ORCID Profile
0000-0001-5367-0241
Current Organisation
University of Adelaide
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Wiley
Date: 24-04-2018
DOI: 10.1111/AVJ.12690
Abstract: This study reports necropsy findings of koalas from the Mount Lofty Ranges region in order to identify health threats to this mainland South Australian population. Koalas from the Mount Lofty Ranges region (n = 85) that had died or been euthanased on welfare grounds were examined at necropsy during 2012-13 at the School of Animal and Veterinary Sciences, University of Adelaide. Disease findings, approximate age, sex and body condition of koalas were recorded. Histopathological examination was undertaken on gross lesions and in suspect cases, skin scrapings taken for microscopy and PCR performed for Chlamydia pecorum detection. Traumatic injury was the most common necropsy finding (48/85 57%), caused by motor vehicle accidents (35/48 73%), canine attacks (11/48 23%) or bushfire burns (2/48 4%). Oxalate nephrosis (27/85 32%) was also more common than other conditions. Infectious diseases included chlamydiosis (10/85 12%) and sarcoptic mange (7/85 8%). Marked testis asymmetry was evident in 11% (6/56) of males, with histopathology suggestive of atrophic change in four animals. Other pathological conditions included gastrointestinal disease (7/85 8%) and respiratory disease (3/85 4%). Almost half of the koalas (38/85 45%) were found to have two or more abnormalities at necropsy. This study found trauma, mainly from motor vehicle accidents, and oxalate nephrosis to be the predominant causes of death and/or disease in koalas from the Mount Lofty Ranges region. Recent emergence of both clinical chlamydiosis and sarcoptic mange has also occurred, providing insight into the health status and causes of disease or injury in this South Australian mainland koala population.
Publisher: Wiley
Date: 26-06-2017
DOI: 10.1111/AVJ.12598
Abstract: To describe outbreaks of sarcoptic mange caused by Sarcoptes scabiei in free-ranging koalas in Victoria (December 2008 to November 2015) and South Australia (October 2011 to September 2014). Koalas affected by mange-like lesions were reported by wildlife carers, veterinary practitioners or State Government personnel to the Faculty of Veterinary and Agricultural Sciences at The University of Melbourne and the School of Animal and Veterinary Sciences at The University of Adelaide. Skin scrapings were taken from live and dead koalas and S. scabiei mites were identified. Tissues from necropsied koalas were examined histologically. Outbreaks of sarcoptic mange were found to occur in koalas from both Victoria (n = 29) and South Australia (n = 29) for the first time. The gross pathological and histopathological changes are described. We present the first reported cases of sarcoptic mange outbreaks in free-ranging koalas.
Publisher: MDPI AG
Date: 27-08-2020
DOI: 10.3390/V12090948
Abstract: To determine Phascolarctid gammaherpesviruses (PhaHV) infection in South Australian koala populations, 80 oropharyngeal swabs from wild-caught and 87 oropharyngeal spleen s les and swabs from euthanased koalas were tested using two specific PCR assays developed to detect PhaHV-1 and PhaHV-2. In wild-caught koalas, active shedding of PhaHV was determined by positive oropharyngeal s les in 72.5% (58/80) of animals, of which 44.8% (26/58) had PhaHV-1, 20.7% (12/58) PhaHV-2 and 34.5% (20/58) both viral subtypes. In the euthanased koalas, systemic infection was determined by positive PCR in spleen s les and found in 72.4% (63/87) of koalas. Active shedding was determined by positive oropharyngeal results and found in 54.0% (47/87) of koalas. Koalas infected and actively shedding PhaHV-1 alone, PhaHV-2 alone or shedding both viral subtypes were 48.9% (23/47), 14.9% (7/47) and 36.2% (17/47), respectively. Only 45.9% (40/87) were not actively shedding, of which 40.0% (16/40) of these had systemic infections. Both wild-caught and euthanased koalas actively shedding PhaHV-2 were significantly more likely to be actively shedding both viral subtypes. Active shedding of PhaHV-2 had a significant negative correlation with BCS in the euthanased cohort, and active shedding of PhaHV-1 had a significant positive relationship with age in both wild-caught and euthanased cohorts.
