Oral administration of a 2-aminopyrimidine robenidine analogue (NCL195) significantly reduces Staphylococcus aureus infection and reduces Escherichia coli infection in combination with sub-inhibitory colistin concentrations in a bioluminescent mouse model.

We have previously reported promising in vivo activity of the first-generation 2-aminopyramidine robenidine analogue NCL195 against Gram-positive bacteria (GPB) when administered via the systemic route. In this study, we examined the efficacy of oral treatment with NCL195 (± low-dose colistin) in comparison to oral moxifloxacin in bioluminescent Staphylococcus aureus and Escherichia coli peritonitis-sepsis models. Four oral doses of 50 mg/kg NCL195, commencing immediately post-infection, were administered at 4 h intervals in the S. aureus peritonitis-sepsis model. We used a combination of four oral doses of 50 mg/kg NCL195 and four intraperitoneal doses of colistin at 0.125 mg/kg, 0.25 mg/kg, or 0.5 mg/kg in the E. coli peritonitis-sepsis model. Subsequently, the dose rates of four intraperitoneal doses of colistin were increased to 0.5 mg/kg, 1 mg/kg, or 2 mg/kg at 4 h intervals to treat a colistin-resistant E. coli infection. In the S. aureus infection model, oral treatment of mice with NCL195 resulted in significantly reduced S. aureus infection loads (P < 0.01) and longer survival times (P < 0.001) than vehicle-only treated mice. In the E. coli infection model, co-administration of NCL195 and graded doses of colistin resulted in a dose-dependent significant reduction in colistin-susceptible (P < 0.01) or colistin-resistant (P < 0.05) E. coli loads compared to treatment with colistin alone at similar concentrations. Our results confirm that NCL195 is a potential candidate for further preclinical development as a specific treatment for multidrug-resistant infections, either as a stand-alone antibiotic for GPB or in combination with sub-inhibitory concentrations of colistin for Gram-negative bacteria.

CCL2-Mediated Stromal Interactions Drive Macrophage Polarization to Increase Breast Tumorigenesis.

CCL2 is an inflammatory cytokine that regulates macrophage activity and is implicated in increased mammographic density and early breast tumorigenesis. The role of CCL2 in mediating stromal interactions that contribute to breast tumorigenesis has yet to be fully elucidated. THP-1-derived macrophages and mammary fibroblasts were co-cultured for 72 h. Fibroblasts and macrophages were analysed for phenotype, expression of inflammatory and ECM-regulatory genes and collagen production. Mice overexpressing CCL2 in the mammary glands were analysed for global gene expression by RNAseq at 12 weeks of age. These mice were cross-bred with PyMT mammary tumour mice to examine the role of CCL2 in tumorigenesis. The co-culture of macrophages with fibroblasts resulted in macrophage polarization towards an M2 phenotype, and upregulated expression of CCL2 and other genes associated with inflammation and ECM remodelling. CCL2 increased the production of insoluble collagen by fibroblasts. A global gene expression analysis of CCL2 overexpressing mice revealed that CCL2 upregulates cancer-associated gene pathways and downregulates fatty acid metabolism gene pathways. In the PyMT mammary tumour model, CCL2 overexpressing mice exhibited increased macrophage infiltration and early tumorigenesis. Interactions between macrophages and fibroblasts regulated by CCL2 can promote an environment that may increase breast cancer risk, leading to enhanced early tumorigenesis.

Attenuated TGFB signalling in macrophages decreases susceptibility to DMBA-induced mammary cancer in mice.

