Veterinary Science Collected Works - Theses
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ItemEmbryo survival in the critically endangered Southern Corroboree frog (Pseudophryne corroboree) at Melbourne Zoo( 2023-10)The Southern Corroboree frog (Pseudophryne corroboree) is one of Australia’s most critically endangered amphibians and relies on captive assurance populations for survival. However, captive breeding at Melbourne Zoo is limited by high embryo mortality, previously found to be associated with hyphal fungal infections in abnormal embryos. To investigate the aetiology, I examined disease co-factors by characterising the epidemiology of embryo mortality as well as manipulating and assessing various husbandry conditions during the 2022 and 2023 Melbourne Zoo captive breeding seasons. I investigated 1) the epidemiology of embryo mortality, 2) the affect of three substrates on embryo survival, 3) the affect of physically separating eggs on embryo survival, and 4) fertility rates. Intense monitoring in 2022 revealed an overall 52.4% embryo survival rate with most loss occurring within two weeks of laying, and that mortality was higher for eggs laid later in the season. For males that fertilised multiple clutches, there was no decrease in survival in later clutches. Our experiments incubating embryos on three substrates (moss, live plants, gravel) and a trial of egg separation found no differences, indicating that altering these husbandry factors is unlikely to improve outcomes. Fertility did not appear to be a major issue in most of the clutches examined during the 2023 breeding season with a mean fertilisation rate of 77.2%. However, the high loss soon after laying suggests embryo quality rather than husbandry is an issue. A change in captive management in 2023 enabled more females to lay from the beginning of the breeding season rather than holding some for the second half, and embryo survival improved (63.5%). This suggests that egg quality reduces over time if laying is delayed, possibly related to over-maturation, but assessments in further years are needed to confirm that breeding females early in the season improves embryo survival rates. As most Southern Corroboree frog embryo loss occurs within the first two weeks after laying, further work is needed to determine the extent of infertility versus early embryonic death affecting this early period, and whether the fungi impacting unhealthy embryos is opportunistic or pathogenic. This may guide the development of other management options.
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ItemLean body weight adjusted intravenous contrast medium dose for abdominal Computed Tomography in dogs( 2022-01)Contrast-enhanced computed tomography (CT) is a common diagnostic modality to investigate abdominal pathology in dogs. For the animal’s safety, the minimum contrast media (CM) dose to achieve diagnostically appropriate contrast enhancement should be administered. Although acute adverse reaction to non-ionic iodinated CM is rare, moderate (>20% from baseline) alteration of heart rate and systemic blood pressure has been reported in dogs. Use of less iodinated contrast is particularly crucial in patients with pre-existing renal dysfunction, as CM is concentrated in renal tubules, having a direct toxic effect, modulating tubular regulatory mechanisms, and producing renal vasoactive substances. Risk of contrast induced nephropathy is considered low in human patients with no history or symptoms of renal disease. In dogs, iodinated contrast dose is commonly linearly increased based on total body weight (TBW). Lean body weight (LBW) has been considered in particularly obese human patients when prescribing a dose of CM, as body fat is not metabolically active and contributes little to dispersing or diluting the CM in the blood. This thesis consists of two published articles (chapter 2 and 4), of which the final research aim was to determine if less iodinated contrast per kilogram TBW can be administered to overweight/obese dogs while maintaining adequate organ and vessel opacification to make a confident radiologic diagnosis. Chapter 2 is a retrospective study performed to determine the variability of major abdominal vessel and organ contrast enhancement and to establish any relationship with abdominal fat percentage in contrast enhanced CT studies, performed on 62 clinical patients at U-Vet Werribee Animal Hospital between February 2014 and February 2019. Intravenous Iohexol (240 or 350 mgI/ml) with a dose range of 660-880 mgI/kg TBW administered by a power injector (1.8 - 3.0 ml/s) and saline chaser was the standard injection protocol used at this institution. Findings based on a linear regression model showed a positive association of aorta (p = 0.005), liver parenchymal (p = 0.045) and portal vein (p = 0.001) enhancement to abdominal fat percentage during the portal venous phase. Following this retrospective study, variability of abdominal organ/vessel contrast enhancement contributed by CM injection method was evaluated and outlined in