Melbourne Veterinary School - Theses
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ItemSome characteristics of the Phantom Cow Syndrome in lactating Holstein-Friesian cows(University of Melbourne, 2004)
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ItemStudies on various aspects of tibial plateau angles in dogs(University of Melbourne, 2005)Cranial cruciate ligament rupture is one of the most common diseases of the hind limb in dogs. Tibial Wedge Leveling Osteotomy (TWLO) is a relatively new technique designed to alter stifle biomechanics and negate the need for a cranial cruciate ligament. In order for the (TWLO) to be performed successfully, measurement of the tibial plateau angle is an important criterion. The first study looks at the variability in measurement of the tibial plateau angle using two observers and two methods of measurement. The methods used were the traditional method and a new method utilising the fibular head as a marker of the tibial plateau. The repeatability co-efficients of Observer 1 was 6.4 (4.9 to 9.1) and Observer 2 was 3.5 (2.7 to 5.0). The summary of the intra-observer standard deviation is +/- 2.5�. The summary of the inter-observer standard deviation is +/- 3.8�. These were higher than in previous studies. The high variation in measurement of Observer 1 using the new method led us to conclude that it was unlikely to be a better method than the one currently used. The second study compared the tibial plateau angles between dogs with and without cranial cruciate ligament rupture. No statistical difference was found by means of a paired t-test. Tibial plateau angles are unlikely to be useful as a predictor for cranial cruciate ligament rupture. The final study looked at the post-operative tibial plateau angles of a sample population of dogs that had undergone TWLO at The University of Melbourne Veterinary Clinic and Hospital. Only 60% of dogs had the desired post-operative tibial plateau angle of less than 11�, the rest were higher than intended. Many factors including inaccuracies of measurement and surgical inaccuracy contributed to the high post-operative tibial plateau angles.
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ItemMolecular tools for the detection and characterization of cryptosporidium(University of Melbourne, 2009)
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ItemThe use of phage display antibodies in defining alloantigens of canine RBC(University of Melbourne, 2008)
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ItemOver-wintering ecology of Lucilia cuprina in South-Eastern Australia(University of Melbourne, 2007)
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ItemMorphometrical study of carpal bones in thoroughbreds, ponies and other breeds of horses(University of Melbourne, 2006)
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ItemMorphometrical study of carpal bones in thoroughbreds, ponies and other breeds of horses(University of Melbourne, 2006)
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ItemPhylogeny and virulence factor genes of canine urinary Escherichia coli in relation to clinical disease and antimicrobial resistance( 2018)Traditionally, urinary tract infections (UTIs) have been categorised as either uncomplicated or complicated in veterinary medicine, with treatment differing for the two categories. In human medicine, there is an additional category: asymptomatic bacteriuria, which is the presence of bacteriuria without symptoms of infection. Escherichia coli is the most common bacterial species involved in UTIs in dogs. Clinical signs can be absent in dogs with complicated UTIs, and this has been likened to asymptomatic bacteriuria in people and has been termed subclinical bacteriuria (SBU). Treatment recommendations for SBU in dogs have been adapted from human recommendations. Many E. coli strains are resistant to multiple antibiotics and uropathogenic E. coli possess virulence factor genes that facilitate overcoming host defence mechanisms. These E. coli commonly belong to phylogenetic groups B2 and D. Some studies suggest that human E. coli isolated from asymptomatic bacteriuria differ from those causing clinical UTI. While the virulence factor genes and phylogeny of canine urinary E. coli isolated from UTIs are well characterised, little is known about virulence factor genes and phylogeny in E. coli isolated from SBU. Furthermore, these genomic characteristics have not been studied in detail in multi-drug resistant (MDR) canine urinary E. coli. Thus, the pathogenic potential of canine urinary E. coli is not well described and the benefit of antibiotic therapy in SBU and MDR infections is unknown. This study used whole genome sequencing to characterise 47 E. coli isolated from dogs with SBU and 67 E.coli from dogs with clinical UTI in terms of their phylogeny and virulence factor gene profile. From those strains, the 15 MDR strains were characterised. When the phylogeny and virulence factor gene profile of E. coli isolated from dogs with SBU were compared with clinical UTIs, results showed that most clinical UTI and SBU E. coli belonged to phylogenetic group B2. The virulence factor gene profile was similar between the two groups, and no association was found between them and the 83 virulence factor genes analysed. Many of the MDR E. coli belonged to phylogenetic group B1 and these isolates possessed fewer virulence factor genes than non-MDR E. coli. Based on the results of this study, it was concluded that phylogeny and the presence of virulence factor genes do not influence the manifestation of clinical disease. Host immunity and rather than presence and the expression of or mutations of virulence factor genes may have a role in the development of clinical disease. ii MDR E. coli have fewer virulence factor genes than non-MDR isolates, with MDR isolates commonly belonging to commensal phylogenetic groups. This suggests that treatment of MDR isolates is not always indicated because they tend to have commensal bacterial phylogeny, which can have implications for reducing the development of antimicrobial resistance. While whole genome sequencing is an accurate method for determining phylogeny and the presence of virulence factors, it is unable to easily differentiate the pathogenicity potential of urinary E. coli and therefore treatment recommendations cannot be made based on this technique.