BACKGROUND: Transforming growth factor beta1 (TGFB1) is a multi-functional cytokine that regulates mammary gland development and cancer progression through endocrine, paracrine and autocrine mechanisms. TGFB1 also plays roles in tumour development and progression, and its increased expression is associated with an increased breast cancer risk. Macrophages are key target cells for TGFB1 action, also playing crucial roles in tumourigenesis. However, the precise role of TGFB-regulated macrophages in the mammary gland is unclear. This study investigated the effect of attenuated TGFB signalling in macrophages on mammary gland development and mammary cancer susceptibility in mice. METHODS: A transgenic mouse model was generated, wherein a dominant negative TGFB receptor is activated in macrophages, in turn attenuating the TGFB signalling pathway specifically in the macrophage population. The mammary glands were assessed for morphological changes through wholemount and H&E analysis, and the abundance and phenotype of macrophages were analysed through immunohistochemistry. Another cohort of mice received carcinogen 7,12-dimethylbenz(a)anthracene (DMBA), and tumour development was monitored weekly. Human non-neoplastic breast tissue was also immunohistochemically assessed for latent TGFB1 and macrophage marker CD68. RESULTS: Attenuation of TGFB signalling resulted in an increase in the percentage of alveolar epithelium in the mammary gland at dioestrus and an increase in macrophage abundance. The phenotype of macrophages was also altered, with inflammatory macrophage markers iNOS and CCR7 increased by 110% and 40%, respectively. A significant decrease in DMBA-induced mammary tumour incidence and prolonged tumour-free survival in mice with attenuated TGFB signalling were observed. In human non-neoplastic breast tissue, there was a significant inverse relationship between latent TGFB1 protein and CD68-positive macrophages. CONCLUSIONS: TGFB acts on macrophage populations in the mammary gland to reduce their abundance and dampen the inflammatory phenotype. TGFB signalling in macrophages increases mammary cancer susceptibility potentially through suppression of immune surveillance activities of macrophages.

Ovarian cycle stage critically affects 21-gene recurrence scores in Mmtv-Pymt mouse mammary tumours.

BACKGROUND: The Oncotype DX 21-gene Recurrence Score is predictive of adjuvant chemotherapy benefit for women with early-stage, estrogen receptor (ER)-positive, HER2-negative breast cancer. In premenopausal women, fluctuations in estrogen and progesterone during the menstrual cycle impact gene expression in hormone-responsive cancers. However, the extent to which menstrual cycling affects the Oncotype DX 21-gene signature remains unclear. Here, we investigate the impact of ovarian cycle stage on the 21-gene signature using a naturally cycling mouse model of breast cancer. METHODS: ER-positive mammary tumours were dissected from naturally cycling Mmtv-Pymt mice at either the estrus or diestrus phase of the ovarian cycle. The Oncotype DX 21-gene signature was assessed through quantitative real time-PCR, and a 21-gene experimental recurrence score analogous to the Oncotype DX Recurrence Score was calculated. RESULTS: Tumours collected at diestrus exhibited significant differences in expression of 6 Oncotype DX signature genes (Ki67, Ccnb1, Esr1, Erbb2, Grb7, Bag1; p ≤ 0.05) and a significant increase in 21-gene recurrence score (21.8 ± 2.4; mean ± SEM) compared to tumours dissected at estrus (15.5 ± 1.9; p = 0.03). Clustering analysis revealed a subgroup of tumours collected at diestrus characterised by increased expression of proliferation- (p < 0.001) and invasion-group (p = 0.01) genes, and increased 21-gene recurrence score (p = 0.01). No correlation between ER, PR, HER2, and KI67 protein abundance measured by Western blot and abundance of mRNA for the corresponding gene was observed, suggesting that gene expression is more susceptible to hormone-induced fluctuation compared to protein expression. CONCLUSIONS: Ovarian cycle stage at the time of tissue collection critically affects the 21-gene signature in Mmtv-Pymt murine mammary tumours. Further studies are required to determine whether Oncotype DX Recurrence Scores in women are similarly affected by menstrual cycle stage.

Pulmonary Actinomycosis in South Australian Koalas (Phascolarctos cinereus).

