Theses and Dissertations (Companion Animal Clinical Studies)

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Physiological variables for the objective detection of intraoperative nerve block failure in dogs
(University of Pretoria, 2023-08) Zeiler, Gareth Edward; Kadwa, Abdur R.; drpebasson@gmail.com; Basson, Pierre Etienne
Objective To identify physiological variables that can be used to objectively detect intraoperative nociception to indicate peripheral nerve block failure. Study design A prospective blinded randomized clinical study. Animals A sample of 14 male (40.8 ± 12 kg; mean ± SD) and 16 female (34.3 ± 11.4 kg) client-owned dogs undergoing a stifle arthrotomy. Methods Dogs were randomly assigned to one of three treatment groups for psoas compartment and proximal sciatic nerve blocks (0.2 mL kg-1 per site): guided bupivacaine (GBB) or saline (GSB) blocks or blind bupivacaine block (BBB). Guided blocks were performed using ultrasound and nerve stimulation. Dogs were premedicated intramuscularly with 0.01 mg kg-1 medetomidine and 0.3 mg kg-1 morphine. General anaesthesia was induced with propofol (to effect to achieve tracheal intubation) and maintained with isoflurane in oxygen (targeted end-tidal concentration of 1.6%). The assigned investigator, based on randomisation, allotted a confidence score [1 (poor) to 4 (high)] that the block will be successful after administering the assigned nerve block treatment. The blinded investigator allotted a binomial subjective score of the nerve block outcome (“Yes”: response to surgical stimulation; “No”: no discernible response) at each time point. Receiver of operator characteristic curve analysis was used to compare actual values and change in values of physiological variables between GSB (Yes nociception) and GBB (No nociception) at the time of the arthrotomy. The Youden index and associated criterions for each physiological variable were used as an objective measure. Fishers exact t-test, McNemar's test and Cohens kappa statistical analysis were used to determine association, differences and inter-score reliability, respectively between the objective and subjective scoring for the BBB. The subjective score was compared to objective scores after being stratified into the assigned confidence scores using Kendall’s tau-b rank correlation coefficient. Results The cardiovascular variables had good discriminating ability in distinguishing a nociceptive response (p < 0.01). The Youden indexes for MAP and DAP had the best potential effectiveness in detecting a response to surgical stimulus. The highest sensitivity was that of delta MAP (100%). Good agreement was indicated between the subjective and objective scores with delta HR or SAP. The use of delta MAP (> 6 mmHg), delta SAP (> 10 mmHg), delta DAP (> 8 mmHg) had the best ability in indicating peripheral nerve block failure (p < 0.001). Conclusions and clinical relevance The use of delta MAP, delta SAP or delta DAP can be considered as objective measures to detect intraoperative peripheral nerve block failure in anaesthetised dogs undergoing stifle arthrotomy. The determination of criterion values for different populations and conditions will benefit future clinical trials.
Liver histopathology in dogs with naturally acquired babesia rossi infection
(University of Pretoria, 2023-09) Leisewitz, Andrew L.; Clift, Sarah J.; heidi.horrell@gmail.com; Horrell, Heidi
Canine babesiosis, which, in sub-Saharan Africa, is caused by the tick-transmitted intraerythrocytic protozoan Babesia rossi, is one of the most common, clinically important tick-borne diseases of dogs in the region. The disease in dogs occurs in two forms, namely uncomplicated and complicated babesiosis. In the former, clinical signs are usually attributable to the effects of hemolysis. In complicated canine babesiosis, the disease is attributable to the host’s immune response, with overwhelming systemic inflammation and multiple organ dysfunction being associated with high morbidity and mortality. The clinicopathological changes associated with complicated canine babesiosis are similar to those reported in fatal malaria and sepsis in humans. There are not many reports on the pathology of the liver in babesiosis and malaria. For the purpose of this study, liver samples were collected from 10 dogs with fatal babesiosis. Haematology, serum biochemistry and histologic data were compared with four healthy control dogs that were sourced from an animal shelter. The most significant elevations in haematology values were decreases in red cell count, haematocrit and platelet concentration, while the most significant increases in biochemistries were increases in ALT and urea. The most significant histologic lesions in the Babesia-infected dogs included dilation of the spaces of Disse due to oedema, cholestasis, hypertrophic Kupffer cells containing bile and haemosiderin pigments, central venous and sinusoidal congestion, multifocal centrilobular necrosis, inflammatory cell infiltrates consisting mostly of monocyte-macrophages (as determined by MAC387, Iba-1 and CD204), and evidence of significant extramedullary haematopoiesis. The hepatocytes showed numerous signs of cell injury such as presence of vesicular nuclei, hydropic vacuolation and anisokaryosis. Most of these changes can be ascribed to severe haemolysis and the associated hypoxia. Similar findings have been shown in the limited histomorphological studies on babesiosis, human malaria, and in patients with sepsis. These results are also complimentary of previous studies involving inflammatory cytokines and chemokines observed during the course of babesiosis, with the most significant increases being IL-6, IL-10, MCP-1, and TNF-a, all of which are monocyte-specific. These findings aid us in the understanding of the pathomechanisms behind the disease and enable us better treat the symptoms that present.
Subtrochlear sclerosis evaluation for medial coronoid disease detection and dynamic distal ulnar ostectomy for reduction of disease progression in Labrador retriever puppies
(University of Pretoria, 2023-09) Irvine-Smith, Greg; Kirberger, Robert M.; jpretorius9529@gmail.com; Pretorius, Jandre D.
Objective To evaluate methods used in the early radiographic detection of subtrochlear ulna sclerosis (STS), which could successfully predict the development of medial coronoid disease (MCD) in four-month-old puppies, and at the same time perform distal dynamic ulnar ostectomy (DDUO) to prevent or reduce disease development. Study design Retrospective descriptive radiographic study. Sample population One hundred and fifty-two Labrador retriever puppies from the South African Guide Dog Association were available for the study. Materials and methods Extended mediolateral radiographs were evaluated for STS by means of a subjective (score 0-3), as well as semi-quantitative and objective grading scores, given as a percentage of an STS region of interest compared to normal ulna medulla. Evaluations were performed by a surgery resident, specialist veterinary radiologist (SVR) and specialist veterinary surgeon. Lameness and pain were also evaluated and were combined with the STS scores to give a total joint involvement score. DDUO was performed on all elbows with >20% joint involvement. At 12-months-old, all dogs underwent elbow computed tomography to determine the development of MCD. Results The only method predictive of disease development was SVR’s subjective evaluation of STS, with a sensitivity of 46% and specificity of 81%. Twenty-two dogs not receiving surgery still developed MCD. One of 21 dogs receiving DDUO surgery developed MCD. The surgery had significant protective effects, with surgical candidates being 13 times less likely to develop MCD (odds ratio = 13.3, P = 0.026). Conclusion Labrador retrievers and other known at-risk breeds should be screened at four months of age for STS through radiographic assessment by an SVR. If deemed at risk, DDUO surgery is advised to prevent or reduce MCD development.
