polarized flares, and no model satisfies all polarimetric and total intensity constraints. On the other hand, if we attribute the mean RM to an external Faraday screen, then the motion of accreting material is inferred to be clockwise, and one model passes all applied total intensity and polarimetric constraints: a model with strong magnetic fields, a spin parameter of 0.94, and an inclination of 150°. We discuss how future 345 GHz and dynamical imaging will mitigate our present uncertainties and provide additional constraints on the black hole and its accretion flow.
Predictors of unsuppressed HIV viral load and low CD4 count among ZIMPHIA 2020 survey participants
(Texila International Journal, 2024-12-27) Mukwenha, Solomon; Dzinamarira, Tafadzwa; Mapingure, Munyaradzi; Chingombe, Innocent; Makota, Rutendo Birri; Mbunge, Elliot; Moyo, Enos; Chemhaka, Garikayi; Batani, John; Moyo, Brian; Musuka, Godfrey
Unsuppressed Viral load and low CD4 counts pose a significant challenge to HIV/AIDS management. Understanding the predictors of unsuppressed viral load and CD4 is critical for developing strategies to mitigate its impact. This study aimed to identify predictors of unsuppressed HIV viral load and low CD4 counts among Zimbabwe population-based HIV impact assessment survey (ZIMPHIA 2020) study participants. We analysed data from the ZIMPHIA 2020 survey. Data collection was done using structured interviews, home-based HIV testing and laboratory testing. Blood samples from participants were tested for HIV and those positive were analysed for CD4 counts and Viral load tests. We then calculated odds ratios for predictors of unsuppressed viral load (viral load ≥1000 copies/mL) and low CD4 counts (CD4< 350). The prevalence of unsuppressed viral load and low CD4 count were 20.7% and 34.7%, respectively. Males were more likely to be virally unsuppressed (25.1%) than females (18.8%) adjusted odds ratio (aOR) (95% confidence interval) 1.74 (1.43-2.11) p-value < 0.001. The odds of having a low CD4 count were higher among males (41%) than females (19%) aOR (95% confidence interval) 3.07 (2.57-3.66). Urban dwellers were more likely to have a low CD4 count (31.1%0 than rural dwellers (23.8%) aOR (95% confidence interval) 1.45 (1.21-1.73) p-value <0.001. The common predictors of both unsuppressed viral load and low CD4 were gender, never tested for HIV and never had a viral load test.
Factors driving virtual running event participation : A CHAID segmentation approach
(Sage, 2024-12) Frost, Bianca Lizelle; Du Preez, Elizabeth; Jordaan, Yolanda; bianca.frost@up.ac.za
Virtual running events (VREs) have emerged as participatory events and are projected to be a legitimate future segment in the sport event industry. This paper considers the most suitable market segment(s) with future intentions to partake in VREs. A Chi-Squared Automatic Interaction Detector (CHAID) algorithm, scarcely used to segment sport consumer markets, was applied based on various motivational factors that may drive VRE participation. Data were collected from 1,017 individuals who had participated in a VRE. Ten distinct market segments with varying intentions to partake in VREs were identified, uncovering at least six viable future VRE segments. Hedonia, perceived psycho-social risk, perceived price and VRE benefits were the strongest predictors of VRE participation intentions. The CHAID analysis allowed a detailed description of the relative importance of the characteristics within each segment, confirming the benefit of using this sophisticated technique to develop targeted marketing strategies.