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ItemAssessment of a ropivacaine ultrasound-guided Transversus Abdominis Plane (TAP) block for peri-operative analgesia in the dog undergoing ovariohysterectomy surgery( 2019)Advances in veterinary medicine have led to the development of further techniques to provide analgesia for our patients. Ovariohysterectomy is a commonly performed surgery in female dogs which causes significant pain. Multimodal analgesia often combining opioids, non-steroidal anti-inflammatories and local anaesthetic techniques is implemented to treat this type of pain. The transversus abdominis plane (TAP) block is a local anaesthetic technique that provides analgesia to the afferent nerves supplying the parietal peritoneum, muscles and skin of the anterior abdominal wall. The TAP block is utilized in human anaesthesia and has been shown to reduce post-operative pain scores and opioid consumption. The TAP block has potential to provide local anaesthesia to the mid-caudal abdomen for dogs undergoing ovariohysterectomy. The initial pilot study was a cadaveric study carried out in 5 dogs with an ultrasound guided two-point TAP injection performed in each hemiabdomen. The study identified that a two-point TAP injection delivered consistent dye dispersion to adequately stain branches of thoracic nerve T13 and lumbar nerves L1, L2 and L3. It concluded that this technique should be assessed in vivo to evaluate the analgesic efficacy in mid to caudal abdominal surgeries. A subsequent randomized controlled trial assessed the two-point ultrasound-guided ropivacaine TAP block for dogs undergoing ovariohysterectomy, with the hypothesis that dogs receiving the ropivacaine TAP block would have a lower minimum alveolar concentration (MAC) isoflurane at skin incision and a lower opioid rescue analgesic requirement post-operatively. The results concluded that the estimated population MACiso for the treatment group was lower than the control group but that this was not significant. There was also no significant difference in pain scores between the groups as measured by the Glasgow composite pain scale short form and mechanical nociceptive threshold testing. The proportion of subjects receiving rescue analgesia in the treatment group was lower than the control group, but this was not significant. The study concluded that the two-point TAP block did not provide significant MAC reduction or additional intra-operative or post-operative analgesia compared with the control for dogs undergoing ovariohysterectomy. Multiple confounding factors such as the administration of morphine as premedication and the low concentration of local anaesthetic used, ropivacaine 0.2%, could have contributed to these findings. Although the cadaver study identified that a two-point TAP injection delivered consistent dye dispersion to thoracic nerve T13 and lumbar nerves L1, L2 and L3, the technique when performed with 0.2% ropivacaine in dogs undergoing ovariohysterectomy did not provide significant additional MACiso reduction or intra-operative or post-operative analgesia compared with the control for dogs. Further assessment of the toxic dose of ropivacaine in dogs and the minimum effective concentration of ropivacaine for TAP blocks in dogs needs to be evaluated in order to further develop and assess this technique.
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ItemInflammation and endothelial perturbation in canine abdominal surgery: the potential modulatory effect of lidocaine( 2019)Complication rates following emergency laparotomy surgery are high, with organ dysfunction being a commonly encountered post-operative complication. Given the endothelium acts as the interface between the systemic circulation and the organs, its function is vital to maintaining organ health. The endothelium is in a constant state of flux, impacted largely by the local environment of which it is a part. In the presence of wide-spread systemic inflammation, inflammatory mediators precipitate change to the structure of the endothelial glycocalyx. These changes result in shedding of the endothelial glycocalyx and alteration of the endothelial phenotype. The endothelium may, as a result, lose the capacity to regulate vasomotor tone, and shift toward a pro-inflammatory and pro-coagulant state. This predisposes to reduced tissue oxygen delivery, and organ dysfunction may ensue. This thesis aimed to answer two key questions: does surgical trauma induced in canine patients undergoing emergent abdominal surgery invoke a systemic inflammatory response and subsequent endothelial activation? And if so, does lidocaine, a proposed immunomodulatory drug, mitigate this effect when given in the post-operative period? Chapter two provides a detailed review of endothelial structure and function, and current literature pertaining to systemic inflammation and endothelial activation in the context of abdominal surgery. Chapter two also examines the literature regarding the proposed mechanisms through which lidocaine acts as an immunomodulatory drug, and reviews publications that investigate the use of lidocaine as an anti-inflammatory drug in human patients after abdominal surgery. Chapter three is a randomized, blinded clinical trial quantifying the effect of emergency abdominal surgery on the concentration of markers of systemic inflammation and endothelial perturbation in canine patients in the post-operative period. The trial also assessed the potential use of lidocaine as a post-operative immunomodulatory therapy in dogs having undergone laparotomy. Fifty canine patients undergoing abdominal surgery were enrolled in the study. Patients were randomized into two separate groups: a study group receiving lidocaine intravenously, and a control group receiving 0.9% NaCl intravenously for a twelve-hour period following abdominal surgery. Blood samples were gathered prior to surgery, followed by six and twelve hours post-operatively. Concentrations of markers of systemic inflammation (IL-6) and markers of endothelial perturbation (VEGF and HA) were quantified via means of ELISA at each time point. Results revealed a significant increase in the concentration of markers of systemic inflammation and endothelial perturbation in post-operative blood samples. No immunomodulatory or endothelial preserving effect of lidocaine was appreciated.