chapter 3. This was done in attempt to minimise contribution of varied CM injection techniques on organ/vessel contrast enhancement variances prior to the second part of the research project. Out of the three injection techniques explored, the fixed injection duration protocol was found to have the smallest organ and vessel enhancement interquartile range. The fixed injection duration protocol; Iohexol 350 mgI/ml at 700 mgI/kg TBW administration by a cephalic vein intravenous catheter, and a CT study performed with a fixed injection duration of 20 s, with the arterial and portal venous acquisition triggered 10 s and 35 s after aortic arrival respectively, was used for the subsequent part of the research project. Chapter 4 was a prospective study where we hypothesised that LBW adjusted dosing would not affect the diagnostic quality of the abdominal CT study, will minimise negative physiological effects, and reduce variability of contrast enhancement in major abdominal organs and vessels as compared to dosing according to TBW. Results from 12 dogs showed that LBW dosed abdominal CT studies were of diagnostic quality (based on subjective radiologist’s assessment) and reduced inter-individual enhancement (smaller interquartile range) variability in dogs. Contrary to our second hypothesis, there was no significant difference in the change in heart rate and blood pressure after CM administration when dosed according to TBW or LBW. Based on reports in the human literature and findings from the present study, LBW is a better body size index for determining CM dose compared to TBW and is discussed in the final chapter.
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ItemPrednisolone in canine medicine: How and why it is prescribed systemically and the impact of bodyweight on prescriptions and pharmacokinetics( 2022-11)Background: Prednisolone is a commonly used medication in canine medicine, for a variety of indications. It is prescribed for physiologic maintenance, as an anti-inflammatory and as an immunosuppressant. Unfortunately, it also comes with a variety of adverse effects. There is a lack of research describing what conditions prednisolone is prescribed for and what factors influence dose in dogs. Additionally, there is evidence to suggest that canine bodyweight influences risk of side effects, therefore published dosing recommendations for dogs over 25 kg recommend dosing by body surface area. However, there is no research on whether bodyweight influences dose prescribed by veterinarians and little research as to how bodyweight affects prednisolone pharmacokinetics. Objectives: The aims of this thesis were to review the current literature on prednisolone use and pharmacokinetics in dogs (Chapter 1); to describe prednisolone prescribing practices to for dogs in Australia, indication for prescription and to evaluate what factors influence dose prescribed (Chapter 2); to observe prednisolone pharmacokinetics in client-owned dogs and describe any effect of bodyweight (Chapter 3). Method: Chapter 2 was a cross-sectional study using individual canine clinical records acquired from the VetCompass Australia database. Dogs prescribed prednisolone between 1 July 2016 to 31 July 2018 were identified and a random sample of 2,000 dogs from this population were used for data acquisition. Chapter 3 was a prospective, observational study where dogs receiving prednisolone for medical reasons had a series of plasma samples taken after their normal prednisolone dose. Plasma prednisolone concentrations were measured via liquid- chromatography tandem mass spectrometry and the relationship between dog bodyweight, prednisolone dose and prednisolone area-under-the-curve (AUC) was described. Results: Prednisolone was found to be most prescribed for inflammatory conditions, at an anti-inflammatory dose to Australian dogs. Disease of the integument was the most common indication for prescription. Notably, 8% of dogs (n = 152) were prescribed an immunosuppressant dose, for an inflammatory condition, which was considered inappropriate. Bodyweight was found to have a small, independent, negative effect on dose prescribed. The pharmacokinetic study found that dosing by bodyweight (milligrams per kilogram) resulted in AUC being positively associated with bodyweight. Conclusions: This research describes, for the first time, prednisolone prescriptions for dogs in Australia and confirms that bodyweight influences dose prescribed and impacts prednisolone pharmacokinetics. Veterinary clinicians appear to reduce the prednisolone dose prescribed, in milligrams per kilogram, to larger dogs. Regarding pharmacokinetics, when dosed equivalently in milligrams per kilogram, a larger dog has larger plasma prednisolone AUC compared to a smaller dog. This is potentially a cause for the increased adverse effects experienced by larger dogs. This research will improve veterinary clinician awareness to the potential risk to larger dogs prescribed prednisolone and provide groundwork to further research on prednisolone pharmacokinetics in dogs.