Publisher: Wiley
Date: 25-04-2019
DOI: 10.1111/AVJ.12799
Abstract: Koalas in the Mount Lofty Ranges, South Australia, have a high prevalence of oxalate nephrosis, or calcium oxalate kidney crystals. Gastrointestinal tract oxalate-degrading bacteria, particularly Oxalobacter formigenes, have been identified in other animal species and humans, and their absence or low abundance is postulated to increase the risk of renal oxalate diseases. This study aimed to identify oxalate-degrading bacteria in the gastrointestinal tract of koalas and determine their association with oxalate nephrosis. Caecal and faecal s les were collected at necropsy from 22 Mount Lofty Ranges koalas that had been euthanased on welfare grounds, with 8 koalas found to have oxalate nephrosis by renal histopathology. S les were analysed by PCR for the oxc gene, which encodes oxalyl-CoA decarboxylase, and also by Illumina sequencing of the V3-V4 region of the bacterial 16S rRNA gene. The oxc gene was detected in 100% of koala s les, regardless of oxalate nephrosis status. Oxalobacter formigenes was detected in all but one faecal s le, with no difference in abundance between koalas affected and unaffected by oxalate nephrosis. Other species of known oxalate-degrading bacteria were infrequently detected. This is the first study to identify Oxalobacter and other oxalate-degrading bacterial species in koalas, but an association with oxalate nephrosis and absence or low abundance of Oxalobacter was not found. This suggests other mechanisms underlie the risk of oxalate nephrosis in koalas.
Publisher: MDPI AG
Date: 12-11-2021
DOI: 10.3390/ANI11113237
Abstract: In the 2019–2020 Australian bushfires, Kangaroo Island, South Australia, experienced catastrophic bushfires that burnt approximately half the island, with an estimated 80% of the koala population lost. During and after the event, rescued koalas were triaged at a designated facility and a range of initial data were recorded including rescue location and date, sex, estimation of age, body condition and hydration, and assessment of burn severity (n = 304 records available). Koalas were presented to the triage facility over a span of 10 weeks, with 50.2% during the first 14 days of the bushfire response, the majority of which were rescued from regions of lower fire severity. Burns were observed in 67.4% of koalas, with the majority (60.9%) classified as superficial burns, primarily affecting the limbs and face. Poor body condition was recorded in 74.6% of burnt koalas and dehydration in 77.1%. Negative final outcomes (death or euthanasia, at triage or at a later date) occurred in 45.6% of koalas and were significantly associated with higher mean burn score, maximum burn severity, number of body regions burnt, poor body condition score, and dehydration severity. The findings of this retrospective study may assist clinicians in the field with decision making when triaging koalas in future fire rescue efforts.
Publisher: MDPI AG
Date: 13-04-2022
DOI: 10.3390/ANI12081005
Abstract: The koala (Phascolarctos cinereus) is an arboreal marsupial that is found throughout much of eastern and southeastern Australia, and it relies primarily on eucalypt trees for food, water and shelter [...]
Publisher: Wiley
Date: 09-02-2020
DOI: 10.1111/AVJ.12923
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/ZO13049
Abstract: Oxalate nephrosis is a leading disease of the Mount Lofty Ranges koala population in South Australia, but the cause is unclear. In other herbivorous species, a common cause is high dietary oxalate therefore this study aimed to determine the oxalate content of eucalypt leaves. Juvenile, semimature and mature leaves were collected during spring from eucalypt species eaten by koalas in the Mount Lofty Ranges and compared with those from Moggill, Queensland, where oxalate nephrosis has lower prevalence. Total oxalate was measured as oxalic acid by high-performance liquid chromatography. The oxalate content of eucalypts was low ( % dry weight), but occasional Mount Lofty leaf s les had oxalate levels of 4.68–7.51% dry weight. Mount Lofty eucalypts were found to be higher in oxalate than those from Queensland (P 0.001). In conclusion, dietary oxalate in eucalypt leaves is unlikely to be the primary cause of oxalate nephrosis in the Mount Lofty koala population. However, occasional higher oxalate levels could cause oxalate nephrosis in in idual koalas or worsen disease in those already affected. Further studies on the seasonal variation of eucalypt leaf oxalate are needed to determine its role in the pathogenesis of oxalate nephrosis in koalas.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/ZO14011
Abstract: Studies characterising the thyroid gland structure of koalas are limited and have not previously been undertaken in South Australian populations. Hence, this study aimed to describe the thyroid gland morphology of koalas from the Mount Lofty region, South Australia. Results showed that thyroid gland morphology was highly variable between in idual koalas (n = 36), ranging from that considered typical for healthy mammals, in which small colloid-filled follicles were lined by cuboidal epithelium, to that consistent with colloidal goitre, in which macrofollicles distended with colloid were lined by flattened epithelium. Juvenile koalas more frequently showed typical thyroid gland morphology than adults, with significantly higher thyroid follicle density (P 0.05) and a higher proportion of follicles lined by cuboidal epithelium compared with flattened epithelium (P 0.05). Thyroid glands of most adult koalas were characterised by colloidal macrofollicles (P 0.01), and classified as colloidal goitre. There were no significant differences in thyroid gland morphology based on health status or sex of koalas. These findings suggest that an age-dependent colloidal goitre occurs in adult koalas, which is unlikely to have ill effects and may be associated with the low metabolic rate of this species, or exposure to a dietary goitrogen.
