Theses and Dissertations (University of Pretoria)

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

Browse

Now showing 1 - 20 of 23872

Neutrophil gelatinase-associated lipocalin and symmetric dimethylarginine concentrations in dogs with carcinoma and sarcoma
Rixon, Anouska Jade Rixon (University of Pretoria, 2024-11)
Although neutrophil gelatinase-associated lipocalin (NGAL) and symmetric dimethylarginine (SDMA) are considered sensitive biomarkers of kidney injury and function, respectively, their specificity is affected by extra-renal factors. The extra-renal effect of tumours on biomarker concentrations is yet to be fully elucidated despite their association with tumourigenesis. Due to the lack of renal histopathology in previous studies, it remains unclear if tumours or concomitant kidney disease is responsible for the appreciable increases in serum and urinary NGAL and SDMA concentrations reported in various cancers in both humans and dogs. This study aimed to determine the extra-renal effect of tumours on serum and urine NGAL and SDMA concentrations in dogs with carcinoma or sarcoma without significant kidney disease. Additionally, this study aimed to evaluate the association between biomarker concentrations and tumour type, as well as metastasis. If biomarker concentrations were found to be increased in tumour-bearing dogs, the potential contribution of tumour-associated systemic inflammation on NGAL concentrations would also be investigated. Concentrations of serum NGAL (sNGAL), SDMA, urinary NGAL (uNGAL) and uNGAL-to-creatinine ratio (uNGAL/Cr) were measured on stored samples from a previous prospective study. Patient clinicopathological and histopathology records were reviewed and those with renal azotaemia or moderate-severe histopathological renal changes were classified as having significant kidney disease. Biomarker concentrations were compared between tumour-bearing dogs without significant kidney disease and healthy age-controlled dogs. Additionally, comparisons between dogs with carcinoma and sarcoma; and dogs with and without metastasis; as well as correlations between urinary and serum NGAL and acute phase protein (APP) concentrations were analyzed. Twenty-one dogs with carcinoma, 18 dogs with sarcoma and 20 healthy age-controlled dogs were included. Tumour-bearing dogs without significant kidney disease had significantly increased uNGAL/Cr (P < .001), but not sNGAL, compared to healthy controls. Although median SDMA concentrations did not significantly differ between groups, increased concentrations were found in 32% and 20% of dogs with carcinoma and sarcoma, respectively. Additionally, no differences between dogs with carcinoma or sarcoma or those with and without metastasis were found. Urinary NGAL concentrations were moderately correlated with sNGAL concentrations, with moderate to no correlations shown with APPs, respectively. In conclusion, this study found that tumour presence, but not metastasis, effects uNGAL/Cr and SDMA concentrations in dogs with carcinoma and sarcoma. uNGAL should therefore not be used, and SDMA used with caution, as renal biomarkers in dogs with carcinoma and sarcoma. Additionally, the disproportionate increase in urinary, as compared to serum, NGAL concentrations in this cohort of dogs with carcinoma and sarcoma is suggestive of a potential glomerulopathy and increased glomerular permselectivity secondary to tumour presence.
Disposable diaper use and perception of health and environmental risks in a rural community from Bushbuckridge, South Africa
Lowe, Amy L (University of Pretoria, 2024-10)
Littering of disposable diapers is a problem with One Health implications and has been identified as an issue within the Mnisi community, a rural area within Bushbuckridge, South Africa. Several environmental and public health related concerns arise from this, including contamination of waterways used by animals and people with human waste, scavenging by domestic and wild animals, and the aesthetic impact on the environment. The aim of this study was to gain an understanding of the use and sanitation practices associated with disposable diapers, with the ultimate goal of identifying possible community-led initiatives and solutions which can be used for training and education. Focus group discussions were conducted within the community which included a participatory mapping exercise used to map general diaper disposal sites. Focus group data was analyzed according to three themes: decisions and factors around diaper use and disposal, perceptions of impact and health risk of diaper use for people and animals, and barriers and solutions for proper disposal. Most participants used disposable diapers and disposed of them within the environment because they lacked access to municipal waste collection. Regarding decisions around diaper use, common factors discussed were convenience, social perception and beliefs, cost, water access, and diaper disposal logistics. Convenience and societal perception and beliefs were determined as key factors behind diapering choices, and both a gender and a generational divide was revealed. Participants express general understanding of negative impacts associated with diaper disposal, but knowledge gaps exist, notably regarding water pollution and pathogen spread, that could be a focus of educational campaigns. Regarding solutions, participants proposed the provision of a central collection point as well a return to reusable diapers, each of which has its own considerations and hurdles. Any interventions should retain the perceived convenience factor of disposable diapers and be implemented on a community rather than individual basis. Solutions should be multifaceted, involve opportunities for community collaboration amongst all ages and genders, and should also engage local leadership. Focus groups should be considered as the first steps towards continued discussions amongst stakeholders.