Evaluating factors influencing youth participation in agricultural enterprises : implications for food security and agribusiness
(AOSIS, 2024-11-08) Giwu, Ongama; Mdoda, Lelethu; Ntlanga, Samuel S.; Loki, Olwethu
BACKGROUND : Agriculture is crucial for economic growth, yet youth engagement in agricultural enterprises is declining due to concerns related to perceived profitability, resource access, and social stigmas. Understanding these determinants is vital for fostering youth interest in agriculture and promoting sustainable rural development and food security. AIM : This study examines the factors affecting youth engagement in agricultural enterprises in Umzimvubu Local Municipality, South Africa, and their implications for food security and agribusiness. SETTING : Addressing youth unemployment and enhancing agriculture’s contribution to gross domestic product (GDP) require understanding barriers to youth participation. This study was conducted in Umzimvubu Local Municipality, South Africa. METHODS : A structured questionnaire was administered to 210 youths through stratified random sampling. Descriptive statistics and a univariate probit regression model were used for analysis. RESULTS : Findings indicate male dominance in agriculture, with educational background positively correlating with participation. Single youths showed greater interest than married counterparts. Challenges like land availability and a lack of financial support hinder engagement. Significant determinants include age, education, farming skills, social group membership, and household revenue, while factors like household size, gender, and limited access to credit negatively impact willingness to participate. CONCLUSION : Addressing financial barriers through improved access to loans is essential to enhance youth involvement. Policies should cater to youth-specific traits and environmental challenges to build a resilient agricultural sector driven by young innovators. CONTRIBUTION : The study emphasises the need for a comprehensive policy framework collaboratively developed by the government, the Department of Agriculture, and non-governmental organisations.
Effect of infrared heat-moisture treatment and cooling rate on the material properties of amylose-lipid complex nanomaterials
(Wiley, 2025-08) Maphumulo, Njabulo Gideon; Masanabo, Mondli Abednicko; Ray, Suprakas Sinha; Emmambux, Mohammad Naushad; naushad.emmambux@up.ac.za
Please read abstract in the article.
Help-seeking among adults with tinnitus : examination of a tinnitus cohort from the Busselton healthy ageing study
(Taylor and Francis, 2025) Carmody, Natalie; Hunter, Michael; Eikelboom, Robert H.
The aim of this study was to examine the help-seeking behaviour of adults with tinnitus and the factors associated with help-seeking. A tinnitus cohort (n = 131) from the Busselton Healthy Ageing Study (BHAS) completed surveys assessing demographic and clinical factors, tinnitus characteristics and distress, health status, and help-seeking behaviour. The study found that of the 131 participants that took part 43.5% sought help for tinnitus. Binomial logistic regression was used to examine the association of health status (Glasgow Health Status Inventory – all purpose (GHSI) total score) and tinnitus distress (Tinnitus Reaction Questionnaire (TRQ) total score) with self-reported hearing loss and self-reported anxiety. The results of the binomial logistic regression found that help-seeking was significantly associated with higher tinnitus distress (odds ratio [OR] 1.04, 95% confidence interval [CI] [1.01, 1.07], p = 0.01) and lower self-reported anxiety levels (OR 0.43, 95% CI [0.18, 1.00], p = 0.05). However, no significant association was found between help-seeking and self-reported hearing loss. Whilst increased tinnitus distress can be expected to be associated with help-seeking, lower anxiety may encourage help-seeking or may be barrier to seeking help. Further work is needed to better understand the relationship with tinnitus, anxiety and help-seeking.
Attribute based spatial segmentation for optimising POI placement
(Elsevier, 2025-08) De Klerk, Michelle; Fabris-Rotelli, Inger Nicolette
Effective spatial planning and resource optimisation require precise demarcation of potential spatial accessible areas and optimal placement of points of interest (POIs). Our approach introduces a novel attribute based spatial segmentation methodology that utilises an iterative clustering approach to create unique macro-regions, each associated with key structural and attribute specific properties. By integrating a probabilistic attribute based structure with k-means clustering, we adaptively segment spatial regions to balance area based attributes and topological characteristics. The full geographical network is segmented into attribute based macro-regions for all spatially accessible and spatially disjoint regions. Attribute based spatial segmentation offers insights into why certain areas may be spatially disjoint and if it is identified as potential spatially accessible areas to determine which POIs can be placed to maximise accessibility. This approach transforms city planning and resource allocation by aligning POI placement with regional needs and characteristics.