Investigation of haematologic, inflammatory, and haemostatic in horses experimentally infected with African horse sickness virus
(University of Pretoria, 2023) Goddard, Amelia; Hooijberg, Emma H.; tine.schliewert@web.de; Schliewert, Eva-Christina
African horse sickness (AHS) is an infectious disease affecting equids. It is caused by the African horse sickness virus (AHSV), a double-stranded RNA Orbivirus with 9 different serotypes which is transmitted by insect vectors, particularly Culicoides midges and is endemic in sub-Saharan Africa. Infection with AHSV results in one of four disease forms, the pulmonary (“dunkop”), cardiac (“dikkop”), mixed, and fever form and morbidity and mortality ranges of up to 100% are described in naïve horses. Clinical signs such as dyspnoea, fever, haemorrhages, and pulmonary oedema are thought to be reflective of inflammation and endothelial damage due to viral replication in the vascular endothelial cells. To date, the understanding of the underlying pathology is marginal, and no therapy has been recognized as effective. The enzootic virus has important implications on animal welfare, the equine industry and the local economy of rural communities which depends on working equids. Given the limited knowledge of the inflammatory response to infection with AHSV and the resulting haematological changes and alterations in haemostasis, the broad objectives of this study were to 1) evaluate the haematological changes and changes in acute phase reactants; 2) describe the changes in selected cytokines; and 3) characterize the haemostatic changes occurring in horses experimentally infected with AHSV. The study was designed as a prospective, longitudinal, experimental study which included four healthy AHS-susceptible Boerperd cross horses that had tested negative for AHSV group-specific antibodies using a commercial competitive enzyme-linked immunosorbent assay (ELISA) against all nine AHSV serotypes. These horses were infected intravenously with low passage mouse brain suspension (5 mL) that contained at least 105 mouse infective doses/mL of virulent AHSV serotypes. Each horse was inoculated with a different AHS serovar: horse 1, AHSV-2 (horse origin); horse 2, AHSV-4 (horse origin); horse 3, AHSV-6 (horse origin) and horse 4, AHSV-6 (dog origin). All horses developed severe clinical signs typical of AHS post infection and were humanely euthanized. All horses developed significant haemoconcentration in the late stages of the disease. Significant thrombocytopenia with increased markers of platelet activation developed; however, changes in leukocytes and acute phase reactants serum amyloid A (SAA) and serum iron were significant but not considered clinically relevant. This suggested possible derangements in the host’s immune response which contribute to the observed dampened immune response in reaction to the inflammatory stimuli triggered by the virus. To further elucidate the immune response to infection with AHSV, selected plasma cytokines interleukin (IL)-1α, IL-2, IL-6, IL-8, IL-10, IL-12, IL-17, interferon (IFN)-, tumour necrosis factor (TNF)-α, and monocyte chemoattractant protein (MCP)-1, which represent mediators of both innate and adaptive immunity pathways, were evaluated throughout the course of the disease. Unexpectedly, an almost complete absence of proinflammatory cytokines in blood was observed, as only TNF-α increased in the final stages of the disease while an increase in IL-10, considered an anti-inflammatory cytokine, was predominant. This correlates with the previous findings of a mild acute phase response and mild haematological changes as these responses are mediated by cytokines. The lack of a significant cytokine response could indicate viral immune evasion mechanisms. In Orbiviruses, in vivo studies have documented inhibition of the immune response by the virus – specifically of IFN and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathways and this is a likely cause of the lack of a proinflammatory response. Horse infected with AHSV develop haemorrhages; this finding is thought to be mainly due to the endothelial damage caused directly by viral replication in endothelial cells. It is now understood that inflammation and haemostasis are closely integrated, and inflammatory cytokines activate haemostatic pathways by increasing tissue factor expression on circulating endothelial cells, monocytes and macrophages. Specifically, horses developed overt disseminated intravascular coagulation (DIC), a consumptive coagulopathy, and clinical signs of bleeding, and procoagulant activation, inhibition of anticoagulants and fibrinolysis was detected on both traditional coagulation tests and viscoelastic tests. Given the lack of proinflammatory cytokines, inflammatory activation of the haemostatic pathways is likely secondary while endothelial damage is the probable primary trigger for activation of haemostasis. The findings of this study further elucidate the pathogenesis of the AHSV. The results suggest that AHSV is capable of interfering with the innate immune response, possibly via interference with the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signalling pathways or promyelocytic leukaemia nuclear bodies (PML-NBs), while simultaneously initiating haemostatic pathways, most likely via endothelial damage, and causing overt DIC. Early identification of haemostatic derangements allows for earlier intervention which may improve outcome. Recognition of the virus’s capability to interfere with the innate immune system may be used to develop new treatment strategies, including direct cytokine or antibody therapy to improve the development of more effective vaccines.
Clinical signs and clinical pathology findings in horses with equine encephalosis at the Onderstepoort Veterinary Academic Hospital, South Africa
(University of Pretoria, 2024-06) Eberhardt, Christina; Viljoen, Adrienne; graeme.piketh@up.ac.za; Piketh, Graeme
Introduction: Equine encephalosis is a systemic disease of horses caused by equine encephalosis virus. This virus is an Orbivirus that is transmitted by biting midges (Culicoides species). Equine encephalosis is often reported as a subclinical infection with a relatively limited number of clinical cases showing predominantly fever, with minimal morbidity and mortality. Rare instances of neurological disease have also been associated with the virus. Clinical relevance: Information regarding the clinical presentation of equine encephalosis is underrepresented in current scientific literature. This study aims to contribute to a more detailed conceptualization of the significance of the disease and its clinical impact. Method: A retrospective, descriptive, observational study was performed on data obtained from the University of Pretoria’s clinical database for cases identified with equine encephalosis over the period 2013-2023. Data from the history, clinical signs and clinicopathological findings were analysed. The clinical presentation and clinicopathological findings are reported. Results: A total of 28 horses conformed to the study parameters as having clinical infection with equine encephalosis virus. Pyrexia was apparent in 89.2% of these cases. Other clinical findings included tachycardia (64.3%), tachypnoea (46.4%), colic (39.3%), neurological signs (21.4%), peripheral oedema (14.3%), and icterus (10.7%). Evaluation of the clinicopathological findings identified lymphopenia (86.7%), thrombocytopenia (76.0%), leukopenia (48.0%), immature neutrophilia (31.8%), and mature neutropenia (27.3%). Conclusion: Equine encephalosis can result in a wide variety of clinical signs in horses and is associated with changes in haematology variables. These haematological changes suggest a systemic response to the viral infection. Further research into the pathophysiology of equine encephalosis is required to better understand the disease and its clinical relevance.