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ItemPigeon paramyxovirus type 1 in pigeons in Victoria( 2022)Pigeon paramyxovirus type 1 (PPMV-1) is a variant strain of avian paramyxovirus type 1 (APMV-1). Although PPMV-1 is mainly detected in birds from the Columbidae family, infection in other avian species has also been reported. PPMV-1 was first isolated from racing pigeons in the Middle East in the 1970s. Several studies have indicated that PPMV-1 has similar genomic features to virulent NDV based on amino acid sequences at the fusion protein cleavage site. Thus, it is important to monitor for genomic mutations at these sites since pigeons can potentially transmit the virus to poultry leading to virulent NDV outbreaks. In 2011, PPMV-1 was first detected in Australia. Details of the virus in Australia are limited and most information available relates to domestic pigeons. Therefore, this thesis reviewed the incursion of PPMV-1 into Australia in detail and estimated its seroprevalence in feral pigeons in Victoria. It also aimed to consider the potential routes of virus transmission from feral pigeons to commercial poultry. PPMV-1 was first identified in 2011 in Victoria before spreading to other Australian states. Data was compiled with contributions from the relevant biosecurity authorities from each Australian State and Territory as well as Wildlife Health Australia. It was then validated using case submission data from the Australian Centre for Disease Preparedness (ACDP). Results showed that PPMV-1 has been found in all Australian states excepted the Northern Territory. Infected birds were mainly detected in Victoria (VIC) and New South Wales (NSW), and largely found in urban areas. The overall epidemic curve started with a point source epidemic pattern reflecting that PPMV-1 was previously exotic to Australian pigeons. In the following years, the pattern became endemic. Most of this PPMV-1 data in Australia was on domestic pigeons. Data on feral pigeons and wild birds was severely limited, and only available through passive collection, if detected. In an attempt to estimate the prevalence of PPMV-1 in feral pigeons in Victoria and to investigate potential routes of virus shedding, feral pigeons in different locations were sampled. Pigeons were either provided by pest controllers or captured using traps and alpha-chloralose bait. Blood samples were taken and tested by the hemagglutination inhibition test, whereas swab samples were investigated using real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Amongst the study population, feral pigeons in Victoria had an apparent seroprevalence of 45% (95% CI: 38, 53) while the adjusted true prevalent estimate was 53.9% (95% CI: 45, 64). Although, PPMV-1 exposure appears to be the highest in Victorian poultry dense locations, especially in the Southeast region, only a small number of the exposed feral pigeons seem to be actively shedding PPMV-1. There is also a risk of PPMV-1 transmission to poultry though contamination of feed at storage facilities accessed by pigeons. The PPMV-1 isolate from this research was phylogenetically close to the PPMV-1 isolate detected in the 2011 Australian outbreak and appears to be highly virulent. To maintain Australia’s Newcastle disease-free country status, the variant strain of PPMV-1 should remain a focus of attention given it represents a risk for ND outbreaks in poultry.