Publisher: Cold Spring Harbor Laboratory
Date: 09-11-2017
DOI: 10.1101/211466
Abstract: Koala retrovirus (KoRV) is unique amongst endogenous (inherited) retroviruses in that its incorporation to the host genome is still active, providing an opportunity to study what drives this fundamental process in vertebrate genome evolution. Animals in the southern part of the natural range of koalas were previously thought to be either virus free or to have only exogenous variants of KoRV with low rates of KoRV induced disease. In contrast, animals in the northern part of their range universally have both endogenous and exogenous KoRV with very high rates of KoRV induced disease such as lymphoma. This paper uses a combination of sequencing technologies, Illumina RNA sequencing of “southern” (south Australian) and “northern” (SE QLD) koalas and CRISPR enrichment and nanopore sequencing of DNA of “southern” (South Australian and Victorian animals) to retrieve full length loci and intregration sites of KoRV variants. We demonstrate that koalas that tested negative to the KoRV pol gene qPCR, used to detect replication competent KoRV, are not in fact KoRV free but harbour defective, presumably endogenous, “RecKoRV” variants that are not fixed between animals. This indicates that these populations have historically been exposed to KoRV and raises questions as to whether these variants have arisen by chance or whether they provide a protective effect from the infectious forms of KoRV. This latter explanation would offer the intriguing prospect of being able to monitor and selectively breed for disease resistance to protect the wild koala population from KoRV induced disease.
Publisher: Wiley
Date: 28-04-2014
DOI: 10.1111/VCP.12145
Abstract: Oxalate nephrosis is a highly prevalent disease in the Mount Lofty Ranges koala population in South Australia, but associated clinicopathologic findings remain undescribed. The aims of this study were to determine plasma biochemical and urinalysis variables, particularly for renal function and urinary crystal morphology and composition, in koalas with oxalate nephrosis. Blood and urine s les from Mount Lofty Ranges koalas with oxalate nephrosis were compared with those unaffected by renal oxalate crystal deposition from Mount Lofty and Kangaroo Island, South Australia and Moggill, Queensland. Plasma and urine biochemistry variables were analyzed using a Cobas Bio analyzer, and urinary oxalate by high-performance liquid chromatography. Urinary crystal composition was determined by infrared spectroscopy and energy dispersive X-ray analysis. Azotemia (urea > 6.6 mmol/L, creatinine > 150 μmol/L) was found in 93% of koalas with oxalate nephrosis (n = 15). All azotemic animals had renal insufficiency (urine specific gravity [USG] < 1.035), and in 83%, USG was < 1.030. Koalas with oxalate nephrosis were hyperoxaluric compared with Queensland koalas (P < .01). Urinary crystals from koalas with oxalate nephrosis had atypical morphology and were composed of calcium oxalate. Mount Lofty Ranges koalas unaffected by renal oxalate crystal deposition had renal insufficiency (43%), although only 14% had USG < 1.030 (n = 7). Unaffected Mount Lofty Ranges and Kangaroo Island koalas were hyperoxaluric compared with Queensland koalas (P < .01). Koalas with oxalate nephrosis from the Mount Lofty Ranges had renal insufficiency, hyperoxaluria, and pathognomonic urinary crystals. The findings of this study will aid veterinary diagnosis of this disease.