Pathogenicity of Pythium myriotylum on Acacia crassicarpa and Acacia mangium x Acacia auriculiformis clones in Indonesia
(Taylor and Francis, 2025) Tarigan, Marthin; Wingfield, Michael J.; Jami, Fahimeh; Oliveira, Leonardo S.S.; Saha, Muhammad A.; Duran, Alvaro; Pham, Nam Q.; nam.pham@fabi.up.ac.za
The oomycete Pythium myriotylum is an important pathogen of several crops, causing wilt and damping-off during nursery propagation. The pathogen was recently reported as the causal agent of wilt and damping-off on Acacia crassicarpa plants in nurseries located in Riau, Indonesia. The aim of this study was to evaluate the relative pathogenicity of P. myriotylum on different clones of A. crassicarpa and Acacia mangium × Acacia auriculiformis hybrids. Based on the results, greater tolerance was found on the A. mangium × A. auriculiformis hybrid clones than on those of pure A. crassicarpa. The different Acacia clones also displayed different levels of tolerance of infection. Overall the results showed that screening for tolerance to infection by P. myriotylum will be important in the Acacia breeding programme and make it possible to produce sufficient nursery stock for plantation establishment.
Analytical and quality control validation of a novel symmetric dimethylarginine assay in dogs and cats
(Wiley, 2025-09) Mashego, Portia Tshidi; Hooijberg, Emma Henriette
BACKGROUND : An immunoturbidometric assay for symmetric dimethylarginine (SDMA) measurement on automated chemistry analyzers has recently become available. OBJECTIVE : To perform analytical validation of the EUROLyser SDMA assay in dogs and cats. METHODS : Method validation experiments were performed using stored canine and feline serum. Quality control validation was performed according to Westgard. Performance goals were derived from SDMA biological variation data for both species. RESULTS : Imprecision ranged from 3.7%-7.8% (dogs) to 6.0%-11.8% (cats) with a dispersion of ±35% for dogs and ±44% for cats. The assay showed linearity (up to 85 μg/dL [dogs], 75 μg/dL [cats]); the preliminary LoQ was 9.5 and 6.9 μg/dL, respectively. Recovery was 19.7% and 6.5%, respectively. Severe hemolysis resulted in a significant bias in both species. The EUROLyser method showed a significant negative proportional and constant bias in dogs and a significant positive proportional and negative constant bias in cats, compared to the comparative method. In dogs, the mean bias (-19.5%) and the bias at clinical decision limits exceeded the desirable bias; in cats, the mean bias (-4.0%) and the bias at clinical decision limits was < 8%. Because of high imprecision, the TEA that could be controlled for was 35%, with a 1-2.5 s rule using patient pools as quality control material. CONCLUSIONS : The novel SDMA assay showed acceptable analytical performance, but high dispersion has consequences for the interpretation of results at reference limits and serial measurements. Method-specific reference intervals and decision limits should be generated for both species, particularly for dogs, given the significant bias vs. the comparative method.