Pneumonia has been reported in both free-ranging and captive koalas and a number of causative agents have been described. Between 2016 and 2019, 16 free-ranging and 1 captive koala (Phascolarctos cinereus) from the Mount Lofty Ranges of South Australia were identified with pyogranulomatous lobar pneumonia, which involved the left caudal lobe in 14/17 (82%) cases. Within lesions, numerous gram-positive or gram-variable, non-acid-fast filamentous bacteria were observed in association with Splendore-Hoeppli phenomenon. Culture yielded growth of anaerobic bacteria, which were unidentifiable by MALDI-TOF-MS (matrix-assisted laser desorption ionization-time of flight mass spectrometry) analysis in 5/5 cases. Sequencing of the bacterial 16S rRNA gene identified a novel Actinomyces species in 4 samples, confirming a diagnosis of pulmonary actinomycosis. Concurrent examination of resin lung casts from healthy koalas suggested greater laminar flow of air to the left caudal lung lobe in koalas. Actinomyces spp. have been reported as commensals of the oral microbiome in other species, and an association with similar pulmonary lesions in other species. Considering the predilection for involvement of the left caudal lung lobe, aspiration is suggested as the likely cause in some cases of pulmonary actinomycosis in koalas. Pulmonary actinomycosis has not been previously described in koalas and further work needs to be undertaken in order to classify this organism within the Actinomyces genus.

Lethal fishing hook penetration and line entanglement in an adult bottlenose dolphin (Tursiops aduncus).

The carcass of a 15-year-old female Bottlenose dolphin (Tursiops aduncus) was retrieved from the Port River near Adelaide, South Australia, Australia. The animal was emaciated with five thick nylon fishing lines emerging from the oropharynx attached to a tangle of nylon and monofilament fishing line that also contained wire and eight fishing hooks. The mouth had been cut by the line and a circumferential curvilinear superficial abrasion/indentation from fishing line encircled the entire distal rostrum. Dissection of the upper aerodigestive tract revealed a large fish hook embedded in the lower blowhole associated with an adjacent abscess at the base of the epiglottis. The stomach contained two unattached fish hooks, parts of a plastic squid lure and two heavy duty work gloves. Further examination revealed a severe necrotising pneumonia with microabscesses in the kidneys and adrenal glands with scattered thromboemboli in keeping with terminal disseminated intravascular coagulation. Death had resulted from septic complications of fishing hook impalement and line entanglement with inanition. The case provides a graphic illustration of the effects of entanglement and fishing hook penetration, as well as ingestion of non-degradable plastic materials, in a free living Bottlenose dolphin.

SERUM BIOCHEMISTRY OF FREE-RANGING SOUTHERN HAIRY-NOSED WOMBATS (LASIORHINUS LATIFRONS).

Listed as near-threatened by the International Union for Conservation of Nature (IUCN), the southern hairy-nosed wombat (SHNW, Lasiorhinus latifrons) faces threats such as drought, habitat degradation and loss, disease, and persecution because of competition with agriculture. To assist with evaluation of wombat health, this study reports serum biochemical reference intervals (RIs) for wild-caught SHNW from South Australia established from 126 apparently healthy SHNW using a Beckman Coulter AU480® Automated Chemistry Analyzer using RefVal Advisor. Partitioning of RIs for male and female wombats and for the two methods of sampling was performed as appropriate, and additional significant differences (P < 0.05) in biochemical profiles were identified across age class and season examined. A number of differences were observed between male and female wombats, most notably higher creatinine, urea, and sodium in females. Subadult and juvenile wombats had significantly lower total protein, globulin, and ALT activity, and significantly higher ALP activity than adults. Wombats sampled in winter and spring had significantly higher total protein, albumin, potassium, bicarbonate, and enzyme activities (ALP, ALT, AST, GGT, GLDH, lipase), and significantly lower glucose and creatinine when compared to individuals sampled in summer and autumn. Differences in CK activity and anion gap observed between the two methods of sampling likely reflect delay and handling of animals between capture and blood collection. The serum biochemical RIs documented here are considered representative of a population of healthy SHNW, providing a tool for health assessment and monitoring of SHNW health in South Australia and elsewhere.

