Non-essential heavy metals and protective effects of selenium against mercury toxicity in endangered Australian sea lion (Neophoca cinerea) pups with hookworm disease.

The endangered Australian sea lion, Neophoca cinerea, faces ongoing population decline. Identification of key threats to N. cinerea population recovery, including disease and pollutants, is an objective of the species' recovery plan. Previous studies have identified Uncinaria sanguinis, an intestinal nematode, as a significant cause of disease and mortality in N. cinerea pups. Given the impact of heavy metals on the immune response, investigation of these pollutants is critical. To this end, the concentrations of arsenic (As), total mercury (Hg), cadmium (Cd), chromium (Cr), lead (Pb) and selenium (Se) were determined in blood collected from N. cinerea pups sampled during the 2017/18, 2019 and 2020/21 breeding seasons at Seal Bay Conservation Park, South Australia. Significant differences (p < 0.05) in Hg, As, Cr, and Se concentrations and molar ratio of Se:Hg were seen between breeding seasons. Pup age, maternal parity and inter-individual foraging behaviour were considered factors driving these differences. The concentrations of Hg (357, 198 and 241 µg/L) and As (225, 834 and 608 µg/L) were high in 2017/18, 2019 and 2020/21 respectively with Hg concentrations in the blood of N. cinerea pups above toxicological thresholds reported for marine mammals. The concentration of Se (1332, 647, 763 µg/L) and molar ratio of Se:Hg (9.47, 7.98 and 6.82) were low compared to other pinniped pups, indicating potential vulnerability of pups to the toxic effects of Hg. Significant (p < 0.05) negative associations for Pb and Cd with several red blood cell parameters suggest they could be exacerbating the anaemia caused by hookworm disease. Temporal (age-related) changes in element concentrations were also seen, such that pup age needs to be considered when interpreting bioaccumulation patterns. Further investigation of the role of elevated heavy metal concentrations on N. cinerea pup health, disease and development is recommended, particularly with respect to immunological impacts.

Biological variation of total thyroxine (T4), free T4 and thyroid-stimulating hormone in 11 clinically healthy cats.

OBJECTIVES: The aim of this study was to investigate the biological variation of total thyroxine (T4), free T4 (fT4) and thyroid-stimulating hormone (TSH) in 11 clinically healthy cats aged between 3 and 15 years old, in Sydney, Australia. METHODS: Blood was collected weekly for up to 6 weeks and serum T4, fT4 and TSH concentrations were analysed using canine-specific reagents. Restricted maximum likelihood was used to estimate within-subject, between-subject and analytical variance components, which were recorded in terms of the related coefficients of variation. The index of individuality and reference change values were then calculated for each analyte. RESULTS: T4 and TSH had intermediate individuality, indicating both subject-based and population-based reference intervals (RIs) could be used, with the knowledge that population-based RIs are suboptimally sensitive. fT4 had high individuality, indicating subject-based RIs are more appropriate than population-based RIs. CONCLUSIONS AND RELEVANCE: This study has demonstrated that subject-based RIs could be more sensitive than population-based RIs for the diagnosis of thyroid dysfunction in cats.

Per and polyfluoroalkyl substances (PFAS) at high concentrations in neonatal Australian pinnipeds.

Per and polyfluorinated substances (PFAS) exposure was investigated in Australian pinnipeds. Concentrations of 16 PFAS were measured in the livers of Australian sea lion (Neophoca cinerea), Australian fur seal (Arctocephalus pusillus doriferus) and a long-nosed Fur Seal (Arctocephalus forsteri) pup sampled between 2017 and 2020 from colonies in South Australia and Victoria. Findings reported in this study are the first documented PFAS concentrations in Australian pinnipeds. Median and observed range of values in ng/g wet weight were highest for perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) in the liver of N. cinerea (PFOS = 7.14, 1.00-16.9; PFOA = 2.73, 0.32-11.2; PFNA = 2.96, 0.61-8.22; n = 28), A. forsteri (PFOS = 15.98, PFOA = 2.02, PFNA = 7.86; n = 1) and A. p. doriferus (PFOS = 27.4, 10.5-2119; PFOA = 0.98, 0.32-52.2; PFNA = 2.50, 0.91-44.2; n = 20). PFAS concentrations in A. p. doriferus pups were significantly greater (p < 0.05) than in N. cinerea pups for all PFAS except PFOA and were of similar magnitude to those reported in northern hemisphere marine animals. These results demonstrate exposure differences in both magnitude and PFAS profiles for N. cinerea in South Australia and A. p. doriferus in Victoria. This study reports detectable PFAS concentrations in Australian pinniped pups indicating the importance of maternal transfer of these toxicants. As N. cinerea are endangered and recent declines in pup production has been reported for A. p. doriferus at the colony sampled, investigation of potential health impacts of these toxicants on Australian pinnipeds is recommended.