Peri-lacrimal gland injection of allogenic adipose-derived mesenchymal stem cells compared to tacrolimus eyedrops in the treatment of canine keratoconjunctivitis sicca
(University of Pretoria, 2024) Odayar, Lo-An; Zeiler, Gareth Edward; morrislaurie7@gmail.com; Morris, Laurie Megan
Objective To describe and compare the efficacy in treatment between a single peri-lacrimal gland injection of adipose-derived mesenchymal stem cells (Stem Cells group) and a twice-daily application of tacrolimus eyedrops (Tacrolimus group) in client-owned dogs suffering from unilateral or bilateral early-stage immune-mediated keratoconjunctivitis sicca (KCS). Animals Studied Twenty-two, client-owned dogs (44 eyes), suffering from presumed unilateral or bilateral immune-mediated keratoconjunctivitis sicca (KCS) were enrolled in the study. The immune-mediated aetiology was made by exclusion, with animals suffering from unilateral or bilateral disease with no concurrent systemic disease or neurological deficits. The inclusion criteria were dogs of any age or breed with unilateral or bilateral, immune-mediated KCS (symptoms consistent with KCS and a Schirmer Tear Test type 1 [STT-1] ≤ 15 mm/min; confirmed on examination and previous history); with no co-existing ocular pathologies; and no previous history of treatment, including tear replacements or artificial tears. Exclusion criteria were dogs with bilateral end-stage KCS (advanced corneal pigmentation, fibrosis and/or recurrent corneal ulceration with possible corneal perforation and blindness), as well as the presence of concurrent systemic disease and medications. Procedures The dogs were followed for a 2-month period beginning at Day 0, with subsequent follow-ups at Day 30 and Day 60. Dogs were assigned to the various treatment groups based on owner preference. Dogs in the Stem Cells group received a one-time, bilateral, peri-lacrimal gland injection under heavy sedation using a commercially available mesenchymal stem cell solution (5 million viable MSC/mL; 2 mL per vial; VetRenew; South Africa). Dogs in the Tacrolimus group received a twice-daily application of eyedrops using a standard tacrolimus 0.02% eyedrop solution with the same oil carrier, from the same compounding pharmacy and batch. With investigators not being masked to the treatment groups, STT-1 and Tear Break Up Time (TBUT) were recorded, and corneal health subjectively scored using an author-derived simple descriptive scale (0: best; 5: end-stage cornea). Data for each eye was classified as either healthy (STT-1 > 15 mm/min) or having KCS (STT-1 ≤ 15 mm/min), then data within each classification were compared between treatments using a mixed effect model (fixed effect: time, treatment; random effect: dog, eye) using the following interactions: treatment, time, and treatment x time. Significance was interpreted a P < 0.05. All data is reported as mean (95% confidence interval of the mean). Results Dogs included in the study had a mean (min; max) of 8.7 (1.5 ; 14.0) years, with no difference between treatment groups. A total of 22 dogs began the study, however, 17 dogs (9 in Stem Cells group and 8 in Tacrolimus group) completed the study. One dog in Stem Cells group and 2 dogs in Tacrolimus group were excluded from the study for not meeting STT-1 inclusion criteria, and 2 dogs in Tacrolimus group were lost at the 60-day follow up. In KCS eyes (n = 26), STT-1 before treatment Day 0 in were 11 (9, 13) and 11 (8, 14) mm/min for Stem Cells and Tacrolimus, respectively. The STT-1 increased in both treatment groups over time and measured as 18 (16, 21) and 19 (15, 22) mm/min for Stem Cells and Tacrolimus at Day 30, respectively (both P < 0.001). The STT-1 stabilised at Day 60 with values of 18 (15, 22) and 19 (15, 23) mm/min for Stem Cells and Tacrolimus, respectively (both P < 0.001). The TBUT at Day 0 were 21 (11, 32) and 18 (12, 25) seconds for Stem Cells and Tacrolimus, respectively. The TBUT increased in both treatment groups over time and measured as 23 (16, 30) and 27 (21, 33) seconds at Day 30, and at Day 60 were 36 (27, 44) and 30 (22, 39) seconds for Stem Cells and Tacrolimus, respectively (both P < 0.001). Corneal scores improved over time (i.e., healthier corneas) and were significantly different to Day 0 at Day 30 (P < 0.001) and Day 60 (P < 0.001) for both treatment groups but not different between groups. Conclusion A single peri-lacrimal gland injection of adipose-derived mesenchymal stem cells may be an effective treatment in dogs with early-stage immune-mediated KCS and demonstrated similar outcomes as twice-daily application of 0.02% tacrolimus eyedrops over a 60-day period.
Small colon impaction outbreak and associated risk factors in horses at the Onderstepoort Veterinary Academic Hospital, South Africa in 2021
(University of Pretoria, 2024) Smit, Yolandi; Fosgate, Geoffrey Theodore; elza.hollenbach@up.ac.za; Hollenbach, Elza
Background During June-July 2021, the Onderstepoort Equine Clinic experienced an increase in diffuse faecal small colon impactions (SCI). Typically, SCI is diagnosed in 1.3–3% of horses admitted to referral centres for colic. Objectives This study aimed to describe the distribution, diagnosis, treatment, and outcomes of colic cases in 2021, focusing on SCI and to identify risk factors for SCI compared to large colon impactions (LCI). Method Medical records from the Onderstepoort Veterinary Teaching Hospital were reviewed to identify colic cases in 2021 and the population distribution, diagnosis, treatment, and outcome recorded. Cases of SCI were identified and compared to LCI. Owner questionnaires assessed potential SCI risk factors. Results Colic cases(182), comprised mainly LCI(26%), large colon displacements(20%), and SCI(13%). Treatments included medical(65%), surgical(32%), or euthanasia(3%). Most horses(85%) were discharged. SCI was diagnosed in 13% of cases, higher than previously reported rates. Immediate surgical treatment was performed in 30% of cases. In the remaining cases medical management was initiated although surgical intervention was later pursued in 43% of cases. Short-term survival was 87%, with surgical cases showing higher survival (94%) than medical (67%). Stallions were at risk to develop SCI compared to “all colic” diagnoses (OR 4.17). Friesians were more likely to develop SCI compared to “all colic” (OR 7.00). Draft breed horses were more likely to develop SCI compared to compared to “all colic” (OR 8.20) and compared to LCI (OR 32.7). The study identified a risk for horses to develop SCI in winter compared to “all colic” (OR 43.2) and compared to LCI (OR 124). Conclusion A SCI outbreak occurred in 2021, with increased risks in stallions, Friesians, and draft breeds, particularly in winter. Horse owners and veterinarians should be alerted to this, especially in at-risk groups during winter. Outcomes are favourable for SCI especially when treated surgically.