Organ Histopathology and Hematological Changes Associated With Heat Exposure in Australian Desert Birds.

An inability of the body to appropriately respond to extreme temperatures will result in pathological changes to vital organs and adverse hematological changes. Mild heat exposure of a bird to a temperature above the zone of thermoneutrality can induce subclinical heat stress, which may be a precursor to illness. The ability to identify subtle changes that may be associated with subclinical heat stress can be important in early diagnosis and treatment of heat stress in birds. Pathological changes to internal body organs, post-heat exposure, were microscopically examined in 13 budgerigars (Melopsittacus undulatus), 15 zebra finches (Taeniopygia guttata), and 8 diamond doves (Geopelia cuneata) as model species for the bird orders Psittaciformes, Passeriformes, and Columbiformes, respectively. There was mild to moderate congestion of the lungs of 28/36 birds examined, including all of the budgerigars and diamond doves. In 8/15 zebra finches no significant lung congestion was noted. Interstitial and pulmonary hemorrhage was in observed in one diamond dove. The most common hepatic pathologic change identified was micro- and macro-vesicular hepatocellular vacuolation (4/15 zebra finches, 5/13 budgerigars, and 8/8 diamond doves). There was mild to moderate congestion in the kidneys of 1/15 zebra finch, 2/ 13 budgerigars, and 4/8 diamond doves, as well as in the gastrointestinal tract of 1/15 zebra finch and 7/8 budgerigars. Budgerigars showed a decrease in hematocrit and a significant change in the numbers of heterophils and lymphocytes following heat exposure. The basophil population of cells remained relatively stable in both budgerigars and diamond doves. These findings indicate avian species differences in body organ and hematological changes following exposure to similar elevations in environmental temperatures.

Genetic diversity of Koala retrovirus env gene subtypes: insights into northern and southern koala populations.

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 diversity of the KoRV env gene in both proviral DNA and viral RNA forms in two distinct populations representative of the 'northern' and 'southern' koala genotypes. The current study demonstrated that the full range of KoRV subtypes is present across both populations, and in both healthy and sick animals. KoRV-A was the predominant proviral subtype in both populations, but there was marked diversity of DNA and RNA subtypes within individuals. Many of the northern animals displayed a higher RNA viral diversity than evident in their proviral DNA, indicating relatively higher replication efficiency of non-KoRV-A subtypes. The southern animals displayed a lower absolute copy number of KoRV than the northern animals as reported previously and a higher preponderance of KoRV-A in individual animals. These discrepancies in viral replication and diversity remain unexplained but may indicate relative protection of the southern population from KoRV replication due to either viral or host factors and may represent an important protective effect for the host in KoRV's ongoing entry into the koala genome.

Physiological, biochemical and histopathological changes associated with heatstroke in the galah (Eolophus roseicapilla) and rock dove (Columba livia).

The pathophysiology of heat illnesses in birds has not been well characterized. In this study, we describe the changes in heart rate, respiratory rate, blood biochemistry and histopathological findings in galahs and rock doves after heat exposure under standardized conditions designed to induce heatstroke. Birds in the heat-exposed group were exposed to environmental heat stress and compared to control birds. Both groups of birds were under general anaesthesia throughout the experiment and serial blood collections were performed for biochemical analyses, while organs were collected at the end of the experiment for histopathology. No electromyography traces consistent with the onset of heat cramps were observed in any of the birds. Biochemical changes suggestive of skeletal muscle and hepatocellular injury, including hyperkalaemia and increased serum muscle and hepatic enzyme activities, were often observed in heat-exposed galahs and rock doves at the onset of heatstroke. Microscopic analyses did not reveal any significant cardiac changes, although some lungs had signs of acute congestion. Some heat-exposed rock doves had microscopic changes indicative of necrosis in the pectoral muscle. There were significant hepatic changes in some heat-exposed galahs, but not in rock doves. This suggests that there may be species differences amongst birds in the organs most affected by heatstroke. The observed species differences in the physiological, biochemical and histopathological changes indicate that bird species should be studied separately for clinical syndromes such as heatstroke. RESEARCH HIGHLIGHTS Biochemical changes suggestive of skeletal muscle and hepatocellular injury in heat-exposed galahs and rock doves at the onset of heatstroke No electromyography traces consistent with the onset of heat cramps were observed Some heat-exposed rock doves had indications of necrosis in the pectoral muscle There were significant hepatic changes in some heat-exposed galahs.