Describing blood acid-base response in dogs with acute haemorrhagic diarrhoea syndrome using three different methods
Michaletos, Anthea Francis (University of Pretoria, 2025-09)
Objective: To describe blood acid-base response in dogs with acute haemorrhagic diarrhoea syndrome (AHDS) using three different methods of analysis. Hypothesis: Dogs with AHDS have increased unmeasured strong anions compared to healthy dogs. Design: Prospective, observational study. Setting: Private referral hospital. Animals: A total of 20 dogs used in two groups as follows: 10 healthy age-, weight- and breed-matched dogs and 10 dogs with AHDS. Interventions: Blood that was collected from healthy dogs were used to establish an expected normal range (minimum and maximum limits of the ranges were calculated as mean ± 2 standard deviations). Jugular venous blood, AHDS index scores (0 – 3: insignificant disease; 4 – 5: mild AHDS; 6 – 8: moderate AHDS; 9 – 18: severe AHDS) and intravenous fluid infusion volumes (mL/kg) were collected at presentation (0H) and then at set hour-intervals post presentation (4H, 8H, 12H, 16H, 20H, 24H, 36H, 48H and 60H). Blood was analysed to measure or calculate acid-base variables used in three different methods of analysis: 1) traditional, 2) Stewart theory, and 3) semi-quantitative theory approaches. Longitudinal data were compared using a general lineal mixed model with post-hoc comparisons using Dunnett's method (control variable: values at 0H) and significance was P < 0.05 and data were reported as median (minimum – maximum). Measurements and main results: The pH, at 0H, was 7.31 (7.22 – 7.49) and classified as acidaemic with a wide anion gap of 24.6 (13.1 – 27.6) mmol/L because of a raised venous carbon dioxide tension [48 (26 – 51) mmHg], negative base excess of extracellular fluid [-5.4((-8.0) – (-2.4)) mmol/L] and acidaemic lactate effect [-3.5 ((-5.4) – (-1.2)) mmol/L]. The pH normalised by 4H (P < 0.0001) in response to fluid administration where 37 (29 – 63) mL/kg was given over the 4-hour period. Whereas the AHDS clinical index score was classified as ‘insignificant disease’ by 48H. The pH remained within normal reference intervals until 60H and fluid rates were 3 mL/kg/hour from 8H onwards. The bicarbonate and haemoglobin buffer systems played a role in blood acid-base homeostasis. Conclusions: The acidaemia at presentation in dogs with AHDS was related to hypovolaemia and all derangements were corrected by fluid resuscitation. All three methods of analysis were useful in interpreting the complex interplay between acidifying and alkalinising effects and blood buffers.
Disposable diaper use and perception of health and environmental risks in a rural community from Bushbuckridge, South Africa
Lowe, Army L (University of Pretoria, 2024-10)
Littering of disposable diapers is a problem with One Health implications and has been identified as an issue within the Mnisi community, a rural area within Bushbuckridge, South Africa. Several environmental and public health related concerns arise from this, including contamination of waterways used by animals and people with human waste, scavenging by domestic and wild animals, and the aesthetic impact on the environment. The aim of this study was to gain an understanding of the use and sanitation practices associated with disposable diapers, with the ultimate goal of identifying possible community-led initiatives and solutions which can be used for training and education. Focus group discussions were conducted within the community which included a participatory mapping exercise used to map general diaper disposal sites. Focus group data was analyzed according to three themes: decisions and factors around diaper use and disposal, perceptions of impact and health risk of diaper use for people and animals, and barriers and solutions for proper disposal. Most participants used disposable diapers and disposed of them within the environment because they lacked access to municipal waste collection. Regarding decisions around diaper use, common factors discussed were convenience, social perception and beliefs, cost, water access, and diaper disposal logistics. Convenience and societal perception and beliefs were determined as key factors behind diapering choices, and both a gender and a generational divide was revealed. Participants express general understanding of negative impacts associated with diaper disposal, but knowledge gaps exist, notably regarding water pollution and pathogen spread, that could be a focus of educational campaigns. Regarding solutions, participants proposed the provision of a central collection point as well a return to reusable diapers, each of which has its own considerations and hurdles. Any interventions should retain the perceived convenience factor of disposable diapers and be implemented on a community rather than individual basis. Solutions should be multifaceted, involve opportunities for community collaboration amongst all ages and genders, and should also engage local leadership. Focus groups should be considered as the first steps towards continued discussions amongst stakeholders.
Toxoplasma gondii infection in impala (Aepyceros melampus) from the Timbavati abattoir
Rabe, Shanzelle (University of Pretoria, 2024-10)
Toxoplasma gondii (T. gondii) is a protozoon parasite with a worldwide distribution that infects mainly domestic and wild felids, with virtually all mammal and avian species acting as intermediate hosts. Clinical manifestation known as toxoplasmosis causes encephalitis as well as infertility, abortion or the birth of offspring with central nervous system abnormalities. The feline definitive host ingests the parasite when consuming intermediate hosts with tissue cysts containing T. gondii bradyzoites. Considering the possible presence of the parasite in production and wildlife species, the consumption of undercooked game meat by people, should be regulated because of the potential risk of T. gondii transmission to humans. In this study the prevalence of infection and the tissue cyst predilection sites was determined through serological and molecular assays performed on impala antelope (Aepyceros melampus) samples collected from the Timbavati abattoir, located within the Timbavati Private Nature Reserve (TPNR), on the western boundary of the Kruger National Park (KNP). Impala samples (n = 138) were collected within the TPNR over six months. Serum was used in two serological assays, the Modified Agglutination Test (MAT) and the Latex Agglutination Test (LAT), for assessing the seroprevalence. An optimised in-house sodium acetate method was used to extract DNA from the triceps brachii, cardiac muscle, tongue, diaphragm, spleen, liver, and brain samples, followed by quantitative polymerase chain reaction (qPCR) to amplify an 81-bp fragment of the Repeat element 529-bp sequence to confirm the presence of T. gondii DNA. Due to the limited research on T. gondii in wildlife species in Africa, in terms of both clinical significance and the interface between humans and wildlife in the rural setting, the main focus of the current study was to determine whether the rural communities in and around the Mnisi area are at risk of contracting T. gondii by consuming game meat, and to determine if specific organs/tissues were more prone to containing T. gondii cysts than others. Based on a seroprevalence of 8.70% (MAT) and 13.77% (LAT) in impala in the Mnisi area, the risk of infection via environmental (faecal) contamination is quite low, but still noteworthy. In both assays the two strong positive impala individuals were F18 and F29. When comparing the results between MAT and LAT using the McNemar’s test and Kappa statistics, the LAT yielded a higher seroprevalence, alluding to the possibility of it being the less specific test of the two, however the MAT is more subjective in terms of interpretation of the results. When evaluating the presence of T. gondii DNA using qPCR, 7.25% of individual impala contained T. gondii DNA in at least one of the seven tissues that were sampled, and of these the only samples to have Ct values consistently below 35 were F18 (brain) and F29 (tongue). The presence of DNA within specific tissues (tongue, heart, brain, triceps brachii, and diaphragm) correlates directly with the risk of infection via ingestion of tissue cysts. Undercooked game meat is often sold to nature reserves as biltong or carpaccio, but is most often consumed locally by the population around Timbavati. A lack of resources in the rural community often leads to ingestion of raw or undercooked game meat, and therefore poses a significant risk of contracting toxoplasmosis. Since treatment of T. gondii using drugs such as sulphadiazine, pyrimethamine, clindamycin, or toltrazuril is challenging in people, a better understanding of the prevalence of this parasite within the wildlife population can lead to advances in prevention of disease in and around the Mnisi community. Furthermore, investigating the different strains of T. gondii circulating in wildlife species might shed some light on its genetic diversity within the South African population, and will also help to assess the clinical importance of this disease.