Effects of chemical and mechanical stimulation on laryngeal motion during anaesthetic induction with alfaxalone, thiopentone or propofol in healthy dogs
(University of Pretoria, 2018) Dzikiti, Tarisai Brighton; Zeiler, Gareth Edward; sandra.labuscagne@gmail.com; Labuscagne, Sandra
Objective: To compare the effect of chemical and mechanical stimulation on arytenoid cartilage motion in healthy dogs during anaesthetic induction with alfaxalone, thiopentone or propofol for induction of anaesthesia. Study design: Blinded, randomised, crossover study Animals: Eight adult beagle dogs with median (range) weight and age 15.2 (12.2-19.8) kg and 14 (13-16) months, respectively. Methods: Anaesthesia was induced with thiopentone (7.5 mg kg-1), propofol (3 mg kg-1) or alfaxalone (1.5 mg kg-1) intravenously (IV), which were concurrently paired with either chemical (doxapram hydrochloride at 2.5 mg kg-1 IV) or mechanical (gentle pressure to the corniculate process of the right arytenoid cartilage using a cotton bud) stimulation for enhanced assessment of laryngeal motion, in random order, with a one-week wash-out period between treatments. If deemed inadequately anaesthetised, supplemental boli (25% of induction bolus) of thiopentone (1.8 mg kg-1), propofol (0.75 mg kg-1) or alfaxalone (0.4 mg kg-1) were administered. The calculated induction bolus for each dog was administered over a 60 second period intravenously via a syringe driver and allowed to take effect for 10 seconds. The anaesthetic depth was determined by evaluating jaw tone and palpebral reflexes. Laryngeal examination was performed by the primary investigator (SL) who was blinded to the treatments. Assessment of number of arytenoid motions and vital breaths, among others, began immediately after induction. Chemical and mechanical stimulation were begun 2 minutes after anaesthetic induction (time period 1). Data were collected at 2, 3 and 5 minutes (time period 2) after anaesthetic induction and the Friedman rank sum or repeated measures ANOVA (Analysis of variance) tests were used, when applicable, for statistical analysis. Results: Duration of examination times were significantly different among treatments (p = 0.01). Significant differences were observed regarding the number of arytenoid motions during thiopentone induction combined with chemical stimulation (doxapram hydrochloride) in comparison to alfaxalone (p = 0.0086), thiopentone (p = 0.0108) and propofol (p = 0.0086), when combined with mechanical stimulation at 3 minutes after induction. The laryngeal function score was significantly higher during time period 1 compared to time period 2 for induction with alfaxalone (p = 0.0007), thiopentone (p < 0.0001), and propofol (p = 0.0013) combined with chemical stimulation. No significant differences were observed among treatments or time periods for number of vital breaths recorded during the 3 different time periods, jaw tone, laryngospasm, breath scores, swallowing score or paradoxical motion score. Conclusion and clinical relevance: Doxapram hydrochloride, combined with thiopentone, is the most effective means of stimulating arytenoid motion among the regimens for assessing laryngeal motion in the present study and could improve accuracy of diagnosis of laryngeal paralysis in dogs. Time period 2 (2-5 minute after conclusion of induction) is the optimal time period for laryngeal evaluation. Misdiagnosis of laryngeal paralysis can be avoided by identifying the ideal time period for evaluation. Induction with thiopentone combined with doxapram hydrochloride facilitated increased respiratory efforts, ample arytenoid motions, and adequate arytenoid exposure conducive to laryngeal function evaluation in healthy non-premedicated beagle dogs. The dosages and administration rates used in the present study were effective in achieving adequate depth of anaesthesia for laryngeal function evaluation, without inducing respiratory depression, confirming viable application for diagnosis of laryngeal paralysis.
Gross morphology, radiology and computed tomography of the ear of the southern white rhinoceros (Ceratotherium simum simum)
(University of Pretoria, 2020-01) Steenkamp, Gerhardus; Carstens, Ann; mickael.robert@up.ac.za; Robert, Mickaël Patrice
Since 2008 there has been a dramatic increase in poaching of rhinoceroses in Africa. Today, the southern white rhinoceros is classified as Near Threatened with less than 20000 individuals left. The ear of the rhinoceros appears to be an important organ in the animal’s behaviour and thermoregulation, in population management and also for clinical use. Despite its important roles, there is currently only fragmented information available concerning the rhinoceros's gross ear anatomy as well as radiographic and computed tomographic (CT) anatomy. The aim of this study is to fill this void describing the gross, radiographic and CT anatomy of the ear of the southern white rhinoceros following the standard international veterinary anatomical nomenclature. We used seven intact ears belonging to four southern white rhinoceroses (3 cadavers plus 1 clinical case) of different age (from neonate to adult) to perform radiographic, CT and micro-CT studies before dissecting four of them. We described the gross anatomy of the cartilages, muscles, particular vessels of the ear and associated organs, we presented radiographic views and CT protocols that can be used to assess this region as well as the imaged structures, and we reported on the microanatomy of the southern white rhinoceros ear using micro-CT, allowing tridimensional virtual models of the middle and inner ears to be displayed. The findings of this study will be useful to anatomists, radiologists and wildlife veterinarians, and will also hopefully pave the way for further research providing even more detail of this fascinating but difficult to investigate region.
Ocular biometry and pathology in captive and free-ranging southern white rhinoceros (Ceratotherium simum simum) and south-central black rhinoceros (Diceros bicornus minor) in South Africa
(University of Pretoria, 2024-07-03) Goodhead, Antony Denzil; Grewar, John Duncan; paul@animaleyehospital.co.za; Burger, Joachim Paul
ABSTRACT Title: Ocular biometry and pathology in captive and free-ranging southern white rhinoceros (Ceratotherium simum simum) and south-central black rhinoceros (Diceros bicornus minor) in South Africa. Background: The available literature describing rhinoceros’ ocular abnormalities is limited. This may stem from the rarity of the animals and limited baseline ocular data available. The purpose of the project is to add to current knowledge regarding the normal ocular population parameters and prevalence of ocular pathology in rhinoceroses. Methods: Seventy-three immobilised rhinos underwent ophthalmic examination while immobilised for general veterinary care and procedures. The ophthalmic examinations were performed by the author of the study, a registered veterinarian with the South African Veterinary Council (SAVC), and by a registered SAVC specialist veterinary ophthalmologist, when he was available. The ophthalmic examination included the Schirmer Tear Test (STT), intraocular pressure (IOP), slitlamp biomicroscopy, fluorescein staining, keratometry and ocular ultrasonography and biometry. Exploratory data analysis was performed to establish the baseline parameters with binomial exact methods used to establish 95% confidence intervals for the estimate of the means of normal ocular parameters. Results: Seventy-three animals were examined, 68 were white rhino and 5 were black. Twenty-four were male and 49 were female. Mean STT OD: 19.09 mm/min (95%CI: 17.48 – 20.69); mean STT OS: 17.64 mm/min (95% CI: 16.14 – 19.14); mean IOP OD: 41.12 mmHg (95% CI: 36.74 – 45.51); mean IOP OS: 42.66 mmHg (95% CI: 38.52 – 46.81). The most common ocular abnormalities were keratitis (23 animals, 31.51%), corneal scar (12 animals, 16.44%), cataract (11 animals, 15.07%), corneal ulcer (7 animals, 9.59%), pigmentary keratitis (3 animals, 4.11%), corneal foreign body, posterior synechiae and persistent pupillary membrane was present in two animals each (2.74%), follicular conjunctivitis (1 animal, 1.37%); 6 right eyes were fluorescein positive (8.2%) and 3 left eyes were fluorescein positive (4.1%). Mean AGL OD: 26.2 mm (95% CI: 2.57 – 2.66); mean AGL OS: 26.0 mm m (95% CI: 2.55 – 2.65); mean ACD OD: 2.7 mm (95% CI: 0.25 – 0.28); OS: 2.7 mm (95% CI: 0.25 – 0.28 OS); mean CLT OD: 6.5 mm (95% CI: 0.64 – 0.66); mean CLT OS: 6.4 mm (95% CI: 0.63 – 0.66); mean PSD OD: 16.3 mm (95% CI: 1.6 – 1.66); mean PSD OS: 1.62 (95% CI: 1.6 – 1.65). Conclusion: The findings regarding normal biometry will aid in future examinations of the species. The prevalence of ocular disease is high and has seemingly little impact on their natural life.