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ItemBiomechanical and microstructural properties of subchondral bone from three metacarpophalangeal joint sites in Thoroughbred racehorses( 2022)Reasons for performing the study: Fatigue induced subchondral bone (SCB) injury is common in racehorses. Understanding how subchondral microstructure and microdamage influence mechanical properties is important for developing injury prevention strategies. Mechanical properties of the disto palmar third metacarpal condyle (MCIII) correlate poorly with microstructure, and it is unknown whether the properties of other sites within the metacarpophalangeal (fetlock) joint are similarly complex. Objectives: We aimed to investigate the mechanical and structural properties of equine SCB from three sites within the metacarpophalangeal joint: the disto-palmar MCIII, disto-dorsal MCIII and proximal sesamoid bone. Two regions of SCB within each specimen were compared, a 2 mm superficial and underlying 2 mm deep layer. Methods: Cartilage-bone specimens were analysed with micro-computed tomography to determine bone volume fraction (BVTV) and bone mineral density (BMD), then loaded in cyclic compression for 100 cycles at 2 Hz. Disto-dorsal MCIII specimens were loaded to 30 MPa (n = 10), while disto-palmar MCIII (n = 10) and proximal sesamoid (n = 10) specimens were loaded to 40 MPa. Digital image correlation was performed on the first nine cycles to determine local strains. Specimens were stained with lead-uranyl acetate for volumetric microdamage quantification. Results: The dorsal MCIII SCB had lower BVTV, BMD, and stiffness compared to the palmar MCIII and sesamoid bone (P < 0.05). Superficial SCB had higher BVTV and lower BMD than deeper SCB (P < 0.05), except at the palmar MCIII site where there was no difference in BVTV between depths (P = 0.419). At all sites the deep bone was stiffer (P < 0.001), although the superficial to deep gradient was smaller in the dorsal MCIII. Hysteresis (energy loss) was greater superficially in palmar MCIII and sesamoid (P < 0.001), but not dorsal MCIII specimens (P = 0.118). Stiffness increased with cyclic loading in total cartilage-bone specimens (P < 0.001), but not in superficial and deep layers of the bone, whereas hysteresis decreased with cycle for all sites and layers (P < 0.001). Main limitations: Small sections of bone from each site were examined. Surface staining complicated volumetric microdamage quantification. Unconfined compression and end artefacts may have contributed to initial changes in stiffness and hysteresis. Conclusions: Superficial equine SCB is uniformly less stiff than deeper bone despite non uniform differences in bone density and damage levels. The more compliant superficial layer has an important role in energy dissipation, but whether this is a specific adaptation or a result of microdamage accumulation is not clear.
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ItemSouth-west Victorian dairy herd gastrointestinal parasite prevalence study( 2022)It is widely accepted that healthy adult cattle are generally not affected by worm burdens. However, the stress of intensive dairy situations globally has been thought to reduce cows’ immunity to gastrointestinal parasites and subsequently allow milk production losses due to these parasite burdens. Numerous global studies have indicated production benefits to anthelmintic use in lactating dairy cattle, but there have also been several publications showing marginal or no significant milk production benefit following anthelmintic use. Anthelmintic resistance has been illustrated in multiple studies and is likely to be reducing the overall production benefit seen with anthelmintic use. In adult cattle our gastrointestinal parasite measurement systems are largely flawed or insensitive. The aim of this project was to assess the use of highly sensitive faecal egg counts (FEC) to document the gastrointestinal worm burden of lactating dairy cows in south-west Victoria. We also aimed to investigate the relationship between farm management, previous anthelmintic use, milk production, faecal egg count and bulk milk anti-O. ostertagi antibody ELISA optical density ratio (ODR) testing in this region. Sensitive FECs from individual recently calved adult dairy cows were obtained through use of a modified Mini-FLOTAC procedure achieving an analytical sensitivity of 2.5 eggs per gram of faeces (epg). Individual faecal egg counts were collected on 18 farms from cohorts of primiparous and multiparous recently calved cows. Vat milk was also collected on the day of faecal sampling for laboratory assessment of ODR. Milk production data was available from 10/18 farms providing 247 individual milk production records. Faecal egg counts greater than or equal to 2.5 epg were much more likely to be recorded in primiparous cows (45%) than in multiparous cows (26%). Multiparous cows with a body condition score of < 4 were significantly more likely to have a positive FEC when compared with higher conditioned multiparous cows (p=0.002). O. ostertagi was the most abundant gastrointestinal species amongst all cohorts on all farms making up 85% of overall larvae cultured. ODR was not related to mean FEC on corresponding farms, nor was it related to the proportion of individual animals with a FEC