Neutrophil Myeloperoxidase Index in Dogs with Babesiosis
Celliers, Anri (University of Pretoria, 2018-08)
Babesiosis caused by the more virulent tick-borne haemoprotozoan, Babesia rossi, results in a marked systemic inflammatory host response in dogs. Neutrophils are part of the innate immune system and myeloperoxidase is the predominant component of the neutrophil lysosomal protein in azurophilic granules. This enzyme plays a crucial role in the process of destruction of microbes by neutrophils. Neutrophil myeloperoxidase index (MPXI) is a reflection of the intracellular myeloperoxidase content in circulating neutrophils. The aims of this study were to: (a) compare MPXI in dogs with babesiosis with healthy control dogs, using the ADVIA 2120; (b) compare MPXI in dogs that died from babesiosis with dogs that survived and controls; and (c) correlate the MPXI results with (i) total band and segmented neutrophil count and (ii) various cytokine concentrations. Data for 140 dogs, naturally infected with B. rossi, and 20 healthy control dogs were retrospectively evaluated. Approval was obtained from the University of Pretoria’s Animal Ethics committee, as well as the Faculty Research Committee. Owner consent was obtained for enrolment of each case. MPXI was generated on an automated cell counter, ADVIA2120, and various cytokine concentrations, including interleukin-2 (IL-2), IL-6, IL-8, IL-10, IL-18, granulocyte-macrophage colony stimulating factor (GM-CSF) and monocyte chemoattractant protein-1 (MCP-1), were determined using a canine-specific multiplex immunoassay (MILLIPLEX MAP Canine Cytokine/Chemokine Magnetic Bead Panel CCYTO-90K-07, Millipore, Billerica, USA). The mortality rate of the Babesia-infected dogs was 11% (15/140). MPXI was significantly higher in the Babesia-infected dogs (P = 0.033), as well as the Babesia-infected nonsurvivors (P = 0.011), compared to the controls. For the Babesia-infected group a significant positive correlation was found between MPXI and IL-10 (r = 0.211, P = 0.039), and a significant negative correlation between MPXI and IL-8 (r = -0.350, P < 0.001). For the dogs that died, significant positive correlations were found between MPXI and IL-2 (r =0.616, P = 0.033), IL-6 (r = 0.615, P = 0033), IL-18 (r = 0.613, P = 0.034), GM-CSF (r =0.630, P = 0.028) and MCP-1 (r = 0.713, P = 0.009). In dogs that survived, a significant negative correlation was found between MPXI and IL-8 (r = -0.363, P = 0.001). The higher MPXI value in Babesia-infected dogs and especially Babesia-infected nonsurvivors, in conjunction with cytokines, could indicate an increased inflammatory response, as is expected in B. rossi-infections. The potential of MPXI as a novel marker of inflammation and prognosis in Babesia rossi-infected dogs, warrants further exploration.
Expression analysis of selected maize primary metabolism genes in response to Cercospora zeina inoculation in the glasshouse
Mlunjwa, Zimbili Ethel. (University of Pretoria, 2018-09)
Maize is one of the most important grain crops in Africa especially in Southern and sub-Saharan Africa. This crop contributes not only to food security but also to the economy. However, there are factors that affect the development of maize including diseases, which pose as threats to food security. Grey leaf spot (GLS), a foliar disease of maize, is caused by Cercospora zeina, an economically important ascomycete worldwide. It causes over 65% yield losses, thereby being a great threat to food security. This disease was first reported in KwaZulu-Natal province, a GLS hot spot in South Africa in 1988. Strategies such as crop rotation, conventional tillage and fungicides are widely used to manage the progression of GLS. However, these strategies are labour-intensive and expensive for farmers. An alternative cost-effective method is the utilization of host resistance. To better understand the mechanism of host resistance, two primary metabolism genes, isocitrate lyase (ICL) and malate synthase (MS), involved in the glyoxylate pathway, were previously shown to be highly induced by the fungus in a field RNAseq study. This research was aimed at elucidating expression of these two primary metabolism genes. Glasshouse trials were conducted by inoculating the maize genotypes B73 (susceptible) and B73-QTL (resistant) with C. zeina. Genomic DNA was extracted and the fungal CTB7 gene region amplified to confirm that the infection was due to C. zeina. RNA was also extracted, and reverse transcribed to copy DNA (cDNA). The quality of RNA was confirmed by performing a reverse transcriptase PCR (RT-PCR) with banana actin primers as a positive control. Primer pairs flanking an intron in the ICL and MS genes were successfully designed to specifically amplify their respective cDNA. To further confirm these results, the amplified gene products were sequenced using Sanger sequencing platform and thereafter aligned to respective reference genes obtained from NCBI. Overall, ICL and MS genes were successfully amplified from the infected maize genotypes. The ICL amplification needs further optimisation as the bands were not intense to continue with expression analysis. The expression of the two MS transcripts increased at the different progression stages indicated that the glyoxylate pathway plays a role in fungal pathogenicity.