Patient demographics, and outcome of striate keratotomy versus diamond burr debridement for treatment of spontaneous chronic corneal epithelial defects in dogs in South Africa
(University of Pretoria, 2024-06-18) Goodhead, Antony Denzil; u23090759@tuks.co.za; Sirrals, Brent
Background: Spontaneous chronic corneal epithelial defects (SCCED) are a common finding in canine patients referred for non-healing corneal ulceration. Various names have been used for this condition historically. The classic lesion and history include an axial or paraxial, superficial, corneal epithelial ulcer, that is non-responsive to topical therapy and is recurrent in nature. The lesions are not infected and not associated with any physical cause preventing healing. Pathology is well described, and various topical and surgical treatments have been used to treat SCCED lesions. Patient demographics for referral cases treated at a specialist veterinary ophthalmology hospital in South Africa, and the surgical outcome between striate keratotomy (SK) and diamond burr debridement (DBD) are reported in this study. Methods: Clinical records for dogs that presented with SCCED lesions over a five-year period between 1st January 2019 and 31 December 2023 were retrospectively evaluated. The patients were included if they were positively diagnosed with a SCCED lesion and underwent either a SK or DBD surgery. Year of surgery, patient demographics, intra-ocular pressure (IOP), Schirmers tear test (STT), laterality, surgeon, surgical procedures, follow-up surgeries and fluorescein stain results were manually evaluated. Results were captured in Excel and statistical analysis was performed in “R”. Patients were excluded if they had confounding pathology that may have affected healing post-operatively. Results: 441 unique surgeries were identified for SCCED lesions and after exclusions were applied a total of 288 surgeries were included in the results. 240 dogs and 274 eyes made up these cases. French Bulldogs, Staffordshire Bull Terriers, Boxer dogs, and Labrador Retrievers were the most common breeds (54.1%) presented for SCCED lesions. Male dogs (58.0%) were over-represented. The average age of the dogs were 8.3 years, and the average body weight was 19.3 kg. Affected and unaffected eyes had a mean IOP of 17.12 mmHg and 17.41 mmHg respectively. Affected and unaffected eyes had a mean STT of 25.59 mm/min and 22.49 mm/min respectively. The STT of affected eyes was significantly raised compared to unaffected eyes. The most reported clinical signs at initial presentation were keratitis, blepharospasm, lacrimation, and corneal oedema. Left or right eyes were equally likely to be affected. The contralateral eye was subsequently affected in 7.6% of dogs during the study period. Bilateral SCCED lesions were diagnosed in 10.4% of the dogs, and 4.9% of the eyes required a second follow-up surgery. The surgical outcome, between day 10-14 post-operatively, were not significantly different for SK and DBD. Both SK and DBD resulted in surgical success in 87.6% and 85.1% of eyes respectively. The main predictive variables for surgical procedure outcome were increased lacrimation at the initial examination and repeated follow-up surgeries for a single eye.
Canine blood oxygenation using ultra-low blood flow in an in vitro, single-circuit, extracorporeal membrane oxygenator model
(University of Pretoria, 2021-07) Zeiler, Gareth Edward; Buck, Roxanne; abdur.kadwa@up.ac.za; Kadwa, Abdur Rahmaan
Objective To ascertain the efficacy of a single circuit, in vitro extracorporeal membrane model at oxygenating blood and removing carbon dioxide (CO2) with ultra-low blood flow, in replicates either exposed to room air (fraction inspired oxygen 0.21) (n = 6) or ultra-low 100% oxygen flow (n = 6) driven by a linear peristaltic volumetric infusion pump. The effects of both replicates on free plasma haemoglobin (fHb) concentration was also determined. Furthermore, the ability of the oxygen replicates to maintain global oxygen delivery (DO2) was predicted in a theoretical model. Study Design In vitro, experimental study. Methods Twelve units of canine stored whole blood were used, with a median (minimum - maximum) volume of 465 (440 – 500) mL, packed cell volume of 0.5 (0.36 – 0.56) L L-1 and storage time of 3 (1 – 41) days. The blood circuit was constructed in the following order, assembled in series; blood reservoir, oxygenator, linear peristaltic infusion pump and tubing to complete the circuit by returning the blood to the reservoir. The water circuit was constructed by connecting a bath warmed to 44°C containing lactated Ringer’s solution to the water inlet of the oxygenator by tubing and a linear peristaltic infusion pump. Tubing connected to the water outlet of the oxygenator completed the water circuit by returning the water to the bath. Gas supply to the room air replicates was ensured by removing the gas inlet safety protection cap during assembly. For the oxygen replicates, an oxygen supply rig was constructed to split the oxygen flow to supply an ultra-low flow of oxygen (0.03 L minute-1) to each oxygen replicate. Before the sampling commenced, the blood and water phases of the oxygenators were primed. After 2 minutes of the blood and water circulation (both flows at 0.02 L minute-1), the first samples were collected (T0). Samples were collected for blood gas analysis post oxygenator (PaO2 and PaCO2) and pre-oxygenator (PvO2 and PvCO2). In the room air replicates, samples were collected hourly for the first 8 hours (T1, T2, T3, T4, T5, T6, T7 and T8) then at 24, 32, 48 and 56 hours (T24, T32, T48 and T56). In the oxygen replicates, the oxygen supply was connected after T0 and samples were then collected at 15-minute intervals for the first hour (T0.25, T0.5, T0.75 and T1) and then hourly for 8 hours (T2, T3, T4, T5, T6, T7 and T8) and then at 24 hours (T24). All the post-oxygenator samples in both replicates were centrifuged and analysed for fHb concentrations, except at T0.25, T0.5 and T0.75 in the oxygen replicates. Data was compared using a linear mixed model (fixed effect: time; random effect: replicates) and post-hoc analysis using Dunnet’s method within each replicate where each time point was compared to T0. Statistical significance was set at p < 0.05. A theoretical model predicting the effect on DO2 over a range of weights was constructed assuming that the oxygenator was augmenting mixed venous oxygen content. The effects on DO2 were extrapolated using PaO2, arterial oxyhaemoglobin saturation (SaO2) and haemoglobin concentrations (Hb) from the study as well as 2 hypoxaemia scenarios: hypoxic hypoxaemia (PaO2 40 mmHg; SaO2 75%) and anaemic hypoxaemia (Hb 6.7 g dL-1). These theoretical DO2 values were compared to a critical DO2 of dogs which is reported to be 9.8 mL kg-1 minute-1. Results All replicates were operational for the duration of the study period, except 2 of the room air replicates which failed due to thrombosis between T32 and T48. In the room air replicates, the PaO2 significantly increased from T0 during T1 to T8; the PaCO2 significantly decreased from T0, during T2 to T56. In the oxygen replicates, the PaO2 significantly increased from T0 for the entire study duration; the PaCO2 significantly decreased from T0 at all time points. In the room air replicates, the rate of change of fHb concentration did not change from T0 for the study duration. However, in the oxygen replicates, the rate of change of fHb concentration was increased from T0 at T3, T4 and T6. In the theoretical model, the predicted DO2 was maintained above the critical DO2 when calculated from study variables and the hypoxic hypoxaemia scenario. However, in the anaemic scenario, the predicted DO2 fell below the critical DO2. Conclusion and clinical relevance The extracorporeal membrane oxygenator configured for ultra-low blood and oxygen flow significantly increased the PaO2 and decreased the PaCO2 for 24 hours. Furthermore, the rate of change of fHb concentrations within the replicates indicate acceptable blood handling characteristics by the circuit components. An increase in DO2 was identified using the theoretical model and may clinically improve myocardial oxygenation in pathological conditions characterised by an oxygen debt. Further studies are needed to ascertain whether this study can be translated into clinical setting.