greater than or equal to 2.5, 5 or 10 epg. ODR was strongly related to the interval, in days, between calving and prior anthelmintic use. Milk production data was analysed for the first 100 days of lactation and was divided into two groups: primiparous and multiparous. The primiparous cohort had a much higher proportion of animals with FEC greater than or equal to 2.5epg and produced on average 29% less milk than the multiparous cohort, subsequently the primiparous and multiparous groups were analysed separately. Across both primiparous and multiparous data sets, we did not observe a difference in the milk production of FEC positive or negative cows at various cut point thresholds (2.5, 5 or 10 epg. Great variation across farms was seen with milk production, when data was arranged into quartiles, based on production relative to peers on each farm, we did not observe a relationship between FEC and milk production. Mini-FLOTAC and sensitive FECs are successful in identifying adult cattle with worm burdens, but the application of these tests requires further investigation to make treatment or management guidelines. ODR should not be used as a sole decision-making tool in assessment of the requirement for anthelmintic use in pasture based dairy cattle of south-west Victoria. We did not find a difference in milk production of cows with and without FECs at 2.5 or 10 epg, because of these findings we would not suggest that FEC is useful in differentiating animals that may or may not benefit from anthelmintic treatment. Further work is required to establish a means to select individual cows for beneficial anthelmintic treatment.
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ItemEvaluation of the analytical performance of a clinical laboratory coagulation analyser for coagulation factor measurement in canine plasma( 2022)Abstract Objective: To evaluate the analytical performance of a clinical laboratory coagulation analyser (Stago Compact Max) for coagulation factor activity measurement in canine plasma. Design: Prospective, observational, analytical study. Methods: Whole blood was collected from 15 privately owned dogs aged between 1 and 8 years old. Dobermans and greyhounds were excluded from sample collection. Five dogs (Pool A) over 25kg had up to 175mL of blood drawn from the jugular vein, and this was processed to citrated, platelet free plasma, and combined to provide a sample pool. Ten dogs (Pool B) over 10kg had 20mL of whole blood drawn from the jugular vein, and this was processed to citrated, platelet free plasma and combined to provide a comparison pool. Complete blood count, biochemistry testing and prothrombin (PT) and activated partial thromboplastin time (aPTT) testing was performed on all dogs prior to blood draw. Samples were excluded if they were visually haemolysed, lipaemic or jaundiced. Pool A was used to assess linearity, within-run and between-run precision of fibrinogen, factor II (FII), factor V (FV), factor VII (FVII), factor VIII (FVIII) and factor X (FX). A modified one stage PT assay utilizing human factor deprived plasmas was performed for FII, FV, FVII and FX. A modified aPTT assay utilizing human factor deprived plasma was performed for FVIII. Fibrinogen was measured via the modified clotting method of Clauss. All coagulation testing was performed as per the manufacturer’s guidelines (Diagnostica Stago). Barbitone buffer was used to perform dilutions on aliquots of Pool A, and 7 dilutions were each tested 20 times on the first day of testing to supply data for within-run precision and linearity, and then tested 5 times further for 4 consecutive days to provide data for between-run precision. The following sample: buffer dilutions were tested: undiluted, 9:1, 7:3, 1:1, 3:7, 1:9, 1:19. For coagulation factor activity testing, time to clot formation was measured and interpolated with a standard curve prepared from Pool B plasma. Fibrinogen was interpolated with the calibration curve provided by the manufacturer. Limit of the blank was assessed by performing each coagulation test 5 times with barbitone buffer only. Results: Results were tabulated and mean, standard deviation and coefficient of variation calculated for each factor, for within-run and between-run precision. Concentration vs measured activity were plotted and line of best fit and linear regression analysis performed. Acceptable linearity was determined as an R squared value >0.95. R squared values were as follows: Fibrinogen 0.99, FII 0.99, FV 0.99, FVII 0.99, FVIII 0.99, FX 0.99. Acceptable coefficient of variation was determined based on manufacturer’s data and factor activity levels of importance. Coefficient of variation was above the acceptable range for FV (between-run precision) at an analyte concentration of 5%, FVII (between-run precision) at analyte concentrations of 50%, 30% and 5% and FX (between-run precision) at an analyte concentration of 5%. Relevance: Investigation of coagulation disorders in dogs is a rapidly growing field in veterinary medicine, and the effects of critical illness on coagulation factor activity are poorly understood. Evaluation of the analytical performance of a clinical laboratory coagulation analyser for coagulation factor activity measurement in dogs is the first step in increasing research and clinical assessment in this area.