Long bone fractures i n impala (Aepyceros melampus) : a classifica tion system and review of 55 cases
van Heerden, Frans G. (University of Pretoria, 2019-01)
Aim and objective:To introduce and apply a modified-Unger fracture classification in impala, determine the long bone fracture distribution based on 58 long bone fractures, and report the fracture fixation methods used to treat some of the fractures studied. Study design : Retrospective descriptive radiographic study. Sample population: Fifty eight long bone fractures in 55 impala. Materials and methods: This radiographic study evaluated 122 radiographs of 58 long bone fractures in 55 impala. The Unger fracture classification was modified and fracture illustrations for the metacarpal and metatarsal bones added. Each fracture was classified and assigned a four symbol alpha-numeric code using this classification. The long bone fracture distribution, patient signalment, skeletal maturity, fracture associated soft tissue changes, presence of fissure lines, periosteal reaction, fracture displacement, cause of the fracture and treatment were recorded. Results :The overall fracture distribution based on location, found tibial (n=17) fractures to be the most common. Seventy eight percent of the cases had fractures in the diaphysis. The fracture distribution based on complexity was 46% simple, 28% wedge and 26% multi-fragmentary fractures and based on severity was 36% severity 1, 36% severity 2 and 28% severity 3. Fifty seven percent of the fractures affected rams and 43% ewes, with 68% of all cases being skeletally immature. Fifty three percent of cases had open fractures and fissure lines were detected in 34% of fractures. Eighty two percent of all cases had no periosteal reaction associated with the fracture. The average displacement in a cranio-caudal direction was 18 mm, medio-lateral 16 mm and proximo-distal 32 mm. The cause in the majority of fractures was unknown, with some fractures caused by an immobilization dart (n=6). Most patients were treated with external fixation (n=18) only, followed by internal fixation (n=6) or a combination of internal and external fixation methods (n=4). Conclusion :The modified-Unger fracture classification was applicable in classifying 58 long bone fractures in impala, and facilitated determining the long bone fracture distribution. This classification, the determined fracture distribution and the reported fracture fixation methods, should provide a foundation for further advances in veterinary and comparative ungulate, and particularly antelope, orthopaedics and traumatology.
Histology of the female reproductive tract of the cheetah (Acinonyx jubatus)
Penfold, Miles J. (University of Pretoria, 2018-11)
Cheetahs are listed as vulnerable by the IUCN (International Union for Conservation of Nature) with their total worldwide population estimated at 6674 individuals. Ongoing habitat destruction, fragmentation, human animal conflict and predation threaten the survival of the wild cheetah population. Zoos and wildlife parks are tasked with maintaining a genetically healthy population as insurance against catastrophic extinctions. In contrast to reproduction in the wild, reproductive success in captivity has been poor, with only a handful of facilities achieving reasonable success. Much research has been done to try identify why. Both husbandry and spermatic factors have been investigated. Recently the focus has shifted to investigating the role of uterine health in reproductive success. Since the identification of pathology in any organ or system is made with reference to the normal, it was decided to investigate and document the normal histology of the female cheetah reproductive tract. Six captive female cheetah uteri, obtained from post-mortems after elective euthanasia of cheetahs aged 7-10.5 years, and one uterus, from a 3 year-old cheetah that died acutely, were sectioned and processed by routine histological methods. Histological sections were stained with haematoxylin and eosin and studied and photographed with an Olympus BX63 light microscope using bright field illumination and fitted with an Olympus DP72 digital camera. Very early signs of cystic endometrial hyperplasia were identified in 4 of the 7 uteri. These sections were disregarded and only sections with no pathological changes were included in the histological atlas. The histology of the female reproductive tract of the cheetah generally resembled that of the domestic dog, cat and African lioness. In the cheetah the suspensory ligament mostly branched in the region of the tubal pole of the ovary with the branch running in the mesosalpinx to join the tip of the uterine horn. The reproductive ligaments were comprised predominantly of smooth muscle, which was very well developed and supported the entire length of the uterus up to the cervix, similar to the African lioness. Cyst-like structures were found in the region of the UTJ. The uterine tube opened into the uterine lumen from a microscopic, well-defined papilla. The papillary glands were morphologically distinct to the uterine glands. The cyst like structures appeared to be dilations of the papillary glands, potentially acting as a storage cistern. The cyst-like structures are of importance to pathologists examining uterine sections in the UTJ region as they could easily be confused with cystic endometrial hyperplasia. It is therefore advised that sections for histopathology of the uterus of the cheetah be taken at least 5 mm distal to the UTJ to preclude accidental inclusion of these cyst-like structures. The Tunica muscularis of infundibulum to the ampulla, before increasing in thickness in the isthmus. The uterus and uterine glands were lined by a low cuboidal to cuboidal epithelium which contrasts with the dog and lioness. No ciliated cells were present in the uterus. The cervix displayed very few tertiary folds, no mucigenous nor goblet cells which is similar to the lioness but contrasts to the dog. The cervix contained no elastic fibres. Further research needs to be done to document the histology of the vestibule and clitoris as well as to determine the presence or absence of striated muscle in the distal two thirds of the round ligament as described in the lioness. The function of the papillary glands and significance of their cyst like appearance also needs to be further investigated.
A comparison of perceptions of the tuberculin skin test and an incentive postmortem-based surveillance system in the Mnisi community, Mpumalanga, South Africa
Marange, Rudo (University of Pretoria, 2018-10)
Tuberculosis (TB) is a global health concern. Mycobacterium bovis (M. bovis) and Mycobacterium tuberculosis (M. tuberculosis) are the most common causes of TB in animals and humans respectively. As part of TB control strategies most governments have instituted test and slaughter policies to eradicate bovine TB (bTB). While this has been met with some success, innovative and effective strategies to control TB are needed. We evaluated the postmortem surveillance (PMS) system as an alternative to the tuberculin skin test (TST) and found it to be a potentially cheaper and effective surveillance method. The level of TB awareness in the Mnisi community was also evaluated. Tuberculosis awareness by the community is also an effective way of TB control as education empowers people to make informed choices with regards to mitigating TB risk factors in their daily lives.