Publisher: Springer Science and Business Media LLC
Date: 20-02-2018
DOI: 10.1038/S41598-018-21723-0
Abstract: To better understand host and immune response to diseases, gene expression studies require identification of reference genes with stable expression for accurate normalisation. This study describes the identification and testing of reference genes with stable expression profiles in koala lymph node tissues across two genetically distinct koala populations. From the 25 most stable genes identified in transcriptome analysis, 11 genes were selected for verification using reverse transcription quantitative PCR, in addition to the commonly used ACTB and GAPDH genes. The expression data were analysed using stable genes statistical software - geNorm, BestKeeper, NormFinder, the comparative ΔCt method and RefFinder. All 13 genes showed relative stability in expression in koala lymph node tissues, however Tmem97 and Hmg20a were identified as the most stable genes across the two koala populations.
Publisher: Springer Science and Business Media LLC
Date: 14-01-2020
DOI: 10.1038/S41598-019-56546-0
Abstract: Koala retrovirus (KoRV) displays features of both an endogenous and exogenous virus and is linked to neoplasia and immunosuppression in koalas. This study explores the apparent differences in the nature and impact of KoRV infection between geographically and genetically separated “northern” and “southern” koala populations, by investigating the disease status, completeness of the KoRV genome and the proviral (DNA) and viral (RNA) loads of 71 northern and 97 southern koalas. All northern animals were positive for all KoRV genes ( gag , pro-pol and env ) in both DNA and RNA forms, whereas many southern animals were missing one or more KoRV genes. There was a significant relationship between the completeness of the KoRV genome and clinical status in this population. The proviral and viral loads of the northern population were significantly higher than those of the southern population (P 0.0001), and many provirus-positive southern animals failed to express any detectable KoRV RNA. Across both populations there was a positive association between proviral load and neoplasia (P = 0.009). Potential reasons for the differences in the nature of KoRV infection between the two populations are discussed.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/AM15028
Abstract: The Australian water rat (Hydromys chrysogaster), unlike most murine rodents, has a carnivorous diet. In the present study the morphology of its gastrointestinal tract is described and compared with that of other muroid rodents with more typical diets. It was found that the stomach of the water rat is relatively small and has a greater proportion of glandular epithelium than that of other species so far investigated. Comparisons of relative intestinal lengths showed that in the Australian water rat there is a comparatively long small intestine that constitutes ~90% of the total intestinal length, a short large intestine, and a small caecum. This ergent morphology of the gastrointestinal tract of the Australian water rat probably relates to the animal’s protein-rich diet, with the differences from those of other hydromyine rodents indicating considerable plasticity in the evolution of the gastrointestinal tract in this group of mammals. It suggests that, whilst the morphological adaptations of the water rat’s gastrointestinal tract probably evolved before the colonisation of Australia, its highly derived morphology has enabled this species to exploit the Australian environment as an aquatic carnivore.
Publisher: Australian Museum
Date: 21-06-2023
DOI: 10.3853/J.1835-4211.38.2023.1839
Abstract: Koala retrovirus (KoRV) infection, endogenous in all northern koalas (Phascolarctos cinereus), has been found to occur at lower, but increasing, prevalence in the Kangaroo Island and Mount Lofty Ranges koala populations in South Australia. Proviral and viral loads are also lower than in Queensland koalas, which may be due to exogenous spread of infection, or may be related to the variable presence of viral genes and fragmented expression that has been found in positive Mount Lofty Ranges koalas. However, high proviral loads and full expression across the KoRV genome in South Australian koalas has been found in in iduals with neoplasia, particularly lymphoma, which can be as extensive and as severe as that observed in northern koalas. KoRV-A is the predominant subtype and no association with chlamydial status has been found except that high viral loads correlate with severity of chlamydiosis. Based on the complexity of KoRV infections in South Australian koalas, further research is needed to understand the differences in transmission and pathogenesis that occur.