Circulating markers of endothelial activation in canine parvoviral 4 enteritis
(University of Pretoria, 2021-04) Pazzi, Paolo; sunepretorius@rocketmail.com; Pretorius, Suné
Canine parvovirus (CPV) is a debilitating disease affecting young wild and domestic canines. Canine parvovirus attacks rapidly dividing cells including intestinal epithelium, lymphoid tissue and bone marrow. The most common clinical manifestations of CPV infection are severe gastrointestinal signs and immunosuppression. During CPV, endotoxins are released from the compromised gastrointestinal tract. Increased inflammatory cytokines have been described in previous studies. The endotoxins, raised inflammatory cytokines and the severe immunosuppression stimulates the systemic inflammatory response causing widespread peripheral vasodilation, capillary permeability is increased, cardiac function depression and the coagulation cascade is activated. The state of the endothelium in CPV has not been investigated. Markers of endothelial activation including intercellular adhesive molecule-1 (ICAM-1), vascular adhesive molecule-1 (VCAM-1) and high mobility group box-1 protein (HMGB-1) give insight into the state of vascular endothelium during disease. These markers of endothelial activation have been investigated in inflammatory diseases in humans and animals. In this study, we aimed to investigate the concentration of circulating markers of endothelial activation to gain insight into the state of vascular endothelium during CPV. Thirty dogs naturally infected with CPV were used in the study and compared to ten age-matched control dogs. A significant lower median value for ICAM-1 was found in dogs with CPV compared to control dogs. No significant difference was seen for VCAM-1 or HMGB-1. This indicates that despite the systemic inflammation and raised cytokine levels seen in dogs with CPV there seems to be a lack of endothelial activation based on the circulating levels of the markers of endothelial activation. The significance of these findings warrants further investigation.
Kinetics of the inflammatory response during experimental Babesia rossi infection of Beagle dogs
(University of Pretoria, 2021-03) Leisewitz, Andrew L.; Mukorera, Varaidzo; drbroganka@gmail.com; Atkinson, Brogan Kim
Background: Babesia rossi, the most virulent canine Babesia parasite, causes severe clinical disease and death in dogs in sub-Saharan Africa. Complications and multiple organ dysfunction seen with babesiosis are likely caused by the effects of an unfocused, imbalanced and excessive inflammatory response. The aim of this study was to investigate markers of inflammation and cytokine kinetics from the point of inoculation with B. rossi throughout the course of clinical disease and determine if infectious dose influenced rate and severity of disease progression. Hypothesis: Dogs infected with a higher inoculum dose would experience more severe clinical disease and systemic inflammation over a shorter disease course. Measurable differences would be found between the baseline, low dose and high dose groups for clinical, clinicopathological and cytokine variables. Materials and Methods: This experimental study was performed on 6 healthy sterilised male beagle dogs. One dog was splenectomised and used to raise a viable parasite inoculum. Three dogs were given a high infectious dose (HD group) and 2 dogs a low infectious dose (LD group) of parasite. Appetite, habitus, clinical examination, glucose, lactate and CBC was performed daily and EDTA plasma was stored at -80⁰C. C-reactive protein and albumin were determined every second day. Cytokines were quantified on the stored plasma using a canine specific cytokine magnetic bead panel (Milliplex©). Dogs were monitored and parasitaemia was determined daily until predetermined endpoints for treatment were reached. The dogs in the high dose group were treated at 96 hours and those in the low dose group were treated at 108 hours post infection. Results: The infection was allowed to run its course for 4 days prior to intervention. The HD group was treated at 96 hours and the LD group was treated 12 hours later, at 108 hours. No significant difference was noted for baseline data between the LD and HD groups for any variable. Post inoculation, initial parasitaemia occurred at 24 hours in the HD group and 72 hours in the LD group. The rate of increase in parasitaemia in the HD group was considerably faster than that seen in the LD group. The mean temperature peaked 36-hours earlier in the HD group. The pyrexia persisted for at least 24 hours after treatment in both groups. In addition to the difference seen in vital parameters between the two groups, the HD group also demonstrated a more pronounced decline in habitus and appetite during the course of the infection. The red cell count showed a significant decline from 96 hours in the HD group, worsening after treatment with the lowest count at 120 hours. The dogs in the HD group required multiple blood transfusions before the red cell count stabilised and started to improved. Although there was a drop in the red cell counts of the LD group after treatment, it resulted in tolerable clinical levels of anaemia which did not require transfusions. The C- reactive protein also peaked 36-hours earlier in the HD group. A neutropenia was seen in both groups, but the nadir was earlier and more dramatic in the HD group. Thirteen cytokines were evaluated in total and the results are divided into 4 groups by pattern of change. The categories for the kinetic patterns identified include: a. Cytokines that rose during the infection and fell after treatment: IFNγ and KC-like. Both these cytokines peaked earlier in the high dose group and declined rapidly after treatment. b. Cytokines that rose and remained high even after treatment: MCPI-1, IL-6, IL-8 and IL-10. Both MCP-1 and IL-6 gradually increased during infection in the HD group with minimal changes in the LD group. After treatment, these cytokines increased drastically in the HD group, with only 1 dog in the LD group showing an increase at 192 hours. IL-8 had a different kinetic pattern between HD and LD groups, not only a delay in the increase. The anti-inflammatory cytokine IL-10 increased progressively during parasite replication in both groups. c. Cytokines that rose dramatically after treatment: GM-CSF, TNFα, IL-2 and IL-7 were all markedly increased after treatment in the HD group with moderate increases seen in one dog the LD group. d. Cytokines that showed no distinct pattern of change: IL-15, IL-18 and IP-10. Conclusion: Our findings suggest that the initiation of inflammation occurs before the onset of clinical disease with a possible imbalance in the pro- and anti-inflammatory cytokine concentrations during parasite replication. Infectious dose influenced the course of inflammation as well as the course and severity of disease. Treatment of the infection did not result in the resolution of inflammation. In fact, many markers of inflammation and cytokines were significantly increased following treatment. This is in agreement with the hypothesis that severe inflammation and complications are associated with an unfocused, imbalanced and pronounced inflammatory response that may even be perpetuated by chemotherapeutic intervention.