Vaccination of on-farm cattle against heartwater : safety and efficacy of Ehrlichia ruminantium (Welgevonden) vaccine
Marumo, Ratselane Daniel (University of Pretoria, 2018)
Ehrlichia ruminantium (Rickettsiales, Rickettsiaceae) is the causative agent of heartwater disease transmitted to cattle, sheep, goats and wild ruminants e.g. springbok by Amblyomma hebraeum in South Africa (SA). The current live blood vaccine (Ball 3) used in SA has limitations; it does not show efficacy against most field strains, it is virulent and concurrent treatment with antibiotic is necessary and it is produced in life animals which hinders its quality control. Second generation vaccines have not yet been developed to commercial stages. Previous experiments using an attenuated E. ruminantium (Welgevonden) tissue culture experimental vaccine in Merino sheep, Boer goats and Angora goats, administered through intramuscular (I/M) and intravenous (I/V) routes, without the use of antibiotic, showed promising results in terms of safety and efficacy. The objective of the current study was to test the safety and efficacy of this attenuated tissue culture vaccine in cattle, administered by the I/M route. One sheep injected with 10 ml of the virulent Welgevonden heartwater strain was used to infect Amblyomma hebraeum nymphs. Twenty (8-24 months old) male Friesian Holstein cattle obtained from a heartwater and vector free area were used; ten were vaccinated with the attenuated Welgevonden tissue culture isolate intramuscularly and ten were untreated controls. The vaccine was prepared and inoculated with an estimated concentration of 1.11 X 10⁶ E. ruminantium organisms in 2 ml. Tick challenge of both cattle groups was performed with 17 infected A. hebraeum (7 males/10 females) 35 days following vaccination. Cattle were screened serologically by the indirect fluorescent antibody test (IFAT) and by molecular tools using pCS20 quantitative real-time TaqMan (qPCR) before and after vaccination and challenge. Cattle were weighed before vaccination, during vaccination reactions and tick challenge (Days 0-77). Animals were monitored for clinical signs of heartwater disease and treated according to a score sheet when appropriate. Samples of ticks that dropped from infected sheep on different days were highly infected (103) with E. ruminantium (Welgevonden) organisms as tested using qPCR and deemed suitable for animal challenge. The group of cattle (n=10) which were vaccinated intramuscularly, showed no clinical or local vaccine related reactions and no treatment was required. The vaccinated group was challenged 35 days post vaccination together with the untreated controls (n=10). The mean number of engorged female ticks that dropped from the vaccinated (n=7.7) and unvaccinated (n=8.3) groups showed no statistical difference. The vaccinated group did not show any clinical reactions, while 8/10 of the unvaccinated controls developed severe reactions and received treatment while one animal was euthanized following the score sheet. There was a statistical significant mean difference (p-value = 0.0003) in the final weight gain/loss between the vaccinated (mean 5.6 + 2.84 Kg) and unvaccinated (mean -0.33 + 2.78 Kg) groups. On Day 37 after tick challenge, 100% of the vaccinated and 80% of the unvaccinated cattle showed sero-conversion (1/180) in the IFAT. The results of the study have demonstrated the safety and efficacy of the attenuated E. ruminantium (Welgevonden) experimental vaccine against homologous challenge in cattle as judged by the severe clinical reactions in the unvaccinated group. The vaccinated group also had a gain in mean body weight compared to the unvaccinated group after challenge.
Investigating the ultrastrctural and viscoelastic properties of whole blood, with specific focus on erythrocytes , in poorly controlled type 2 diabetes
Meijer, Wikus (University of Pretoria, 2018-12)
Type 2 diabetes mellitus is a metabolic disease associated with three main glycaemic disorders: Chronic hyperglycaemia, glycaemic variability and iatrogenic hypoglycaemia. Some comorbidities that often accompany type 2 diabetes mellitus are dyslipidemia and hypertension. There is no one particular cause of type 2 diabetes mellitus, but rather a series of risk factors that play a role in developing the disease. The most common risk factors include obesity, high blood pressure and a sedentary lifestyle. However, there are other factors such as age, polycystic ovarian syndrome, family history of type 2 diabetes and race, which may also contribute to the development of the disease. Type 2 diabetes mellitus can be diagnosed by measuring the glycated haemoglobin (HbA1c) of a patient. When the HbA1c is above a 6.5% the condition can be described as poorly controlled type 2 diabetes mellitus. There is evidence suggesting that diabetes is associated with chronic low-grade systemic inflammation. One of the signs of low-grade systemic inflammation is hypercoagulability of the blood. Hypercoagulability and the change in viscoelastic properties of the haemostatic system was the focus of this study, looking specifically in poorly controlled type 2 diabetes mellitus, by measuring erythrocyte sedimentation rate (ESR), thromboelastographic (TEG) parameters and viewing the ultrastructure of erythrocytes using scanning electron microscopy (SEM). Two groups, a healthy control group and poorly controlled type 2 diabetes mellitus group were compared in this study. ESR was used to measure inflammation and showed a significant increase in poorly controlled type 2 diabetes mellitus. Viscoelastic properties were measured with thromboelastography and displayed a decrease in clot formation time in poorly controlled type 2 diabetes mellitus as opposed to the control group. Scanning electron microscopy analysis of whole blood showed an increase in fibrin formation as well as an increase in the number of eryptotic cells in the poorly controlled type 2 diabetes mellitus group when compared to the control group. An increase of platelets was also observed in the full blood count. Results from this study showed a distinct difference between the two groups, indicating a significant change in the viscoelastic properties of individuals with poorly controlled type 2 diabetes mellitus but also an increase in the number of eryptotic cells.