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ItemUse of telesimulation to teach veterinary cardiopulmonary resuscitation advanced life support management: a comparison with traditional online training modalities( 2022)Cardiopulmonary resuscitation (CPR) is the only means of treatment for cardiopulmonary arrest. The goal of CPR is not only to achieve return of circulation in the patient, but ultimately for survival to hospital discharge. Guidelines outlining best practice for CPR have existed for several decades in humans and similar guidelines for companion animals, known as the Reassessment Campaign on Veterinary Resuscitation (RECOVER) guidelines were published in 2012. There is strong evidence that adherence to CPR guidelines leads to improved patient outcomes in humans, and a similar trend is seen in companion animals with the RECOVER guidelines. Over the last 10-20 years, the importance of education in CPR has been recognised. Without adequate training in the delivery of high-quality CPR, patient survival is compromised. Simulation training for CPR is widely accepted in human medicine, but is not well studied in veterinary medicine. This thesis aims to review the development of CPR, the evidence surrounding the impact of CPR guidelines and the merits of simulation training. It includes a prospective, randomised crossover study comparing simulation to more conventional online learning methods to teach veterinary CPR advanced life support (ALS). Changes to the project due to impacts of the Covid-19 pandemic meant a type of simulation known as telesimulation was utilised. Six cases covering CPR topics were developed for both the case-based learning and telesimulation training modules. Forty-five students undertook the training using both modalities. Pre-, mid- and post-training telesimulation assessments were used to assess trainee compliance to veterinary ALS guidelines. Students also completed self-efficacy scores and provided feedback on the training course. A mixed effects logistic regression model was used to analyse student ALS compliance. Results showed telesimulation training was as effective as online lectures and cases for student compliance (OR 1.1, 95% CI 0.8-1.5). There was no difference in student self-efficacy scores between the two training modalities. Student feedback favoured telesimulation training (55%) or a combination of the two training methods (43%), as opposed to online lectures and case-based teachings alone (2%). The study highlights the benefits of telesimulation including the ability to provide remote simulation training to learners, opportunities for shared resource management between institutions, and an overall engaging learning experience for trainees. Limitations include technical difficulties, increased complexities of educational resources compared to online lectures and case-based learnings, and lack of validation given the relative novelty of telesimulation. The findings can be used to guide future veterinary CPR training and contributes to the growing body of literature on telesimulation.
