A RETROSPECTIVE ANALYSIS OF MORBIDITY AND MORTALITY IN THE CAPTIVE LEADBEATER'S POSSUM (GYMNOBELIDEUS LEADBEATERI) POPULATION FROM 1970 TO 2021.

The Leadbeater's possum (Gymnobelideus leadbeateri) is a critically endangered nocturnal marsupial with a restricted range in the Central Highlands of Victoria, Australia. There are two genetically distinct populations divided by location: highland and lowland. Lowland possums exist in one remnant swamp forest and entered captivity in 2012 when ∼60 individuals remained. Today, with less than 20 lowland individuals remaining, any information that informs the yet-unsuccessful breeding program is critical. This study encompasses a retrospective analysis of the causes of mortality and significant histological lesions in captive highland and lowland individuals across seven institutions internationally from 1970 to 2021. During this time, 245 possums lived in captivity. Postmortem records exist for 99 animals, including 349 histopathology diagnoses from 80 reports and 264 gross necropsy diagnoses from 78 reports. Diagnoses were assigned into two categories based on the importance to the individual (causing death or morbidity to a single animal [n = 194]), or importance to the wider population (causing death or morbidity to more than one animal or was related to reproduction [n = 155]). Individual animals had multiple diagnoses, which were tallied as individual data points. Renal disease was diagnosed 57 times; the most common finding was chronic nephropathy (43/57). Cardiovascular disease was diagnosed 33 times; atherosclerosis associated with obesity was common (n = 10/33). Both categories suggest causal association with captive husbandry but elicit no comment on the lack of success of the breeding program. Reproductive disease was diagnosed 36 times in 24 animals (14 females and 10 males). In females, 11 cases of uterine inflammation and associated clinical signs were associated with ascending infection or neoplasia. Of the seven lowland male possums with mortality data, five were infertile (azoospermia or testicular atrophy). More investigation into the reproductive health of this population is indicated to understand the lack of success in the current breeding program.

An assessment of ectoparasites across highland and lowland populations of Leadbeater's possum (Gymnobelideus leadbeateri): Implications for genetic rescue translocations.

Leadbeater's possum (Gymnobelideus leadbeateri) is a nocturnal arboreal marsupial with a restricted range centered on the Victorian Central Highlands, south-eastern Australia. Most populations inhabit wet montane ash forest and subalpine woodland, with one notable exception - a small, outlying and genetically-distinct lowland population inhabiting swamp forest at Yellingbo, Victoria. The species has been listed as critically endangered since 2015. Translocations are the mainstay of critical genetic rescue and this study explores the ectoparasites that are 'along for the ride' during translocation activities. Ectoparasites (133 fleas, 15 ticks and 76 mites) were collected opportunistically from 24 Leadbeater's possum colonies during population monitoring and genetic sampling across the lowland and highland populations. The composition of the flea assemblage varied by habitat type. Significantly greater numbers of the general marsupial fleas Acanthopsylla r. rothschildii. and Choristopsylla tristis (as a proportion of total flea numbers) were detected in lowland habitats, compared to highland habitats (Fishers exact test, P < 0.0001). Two host-specific flea species, Stephanocircus domrowi and Wurunjerria warnekei were detected only on possums in highland habitats. As a proportion of total fleas this was significantly different to possums in lowland habitats (Fisher's exact test, P = 0.0042 and P < 0.0001, respectively). Wurunjerria warnekei was suspected to be extinct prior to this study. Ticks (Ixodes tasmanii, n = 15) and mites (Haemdoelaps cleptus, n = 47 and H. anticlea, n = 29) have been identified in Leadbeater's possums historically. The possible causes of the different flea assemblages may be environmental/climatic, or due to the historic geographic division between highland and lowland animals. The planned translocations of highland individuals to lowland habitats will expose lowland individuals to novel species of previously exclusively highland fleas with unknown indirect consequences, thus careful monitoring will be required to manage any potential risks.

Detection of Breinlia sp. (Nematoda) in the Leadbeater's possum (Gymnobelideus leadbeateri).

The Leadbeater's possum (Gymnobelideus leadbeateri) is a critically endangered marsupial in south-eastern Australia. Among other conservation efforts, free-ranging animals in the two remaining geographically separate populations (highland and lowland) have been extensively studied; however, little is known about their health and mortality. Although some wild populations are frequently monitored, cadavers are rarely recovered for post mortem examination. In June 2019, a recently deceased, wild, adult male lowland Leadbeater's possum was collected from a nest box and a comprehensive post mortem examination was conducted. Microfilariae of a filarioid nematode were observed in testes, liver, lung and skin samples in tissue impression smears and upon histopathological examination. No gross or histological changes were seen associated with the parasites, except for a focal area of tissue damage in the skin, suggesting that the possum is a natural host. Using a PCR-coupled sequencing method the filarioid was identified as a species of Breinlia. Species of Breinlia occur in other Australian marsupials and rodents.

STEROIDAL SAPONIN TOXICITY IN EASTERN GREY KANGAROOS ( MACROPUS GIGANTEUS): A NOVEL CLINICOPATHOLOGIC PRESENTATION OF HEPATOGENOUS PHOTOSENSITIZATION.

We describe the clinicopathologic features of a mortality event characterized by blindness and dermatitis affecting eastern grey kangaroos ( Macropus giganteus), secondary to hepatogenous photosensitization. Affected animals exhibited photophobic behavior, blindness, ataxia, recumbency, lethargy, ear shaking, and behavior consistent with distress or depression. The photophobia manifested as abnormal shade-seeking during the day, including finding refuge under or in structures used frequently by people. Severely affected kangaroos were jaundiced and had markedly elevated serum bilirubin and gamma glutamyl-transpeptidase concentrations. Blindness in affected animals was attributed to moderate to severe corneal opacity due to corneal edema and inflammation. Skin lesions were typically subtle on gross examination even in cases which had severe necrotizing dermatitis histologically. Histologic lesions in the liver of affected animals included the presence of acicular clefts typical of steroidal saponins. The outbreak was associated with pasture dominated by the invasive grass, Panicum gilvum, which is a recognized source of saponin-induced photosensitization in livestock.