Identification of African swine fever virus proteins that activate T-cell immune responses
Mabetlela, Freddy Mokadi (University of Pretoria, 2018-09)
African swine fever (ASF) is a highly contagious haemorrhagic disease of domestic pigs, which affects wild boar as well and for which there is currently no commercial vaccine. African swine fever virus (ASFV), the causal agent of ASF infects warthogs (Phacochoerus africanus), bush pigs (Potamochoerus porcus), giant forest hogs and members of the soft tick genus (Ornithodoros moubata complex) without causing disease. Virulent isolates of this virus causes mortality in domestic pigs within seven to ten days post infection, leading to negative economic consequences. Vaccination attempts using different strategies only protect against homologous strains with inadequate protection against heterologous strains of ASFV. The immunological characterisation of ASFV proteins could assist in the development of an effective vaccine against ASF. The aim of this study was therefore to immunologically characterise a selected range of ASFV proteins (p22, CD2V, pp220 fragments (F)1-F4, pS273R, pA104R, pE165R, pF334L, pK205R and pL11L) by identifing the cytokines they induce in peripheral blood mononuclear cells (PBMC) from a pig that was infected with ASFV via tick feeding (pig 1) and an incontact ASFV infected pig (pig 2). The benefits of identifying immunilogical characteristics of the cytokines can lead to possible vaccine development and decrease of animal losses due to ASF. Several proteins (p22, pp220 F1-4, pS273R, pA104R, pE165R and pK205R) from the genotype II ASFV isolate MAL/11/02 were successfully expressed using a pET102/D-Topo isomerase enzyme (TOPO)® bacterial expression system. Plasmids with gene inserts were amplified using the Invitrogen E. coli TOP10 cloning cells and proteins were expressed in BL21 DE3 cells using isopropyl β-D-1-thiogalactopyranoside (IPTG) induction. The protein product of genes EP402R (CD2V), pF334L and pL11L did not express and were excluded from futher experiments. The expressed proteins were purified by affinity chromatography using Nickel columns with affinity to the His-tag on the recombinant proteins. The immunological assays, interferon gamma (IFN)-γ enzyme-linked immunospot (ELISpot) and cytokine [Interleukin (IL)-2, IL-4, IL-8, IL 10, IL-12, IFN-γ and IFN-alpha (α)] reverse transcription (RT) quantitative real time polymerase chain reaction (RT-qPCR), were conducted using PBMCs. PBMC was collected from pig 1 after ten days post infection (pi) with the genotype XIX ASFV isolate RSA/12/15 strain of ASFV and pig 2 ten days after co-habitation with pig 1. Only four of the nine recombinant ASFV proteins produced significant cytokine levels. The recombinant p22 protein up-regulated cytokines IL-2, IL-4, IL-8, IL-10 and IFN-γ in pig 1 and IFN-α in pig 2. Fragment four (F4) of polyprotein (pp) 220 up-regulated IL-4, IL-8, IL-12 and IFN-α in pig 1 and IFN-α in pig 2. Recombinant proteins pA104R up-regulated IFN-α in pig 1 and pS273R significantly down-regulated IFN-α in pig 1. In conclusion, the study revealed that ASFV recombinant proteins p22 and pp220-F4 induced all the study cytokines which are important in antiviral immunity. This data can be applied in future ASFV vaccinology studies.
Fraud detection using operational risk modelling with incomplete data
Muzerengwa, Kudzai Calvin (University of Pretoria, 2019-02)
Systems and processes may fail and employees can engage in fraudulent ac-tivities that can go unnoticed for a very long time and the resulting losses can be very high and catastrophic to an institution. Setting a minimum threshold or a level of completeness will not guarantee that all losses above this point will be reported. In order to model operational risk data, a method that does not depend on the level of completeness is suggested. This can be done by introducing a de-tection probability that is combined with the underlying loss distribution to give a 3-parameter gamma distribution and fitted to a simulated dataset. It is found that the methodology is able to accurately estimate parameters when the data is incomplete.
Anti-biofilm activity of the tick-derived antimicrobial peptide Os(11-22)NH2 against candida albicans ATCC 90028
Chiramba, Court Kudakwashe (University of Pretoria, 2019-02)
The growing occurrence of antimicrobial resistance (AMR) is a global cause for concern due to the decreased availability of effective antimicrobial drugs. Therefore, treating resistant infections can become costly or even impossible. Furthermore, the increase in resistant infections leads to longer hospital stays and higher mortality rates. Resistance is prevalent because microorganisms can form biofilms; communities of cells bound to a surface and covered in an extracellular matrix (ECM), that protects cells from the effects of antimicrobial agents. Besides the ECM, biofilm cells further resist antimicrobial drugs by rapidly developing a number of mechanisms. Therefore, development of novel antimicrobial agents is key to overcoming AMR. One potential alternative to conventional antimicrobial drugs are cationic antimicrobial peptides (AMPs) which are short and amphipathic molecules. Some AMPs possess both anti-planktonic and anti-biofilm activity among other beneficial properties which make them a suitable alternative to conventional antimicrobial drugs. In this study, the anti-biofilm activity of Os(11-22)NH2, a short peptide derived from Os, a derivative of a defensin identified in the tick Ornithodoros savignyi, was investigated. For the purpose of this study, the opportunistic fungal pathogen Candida albicans, one of the leading causes of hospital-acquired infections, was used as the model microorganism. Os was inactive, while the derivative Os(11-22)NH2 was active against planktonic (free-floating) C. albicans with a minimum inhibitory concentration that reduces growth by 50% (MIC50) of 47 μM. The CellTiter Blue (CTB) cell viability assay was used to determine the biofilm inhibiting and eradicating activity. Os(11-22)NH2 inhibited biofilm formation with a minimum concentration of the antifungal agent that reduced biofilm formation by 50% (BIC50) of 81 μM. Inverted light microscopy images confirmed CTB cell viability results and reduced hyphal formation was observed. Treatment of preformed biofilms with Os(11-22)NH2 led to biofilm eradication by Os(11-22)NH2 with a minimum concentration of the antifungal agent that decreased cell viability in a pre-grown biofilm by 50% (BEC50) of 210 μM. Most AMPs target the cell membrane, therefore, membrane permeabilizing activity was investigated using confocal laser scanning microscopy (CLSM) and the DNA binding dyes propidium iodide (PI) and 4',6- diamidino-2-phenylindole (DAPI). Results indicated that cell membranes were permeabilized by treatment with Os(11-22)NH2 during biofilm inhibition and eradication.Some AMPs are known to induce the production of reactive oxygen species (ROS) in microorganisms, leading to cell death. Therefore, the fluorescence producing dye 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) was used to determine whether Os(11-22)NH2 induces ROS production. Os(11-22)NH2 induced ROS production during biofilm inhibition and eradication. In the presence of ascorbic acid, a scavenger of ROS, the production of ROS by the peptide was significantly reduced (p < 0.0001). Furthermore, the effect of ascorbic acid on the biofilm inhibiting and eradicating activity of Os(11-22)NH2was determined using the CTB cell viability assay. For biofilm inhibition, no significant difference was observed between treatments in the presence and absence of ascorbic acid, therefore killing during biofilm inhibition was not due to ROS production. For eradication, a significant increase (p < 0.0001) in biofilm eradicating activity was observed in the presence of ascorbic acid indicating that the biofilm eradicating activity of Os(11-22)NH2 was enhanced by ascorbic acid. In conclusion, anti-biofilm activity of Os(11-22)NH2 was determined at micromolar concentrations, indicating a potential antifungal application for this peptide. Future research should reveal its mode of action and combination with other antifungal agents.