CCL2-driven inflammation increases mammary gland stromal density and cancer susceptibility in a transgenic mouse model.

BACKGROUND: Macrophages play diverse roles in mammary gland development and breast cancer. CC-chemokine ligand 2 (CCL2) is an inflammatory cytokine that recruits macrophages to sites of injury. Although CCL2 has been detected in human and mouse mammary epithelium, its role in regulating mammary gland development and cancer risk has not been explored. METHODS: Transgenic mice were generated wherein CCL2 is driven by the mammary epithelial cell-specific mouse mammary tumour virus 206 (MMTV) promoter. Estrous cycles were tracked in adult transgenic and non-transgenic FVB mice, and mammary glands collected at the four different stages of the cycle. Dissected mammary glands were assessed for cyclical morphological changes, proliferation and apoptosis of epithelium, macrophage abundance and collagen deposition, and mRNA encoding matrix remodelling enzymes. Another cohort of control and transgenic mice received carcinogen 7,12-Dimethylbenz(a)anthracene (DMBA) and tumour development was monitored weekly. CCL2 protein was also quantified in paired samples of human breast tissue with high and low mammographic density. RESULTS: Overexpression of CCL2 in the mammary epithelium resulted in an increased number of macrophages, increased density of stroma and collagen and elevated mRNA encoding matrix remodelling enzymes lysyl oxidase (LOX) and tissue inhibitor of matrix metalloproteinases (TIMP)3 compared to non-transgenic controls. Transgenic mice also exhibited increased susceptibility to development of DMBA-induced mammary tumours. In a paired sample cohort of human breast tissue, abundance of epithelial-cell-associated CCL2 was higher in breast tissue of high mammographic density compared to tissue of low mammographic density. CONCLUSIONS: Constitutive expression of CCL2 by the mouse mammary epithelium induces a state of low level chronic inflammation that increases stromal density and elevates cancer risk. We propose that CCL2-driven inflammation contributes to the increased risk of breast cancer observed in women with high mammographic density.

Genetic diversity in the plasticity zone and the presence of the chlamydial plasmid differentiates Chlamydia pecorum strains from pigs, sheep, cattle, and koalas.