An evaluation of alternative treatment strategies in mitigating colistin resistance : targeting plasmid transfer through the use of Bambermycin or the protein coded by the Mcr-1 gene with antibodies and Streptomycin
(Wiley, 2025-09) Hassan, Ibrahim Zubairu; Qekwana, Daniel Nenene; Naidoo, Vinny; hassan.ibrahim@up.ac.za
BACKGROUND : Plasmid mediated antimicrobial resistance continues to be a source of global concern, especially given the limited pipeline of novel antibiotics. The horizontal transfer of the plasmid mediated colistin resistance gene (mcr-1) between microorganisms confer resistance to previously susceptible bacterial strains and renders colistin and polymyxin B antimicrobials ineffective. OBJECTIVE : To mitigate plasmid mediated colistin resistance using bambermycin and streptomycin on mcr-1 positive field strains of Escherichia coli. Furthermore, to assess if a commercial MCR-1 polyclonal antibody would have any synergistic effect on colistin in killing mcr-1 gene associated colistin-resistant E. coli in vitro. METHODS : Colistin-resistant E. coli strains recovered from clinical cases were subjected to checkerboard assays and conjugation assays using varying drug combinations viz colistin, bambermycin, streptomycin, MCR-1 antibody and human complement serum, to mitigate drug resistance. RESULTS : Following conjugation assay, the plasmid bound resistance gene was successfully transferred to J53 E. coli strain with colistin minimum inhibitory concentration (MIC) rising from ≤0.125 to >2 µg/mL conferring resistance to the former organism. The combination of bambermycin and colistin in a checkerboard assay proved to be synergistic in killing mcr-1 associated colistin-resistant strains. The combination of streptomycin, colistin and MCR-1 polyclonal antibody showed additive lethal effect on mcr-1 associated colistin-resistant strains. Bambermycin did not interfere with the transfer of mcr-1 bound plasmid from donors to recipient organism. CONCLUSION : Further studies on bambermycin's mechanism of action are required, as both inhibiting and enhancing effects have been documented. Similarly, the addition of MCR-1 polyclonal antibody in a checkerboard assay did not enhance colistin's lethal effect on mcr-1 carrying E. coli strains, thus highlighting the need for further research.
Seroprevalence and risk factors associated with Brucellosis in goats in Nyagatare District, Rwanda
(Wiley, 2025-08) Habimana, Jean Paul; Ntivuguruzwa, Jean Bosco; Uwimana, Aime Lambert; Ugirabe, Marie Aurore; Gasana, Eric; Van Heerden, Henriette
Given the endemic nature of bovine brucellosis in Rwanda, caprine brucellosis, primarily caused by Brucella melitensis in goats, may also be prevalent. However, no data exist on the disease’s prevalence and associated risk factors in goats, particularly in Nyagatare district. A cross-sectional study was therefore conducted to determine the seroprevalence of brucellosis and to identify herd-level risk factors associated with the disease among goat herds (n = 102) across six sectors of Nyagatare district. Serum samples from 612 goats were tested using both the indirect enzyme-linked immunosorbent assay (i-ELISA) and the Rose Bengal Test (RBT), applied in parallel. A systematic questionnaire, pretested for reliability, was used to gather data on potential risk factors for caprine brucellosis. The study found a brucellosis true adjusted seroprevalence of 6.08% and 10.7% using RBT and i-ELISA, respectively. When combining the results from both tests, the overall seroprevalence was 6.08% at the animal level and 16.6% at the herd level. The most significant risk factors for Brucella seropositivity were mixing of cattle and goats within the same herd and a history of abortions in the herd (p < 0.05). This study confirms that caprine brucellosis is endemic in Nyagatare district, highlighting the need for a One Health approach to control and prevent the disease in both livestock and humans. The study recommends implementing awareness campaigns to educate livestock farmers about brucellosis and calls for further research to characterize Brucella spp. in small ruminants in Rwanda and to establish appropriate control measures.
Predicting tick distributions in a changing climate : an ensemble approach for South Africa
(Elsevier, 2025-08) Motloung, R.F.; Chaisi, Mamohale E.; Sibiya, M.S.; Nyangiwe, N.; Shivambu, T.C.
