Theses and Dissertations (Companion Animal Clinical Studies)

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Cardiac troponin I immunoassay validation, reference interval determination and serum cardiac troponin I changes in translocated southern-central black rhinoceros (Diceros bicornis minor) and southern white rhinoceros (Ceratotherium simum simum)
Rautenbach, Yolandi (University of Pretoria, 2024-10)
The abundance and range of occurrence of the two rhinoceros species in sub-Saharan Africa, the southern-central black (Diceros bicornis minor) and southern white (Ceratotherium simum simum) rhinoceros, have decreased dramatically. Common threats to rhinoceros conservation include poaching, habitat fragmentation and loss,international trade in illegal rhinoceros products, and reduced financial resources due to global financial recessions and pandemics. Translocation of wildlife species is a commonly used tool for the conservation of threatened and endangered animals, with a focus on restoring and enhancing populations. It plays an integral part in national and international conservation plans for African rhinoceros. Chemical immobilisation is often used during translocation, with etorphine forming the basis of most drug combinations used. Ensuring animal welfare during wildlife transport is critical and dehydration, electrolyte imbalances, a negative energy balance, muscle damage, protein catabolism, stress-induced immunomodulation, and oxidative stress are the main pathophysiological findings reported in rhinoceros translocated over long distances. Investigation into possible cardiomyopathy in transported rhinoceros has been hampered by the lack of validated immunoassays to measure serum biomarkers, specifically cardiac troponin I (cTnI), in rhinoceros. The broad objectives of this study were therefore to 1) sequence the cTnI gene in both rhinoceros species, to obtain the inferred amino acid sequences from the messenger ribonucleic acid (mRNA) transcript sequences, and assess the potential a^inity of several commercial cTnI immunoassays for detecting cTnI in African rhinoceros; 2) validate two point-of-care (POC) cTnI immunoassays for use in African rhinoceros; 3) to generate cTnI reference intervals (RIs) on the high-sensitivity (hs)-cTnI immunoassay in both rhinoceros species and apply subset partitioning in white rhinoceros that were chased by helicopter during capture versus those that were captured in a boma and therefore not chased; and 4) investigate the serum cTnI changes in long-distance translocated rhinoceros and in rhinoceros chemically immobilised with di^erent drug protocols during capture. Best practice guidelines for method validation, quality control (QC) and RI generation as published by the American Society for Veterinary Clinical Pathology were followed. Expert consensus recommendations on the clinical laboratory practice for hs-cTnI assays as advised by the International Federation of Clinical Chemistry Task Force on Clinical Applications of Biomarkers (IFCC TF-CB) were also complied with. The mRNA cTnI transcript sequences were obtained by RNA extraction from myocardium of deceased rhinoceros followed by primer design, complementary deoxyribonucleic acid (cDNA) synthesis using reverse transcription polymerase chain reaction, and Sanger sequencing. The percentage identity between black and white rhinoceros cDNA nucleotide sequences was 99%, while inferred amino acid sequences were identical. There were five amino acid di^erences between humans and rhinoceros in the epitope binding sites of immunoassay antibodies and five assays contained antibodies against epitopes that were not conserved. Nevertheless, only one assay was deemed unlikely to cross-react with rhinoceros cTnI and five assays were found to be suitable for further investigation into cTnI measurement in African rhinoceros. The Siemens Stratus CS Acute Care troponin I cTnI and Siemens Atellica VTLi hs-cTnI were the two POC cTnI immunoassays selected for analytical method validation. Validation experiments included precision studies, reportable range, haemoglobin interference studies, recovery studies, and detection limit studies with results assessed against two total allowable error (TEa) performance goals, namely 30% and 70%. Imprecision was acceptable and met low cTnI concentration performance goals. Thereportable ranges were similar to the manufacturer’s specifications. For the Stratus CS, high haemoglobin concentrations in white rhinoceros resulted in bias. The QC validation results showed that a simple 13s QC rule using two levels of QC material and a TEa of 70% could be used in both analysers, except at very low cTnI concentrations in the Atellica VTLi. This study showed that both cTnI POC analysers are suitable for use in African rhinoceros and analytical performance goals for low cTnI concentrations in hs-cTnI assays were met. To allow for the identification of cardiomyocyte injury in African rhinoceros, RIs were established for both