BACKGROUND: Chlamydia pecorum is a globally recognised pathogen of livestock and koalas. To date, comparative genomics of C. pecorum strains from sheep, cattle and koalas has revealed that only single nucleotide polymorphisms (SNPs) and a limited number of pseudogenes appear to contribute to the genetic diversity of this pathogen. No chlamydial plasmid has been detected in these strains despite its ubiquitous presence in almost all other chlamydial species. Genomic analyses have not previously included C. pecorum from porcine hosts. We sequenced the genome of three C. pecorum isolates from pigs with differing pathologies in order to re-evaluate the genetic differences and to update the phylogenetic relationships between C. pecorum from each of the hosts. METHODS: Whole genome sequences for the three porcine C. pecorum isolates (L1, L17 and L71) were acquired using C. pecorum-specific sequence capture probes with culture-independent methods, and assembled in CLC Genomics Workbench. The pairwise comparative genomic analyses of 16 pig, sheep, cattle and koala C. pecorum genomes were performed using several bioinformatics platforms, while the phylogenetic analyses of the core C. pecorum genomes were performed with predicted recombination regions removed. Following the detection of a C. pecorum plasmid, a newly developed C. pecorum-specific plasmid PCR screening assay was used to evaluate the plasmid distribution in 227 C. pecorum samples from pig, sheep, cattle and koala hosts. RESULTS: Three porcine C. pecorum genomes were sequenced using C. pecorum-specific sequence capture probes with culture-independent methods. Comparative genomics of the newly sequenced porcine C. pecorum genomes revealed an increased average number of SNP differences (~11 500) between porcine and sheep, cattle, and koala C. pecorum strains, compared to previous C. pecorum genome analyses. We also identified a third copy of the chlamydial cytotoxin gene, found only in porcine C. pecorum isolates. Phylogenetic analyses clustered porcine isolates into a distinct clade, highlighting the polyphyletic origin of C. pecorum in livestock. Most surprising, we also discovered a plasmid in the porcine C. pecorum genome. Using this novel C. pecorum plasmid (pCpec) sequence, a) we developed a pCpec screening assay to evaluate the plasmid distribution in C. pecorum from different hosts; and b) to characterise the pCpec sequences from available previously sequenced C. pecorum genome data. pCpec screening showed that the pCpec is common in all hosts of C. pecorum, however not all C. pecorum strains carry pCpec. CONCLUSIONS: This study provides further insight into the complexity of C. pecorum epidemiology and novel genomic regions that may be linked to host specificity. C. pecorum plasmid characterisation may aid in improving our understanding of C. pecorum pathogenesis across the variety of host species this animal pathogen infects.

Mycobacterium pinnipedii tuberculosis in a free-ranging Australian fur seal (Arctocephalus pusillus doriferus) in South Australia.

This report describes the first case in South Australia, Australia, of Mycobacterium pinnipedii tuberculosis in a free-ranging Australian fur seal (Arctocephalus pusillus doriferus). Severe pyogranulomatous pleuropneumonia with intrahistocytic acid-fast beaded filamentous bacilli was seen on histology. M. pinnipedii was confirmed by full 24-loci mycobacterial interspersed repetitive-unit-variable-number tandem-repeat (MIRU-VNTR) typing. Spillover concerns for public health and cattle are discussed.

Sirenian genomes illuminate the evolution of fully aquatic species within the mammalian superorder afrotheria.

Sirenians of the superorder Afrotheria were the first mammals to transition from land to water and are the only herbivorous marine mammals. Here, we generated a chromosome-level dugong (Dugong dugon) genome. A comparison of our assembly with other afrotherian genomes reveals possible molecular adaptations to aquatic life by sirenians, including a shift in daily activity patterns (circadian clock) and tolerance to a high-iodine plant diet mediated through changes in the iodide transporter NIS (SLC5A5) and its co-transporters. Functional in vitro assays confirm that sirenian amino acid substitutions alter the properties of the circadian clock protein PER2 and NIS. Sirenians show evidence of convergent regression of integumentary system (skin and its appendages) genes with cetaceans. Our analysis also uncovers gene losses that may be maladaptive in a modern environment, including a candidate gene (KCNK18) for sirenian cold stress syndrome likely lost during their evolutionary shift in daily activity patterns. Genomes from nine Australian locations and the functionally extinct Okinawan population confirm and date a genetic break ~10.7 thousand years ago on the Australian east coast and provide evidence of an associated ecotype, and highlight the need for whole-genome resequencing data from dugong populations worldwide for conservation and genetic management.

Cutaneous and Respiratory Lesions in Bushfire-Affected Koalas.

In the wake of increasingly frequent bushfires emerging as a threat to wildlife worldwide, koalas have notably been the most rescued species in Australia. However, our understanding of burns and their severity in koalas is limited; hence, this study investigated the histopathological features and depth of burns in koala skin, as well as the presence of smoke-induced respiratory tract damage. In four bushfire-affected koalas that had been euthanised on welfare grounds, skin burns in various body regions were scored based on clinical appearance as superficial, partial thickness, or full thickness. Histological sections of affected regions of skin were assessed as Grades I-IV and showed that furred regions on the ear margins and dorsum were histologically more severe, at Grade III, compared with the clinical score. There was a similar finding for footpad burns, which were the most common body region affected. In the respiratory tract, pulmonary oedema and congestion were evident in all koalas. Overall, the results highlight that cutaneous burn lesions on furred and palmar/plantar surfaces can have higher severity based on the burn depth than is clinically apparent. Therefore, there is a need to consider this when developing treatment plans and establishing prognosis for burnt koalas at triage, as well as that a high likelihood of pulmonary oedema exists.