Predicting the potential distribution of disease vectors is crucial for vector management and disease transmission surveillance. This study aims to assess changes in the geographic projection of the ecological niche of ticks of veterinary, public health, and economic importance in South Africa, and to predict areas suitable for their establishment under current and future climate scenarios. We used a suite of six algorithms within the ensemble modelling framework of the biomod2 package in R version 4.4.2 to produce species distribution models for current (2021–2040) and future (2041–2060) climate scenarios. Six bioclimatic variables, representing a range of biophysical and anthropogenic factors, were used in combination with tick presence-only occurrence data submitted to SANBI’s Integrated Publishing Toolkit by tick species experts. The model outputs indicate that all 10 tick species will likely experience range shifts over time (2021–2060). All species are projected to gain significant portions of suitable ranges in the future. Notably, Rhipicephalus microplus is predicted to gain the most, with a 14 % increase in its suitable range in South Africa. This predicted range expansion could potentially disrupt ecological balances in the ecosystems it is likely to occupy. Native species such as Amblyomma hebraeum and Hyalomma rufipes are predicted to expand their ranges by 10 and 9 %, respectively, while others may gain less than 6 % of their potential ranges The overall predicted range expansion could also introduce new disease dynamics, potentially leading to increased pathogen transmission, host switching and higher incidences of diseases in humans and animals in currently unaffected areas. The study provides baseline information to support ongoing monitoring and adaptive management strategies to mitigate the negative impacts associated with ticks on ecosystems, public health, and agriculture. The results will help inform tick control programs in South Africa and other similar environments. South Africa must adopt a comprehensive One Health approach to tick management to address the challenges posed by invasive species like R. microplus, which threaten livestock health and have significant veterinary and economic impacts. HIGHLIGHTS • Distribution models developed for 10 zoonotic tick species in South Africa. • An innovative ensemble modelling framework utilized. • Assessed the impact of climate change on zoonotic ticks. • Addressed a critical gap on regional tick distribution data. • Closely related tick species are likely to increase their range sizes.
Smart farming with AI : enhancing anemia detection in small ruminants
(Elsevier, 2025-08) Siddique, Aftab; Khan, Sophia; Terrill, Thomas H.; Mahaptra, Ajit K.; Panda, Sudhanshu S.; Morgan, Eric R.; Pech-Cervantes, Andres A.; Randall, Reginald; Singh, Anurag; Batchu, Phaneendra; Gurrapu, Priyanka; Van Wyk, Jan Aucamp; jan.vanwyk@up.ac.za
Accurate classification of FAMACHA© scores is essential for assessing anemia in small ruminants and optimizing parasite management strategies in livestock agriculture. The FAMACHA© system categorizes anemia severity on a scale from 1 to 5, where scores 1 and 2 indicate healthy animals, score 3 represents a borderline condition, and scores 4 and 5 indicate severe anemia. In this study, a dataset of 4700 images of the lower eye conjunctiva of young male goats was collected weekly over six months using a Samsung A54 smartphone. Traditional FAMACHA© assessment methods rely on subjective visual examination, which is labor-intensive and susceptible to observer bias. To address this limitation, this study implemented machine learning algorithms to automate FAMACHA© classification, leveraging Support Vector Machine (SVM), Backpropagation Neural Network (BPNN), and Convolutional Neural Network (CNN) models. A comparative analysis of these models was conducted using precision, recall, F1-score, and accuracy metrics. The CNN model demonstrated the highest classification accuracy (97.8 %), outperforming both BPNN and SVM. The SVM model achieved a mean accuracy of 84.6 %, with strong performance in severe anemia detection, but limitations in intermediate classes. The overall accuracy of 84 % attained by the BPNN model provided a balanced tradeoff between precision and recall. The CNN model’s superior performance was attributed to its ability to learn spatial and contextual patterns from images, ensuring robust classification across all FAMACHA© categories. These findings underscore CNN’s potential as a reliable, scalable solution for automated anemia detection in livestock, facilitating early intervention and improving herd health management. The study also highlights the need for future research to explore ensemble learning approaches and integration with mobile applications for real-time deployment for both commercial and resource-limited livestock producers.