species of rhinoceros using the validated hs-cTnI assay. Reference intervals were generated from 62 and 87 apparently healthy, free-living immobilised black and white rhinoceros, respectively. Additionally, the 99th percentile upper reference limits were also determined. Of interest is that subclass partitioning was valid for white rhinoceros based on whether they were immobilised in a boma or chased by a helicopter before being immobilised. Although chemical capture and translocation (involving capture and long-distance transport) in African rhinoceros are essential components of conservation strategies aimed at improving the conservation status of the species, several adverse pathophysiological e^ects, specifically hypoxaemia, acidosis and muscle damage, are associated with these processes which negatively impact rhinoceros’ welfare. Serum cTnI concentration was measured using the Atellica VTLI hs-cTnI assay on stored serum samples collected during four long-distance translocation studies in black and white rhinoceros and in one chemical immobilisation study in white rhinoceros. Measurement of serum cTnI concentration in rhinoceros translocated over long distances showed significantly increased cTnI concentrations during transportation and at release when compared to concentrations at capture. The degree of cTnI increase was more significant in cohorts chased and darted from helicopters. Concurrent skeletal and cardiac muscle damage was demonstrated in transported black and white rhinoceros, indicative of capture myopathy (CM) in these animals. Furthermore, hypoxaemia, acidosis and a negative energy balance were correlated with elevated cTnI concentrations, highlighting specific areas in procedures involving chemical immobilisation, capture, and transport that need to be addressed to mitigate these adverse effects. The results of this study will allow wildlife veterinarians involved in African rhinoceros conservation procedures, and in the treatment of injured animals, to assess if cardiomyocyte damage is present. This assessment will allow for cardioprotective adjustments to be implemented in these procedures, resulting in improved animal welfare. Demonstration of concurrent elevated skeletal and cardiac muscle biomarkers in translocated rhinoceros will assist wildlife veterinarians in identifying animals at risk of developing CM that should be kept in confinement (boma) at the receiving end of the journey for monitoring and reduction in stress before release.
Endocrine responses to snouted cobra (Naja annulifera) and African puffadder (Bitis arietans) envenomation in dogs
Fourie-Viljoen, Noeline (University of Pretoria, 2025-01)
The Hypothalamic-Pituitary-Adrenal (HPA) and Hypothalamic-Pituitary-Thyroidal (HPT) axes are pivotal in the pursuit of homeostasis in critical illness. The goal of this study was to investigate the host endocrine response in the snake-envenomed canine patient. This prospective study included 17 client-owned dogs naturally envenomed by either a snouted cobra (Naja annulifera) (n=9) or a puffadder (Bitis arietans) (n=8), that presented within 6 hours of envenomation. The dogs were further subdivided clinically into a neurological (n=5) and nonneurological group (n=4). Serum samples were collected at admission, and thereafter at 12-, 24-, and 36-hours post envenomation. At each time point, the serum total thyroxine (TT4), thyrotropin (TSH), C-reactive Protein (CRP) and cortisol concentrations were measured. Compared to control dogs, the median serum TT4 concentrations of all the snake-envenomed dogs were significantly lower at all time points (P<0.05). The non-neurological cobra subgroup recovered to serum TT4 concentrations comparable to that of the controls within 24 hours of envenomation, while the puffadder and neurological cobra subgroup serum TT4 concentration remained significantly suppressed until 36 hours post envenomation. Serum TT4 concentration was negatively correlated with serum CRP concentration (P<0.05, ρ=-0.326)). The differences in TSH between groups failed to reach significance. The total serum cortisol concentrations of all envenomed dogs were highest at admission, but only the neurological cobra subgroup had a significantly higher concentration at admission compared to the controls. The neurological cobra subgroup had the highest peak in serum CRP concentration, but the correlation between total serum cortisol and CRP concentrations failed to reach significance. Puffadder and snouted cobra envenomation is associated with significant suppression of serum TT4 concentrations that is correlated with the severity of the host inflammatory response. The only significant increase in total serum cortisol concentration was observed in the neurological snouted cobra envenomed subgroup at admission. This study provides novel insights into the temporal endocrine perturbations in Puffadder and snouted cobra envenomation, and the relation thereof to the degree of the host inflammatory response.