Zolazepam-tiletamine-medetomidine versus butorphanol-azaperone-medetomidine for the immobilisation of captive leopards (Panthera pardus)
(University of Pretoria, 2021-05) Buck, Roxanne Kate; Tordiffe, Adrian Stephen Wolferstan; joel@wildscapesvet.com; Alves, Joel Mnandi
Objective To compare the immobilisation time and cardiopulmonary effects of zolazepam-tiletamine-medetomidine (ZM) and butorphanol-azaperone-medetomidine (BAM) in captive leopards (Panthera pardus). Study design Prospective, clinical study Materials and Methods 17 adult, captive leopards were immobilised by remote injection of either a combination of zolazepam-tiletamine (1.5 mg kg-1) and medetomidine (0.04 mg kg-1) (ZM, n = 10) or a combination of butorphanol (0.3 mg kg-1), azaperone (0.12 mg kg-1) and medetomidine (0.12 mg kg-1) (BAM, n = 7). Time to safe approach, judged by absent responses to an ear flick and tail tug, was recorded as the immobilisation time. Following immobilisation, cardiopulmonary parameters were recorded and two arterial blood gas samples analysed. After 40 minutes, anaesthesia was reversed using atipamezole (0.2 mg kg-1) for group ZM or atipamezole (0.6 mg kg-1) and naltrexone (0.3 mg kg-1) for group BAM. Recovery time was recorded as time from injection of reversal agent to head up. Data is reported as mean ± standard deviation and compared using a general linear mixed model (p < 0.05). Results For ZM, doses administered were zolazepam-tiletamine 1.3 ± 0.6 mg kg-1 and medetomidine 0.04 ± 0.018 mg kg-1 while those for BAM were butorphanol 0.33 ± 0.05 mg kg-1, azaperone 0.13 ± 0.02 mg kg-1 and medetomidine 0.13 ± 0.02 mg kg-1. Immobilisation time was significantly faster for BAM (5.8 ± 1.1 minutes) than for ZM (11.8 ± 3.3 minutes, p = 0.008). Both treatments resulted in hypertension, with mean arterial blood pressure of 154 ± 46 mmHg with ZM and 137 ± 12 mmHg with BAM. BAM resulted in clinically significant hypoxaemia (arterial oxygen tension 52.8 ± 4.4 mmHg), while arterial oxygen tension was higher with ZM (72.6 ± 8.0 mmHg, p = 0.027). Arterial carbon dioxide tension was lower with ZM (26.4 ± 2.9 mmHg) than BAM (44.8 ± 3.9 mmHg, p < 0.001). Recovery time was not different between treatments (p = 0.604). Conclusion Both combinations provided acceptable immobilisation for field use. Supplementation with oxygen is recommended, especially when using BAM.
Influence of high-protein and high-carbohydrate diets on serum lipid and fructosamine concentrations in healthy cats
(University of Pretoria, 2021-07) Schoeman, Johan P.; Lobetti, R.G. (Remo Giuseppe); c_berman@hotmail.com; Berman, Chad Farryl
Diabetic cats can benefit from a high-protein and low-carbohydrate diet in terms of higher diabetic remission rates, lower fructosamine concentrations and improved glycaemic control. Hypercholesterolaemia in cats with diabetes mellitus has been associated with lower remission rates. A recent publication demonstrated that a high-protein and low-carbohydrate diet resulted in significantly elevated serum cholesterol concentrations in lean, overweight and diabetic cats. The concept that a traditional high-protein and low-carbohydrate diet causes increased cholesterol concentrations in healthy cats is relatively new and requires further investigation. This mini-dissertation focused on clarifying whether high-protein and high-carbohydrate diets exert differential effects on serum cholesterol, triglyceride, and fructosamine concentrations in healthy cats. This mini-dissertation describes the results of a randomised, crossover diet trial that was performed in thirty-five healthy shelter cats. Prior to enrolment, cats were fed a commercial baseline diet. Following baseline health assessments, cats were randomised into groups receiving either the high-protein or high-carbohydrate diet for four weeks. The cats were then fed a washout diet for four weeks before being transitioned to whichever diet they had not yet been subjected to. Fasting serum cholesterol, triglyceride and fructosamine concentrations were determined at the end of each four-week diet period. Weekly body condition score (BCS), body weight measurements and environmental temperatures were evaluated throughout the study. Cats on the high-protein diet had significantly higher serum cholesterol and triglyceride, yet significantly lower serum fructosamine concentrations than cats on the baseline diet (P<0.001). Among the cats on the high-protein diet, the observed increases in cholesterol and triglycerides were significantly more pronounced in cats with BCS < 5. In contrast, cats on the high-carbohydrate diet had significantly lower serum cholesterol concentrations (P<0.001) relative to cats on the baseline diet. The empirical evidence base currently suggests that diets with high protein but low carbohydrate contents may be beneficial for short-term glucose control in healthy cats. The reduction in cholesterol and triglyceride concentrations among overweight cats on a high-protein diet, relative to lean cats on the same diet, suggests that overweight cats process cholesterol and triglycerides differently from lean cats. These findings from healthy cats, that a high-protein diet significantly increased cholesterol and triglyceride concentrations while a high-carbohydrate diet significantly decreased cholesterol concentrations relative to baseline diets, warrants further investigation.
Prevalence and risk factors for surgical site infection following equine colic surgery at the Onderstepoort Veterinary Academic Hospital, South Africa from 2013 to 2021
(University of Pretoria, 2023-11-01) Munoz, Juan; Smit, Yolandi; theunisgr@gmail.com; Griessel, Theunis Steyn
Surgical site infection (SSI) is a significant cause of postoperative morbidity following exploratory laparotomy as a means of investigation and treatment for equine colic. If risk factors can be identified for the development of surgical site infection, they could be mitigated and morbidity as a result may thus be reduced. Although the prevalence and risk factors of SSI infection after exploratory laparotomy for equine colic have been identified worldwide, these factors have not been established in a referral hospital in South Africa. The objectives of this research study are to report the prevalence of SSI following colic surgery in horses at the Onderstepoort Veterinary Academic Hospital (OVAH), Equine hospital, University of Pretoria, South Africa, and to identify possible pre-, intra-, and postoperative risk factors for the development of SSI. Data was collected, and analysed retrospectively from the clinical records of all the horses that underwent exploratory laparotomy at the OVAH, for the investigation and treatment of colic over a period of 8 years from April 2013 to April 2021. Follow-up telephonic and/or email communication was performed with owners in all horses discharged after exploratory laparotomy. The association between the occurrence of SSI and each potential risk factor was assessed in a univariate analysis model. Only variables found to be significant in the univariate analyses were included for further analysis. The remaining pairs of variables were checked for collinearity, after which a final assessment was performed using a multivariable logistic regression model. From the clinical records of 144 horses that underwent colic surgery, it was found that 119 (82.6%) horses survived until discharge and 25 (17.4%) were euthanised. Of the 144 horses, 39 (27.1%) suffered surgical site infection. Multivariable analysis showed that horses which had no abdominal bandage applied following colic surgery were significantly more likely to acquire SSI than horses with an abdominal bandage placed postoperatively. The odds of horses developing SSI decreased with an increase in preoperative total protein values. The placement of a hernia belt was determined to be a significant postoperative risk factor for SSI. These findings assist with identifying factors that may increase the risk for horses developing SSI following exploratory laparotomy and furthering development of preventative strategies.