A single-centre retrospective study of surgical site infection following equine colic surgery (2013-2021)
(Wiley, 2025-05) Griessel, Theunis Steyn; Moran, Juan Alberto Munoz; Byaruhanga, Charles; Smit, Yolandi
BACKGROUND : Surgical site infection (SSI) is a significant cause of postoperative morbidity following equine laparotomy. Therefore, if risk factors for SSI can be identified, morbidity may consequently be reduced. The objectives of this study were to determine the prevalence of SSI in horses undergoing exploratory laparotomy at a single hospital over an 8-year period (2013‒2021), investigate the risk factors associated with SSI and report on the bacterial isolates identified. METHODS : The medical records of horses that had an exploratory laparotomy performed at the teaching hospital due to colic were retrospectively reviewed. SSI was defined as any purulent or serous discharge from the laparotomy incision for more than 24 hours duration during hospitalisation. Pre-, intra- and postoperative risk factors for SSI were identified using multivariable logistic regression analysis. RESULTS : A total of 143 horses met the criteria for inclusion in the study, of which 38 developed an SSI (26.6%, 95% confidence interval: 19.5–34.6%). Multivariable analysis revealed that the application of a postoperative abdominal bandage was significantly associated with a decreased likelihood of SSI (odds ratio = 0.29, p = 0.026). LIMITATIONS : As this was a retrospective study performed at a single hospital, the findings may have limited generalisability. CONCLUSIONS : The application of a postoperative abdominal bandage is protective against SSI in horses following exploratory laparotomy for colic.
Exploring meiotic recombination and its potential benefits in South African beef cattle : a review
(MDPI, 2025-07) Magagula, Nozipho A.; Ncube, Keabetswe T.; Zwane, Avhashoni Agnes; Mtileni, Bohani
Meiotic recombination is a key evolutionary process that generates novel allele combinations during prophase I of meiosis, promoting genetic diversity and enabling the selection of desirable traits in livestock breeding. Although its molecular mechanisms are well-characterised in model organisms such as humans and mice, studies in African indigenous cattle, particularly South African breeds, remain scarce. Key regulators of recombination, including PRDM9, SPO11, and DMC1, play essential roles in crossover formation and genome stability, with mutations in these genes often linked to fertility defects. Despite the Bonsmara and Nguni breeds’ exceptional adaptability to arid and resource-limited environments, little is known about how recombination contributes to their unique genetic architecture and adaptive traits. This review synthesises the current knowledge on the molecular basis of meiotic recombination, with a focus on prophase I events and associated structural proteins and enzymes. It also highlights the utility of genome-wide tools, particularly high-density single nucleotide polymorphism (SNP) markers for recombination mapping. By focusing on the underexplored recombination landscape in South African beef cattle, this review identifies key knowledge gaps. It outlines how recombination studies can inform breeding strategies aimed at enhancing genetic improvement, conservation, and the long-term sustainability of local beef production systems. SIMPLE SUMMARY By generating novel allele combinations during prophase I of meiosis, meiotic recombination is a fundamental evolutionary mechanism that enhances genetic diversity and supports the selection of desirable traits in livestock breeding. This process is crucial for improving the genetic potential of livestock through selective breeding. While recombination has been studied in commercial cattle breeds from Europe and North America, it remains unexplored and not understood in South African beef cattle, especially the Bonsmara and Nguni breeds. These indigenous breeds are highly valued for their adaptability to harsh, resource-limited environments, yet the genetic mechanisms underlying their resilience and productivity are not well characterised. This review explores how genome-wide technologies, especially those using high-density single nucleotide polymorphism (SNP) markers, can be used to map recombination patterns and identify genes involved in key traits. Applying these tools to South African cattle could enhance breeding strategies by improving the accuracy of selecting animals with a superior genetic merit. Understanding recombination in these breeds will also support their conservation and sustainable use. Ultimately, this knowledge has significant implications for advancing food security, promoting rural development, and ensuring the long-term adaptability of South African beef cattle under climate change.
Comparative analysis of the subsidence of solid polyetheretherketone (PEEK) and 3D printed lattice titanium interbody fusion cages
(EDP Sciences, 2023-12) Moolman, Frans J.; Kat, Cor-Jacques; Du Plessis, Anton; Khodja, Malika
Spinal interbody fusion cages are commonly used to treat various spinal conditions, but their traditional manufacturing methods have limitations in customization and fitting. With the advancement of 3D printing, it is now possible to design and manufacture interbody fusion cages with previously unachievable features and structures. Southern Medical™ is investigating the technical feasibility of 3D-printed cages based on their existing designs and exploring the new features and capabilities enabled by additive manufacturing (AM). The mechanical performance in the subsidence of the 3D-printed devices will be compared to their existing devices as one of the feasibility points for the additively manufactured implants. A gyroid structure is used as the inner lattice of the structures. To investigate the performance of the cages with the new gyroid lattices, subsidence testing according to the ASTM F2267 methods was conducted to compare existing cages to the 3D-printed cages. The 3D printed devices outperformed the PEEK counterparts with a higher test block stiffness of 0.81 kN/mm compared to 0.55 kN/mm.