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.
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.
Endothelial damage and cellular apoptosis in horses experimentally infected with African horse sickness virus
Schonken, Emma (University of Pretoria, 2024-12)
African horse sickness (AHS) is an infectious, non-contagious vector-borne viral disease caused by the African horse sickness virus (AHSV), a non-enveloped, double-stranded RNA Orbivirus belonging to the Sedoreoviridae family (1). Primarily transmitted by Culicoides midges, AHSV infection results in a mortality rate exceeding 90% in susceptible equine populations (2,3). The disease manifests in four clinical forms: pulmonary (“dunkop”), cardiac (“dikkop”), fever, and mixed form, with severity depending on factors such as viral virulence and host immune status (3,4). Clinical signs of severe AHS infection are consistent with vasculitis, characterized by oedema in the supraorbital fossae, ocular conjunctiva, and intermandibular spaces, as well as pulmonary oedema. Hydropericardium and petechial haemorrhages are also commonly observed during clinical examination and necropsy (5). These clinical manifestations suggest significant vascular endothelial damage as a key aspect of AHS pathogenesis. The endothelium, comprising the inner lining of blood vessels, forms a semi-permeable membrane between blood and surrounding tissues. On its luminal surface lies the glycocalyx, a gel-like layer composed of membrane-attached proteoglycans, glycosaminoglycan chains, and glycoproteins. This structure plays a crucial role in maintaining vascular homeostasis, regulating vascular permeability, and exerting anti-coagulant and anti-adhesive effects (6–8). Syndecan-1 (SYND1), a heparan sulphate proteoglycan expressed on endothelial cells, is a key component of the glycocalyx. When endothelial damage occurs, plasma concentrations of SYND1 increase, as reported in human trauma patients, making it a potential biomarker for endothelial injury (9,10). The shedding of glycocalyx components into the circulation may correlate with disease severity in various conditions characterized by endothelial damage. Previous studies have demonstrated AHSV tropism for the heart, lung, and spleen, with the virus successfully identified in these organs using immunohistochemistry (IHC) (11,12). Microscopic evaluation of endothelial cells in these tissues from horses infected with AHSV have reported ultrastructural changes suggestive of apoptosis, as well as loss of intercellular junction integrity, presence of cytoplasmic projections, and nuclear condensation (13). Given the hallmark finding of vascular permeability and tissue oedema in AHSV-infected horses, this study aimed to quantify the extent of endothelial damage using SYND1 concentrations in the blood as a biomarker and to correlate the severity of endothelial damage with apoptosis observed in endothelial cells, using IHC, of horses infected with AHSV. This study retrospectively evaluated stored plasma and tissue samples (spleen, heart, lung) from four Boerperd mix horses that were experimentally infected with AHSV. Syndecan-1 plasma concentrations in horses experimentally infected with AHSV showed no significant change over the course of infection (Skillings-Mack test = 13.516; P = 0.077). Immunohistochemical analysis showed positive staining for AHSV viral protein 7 (VP7) and non-structural protein 4 (NS4) antigens in endothelial cells and some mononuclear cells in spleen, lung, and heart tissues of infected horses. Tissue from control horses were negative for both antigens. Immunolabeling for caspase-3, a marker for cellular apoptosis, in the spleen of AHSV-infected horses showed a marked increase in positive cells (186.0 to 262.4 cells/image) compared to controls (1.0 to 25.0 cells/image). Similarly, in lung tissue, AHSV-positive horses exhibited higher caspase-3 positive cell counts (11.6 to 75.4 cells/image) than controls (0.4 to 7.4 cells/image). However, cardiac tissue showed no significant difference in caspase-3 labelling between infected and control horses. Immunohistochemistry for leucocyte markers in infected horses demonstrated strong labelling for ionized calcium-binding adapter molecule 1 (IBA-1), a marker for mononuclear cells, within splenic lymphoid tissue and lung parenchyma. T lymphocytes observed in splenic periarteriolar lymphoid sheaths and peribronchiolar interstitium stained positive for cluster of differentiation 3 (CD3). CD20-positive B lymphocytes were extensively labelled throughout splenic lymphoid follicles. These findings suggest that AHSV infection does not result in direct damage to endothelial cells; instead, it induces a significant apoptotic response in the spleen and lungs of infected horses, but not in the heart, and is associated with notable changes in mononuclear leucocyte distribution and viability in affected tissues.