COCCIDIOSIS IN GREEN TURTLES (CHELONIA MYDAS) IN AUSTRALIA: PATHOGENESIS, SPATIAL AND TEMPORAL DISTRIBUTION, AND CLIMATE-RELATED DETERMINANTS OF DISEASE OUTBREAKS.

An epizootic of coccidiosis in free-ranging green turtles (Chelonia mydas) occurred in Australia in 1991 and the parasites were thought to be Caryospora cheloniae. Recurring outbreaks over an increased geographic range followed. We used medical records and temporal and spatial data of turtles diagnosed with coccidiosis between 1991 and 2014 to characterize the disease and factors associated with outbreaks. Most affected animals were subadults or older. Neurologic signs with intralesional cerebral coccidia were observed. Coccidia associated with inflammation and necrosis were predominantly found in the intestine, brain, kidney, and thyroid. Cases occurred in the spring and summer. Three major outbreaks (1991, 2002, and 2014) were concentrated in Port Stephens, New South Wales (NSW) and Moreton Bay, Queensland, but cases occurred as far south as Sydney, NSW. Coccidiosis cases were more likely during, or 1 mo prior to, El Niño-like events. Molecular characterization of the 18S rRNA locus of coccidia from tissues of 10 green turtles collected in 2002 and 2004 in Port Stevens and Sydney imply that they were Schellackia-like organisms. Two genotypes were identified. The Genotype 3 sequence was most common (in eight of 10 turtles), with 98.8% similarity to the 18S sequence of Schellackia orientalis. The Genotype 4 sequence was less common (in two of 10 turtles) with 99.7% similarity to the 18S sequence of the most common genotype (Genotype 1) detected in turtles from the 2014 Moreton Bay outbreak. Our study will help with the identification and management of future outbreaks and provide tools for identification of additional disease patterns in green turtles.

Utility of fur as a biomarker for persistent organic pollutants in Australian fur seals (Arctocephalus pusillus doriferus).

Persistent Organic Pollutants (POPs) can cause toxic effects in many species which include endocrine dysfunction, immunotoxicity, developmental defects and neoplasia. Species dominating the upper trophic level are vulnerable to these effects due to bioaccumulation. In Bass Strait, the Australian fur seal (Arctocephalus pusillus doriferus) is an important top order predator and sentinel species for ecosystem health. An alopecia syndrome is seen at high prevalence in juvenile, female Australian fur seals at Lady Julia Percy Island, Victoria, Australia. Previous investigations suggest causality could be due to an endocrine-like toxicant. The alopecia syndrome has significance for thermoregulation and is a likely risk factor for mortality. Fur collected from case (alopecic) and control (unaffected) seals sampled at Lady Julia Percy Island were analysed for POPs. To investigate the utility of fur for monitoring POPs concentrations in pinnipeds, a comparison of POPs concentrations in the fur and blubber of Australian fur seals stranded along the Victorian coast was undertaken. The concentration of selected POPs including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), polybrominated diphenyl ethers (PBDEs) and perfluorooctane sulfonate/perfluorooctanoic acid (PFOS/PFOA) were determined in fur using either High Resolution Gas Chromatography-Mass Spectrometry or Liquid Chromatography-Mass Spectrometry. Results indicate detectable, and in some individuals, elevated levels of dl-PCBs, PCDD/Fs and PBDEs in juvenile fur seals sampled on Lady Julia Percy Island, with significantly higher levels of dl-PCBs in case compared to control seals. Elevated levels of dl-PCBs and PCDD/Fs were found in blubber samples collected from stranded fur seals with significant correlations between blubber and fur concentrations seen, particularly for dl-PCBs. This study discusses the significance of POPs concentrations in relation to the causality of an alopecia syndrome in the Australian fur seal, and assesses the utility of fur as a non-invasive biomarker to monitor POPs exposure in this sentinel species.