Nahiid Stephens

From 2020 to 2022, systematic investigation of wildlife mortalities on Dirk Hartog Island, Western Australia was initiated to inform wildlife disease risk analyses for translocation purposes. As part of this monitoring, in November 2020, a sandy inland mouse (Pseudomys hermannsburgensis) was found deceased with multiple comorbidities. Gross necropsy, histopathology and ancillary molecular testing identified several novel host-parasite associations. Sarcoptes scabiei was identified via molecular methods in association with consistent cutaneous pathology, representing the first known detection of this parasite in an Australian native rodent. A putative novel virus belonging to the subfamily Gammaherpesvirinae was also identified, representing the first known detection of a herpesvirus (Orthoherpesviridae) from this species, although it was not clearly associated with other disease processes. A heavy burden of the cestode Hymenolepis microstoma was also present in the gastrointestinal tract, representing a new host record for this species, whilst a pancreatic adenocarcinoma was also found. Beyond the novelty of these host records, these findings contribute to important health baselines of rodent populations on Dirk Hartog Island and highlight the value of investigating mortalities and implementing health surveillance as part of ecological monitoring and wildlife translocation projects.

Malaria and other haemosporidian parasites are common in reptiles. During baseline health surveys of sea turtles in Western Australia (WA), haemosporidian parasites were detected in flatback (Natator depressus) and green (Chelonia mydas) turtle erythrocytes during routine blood film examination. 130 blood samples were screened via polymerase chain reaction (PCR), including 105 N. depressus, 20 C. mydas, and 5 olive ridley turtles (Lepidochelys olivacea). A novel Haemocystidium sp. was identified, detected exclusively in foraging turtles and not in nesting turtles. The combined prevalence by microscopic and molecular methods was 16.9% (22/130), primarily affecting immature C. mydas (77.3%; 17/22). Mature N. depressus were also affected (22.7%; 5/22). DNA sequencing of a partial fragment of the mitochondrial cytochrome b (cytb) gene together with phylogenetic analysis identified two different Haemocystidium sp. genotypes, A and B, with genotype A being most prevalent. The phylogenetic analysis showed close genetic relationships to Haemocystidium sp. in freshwater and terrestrial turtles, suggesting a shared evolutionary lineage despite ecological differences. Preliminary analysis indicates that this parasite is incidental, as no association between health and parasite presence or grade was detected. This study provides the first formal detection of haemosporidian parasites in sea turtles, contributing essential baseline data while highlighting their evolutionary significance and host–parasite ecological relationships.

The aim of this study was to describe the gross and histopathological features of a neurological syndrome in endangered Western Australian Carnaby's black cockatoos (Zanda laitirostris) that was first observed in 2012. The syndrome, named hindlimb paralysis syndrome in Carnaby's cockatoos (CHiPS), is characterized by annual outbreaks of hindlimb paralysis with occasional loss of deep pain and cloacal tone, typically occurring between January and March. Previous limited investigations suggested a possible toxic aetiology. Full gross necropsy and histopathology examinations were performed on 17 CHiPS cases and on 11 control birds for reference. Histopathological examination was carried out on all major organs including brain, spinal cord, brachial plexus, sciatic nerve and wing and hindlimb muscles. Gross and histopathological examinations did not elucidate a definitive cause of the clinical signs seen in CHiPS cases. There were no substantial gross or histopathological changes within the brain, spinal cord, sciatic nerve or brachial plexus that could explain the hindlimb paralysis. The most noteworthy changes were seen in the hindlimb and wing muscles, with a monophasic to polyphasic myopathy present in the hindlimb muscles of 15 of the 17 CHiPS cases and in the wing muscles in 11 of those cases. The cause and significance of the myopathy is unclear and requires further investigation. Based on the above findings, the most likely differential diagnoses include neurotoxicoses (eg, organophosphate, organochlorine and carbamate) and, less likely, myotoxicosis (eg, ionophore toxicosis), nutritional myopathy (eg, vitamin E/selenium deficiency) or botulism.

Context
Chlamydia species impose major global burdens on both human and animal health. However, chlamydial infections of wild rodents have been understudied, posing limitations on assessments of disease risks for rodent conservation translocations. This is particularly true when there is evidence of infection in proposed source populations, as occurred for the Shark Bay mouse (Pseudomys gouldii) translocations to Dirk Hartog Island.