Publisher: MDPI AG
Date: 20-05-2021
DOI: 10.3390/ANI11051477
Abstract: Koala retrovirus, a recent discovery in Australian koalas, is endogenised in 100% of northern koalas but has lower prevalence in southern populations, with lower proviral and viral loads, and an undetermined level of endogenisation. KoRV has been associated with lymphoid neoplasia, e.g., lymphoma. Recent studies have revealed high complexity in southern koala retroviral infections, with a need to clarify what constitutes positive and negative cases. This study aimed to define KoRV infection status in Mount Lofty Ranges koalas in South Australia using RNA-seq and proviral analysis (n = 216). The basis for positivity of KoRV was deemed the presence of central regions of the KoRV genome (gag 2, pol, env 1, and env 2) and based on this, 41% (89/216) koalas were positive, 57% (124/216) negative, and 2% inconclusive. These genes showed higher expression in lymph node tissue from KoRV positive koalas with lymphoma compared with other KoRV positive koalas, which showed lower, fragmented expression. Terminal regions (LTRs, partial gag, and partial env) were present in SA koalas regardless of KoRV status, with almost all (99.5%, 215/216) koalas positive for gag 1 by proviral PCR. Further investigation is needed to understand the differences in KoRV infection in southern koala populations.
Publisher: Wiley
Date: 18-10-2012
Publisher: Elsevier BV
Date: 08-2017
DOI: 10.1016/J.JCPA.2017.07.011
Abstract: Koala retrovirus (KoRV) infection, thought to be associated with lymphoid neoplasia, and Chlamydia pecorum-related ocular and urogenital disease are both highly prevalent in eastern Australian koala (Phascolarctos cinereus) populations. However, in South Australian koalas, little is known about KoRV infection and C. pecorum-associated disease. We report the first South Australian case of lymphoma in a KoRV-A-positive female koala also affected by severe reproductive chlamydiosis. The koala was from the Mount Lofty Ranges population and was presented with hindlimb lameness. Clinical examination identified right stifle crepitus, enlarged superficial lymph nodes and paraovarian cysts. Necropsy examination revealed extensive cartilage degeneration and loss over the medial femoral condyle, solid femoral bone marrow, mesenteric and ovarian tumours, paraovarian cysts and purulent metritis. Histopathology confirmed lymphoma in the bone marrow, mesenteric lymph nodes and ovary, with infiltration and parenchymal effacement in the pancreas, adrenal glands and other tissues. Lymphoma, KoRV and chlamydiosis are being investigated further in this population.
Publisher: SAGE Publications
Date: 08-2013
Abstract: The wild and captive koala population of the Mt Lofty Ranges in South Australia has a high level of renal dysfunction in which crystals consistent with calcium oxalate have been observed in the kidneys. This study aimed to describe the pathological features of the renal disease in this population, confirm the composition of renal crystals as calcium oxalate, and determine whether any age or sex predispositions exist for this disease. A total of 51 koalas (28 wild rescues, 23 captive) were examined at necropsy, of which 28 (55%) were found to have gross and/or histological evidence of oxalate nephrosis. Histopathological features included intratubular and interstitial inflammation, tubule dilation, glomerular atrophy, tubule loss, and cortical fibrosis. Calcium oxalate crystals were demonstrated using a combination of polarization microscopy, alizarin red S staining, infrared spectroscopy, and energy-dispersive X-ray analysis with scanning electron microscopy. Uric acid and phosphate deposits were also shown to be present but were associated with minimal histopathological changes. No significant differences were found between the numbers of affected captive and wild rescued koalas also, there were no sex or age predispositions identified, but it was found that oxalate nephrosis may affect koalas years of age. The findings of this study suggest that oxalate nephrosis is a leading disease in this koala population. Possible causes of this disease are currently under investigation.