Clinical and epidemiological investigations of Orbivirus infections in domestic dogs (Canis lupus familiaris)
(University of Pretoria, 2023-11-12) Fosgate, Geoffrey Theodore; Guthrie, Alan John; Leisewitz, Andrew L.; joe.hanekom@up.ac.za; Hanekom, Josef Derek
Dogs are atypical host species for some of the most economically important orbiviral diseases, African horse sickness (AHS) and bluetongue (BT). Dogs are the only non-equid species to develop the severe fatal form of AHS, and along with the Eurasian lynx, dogs are the only non-ruminants to develop fatal bluetongue (BT). However, the role of dogs as a host species for orbiviruses has been largely dismissed as incidental or of low significance in the epidemiology of orbiviruses. In light of recent dog mortalities due to AHS which occurred with suspected midge-borne transmission, this thesis examines clinical and epidemiological features of Orbivirus diseases in South African dogs. The author shows that exposure to the African horse sickness virus (AHSV) in dogs in Tshwane, South Africa was common and frequent, with as many dogs estimated to have been exposed to AHSV as the population of horses in the area. At the onset of this investigation, only AHS had been described in South African dogs. The author describes the novel identification of the bluetongue virus (BTV) and possible equine encephalosis virus in South African dogs. The author describes the clinical presentation and management of a pregnant dog diagnosed with naturally occurring BT. The author investigates the farm of origin for this dog and shows a high level of exposure to BTV in dogs on the farm was high and detected the viral RNA from blood samples in three dogs (50%). The author reports the detection of equine encephalosis from samples collected from a puppy with a fatal respiratory disease. The findings of this study suggest dogs could play a greater role in the persistence, spread and introduction of orbiviruses than previously thought.
Echocardiographic evaluation of horses challenged with African horse sickness virus
(University of Pretoria, 2023) Carstens, Ann; Eberhardt, Christina; nicolene.hoepner@up.ac.za; Hoepner, Sara Nicolene
African horse sickness (AHS) is an infectious, often fatal viral disease of equids with a severe impact on the equine industry in sub-Saharan Africa. Clinicopathological mechanisms are poorly understood, and there is limited information on the degree and type of cardiac involvement. This study followed four horses experimentally infected with African horse sickness virus (AHSV) as part of a vaccine trial to describe echocardiographic changes during the course of the disease. Echocardiography was performed once prior to infection, and daily from infection to humane euthanasia of each subject. Both objective and subjective (eFoCUS) evaluations of all appropriate echocardiographic variables were performed. An increase in diastolic myocardial thickness and a decrease in the size of the left cardiac chambers during diastole and systole were consistent findings on the last day of evaluation of each subject and suggestive of hypovolaemia. The cause of the suspected hypovolaemia was not investigated, but increased vascular permeability causing third space volume loss was considered the most likely cause, as this is associated with the disease process. During the eFoCUS evaluation substantial and perfect interobserver agreement were found for an increase in myocardial thickness and diminution of the left ventricle, respectively, suggesting that these variables could be used to subjectively evaluate intravascular volume in clinical cases in an emergency setting. In addition, perfect interobserver agreement for impaired diastolic dysfunction, and almost perfect agreement for pericardial effusion, was found during the eFoCUS evaluation of the final data sets for each subject. Further studies are needed to objectively define the presence, quantify the severity, identify the cause and significance of these findings.
The effect of operative technique and tibial osteotomy ratio on post-surgical complications in dogs with medial patella luxation
(University of Pretoria, 2023-09-21) Kitshoff, Adriaan; Elliott, Ross; peterguyvet@gmail.com; Guy, Peter
Background: Medial patellar luxation is a common cause of hindlimb lameness in dogs, affecting both small and large breeds. The condition arises from developmental abnormalities and anatomical irregularities in the hindlimb. Tibial tuberosity transposition is a widely used surgical technique for realigning the quadriceps mechanism and treating MPL. Postoperative complications are common following surgical treatment. During the routine evaluation of post operative radiographs, osteotomy segment size appeared to be associated with an increased incidence of complications. This prompted investigation into this possible association between osteotomy segment size and the incidence of complications. Hypothesis: The complication rate significantly differs when the osteotomized segment of the tibial tuberosity is transposed medially and measures less than 80% of the mid-tibial diaphysis on preoperative radiographs Animals: Client-owned dogs (n= 88) that underwent MPL surgery Methods: Records of 88 dogs (108 stifles) that underwent TTT for treatment of MPL were reviewed. Data collected included patient signalment, clinical presentation, surgical factors, pre and postoperative radiographs and complications. The dimensions of tibial tuberosity osteotomy were calculated as a ratio to preselected tibial dimensions based on immediate postoperative radiographs. Mixed-effects logistic regression analysis was performed to determine the impact of osteotomy segment size (O1:D3 ratio) on the occurrence of post-surgical complications following TTT. Results: Out of 108 surgical procedures performed, 40 (37%) resulted in complications. There was no significant difference in overall complication rates related to patient factors or surgical variables (such as pin direction, tension band, open physis, and complete osteotomy). However, concurrent trochlear augmentation procedures were associated with a decreased risk of complications (hazard ratio (95% CI): 0.31 (0.13 - 0.70), p=0.005). The predicted probability of surgical complications based on the O1:D3 ratio indicated that osteotomy segment sizes between 0.8-0.99 (hazard ratio (95% CI): 0.23 (0.10 – 0.56) p=0.001) and 1-1.19 (hazard ratio (95% CI): 0.05 (0.01 – 0.38), p=0.004) had a lower risk of complications compared to ratios below 0.8 or above 1.2 (hazard ratio (95% CI): 0.26 (0.07 – 0.90), p=0.033). Conclusions and clinical importance: This study highlighted the clinical importance of considering tibial tuberosity osteotomy segment size in dogs undergoing surgical treatment for MPL by retrospectively analyzing a significant number of cases, the study provided valuable insights into the incidence of postoperative complications related to osteotomy segment size. The findings indicated an association between the O1:D3 ratio (the ratio of osteotomy segment size to preselected tibial dimensions) and the occurrence of complications. Osteotomy segment sizes between 0.8-0.99 and 1-1.19 were associated with a lower risk of complications, while ratios below 0.8 or above 1.2 showed increased risk. Therefore, careful consideration of osteotomy segment size, aiming for sizes equal to or slightly larger than the mid-diaphyseal diameter, is crucial in surgical planning for dogs with MPL.

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