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ItemDevelopment of 3D printed training simulation models for veterinary clinical procedures( 2021)This study aimed to develop 3D printed anatomical models (3DPAM) to be utilised as simulation training tools for three veterinary procedures: equine cranial artery occlusion for the treatment of guttural pouch mycosis, canine bronchoscopy, and canine cerebrospinal fluid (CSF) collection. Creating and validating 3DPAMs enables minimally invasive procedural training methods, thus improving patient safety when novice clinicians transfer simulator-learned skills to live clinical settings. 3DPAMs also provide a safe, low stress learning environment for students compared to learning with live patients or expensive and limited cadavers. The three target veterinary procedures were selected due to being technically demanding, high-risk when performed by novice clinicians, and currently lacking suitable commercially available veterinary-specific simulators. 3D printing produces high fidelity, anatomically accurate models with rapid prototyping at low cost. This study created six 3DPAMs for the three veterinary procedures of interest: an equine skull and vasculature model, two canine airway models, and canine skull and lumbar spine models. The standard of these models has been improved from previous prototypes created by the Small Animal Surgery Service (U-Vet Hospital, Melbourne Veterinary School, University of Melbourne), with the addition of cerebrospinal fluid collection simulators to the suite of models that are currently being developed. We hypothesised that evaluators would deem the occlusion and CSF collection 3DPAMs as sufficient simulators for their respective procedures, while optimisations and improvements would be required due to being rudimentary prototypes. We hypothesised that the most advanced 3DPAM, the canine bronchoscopy model, would achieve face and content validation. The occlusion and cerebrospinal fluid collection 3DPAMs were evaluated for capacity to simulate occlusion procedures or cerebrospinal fluid collection by a small number of veterinarians from the U-Vet Hospital familiar with these procedures. Evaluators deemed that the models simulated their respective procedures, whilst noting that significant improvements and optimisations are required prior to validation testing. A face and content validation study was conducted for the canine airway model with four veterinarians familiar with bronchoscopy procedures. Results suggest that the model has face and content validity and requires further optimisations to enhance the canine airway model as a simulator of canine bronchoscopy.
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ItemSensitivity of canine haematological cancers to BH3 mimetics( 2022)Background: Haematological cancers such non-Hodgkin lymphoma (NHL) and acute and chronic leukaemias are common in both humans and dogs. Whilst these cancers can be treated with cytotoxic chemotherapy (and immunotherapy in people), development of treatment resistance is common. A frequently identified mechanism associated with resistance to chemotherapy-induced cell death is overexpression of the antiapoptotic B cell lymphoma 2 (BCL2) protein. Highly specific small molecule inhibitors of antiapoptotic BCL2 proteins, known as B cell lymphoma Homology 3 (BH3) mimetics, result in rapid induction of apoptosis in vitro and in vivo in human haematological cancer cells. This has led to the approval of the BCL2-specific inhibitor, venetoclax (VEN), for the treatment of chronic lymphocytic leukaemia (CLL) and acute myeloid leukaemia (AML) in Australia, North America and Europe. Expression of BCL2 has been reported in canine nodal lymphoma, however sensitivity of primary canine cells to BH3 mimetics has not been evaluated. Objectives: This study aimed to assess the in vitro sensitivity of non-neoplastic lymphocytes and primary haematological cancer cells from dogs to VEN or the dual BCL2/BCLxL inhibitor, navitoclax (NAV). The second aim was to evaluate the association between BCL2 protein expression and sensitivity to VEN. Methods: Nine dogs without cancer and 30 dogs with haematological cancers were recruited. Lymphocytes were isolated from peripheral blood, lymph node and/or bone marrow and incubated with VEN or NAV for 24 hours. Viable cells were enumerated using flow cytometry and the half maximal effective concentration (EC50) was calculated; BCL2 protein from whole cell lysates was assessed via immunoblotting. Results: Non-neoplastic lymph node-derived B and T canine lymphocytes were more sensitive to VEN than circulating lymphocytes (P = 0.02). Eighteen dogs with haematological cancers were included in the final analysis, including six cases of non-indolent multicentric B cell lymphoma, four cases of acute leukaemia, three cases of non-indolent multicentric T cell lymphoma, two cases each of indolent T-zone lymphoma and T-cell CLL, and one case of multiple myeloma. Neoplastic T lymphocytes (7/7) showed marked sensitivity to BH3 mimetics, with an EC50 <100nM, whilst 6/7 samples of non-indolent B cell cancers were resistant to VEN, with an EC50 >1000nM. All samples of acute leukaemia showed sensitivity to NAV, however sensitivity to VEN varied. Canine BCL2 protein was detected in all samples sensitive to VEN and was variably detected in resistant samples. All samples that lacked BCL2 were resistant to VEN. Conclusion and Clinical Importance: Neoplastic canine T lymphocytes are sensitive to VEN at concentrations achievable in vivo, thus VEN may be a novel therapeutic agent for treatment of canine T cell cancers. Detection of BCL2 protein is insufficient to predict in vitro sensitivity to VEN.