Evaluation of recurrent laryngeal neuropathy in domestic and feral horse populations in Australia using histologic and immunohistochemical analysis: A pilot study.

BACKGROUND: Little is known about potential differences in the left recurrent laryngeal nerve (Lrln) and left cricoarytenoideus dorsalis (LCAD) muscle between domestic and feral horse populations. If a difference exists, feral horses may provide a useful control population for research related to recurrent laryngeal neuropathy (RLN) and increase our understanding of potential population pressures influencing the incidence RLN. OBJECTIVES: The objective of this study was to compare the Lrln and LCAD of domestic and feral horses using histological and immunohistochemical techniques (IHC). METHODS: Sixteen horses, domestic (n = 8) and feral (n = 8), without clinical or ancillary examinations that were processed at an abattoir had the Lrln and LCAD muscle harvested immediately following death. Carcass weights were recorded. Subjective and morphometric histologic assessment were performed on Lrln sections. The LCAD was assessed for myosin heavy chain (fibre type proportion, diameter and grouping using IHC. RESULTS: Fibre-type grouping consistent with RLN was seen in both groups. Regenerating fibre clusters were more common in domestic compared to feral horses (p = 0.04). No other histologic differences occurred between groups. Muscle fibre typing demonstrated a lower mean percentage of type IIX fibres in the feral group compared to the domestic group (p = 0.03). There was no difference in type I or IIA proportions or mean diameter of any fibre type between the groups. CONCLUSIONS: The domestic population showed evidence of nerve regeneration suggesting RLN in this group, yet this was not supported by the higher proportion of type IIX muscle fibres compared to the feral population. Further evaluation to clarify the significance and wider occurrence of the differences is indicated.

A Multicentre Epidemiologic Study of Sudden and Unexpected Death in Adult Cats and Dogs in Australia.

Sudden and unexpected death (SUD) is a common reason for animals to undergo post-mortem examination. There is limited literature examining the causes of SUD in cats and dogs, and no research specific to Australia. The purpose of this study was to investigate the epidemiology and pathology of SUD in cats and dogs in a multicentric study across Australia. Retrospective post-mortem reports of SUD in cats and dogs were obtained from four veterinary schools in Australia distributed across four states. The frequency of SUD between institutes ranged from 2.1% to 6.5%. Dogs composed the majority of the study population (76%), and males outnumbered females, particularly in the feline subpopulation. After necropsy, 37% of SUD remained cause unknown, the largest category in both cats and dogs. When cause was identified, cardiovascular disease was most common in both species, followed by gastrointestinal disease in dogs, and trauma in cats. In dogs, multinomial logistic regression identified age as a risk factor significantly associated with the four largest categories of SUD. This study identified causes of SUD in Australian cats and dogs, including novel causes not previously reported. Further, this study revealed a higher rate of unsolved SUD in Australia than can be found in the literature from other countries.

Eosinophilic Inflammation and Equine Herpesvirus-1 Associated With Haemorrhagic Cystitis in a Horse. Case Report.