Aims
The aim of this study was to reduce uncertainty surrounding the risks posed by Chlamydia for these translocations by: (1) determining the presence, prevalence and diversity of Chlamydia in rodent populations in the Shark Bay region of Western Australia; (2) identifying associations with health parameters; and (3) assessing for evidence of cross-species transmission.

Methods
Swab, faecal and tissue samples from 110 wild-caught individuals (comprising five rodent and two marsupial species) were collected across four islands in Western Australia. These samples were analysed by a Chlamydiaceae 23s rRNA qPCR in a 14-month cross-sectional study conducted between 2020 and 2021.

Key results
In total, 20% of all individuals (22/110; 95%CI 13.6–28.4) from five species, including 19% (19/100; 95% CI 12.5–27.8) of rodents, were positive by the Chlamydiaceae qPCR, although in low loads. Further attempts at species identification of the Chlamydiaceae were unsuccessful. Our results found no detectable adverse health associations, or significant associated pathological findings, with low molecular loads supporting an asymptomatic infection state. Additionally, there were no disease associations in Shark Bay bandicoots (Perameles bougainville) despite the presence of an ocular disease syndrome previously linked to chlamydial infection in this species.

Conclusions and implications
Our findings suggest that sub-clinical chlamydial infections in wild Australian rodents may be widespread, but for the Dirk Hartog Island translocations, the risks of Chlamydia associated with movement of Shark Bay mice are likely low. The results highlight how current knowledge gaps pertaining to wildlife health can be addressed through collaborative approaches to translocation planning and implementation.

Blood reference intervals (RIs) provide an indication of systemic health and are central to any baseline health survey. RIs are available for all sea turtle species, except for the flatback turtle Natator depressus. We developed the first nesting and foraging flatback turtle RIs from a healthy reference population of 211 individuals. We found flatback turtle RIs were generally similar to other published sea turtle RIs. For flatback turtles, we detected significant differences in blood reference values (RVs) by life stage (nesting vs. foraging), sex, and location, as well as by measurement technique (laboratory vs. field). Clinically significant differences justified the establishment of separate RIs for nesting and foraging flatback turtles and for laboratory and field techniques. Clinical application of these blood RIs for individuals in rehabilitation includes disease diagnosis, health monitoring, and the development of prognostic indicators. As sea turtles are regarded as sentinels of environmental health, flatback turtle baseline health data will also be useful for population health monitoring and as a reference for future studies where changes in RIs may indicate an environment in decline.

Routine post mortems of deceased penguins from Penguin Island, Western Australia, found that a temporal cluster of cases presented with characteristic gross and microscopic changes, namely birds in good body condition with hepatomegaly and splenomegaly, multifocal hepatic and splenic necrosis and numerous, 1–2 μm diameter protozoan parasites within the necrotic foci. Electron microscopy identified the protozoa as belonging to the phylum Apicomplexa. Molecular investigations by PCR gave inconsistent results. PCR performed by an external laboratory identified a novel Haemoproteus spp. organism in samples from 4 of 10 cases from this group, while PCR at Murdoch University identified Toxoplasma gondii in 12 of 13 cases (including 9 of the 10 assayed at the external laboratory). Immunohistochemistry of formalin fixed tissues also identified Toxoplasma in the hepatic and splenic lesions. The distinctive mortalities which were observed in this group of penguins are attributed to a fulminant toxoplasmosis, with a concurrent Haemoproteus infection in some cases. Though the clinical signs of infection are unknown, the gross and microscopic appearance at post mortem is sufficiently characteristic to allow a diagnosis to be made on these features. Definitive confirmation of Toxoplasma infection can be made by immunohistochemistry or PCR.

Cervico-thoracic vertebral subluxation (CTVS) in sheep is a collective term that is used to describe various conditions that concomitantly affect the cervical and thoracic vertebrae, leading to their collapse. The aetiology and pathophysiology of CTVS remain unknown. The objective of this study was to conduct an epidemiological farm investigation and describe the clinicopathological findings of CTVS cases occurring in a flock of sheep; as well as to determine awareness of CTVS among sheep producers and ruminant veterinarians in Australia. Diagnostic imaging revealed severe deformities in the vertebrae between C6–C7 and T1–T3. Sheep affected with CTVS were at a four times higher risk of having low body condition scores (< 2 based on a 5-point scale) compared with non-affected sheep, OR = 3.98, 95% CI (1.20–12.65), p = .02. Survey results revealed that only 34% (15/44) of respondents were aware of CTVS. There is a need to further explore the aetiology and pathophysiology of CTVS, and the impact it has on sheep breeding and production.