Antimicrobial resistance of Staphylococcus spp. isolated from canine specimens submitted to a veterinary diagnostic laboratory in South Africa
(Veterinary World, 2025-06) Sigudu, Themba Titus; Oguttu, James Wabwire; Qekwana, Daniel Nenene
BACKGROUND AND AIM : The rising burden of antimicrobial resistance (AMR) in veterinary medicine poses significant threats to animal and public health. In South Africa, inadequate surveillance exacerbates the challenge, particularly regarding Staphylococcus spp. infections in companion animals. This study aimed to investigate the patterns and predictors of AMR and multidrug resistance (MDR) in Staphylococcus isolated from dogs between 2012 and 2017. MATERIALS AND METHODS : A retrospective cross-sectional study was conducted on 1627 Staphylococcus isolates. Data regarding animal demographics and antimicrobial susceptibility were extracted, cleaned, and analyzed. Intermediate susceptibility results were classified as resistant. AMR was defined as resistance to at least one antimicrobial from one class and MDR as resistance to antimicrobials from three or more classes. Descriptive statistics, Cochran-Armitage trend analysis, and binary logistic regression models were employed to assess trends and predictors of AMR and MDR. RESULTS : Overall, 61.2% of isolates exhibited resistance to at least one antimicrobial, and 39.0% were classified as MDR. The highest resistance was observed against penicillins (39.64%), followed by aminoglycosides (22.31%). Significant predictors of AMR included Staphylococcus species, specimen type, and year of isolation, while MDR was significantly associated with specimen type and the age of the dog. Notably, Staphylococcus pseudintermedius showed a markedly higher likelihood of resistance (Adjusted Odds Ratio = 2.23, p < 0.001) compared to other species. Temporal trends indicated a decrease in AMR but an increase in MDR across the study period. CONCLUSION : The high prevalence of AMR and MDR among canine Staphylococcus isolates, particularly in skin infections and among younger dogs, underscores the urgent need to strengthen antimicrobial stewardship, enhance surveillance systems, and target interventions in veterinary practice. These findings serve as critical baseline data for future assessments of AMR trends and can be used to inform strategies to mitigate the dissemination of resistant pathogens between animals and humans.
Enterobacterales use capsules, transporters, mobile genetic elements, and other evolutionary adaptations to survive antibiotics exposure in the absence of resistance genes
(Taylor and Francis, 2025-12) Mmatli, Masego; Mbelle, Nontombi Marylucy; Fourie, Bernard P.; Osei Sekyere, John; j.oseisekyere@up.ac.za
Carbapenems and colistin are last-resort antibiotics used to manage difficult-to-treat infections caused by Gram-negative bacteria. However, resistance to these two antibiotics is rising globally, and there is limited knowledge on how pathogens evolve resistance when known resistance genes are absent. METHODS : Whole-genome sequencing, transcriptomic profiling, and epigenomic analyses were performed. Phenotypic assays were used to evaluate the effects of various inhibitors on antibiotic susceptibility, while bioinformatic pipelines were used to characterize resistance determinants, virulence factors, and mobile genetic elements (MGEs). RESULTS : Phylogenetic analysis revealed widespread carriage of diverse resistance genes, particularly on plasmids of K. pneumoniae, while Enterobacter species possessed fewer known ARGs. Despite lacking known carbapenemase and mcr genes, several isolates demonstrated colistin or carbapenem resistance mediated by upregulation of efflux pumps, overproduction of capsular polysaccharides, mutations in outer membrane proteins, and potential lipopolysaccharide-modifying enzymes. Transcriptomic analysis revealed significant differential gene expression upon antibiotic exposure. Notably, genes encoding ABC transporter proteins were significantly downregulated (p-value <0.0001, fold change > 10), while genes encoding transposases were significantly upregulated (p-value <0.0001, fold change > 11). These changes underscore the critical role of transporters and MGEs in antibiotic resistance adaptation. CONCLUSIONS : In the absence of canonical carbapenemase and mcr genes, K. pneumoniae and Enterobacter species can deploy a spectrum of adaptive mechanisms, including efflux pumps, mobile elements, and altered outer membrane/capsule structures, to overcome colistin and carbapenem treatments. These findings support the need for ongoing surveillance of novel or underrecognized resistance mechanisms to preserve the efficacy of last-line antibiotics.