Publisher: Wiley
Date: 21-10-2019
DOI: 10.1111/AVJ.12863
Abstract: Malocclusions are a misalignment or incorrect positioning of the teeth when the upper and lower jaws close. These are poorly described in the koala and can result in irregular mastication which can have lifelong effects on body condition and oral health. A total of 370 koalas from two populations in Queensland (295) and one in South Australia (75) were examined for malocclusions. The prevalence of malocclusions in South Australian free-ranging koalas, captive Queensland koalas and Queensland free-ranging koalas was 39% (44), 30% (29) and 22% (29) respectively. Four types of malocclusion were identified based on severity of misalignment of the incisor/canine region, types 1, 2, 3 and 4. Maxillary overbite measurements of the molariform teeth were determined and these anisognathic values were then used to describe malocclusions within familial relationships in captive colonies. Captive koalas with a malocclusion had narrower mandibular width that ranged between 0.5 and 1% less than the normal measurements. The specific malocclusions reported in this study affected in iduals by leading to tooth rotation, mobility and erosion with inefficient mastication of food and vegetation compaction. These changes increased the oral cavity pathology, by placing animals at risk of periodontal disease. There was evidence of familial links to malocclusion types in captive animals. Therefore captive breeding recommendations should consider known koala malocclusion traits to minimise their effect on future generations.
Publisher: Wiley
Date: 08-07-2020
DOI: 10.1111/AVJ.12986
Publisher: Wiley
Date: 18-03-2020
DOI: 10.1111/AVJ.12935
Publisher: Wiley
Date: 23-01-2020
DOI: 10.1111/AVJ.12919
Abstract: In northern Australian koala populations (Queensland and New South Wales), periodontal disease (gingivitis and periodontitis) is common while koala retrovirus subtype A is endogenous, with other subtypes transmitted exogenously. Koala retrovirus has been hypothesised to cause immune suppression and may predispose koalas to diseases caused by concurrent infections. In southern Australia populations (Victoria and South Australia) periodontal disease has not been investigated, and koala retrovirus is presumably exogenously transmitted. This study described oral health in South Australian koalas and investigated if an association between periodontal disease and koala retrovirus exists. Oral health was examined for wild-caught koalas from the Mount Lofty Ranges (n = 75). Koala retrovirus provirus was detected in whole blood using nested PCR and proviral load determined with qPCR. Periodontal disease severity was recorded and used to calculate the Final Oral Health Index (0-normal, 24-severe).Results Periodontal disease was observed in 84% (63/75) of koalas 77% had gingivitis (58/75) and 65% (49/75) had periodontitis. The average Final Oral Health Index was 5.47 (s.d 3.13). Most cases of periodontal disease were associated with the incisors. Koala retrovirus-infected koalas were more likely to present with periodontitis (p = 0.042) and the Final Oral Health Index was negatively correlated with proviral load (ρ = -0.353, p = 0.017). South Australian koalas had a high prevalence of gingivitis and periodontitis. Periodontal disease was more prevalent in the incisors. Exogenous koala retrovirus infection may also facilitate the development of periodontitis by modulation of the immune response to concurrent oral bacterial infections.
Publisher: Springer Science and Business Media LLC
Date: 02-08-2018
DOI: 10.1038/S41541-018-0066-4
Abstract: Koala retrovirus (KoRV) infects the majority of Australia’s koalas ( Phascolarctos cinereus ) and has been linked to several life-threatening diseases such as lymphoma and leukemia, as well as Chlamydia and thus poses a threat to the continued survival of this species. While quarantine and antiretroviral drug treatment are possible control measures, they are impractical, leaving vaccination as the only realistic option. In this study, we examined the effect of a recombinant envelope protein-based anti-KoRV vaccine in two groups of South Australian koalas: KoRV infected or KoRV free. We report a successful vaccination response in the koalas with no vaccine-associated side effects. The vaccine induced a significant humoral immune response as well as the production of neutralizing antibodies in both groups of koalas. We also identified B-cell epitopes that were differentially recognized in KoRV-infected versus KoRV-free koalas following vaccination. Importantly, we also showed that vaccination had a therapeutic effect on koalas infected exogenously with KoRV by reducing their circulating viral load. Together, this study highlights the possibility of successfully developing a vaccine against KoRV infection in koalas.