Development and implementation of the Rhinoceros DNA Index System (RhODIS®) for the forensic analysis and biological management of African rhinoceros
Harper, Cindy Kim (University of Pretoria, 2018-10)
Rhinoceros horn is now worth more, per unit weight, than gold, diamonds, or cocaine. Rhinoceros horn has been used in traditional Asian medicine as a presumed cure for a wide range of ailments. Rhinoceros poaching in South Africa has, on average, more than doubled each year over the past 5 years with the rapid economic growth in east and southeast Asia being assumed to be the primary factor driving the increased demand for horn. Here we report on the characterization of methods for genomic DNA extraction from rhinoceros horn and on DNA profiling systems for white (Ceratotherium simum) and black (Diceros bicornis) rhinoceros. The DNA profiling system described includes 22 short tandem repeat (STR), or microsatellite, markers and a gender marker (ZF1), which have been used previously in various studies on rhinoceros. Using a u value of 0.1, a conservative estimate of random match probability in 5 white rhinoceros ranged from 1:7.3 x 106 to 1:3.0 x 108. Given that the total population of white rhinoceros is approximately 20,000 such random match probabilities indicate that the genotyping system described provides data which can be used for evidentiary purposes. Furthermore, the methods are appropriate for use in investigations involving trace amounts of rhinoceros horn and the matching of profiles obtained from seized rhinoceros horn with material collected from live animals or poached carcasses.
The importance of minerals on the prevalence of osteochondrosis in cattle in Southern Africa
Botha, Frederick Kenneth (University of Pretoria, 2018-10)
N/A
Seroprevalence and associated risk factors of West Nile virus in selected equine populations in South Africa
Jeal, Rebecca Eileen (University of Pretoria, 2018-06)
The family Flaviviridae consists of 94 species, which are distributed worldwide. Viruses in this family share aetiological properties such as membrane envelope proteins, resulting in diagnostic cross-‐reactivity. Flaviviruses are divided into two clades; arthropod-‐borne and non-‐arthropod borne viruses. The most predominant flavivirus seen in horses is West Nile virus (WNV), belonging to the arthropod-‐borne clade. West Nile virus has been divided into two lineages, of which, the second lineage is primarily found in South Africa. West Nile virus is transmitted through vector species, of which mosquito species are most predominant. Two genera of mosquitoes in particular, Aedes and Culex are widely distributed and are fundamental in the transmission of the virus to both reservoir hosts and incidental hosts. Other vectors included in the transmission he family Flaviviridae consists of 94 species, which are distributed worldwide. Viruses in this family share aetiological properties such as membrane envelope proteins, resulting in diagnostic cross-‐reactivity. Flaviviruses are divided into two clades; arthropod-‐borne and non-‐arthropod borne viruses. The most predominant flavivirus seen in horses is West Nile virus (WNV), belonging to the arthropod-‐borne clade. West Nile virus has been divided into two lineages, of which, the second lineage is primarily found in South Africa. West Nile virus is transmitted through vector species, of which mosquito species are most predominant. Two genera of mosquitoes in particular, Aedes and Culex are widely distributed and are fundamental in the transmission of the virus to both reservoir hosts and incidental hosts. Other vectors included in the transmission Blood samples were initially tested using the serum neutralization test (SNT). Documented positive and negative samples were then subjected to a capture IgG sandwich enzyme-‐linked immunosorbant assay (ELISA). The results of the two assays were compared with one another, proving to correlate efficiently, giving the resultant seroprevalence percentages for each province, and then were used in comparison with the outcome of the questionnaires to determine significant associated risk factors. Results were analyzed with both univariable and multivariable analyses, taking clustering into consideration, to determine both apparent and prevalence estimate for each province and significance of seropositivity with associated risk factors. A small population of mosquitoes was collected in both Gauteng and Mpumalanga Provinces and were identified and separated into species. A nested SYBR green real-‐time PCR assay was conducted on the pooled species of mosquitoes. All species presented negative for the presence of WNV, which could be a result of a low number of mosquitoes or a low prevalence of WNV in each species. The species identified included: Culex spp., Aedes spp. and Anopheles spp. The SNT were used to determine the apparent seroprevalence of WNV in the collected serum samples, thereafter, the prevalence estimate was calculated with a 95% confidence interval, taking clustering into consideration, for each province. The Free State Province had a high seroprevalence of 73% (95% CI 64-‐81%), the Western Cape Province had a seroprevalence of 65% (95% CI 51-‐79%) and Gauteng Province had a seroprevalence of 61% (95% CI 61-‐62%). Limpopo Province had a seroprevalence of 60% (95% CI 45-‐74%), followed by Northern Cape Province with 57% (95% CI 48-‐66%), KwaZulu-‐Natal Province with 54% (95% CI 43-‐65%) and Mpumalanga Province with 56% (95% CI 40-‐73%). The North West and Eastern Cape Provinces had lower seroprevalences of 43% (95% CI 34-‐52%) and 48% (95% CI 43-‐54%) respectively. Overall, the apparent seroprevalence for South Africa was 59% (95% CI 54-‐64) using the SNT. The ELISA assays showed similar results to the SNT, with a 61% (95% CI 44-‐79%) seroprevalence of WNV for South Africa. Gauteng Province had a seroprevalence of 47% (95% CI 44-‐79%), KwaZulu-‐Natal Province had a seroprevalence of 24% (95% CI 44-‐79%), Northern Cape Province had 78% (95% CI 44-‐79%) seroposivitiy, Eastern Cape Province had a seroprevalence of 68% (95% CI 44-‐79%), North West Province with 59% (95% CI 44-‐79%) and Mpumalanga Province had a seropositivity of 79% (95% CI 44-‐79%). The results obtained using the ELISA had a moderate agreement