Equine idiopathic haemorrhagic cystitis (EIHC) is a recently described form of aseptic cystitis in horses in which there is no discernible underlying cause. This case report describes a 9-year-old Thoroughbred gelding that presented with stranguria, pollakiuria, and haematuria. Cystoscopy revealed ulceration and haemorrhage of the bladder mucosa, diffuse mural hyperaemia and marked urine sedimentation. Histopathological evaluation of the bladder revealed chronic active ulcerative neutrophilic, lymphoplasmacytic, and eosinophilic cystitis. There was no bacterial or fungal growth upon culture but polymerase chain reaction (PCR) testing and sequencing for equine herpesvirus-1 (EHV-1) on bladder mucosa was positive. Conservative therapy with broad spectrum antimicrobials and non-steroidal anti-inflammatory therapy yielded complete resolution of clinical signs with significant improvement of macroscopic lesions in 14 days. Although a positive EHV-1 PCR suggests a viral cause, the horse's clinical signs, histology and recovery rate are more consistent with equine idiopathic haemorrhagic cystitis (EIHC). Neutrophilic and lymphoplasmacytic inflammation is a known feature of EIHC but eosinophilic infiltrates have not been previously described. The significance of the eosinophilic involvement is not certain; however, their presence has been associated with fungal, viral, parasitic, and immune-mediated aetiologies in other body systems. This is the first report of a horse with possible EIHC in Australia, as well as the first case with eosinophilic infiltrates and testing positive for EHV-1.

Investigation of Weather Triggers Preceding Outbreaks of Acute Bovine Liver Disease in Australia.

Acute bovine liver disease (ABLD) is a hepatic disease affecting cattle sporadically in southern Australia, characterised histologically by striking periportal hepatocellular necrosis. The cause of ABLD is unknown; however, the seasonality and acute presentation of outbreaks suggest mycotoxin involvement. We described the geographical and seasonal occurrence of ABLD reports from 2010 to 2020 in Victoria, Australia, and explored potential weather triggers preceding 26 outbreaks occurring across 23 properties using a case-crossover design. Outbreaks occurred most frequently in autumn/early winter and in herds located along the southern coastal plain of Victoria, and occasionally within the low-lying regions of the Great Dividing Range. Lactating adult dairy cattle represented the most reported cases. We observed a significant association between an increase in average daily dewpoint in the 15 days preceding an ABLD outbreak, suggesting that dew formation may be a key determinant for this disease. Our findings support the etiology of a potent hepatotoxic agent that requires moisture for proliferation and/or toxin production.

TESTIS ABNORMALITIES IN A POPULATION OF SOUTH AUSTRALIAN KOALAS (PHASCOLARCTOS CINEREUS).

Testis asymmetry, in which the testes in an individual differ in size, has recently been reported in koalas (Phascolarctos cinereus) in the Mount Lofty Ranges population of South Australia. We describe the morphology and histology of both testes from affected individuals in this population (n=56) and the parameters of koalas with normal-sized testes based on age and breeding season (n=56). Morphologic measurements included testis weight, length, width, and volume; histologic parameters included seminiferous tubule diameter, seminiferous epithelial height, and seminiferous tubule (interstitial tissue ratio and presence or absence of spermatozoa). Of the 56 koalas with intraindividual variation in testes size, 47 were classified as asymmetric and nine as microtestes. For koalas with asymmetric testes, all morphologic parameters were significantly decreased in the smaller testes compared with normal-sized testes, but for the histologic parameters, only seminiferous tubule diameter was significantly less. Histopathologic examination of the asymmetric testes showed 38 with normal parenchyma histologically indistinguishable between intraindividual testes, four with degeneration and atrophy, and three with hypoplasia, whereas examination of microtestes showed degeneration and atrophy in seven, hypoplasia in one, and aplasia in one. No association of testis size difference with Chlamydia pecorum infection was found in a subset of animals. For the 56 koalas with normal-sized testes, morphologic parameters were found to increase with age, and juvenile and young adults were found to have smaller seminiferous tubule diameters than adults. No differences were found between testes of koalas in the breeding and nonbreeding season. Overall, these findings indicate that testis asymmetry in koalas from the Mount Lofty Ranges population is common but not associated with decreased function, except where testis malformations such as hypoplasia or aplasia occur or when parenchyma has been disrupted by acquired disease.