Publisher: Microbiology Society
Date: 28-06-2022
DOI: 10.1099/JGV.0.001749
Abstract: Koala retrovirus (KoRV) is unique amongst endogenous (inherited) retroviruses in that its incorporation to the host genome is still active, providing an opportunity to study what drives this fundamental process in vertebrate genome evolution. Animals in the southern part of the natural range of koalas were previously thought to be either virus-free or to have only exogenous variants of KoRV with low rates of KoRV-induced disease. In contrast, animals in the northern part of their range universally have both endogenous and exogenous KoRV with very high rates of KoRV-induced disease such as lymphoma. In this study we use a combination of sequencing technologies, Illumina RNA sequencing of ‘southern’ (south Australian) and ‘northern’ (SE QLD) koalas and CRISPR enrichment and nanopore sequencing of DNA of ‘southern’ (South Australian and Victorian animals) to retrieve full-length loci and intregration sites of KoRV variants. We demonstrate that koalas that tested negative to the KoRV pol gene qPCR, used to detect replication-competent KoRV, are not in fact KoRV-free but harbour defective, presumably endogenous, ‘RecKoRV’ variants that are not fixed between animals. This indicates that these populations have historically been exposed to KoRV and raises questions as to whether these variants have arisen by chance or whether they provide a protective effect from the infectious forms of KoRV. This latter explanation would offer the intriguing prospect of being able to monitor and selectively breed for disease resistance to protect the wild koala population from KoRV-induced disease.
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/AM17038
Abstract: Many koalas (Phascolarctos cinereus) in the Mount Lofty Ranges, South Australia, are affected by oxalate nephrosis, in which renal calcium oxalate deposition occurs. In other species, suboptimal water intake increases the risk of urinary calcium oxalate crystal formation. Koalas principally rely on eucalypt leaf moisture content to maintain hydration but the Mount Lofty Ranges region has hot, dry summers. This study investigates the association between temperature, rainfall and eucalypt leaf moisture and the occurrence of oxalate nephrosis in this population of koalas. Koalas from the Mount Lofty Ranges population that had died or were euthanased between 2008 and 2016 were necropsied and oxalate nephrosis was determined by histopathology (n=50). Leaf moisture content of Mount Lofty eucalypts was determined seasonally. It was found that increased numbers of koalas with oxalate nephrosis died in the months following high mean maximal temperature and in the months following low rainfall. Eucalypt leaf moisture content was not significantly associated with koala deaths. These findings suggest that hot and dry summer/autumn periods contribute to an increased incidence of koala deaths due to oxalate nephrosis. This is probably due to the effects of evaporative water loss and/or lack of access to supplementary drinking water at this time.
Publisher: Microbiology Society
Date: 09-2019
DOI: 10.1099/JGV.0.001304
Abstract: Koala retrovirus (KoRV) is a recently endogenized retrovirus associated with neoplasia and immunosuppression in koala populations. The virus is known to display sequence variability and to be present at varying prevalence in different populations, with animals in southern Australia displaying lower prevalence and viral loads than northern animals. This study used a PCR and next-generation sequencing strategy to examine the ersity of the KoRV
Publisher: Springer Science and Business Media LLC
Date: 20-02-2021
DOI: 10.1007/S10592-021-01340-7
Abstract: Historical hunting pressures on koalas in the southern part of their range in Australia have led to a marked genetic bottleneck when compared with their northern counterparts. There are a range of suspected genetic disorders such as testicular abnormalities, oxalate nephrosis and microcephaly reported at higher prevalence in these genetically restricted southern animals. This paper reports analysis of differential expression of genes from RNAseq of lymph nodes, SNPs present in genes and the fixation index (population differentiation due to genetic structure) of these SNPs from two populations, one in south east Queensland, representative of the northern genotype and one in the Mount Lofty Ranges South Australia, representative of the southern genotype. SNPs that differ between these two populations were significantly enriched in genes associated with brain diseases. Genes which were differentially expressed between the two populations included many associated with brain development or disease, and in addition a number associated with testicular development, including the androgen receptor. Finally, one of the 8 genes both differentially expressed and with a statistical difference in SNP frequency between populations was SLC26A6 (solute carrier family 26 member 6), an anion transporter that was upregulated in SA koalas and is associated with oxalate transport and calcium oxalate uroliths in humans. Together the differences in SNPs and gene expression described in this paper suggest an underlying genetic basis for several disorders commonly seen in southern Australian koalas, supporting the need for further research into the genetic basis of these conditions, and highlighting that genetic selection in managed populations may need to be considered in the future.
No related grants have been discovered for Natasha Speight.