with the SNT results (Kappa = 0.5).The univariable analysis showed association of WNV seropositive horses with; various agricultural activities, contact with different animal species, presence of annual frost, assorted water sources, occurrence of standing water pools and presence of Culicoides midges. These variables were subjected to multivariab analysis. The variables that indicated a p-‐value of less than 0.05 were considered significant. Among these values were agricultural activities, such as livestock in the Free State Province, forestry in Mpumalanga Province and vineyards in the Western Cape Province. Contact with small ruminants and other species were the only significant species associated with WNV seropositive horses. Both standing pools of water and river sources were associated with seroprevalence in different provinces. Lastly, annual frost was only associated with seroprevalence in the Limpopo Province. Of the medical history and symptoms, fever was the singular variable associated with seropositivity. It is evident that many positive cases of infected horses are either not being reported or are not presenting with substantial clinical signs. The horses included in this study were from various age groups, different sexes and breeds and participated in various disciplines. Racehorses were excluded from the study due to their movement throughout the country making them bad sentinels for the study. The high seroprevalence of WNV in horse populations, determined in this study, indicates a subsequent high exposure rate throughout South Africa, varying amongst provinces. The risk factors associated with seroprevalence were all area specific, indicating the importance of habitats and the role it plays in transmission due to the presence of potential vectors. This study also noted a lack of knowledge about the transmission and prevalence of WNV amongst horse owners in South Africa.
Mathematical analysis and simulations of models for rabies epidemic among African wild dogs (Lycaon pictus)
Dumani, Phindile (University of Pretoria, 2018-11)
Simpliﬁed models representing rabies epidemic are presented to better understand the epidemiological dynamics of the disease. We extensively study the transmission and progression dynamics of rabies in African wild dogs, Lycaon pictus, by adapting a stan-dard sei model to include both the asymptomatic and symptomatic stages to simulate the time-delay. Furthermore, we investigate the contribution of other rabies hosts in the environment (e.g, stray dogs) have on the transmission dynamics. The study is based on the assumption that there are no vaccination programmes introduced, hence, we consider culling as a possible control strategy to reduce the rabid population or the uncontrollable spread of the disease to a level below the threshold. The threshold quantity, the basic reproduction number, which in this case is the expected number of new infectious dogs in a perfectly susceptible population produced by a single infected dog is used to give a quantitative discussion on the control of rabies. We present the mathematical analysis of the proposed continuous and discrete models. Numerical simulations are provided to support theoretical results.
The role of soil hydrophobicity in the cause and maintenance of the mysterious Namibian fairy circles
Hurter, Jean Willem (University of Pretoria, 2018-07)
Circular barren patches, also known as fairy circles (FCs), occur throughout Namibia, devoid of vegetation and surrounded by a matrix of grasses. Several hypotheses regarding the origin and maintenance of FCs have been proposed, none widely accepted. Soil physical properties and chemical constituents were investigated to determine whether differences in properties are present and to what extent they differ. Results obtained from physical property analyses indicated greater hydrophobicity in soil collected from FCs than matrix soil as well as a higher infiltration rate. Extracts prepared from FCs and matrix soil, and from locations where Euphorbia damarana are decomposing (DP), were analysed by GC-MS and NMR to determine the cause of the increased infiltration rate and the FC soil’s hydrophobicity. To identify discriminative signals from GC-MS and NMR data, PCA-plots, OPLS-plots, and S-plots were created to aid compound identification. The PCA-plot created from GC-MS results displayed clear discrimination, segregating matrix (M) sample observations from DP and FC sample observations, simultaneously grouping DP and FC observations. This indicates greater similarity between DP and FC soil, than between DP and M or FC and M observations. Specific compounds were present in both FC and DP soil samples and not in matrix soil. NMR based metabolomics indicated similar concentrations of ester, phenol, alkene and aromatic functional groups within FC and DP soil, while differences between FC and matrix soil were greater. From these results, it is deduced that there’s a definite difference in physical properties and chemical constituents of FC and matrix soil. Causes of these differences can be concluded to be initiated by decomposing Euphorbiaceae species, as indicated by specific compounds such as 1-(4-acetamidoanilino)-3,7-dimethylbenzo[4,5]imidazo[1,2-a]pyridine-4-carbonitrile present in FC and DP soil samples, previously identified in a variety of plants’ non-polar latex. It is thus proposed that the formation of FCs in northern Namibia are indirectly caused by decomposing E. damarana, which alters the soil physical properties at the decomposition site, increasing hydrophobicity and infiltration rates in soil upon decomposition which It is thus proposed that the formation of FCs in northern Namibia are indirectly caused by decomposing E. damarana, which alters the soil physical properties at the decomposition site, increasing hydrophobicity and infiltration rates in soil upon decomposition which decreases the amount of plant available soil water content and leads to the formation of barren patches, devoid of any vegetation, in the same circular shape as the E. damarana plants which once grew at that location. This mechanism of formation is proposed as the most likely cause in other areas of Namibia, where succulent Euphorbia spp. are present.

Browse

Recent Submissions