A distinct ulcerative dermatitis known as “freshwater skin disease” is an emerging clinical and pathological presentation in coastal cetaceans worldwide. In Australia, two remarkably similar mortality events enabled the creation of a case definition based on pathology and environmental factors. The first affected a community of endemic Tursiops australis in the Gippsland Lakes, Victoria, while the second occurred among T. aduncus resident in the Swan-Canning River system, Western Australia. The common features of both events were (1) an abrupt and marked decrease in salinity (from > 30ppt to < 5ppt) due to rainfall in the catchments, with hypo-salinity persisting weeks to months, and (2) dermatitis characterized grossly by patchy skin pallor that progressed to variable circular or targetoid, often raised, and centrally ulcerated lesions covering up to 70% of the body surface. The affected skin was often colonized by a variety of fungal, bacterial and algal species that imparted variable yellow, green or orange discoloration. Histologic lesions consisted of epidermal hydropic change leading to vesiculation and erosion; alternately, or in addition, the formation of intra-epithelial pustules resulting in ulceration and hypodermal necrosis. Thus, the environmental factors and characteristic pathologic lesions, are necessary components of the case definition for freshwater skin disease.

Streptococcus iniae causes high mortality in cultured and wild fish stocks globally. Since the first report in captive Amazon river dolphins Inia geoffrensis in 1976, it has emerged in finfish across all continents except Antarctica. In March 2016, an estimated 17000 fish were observed dead and dying along a remote 70 km stretch of the Kimberley coastline north of Broome, Western Australia. Affected species included finfish (lionfish Pterois volitans, angelfish Pomacanthus sp., stripey snapper Lutjanus carponotatus, sand bass Psammoperca waigiensis, yellowtail grunter Amniataba caudavittata, damselfish Pomacentridae sp.), flatback sea turtles Natator depressus, and olive (Aipysurus laevis) and black-ringed (Hydrelaps darwiniensis) sea snakes. Moribund fish collected during the event exhibited exophthalmia and abnormal behaviour, such as spiralling on the surface or within the water column. Subsequent histopathological examination of 2 fish species revealed bacterial septicaemia with chains of Gram-positive cocci seen in multiple organs and within brain tissue. S. iniae was isolated and identified by bacterial culture, species-specific PCR, Matrix-Assisted Laser Desorption Ionisation Time-Of-Flight (MALDI-TOF) and biochemical testing. This is the first report of S. iniae associated with a major multi-species wild marine fish kill in Australia. Extreme weather events in the region including a marked decrease in water temperatures, followed by an extended period of above-average coastal water temperatures, were implicated as stressors potentially contributing to this outbreak.

Case history: A 2-year-old Rottweiler dog from Perth (WA, Australia) was referred for assessment of a chronic productive cough and weight loss.

Clinical findings: Severely enlarged bilateral superficial cervical lymph nodes and severely enlarged abdominal organs were present. The body condition score was poor and there was moderate muscle wasting. Thoracic and abdominal computed tomography images revealed severe diffuse enlargement of thoracic and abdominal lymph nodes, hepatomegaly and diffuse splenomegaly. A diffuse bronchial pattern with severe multifocal saccular bronchiectasis was identified in the lungs.

Diagnostic findings: Fungal organisms were seen within macrophages on cytological preparations and on histopathological sections of biopsies of the superficial cervical lymph node. Macrophages contained intracytoplasmic, non-filamentous round-to-ovoid organisms, which varied in size from 5–30 µm in diameter with variable morphology. Budding was not observed, and no hyphae were present. Fungal culture of lymph node tissue resulted in growth of Aspergillus (Phialosimplex) caninus which was confirmed by amplification and sequencing of a segment of the 16S-23S rRNA internal transcribed spacer. Concurrent bacterial bronchitis was diagnosed on culture of broncho-alveolar fluid.

Diagnosis: Disseminated aspergillosis caused by Aspergillus caninus.

Clinical relevance: This is believed to be the first report of infection caused by A. caninus in a dog in Australasia. The dog was treated with itraconazole for 7 months and was still alive 7 months after the start of treatment.