Calcium and magnesium abnormalities in dogs with parvoviral enteritis
Mouton, Anneri (University of Pretoria, 2024-10)
Canine parvoviral enteritis (CPE) is a common cause of acute, life-threatening enteritis in young dogs. While gastrointestinal disturbances and immunosuppression are the most recognised sequelae of CPE, a less apparent systemic inflammatory response syndrome (SIRS) also develops in many dogs. Calcium and magnesium abnormalities are increasingly recognised in the critical care setting. Ionised hypocalcaemia (iHypoCa) is well documented among humans with sepsis, and it has been associated with an increased duration in hospital stay in dogs with CPE, as well as mortality in dogs evaluated in an emergency room or intensive care setting. Moreover, critical illness has been identified as the most common cause of iHypoCa in dogs. Hypomagnesaemia is a common occurrence in critically ill people and animals, but it has not been associated with outcome in dogs infected with CPE. A significant correlation has been found between serum calcium and magnesium concentrations in dogs with hypomagnesaemia. The objective of this study were a) to determine the association between the development of iHypoCa and total hypomagnesaemia, and sepsis, and b) to investigate whether ionised calcium (iCa) or total magnesium (tMg) is associated with mortality in dogs with CPE. Sixty-four client-owned dogs with CPE were enrolled in this prospective cohort study. Serum iCa and tMg were measured daily from admission until death or discharge. Fifteen healthy client-owned dogs were used as controls. Mean iCa concentrations of the CPE group on admission were significantly lower compared to the control group (1.35 mmol/L vs 1.52 mmol/L). Ionised calcium concentrations of non-survivors were significantly higher compared to survivors on day two, but not on any other days. Dogs that were hypercalcaemic on day two were also significantly more likely to die than normocalcaemic dogs after adjusting for multiple comparisons (OR = 10.7; 95% CI: 1.7-71). Ionised calcium was not associated with the development of sepsis on any day. In contrast, mean admission tMg concentrations of the CPE group were significantly higher compared to the control group (0.72 mmol/L vs 0.63 mmol/L). However, tMg concentrations were not significantly different between survivors and non-survivors, nor were they associated with the development of sepsis on any day. In summary, dogs with CPE had lower iCa and higher tMg compared to healthy dogs on admission, and the iCa concentrations of non-survivors were significantly higher on day two compared to survivors. Results of this study provide insight into calcium homeostasis in critically ill young dogs with CPE.