Integrating the TOE framework and DOI theory to dissect and understand the key elements of AI adoption in sociotechnical systems
(South African Computer Society, 2024-12-11) Smit, Danie; Eybers, Sunet; Van der Merwe, Alta; Wies, Rene; Human, Nica; Pielmeier, Julia; alta.vdm@up.ac.za
This study is interested in increasing the likelihood of achieving the organisational adoption of artificial intelligence that has a positive outcome. We argue that the technological-organisational-environmental frame-work provides a sound theoretical lens for analysing how an organisation’s context influences the adoption and integration of artificial intelligence solutions. Furthermore, the diffusion of innovation theory is proposed to identify enablers for transforming organisations. Together with the combination of technological-organisational-environmental and diffusion of innovation, the stages of diffusion are proposed as an evaluation paradigm to evaluate the effectiveness of the enabling factors. Furthermore, the elements and objectives of artificial intelligence adoption in the context of data-driven organisations are included. From this, the research develops a comprehensive framework for studying the technical and social AI adoption elements in an organisational environment where complex symbiotic relationships prevail. This study uses generative artificial intelligence as a novel approach to exploring the framework’s usability. The evidence from our research indicates that the developed framework can advance our comprehension of what drives the success or failure of artificial intelligence adoption in organisations. Theoretically, it provides a tool for dissecting and understanding the key elements influencing this process.
Seroprevalence of canid alphaherpesvirus-1 and associated risk factors in domestic dogs in North Queensland, Australia
(Elsevier, 2024-10) Joone, C.J.; Gummow, Bruce; Horwood, P.F.
Canid alphaherpesvirus-1 (CaHV-1) may cause a highly fatal haemorrhagic disease in neonatal pups and is associated with reproductive, respiratory and ocular disease in older dogs. Although assumed to have a worldwide distribution, there have been few reports of CaHV-1 in Australia. The aim of this study was to investigate the seroprevalence of CaHV-1 in household dogs in a residential suburb in Townsville, as well as in dogs attending two dog shows in the region. Study participants were recruited through door-to-door non-probability sampling (Douglas dogs, n = 185) or invited to participate (Show dogs; n = 76). Dog owners completed a questionnaire that investigated possible risk factors for recent exposure to CaHV-1. A serum sample from each dog was assayed for anti-CaHV-1 antibodies using a commercially available ELISA. Associations between seropositive dogs and owner-reported risk factors were analysed using univariable analysis and multivariable logistic regression models. The seroprevalence of CaHV-1 was 11.4 % (95 % CI 6.8–15.9 %) and 17.1 % (95 % CI 5.5–28.8) for the Douglas and Show dogs, respectively, with a pooled seroprevalence of 13 % (95 % CI 8.3–17.7 %). Dogs that had suffered from conjunctivitis within the previous 3 months or were involved in breeding were more likely to be seropositive to CaHV-1. No other significant risk factors were identified. In conclusion, CaHV-1 is circulating in dogs in North Queensland and may be contributing to foetal and neonatal losses in this region.

Browse

Recent Submissions