Prevalence of co-infection with Ehrlichia spp. or Theileria spp. in dogs naturally infected with babesiosis in the Eastern Cape
Cloete, Henry Pieter Pienaar (University of Pretoria, 2025)
This study describes the prevalence of Ehrlichia canis or Theileria equi co-infections in dogs that are naturally infected and clinically sick due to babesiosis. Canine babesiosis and ehrlichiosis are tick-borne diseases of great significance in South Africa. Theileriosis in dogs in South Africa is still poorly understood. Co-infection with multiple tick-borne pathogens has been documented and is perceived as a common occurrence in South Africa. The Mdantsane State Veterinary Clinic in Mdantsane, Eastern Cape Province, South Africa was used as the centre where sample collection took place. Limited data on the prevalence and distribution of tick-borne diseases in the Eastern Cape Province are available and thus this population of dogs can be viewed as a novel study population. The main objective of this study was to determine the prevalence of co-infections with E. canis or T.equi in dogs with babesiosis in the Eastern Cape province. Possible associations of population characteristics and haematological and biochemistry measures with a co-infection in these dogs were also investigated. The study population included 150 dogs naturally infected with babesiosis that presented to the Mdantsane State Veterinary Clinic between January 2021 and November 2021. Quantitative polymerase chain reaction was used to confirm the Babesia spp. that the dogs were infected with and to identify co-infections. Association with co-infection for the following parameters were evaluated: sex, breed, age, duration of sickness, leukocyte count, band neutrophil count, monocyte count, platelet count, absolute reticulocyte count, and serum globulin concentration. Positive and negative predictive values of monocytosis, leukopenia, band neutrophilia, thrombocytopenia, and on regenerative absolute reticulocyte count for co-infection were also calculated. Babesia rossi was identified in 149/150 samples and B. vogeli in only 1/150 samples. A co-infection prevalence of 2.0% (3/149; 95% confidence interval: 0.4–5.7) with B. rossi and E. canis was found. No other co-infections were reported. No investigated variables showed significant associations with coinfections. Monocytosis, in particular, was not associated with co-infection. Co-infection with other tick-borne pathogens in dogs with babesiosis is uncommon in the Eastern Cape province. These findings raise the possibility that B. rossi may have a protective effect against other tick-borne pathogens. It is advised that further testing, ideally with the use of polymerase chain reaction, be done when a co-infection is suspected to practice responsible antibiotic stewardship.
Assessment of coxofemoral joint laxity in juvenile boerboel dogs using mobile phone goniometry
Triegaardt, Christiaan Francois (University of Pretoria, 2024-05-17)
BACKGROUND Canine hip dysplasia (CHD) is closely associated with hip joint laxity (HJL), which is considered as one of the primary precursors to coxofemoral degenerative joint disease. However, the relationship between HJL and hip joint range of motion remains underexplored. OBJECTIVES This study aimed to investigate a correlation between hip joint angles (rotation and abduction) and the laxity index (LI) measured by the Vezzoni Modified Badertscher Distension Device technique (VMBDD) in juvenile boerboels.  METHODS Hip joint angles were measured in 33 boerboels (aged 4-12 months) using mobile phone goniometer-based measurements by three independent examiners for abduction, internal, and external rotation. Stress view radiography with the VMBDD method assessed HJL, and LI's correlation with measured angles were examined. Inter-and-intra-operator variability of hip joint angles were also evaluated.  RESULTS No significant correlation was found between abduction or internal rotation angles and laxity. However, external rotation demonstrated a weak correlation with laxity (r=0.207, p=0.095). Weight had a significant negative correlation with laxity (r=-0.265, p=0.031). Intra-operator variability ranged from 2.2 to 5.9, with the highest variability noted with internal rotation (4.0 to 5.9). Inter-operator variability ranged from 4.4 to 11.4, with the greatest variability observed in internal and external rotation (11.4 and 10.9, respectively).  CONCLUSION Mobile phone goniometry appears unreliable for predicting joint laxity due to high inter- and intra-operator variability with poor repeatability.
Physiological variables for the objective detection of intraoperative nerve block failure in dogs
Basson, Pierre Etienne (University of Pretoria, 2023-08)
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
Horrell, Heidi (University of Pretoria, 2023-09)
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
Pretorius, Jandre D. (University of Pretoria, 2023-09)
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
Schliewert, Eva-Christina (University of Pretoria, 2023)
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
Piketh, Graeme (University of Pretoria, 2024-06)
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
Morris, Laurie Megan (University of Pretoria, 2024)
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
Hollenbach, Elza (University of Pretoria, 2024)
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
Labuscagne, Sandra (University of Pretoria, 2018)
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)
Robert, Mickaël Patrice (University of Pretoria, 2020-01)
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
Burger, Joachim Paul (University of Pretoria, 2024-07-03)
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
Sirrals, Brent (University of Pretoria, 2024-06-18)
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
Kadwa, Abdur Rahmaan (University of Pretoria, 2021-07)
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.

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