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Lindsay SA, Fulham M, Caraguel CGB, Gray R. Mitigating disease risk in an endangered pinniped: early hookworm elimination optimizes the growth and health of Australian sea lion pups. Front Vet Sci 2023; 10:1161185. [PMID: 37180065 PMCID: PMC10168540 DOI: 10.3389/fvets.2023.1161185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 04/04/2023] [Indexed: 05/15/2023] Open
Abstract
The Australian sea lion (Neophoca cinerea) experiences high pup mortality of seasonally alternating severity, partly attributed to endemic hookworm (Uncinaria sanguinis) infection. To further explore health outcomes of early hookworm elimination, a treatment trial was conducted at Seal Bay Conservation Park, South Australia, over consecutive lower and higher mortality breeding seasons (2019, 19.2%; 2020-1; 28.9%). Pups (n = 322) were stratified into two age cohorts (median 14 d and 24 d recruitment ages) and randomly assigned to treated (topical ivermectin 500 μg/kg) or control (untreated) groups. A younger prepatent cohort <14 d old (median 10 d) was identified a posteriori. A seasonally independent growth benefit resulted from hookworm elimination across all age cohorts. The greatest relative improvements (bodyweight + 34.2%, standard length + 42.1%; p ≤ 0.001) occurred in the month post-treatment, in the youngest prepatent cohort. A significant benefit of lesser magnitude (bodyweight + 8.6-11.6%, standard length + 9.5-18.4%; p ≤ 0.033) persisted up to 3 months across all age cohorts - greatest in the youngest pups. Treatment resulted in immediate improvement in hematological measures of health - decreased anemia and inflammation severity (p ≤ 0.012). These results enhance our understanding of host-parasite-environment interactions within the context of hematological ontogenesis, confirm the seasonally independent benefits of hookworm disease intervention, and further inform conservation recommendations for this endangered species.
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Affiliation(s)
- Scott A. Lindsay
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Camperdown, NSW, Australia
- Faculty of Science, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia
| | - Mariel Fulham
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Camperdown, NSW, Australia
| | - Charles G. B. Caraguel
- Faculty of Science, School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, SA, Australia
| | - Rachael Gray
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Camperdown, NSW, Australia
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Fulham M, Power M, Gray R. Gut microbiota of endangered Australian sea lion pups is unchanged by topical ivermectin treatment for endemic hookworm infection. Front Microbiol 2022; 13:1048013. [PMID: 36601397 PMCID: PMC9806137 DOI: 10.3389/fmicb.2022.1048013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 12/02/2022] [Indexed: 12/23/2022] Open
Abstract
The gut microbiota is essential for the development and maintenance of the hosts' immune system. Disturbances to the gut microbiota in early life stages can result in long-lasting impacts on host health. This study aimed to determine if topical ivermectin treatment for endemic hookworm (Uncinaria sanguinis) infection in endangered Australian sea lion (Neophoca cinerea) pups resulted in gut microbial changes. The gut microbiota was characterised for untreated (control) (n = 23) and treated (n = 23) Australian sea lion pups sampled during the 2019 and 2020/21 breeding seasons at Seal Bay, Kangaroo Island. Samples were collected pre- and post-treatment on up to four occasions over a four-to-five-month period. The gut microbiota of untreated (control) and treated pups in both seasons was dominated by five bacterial phyla, Fusobacteria, Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. A significant difference in alpha diversity between treatment groups was seen in pups sampled during the 2020/21 breeding season (p = 0.008), with higher richness and diversity in treated pups. Modelling the impact of individual pup identification (ID), capture, pup weight (kg), standard length (cm), age and sex on beta diversity revealed that pup ID accounted for most of the variation (35% in 2019 and 42% in 2020/21), with pup ID, capture, and age being the only significant contributors to microbial variation (p < 0.05). There were no statistically significant differences in the composition of the microbiota between treatment groups in both the 2019 and 2020/21 breeding seasons, indicating that topical ivermectin treatment did not alter the composition of the gut microbiota. To our knowledge, this is the first study to characterise the gut microbiota of free-ranging Australian pinniped pups, compare the composition across multiple time points, and to consider the impact of parasitic treatment on overall diversity and microbial composition of the gut microbiota. Importantly, the lack of compositional changes in the gut microbiota with treatment support the utility of topical ivermectin as a safe and minimally invasive management strategy to enhance pup survival in this endangered species.
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Affiliation(s)
- Mariel Fulham
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camperdown, NSW, Australia
| | - Michelle Power
- School of Natural Sciences, Faculty of Science and Engineering, Macquarie University, North Ryde, NSW, Australia
| | - Rachael Gray
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camperdown, NSW, Australia,*Correspondence: Rachael Gray,
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Taylor S, Terkildsen M, McQuilty R, Lee D, Wing-Simpson A, Gray R. Non-essential heavy metals and protective effects of selenium against mercury toxicity in endangered Australian sea lion (Neophoca cinerea) pups with hookworm disease. ENVIRONMENT INTERNATIONAL 2022; 169:107521. [PMID: 36148712 DOI: 10.1016/j.envint.2022.107521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 08/06/2022] [Accepted: 09/11/2022] [Indexed: 06/16/2023]
Abstract
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.
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Affiliation(s)
- Shannon Taylor
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia
| | | | - Robert McQuilty
- Department of Chemical Pathology, Royal Prince Alfred Hospital, Camperdown, Sydney 2050, Australia
| | - David Lee
- Department of Chemical Pathology, Royal Prince Alfred Hospital, Camperdown, Sydney 2050, Australia
| | - Aileen Wing-Simpson
- Department of Chemical Pathology, Royal Prince Alfred Hospital, Camperdown, Sydney 2050, Australia
| | - Rachael Gray
- Sydney School of Veterinary Science, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia.
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Meza Cerda MI, Gray R, Thomson PC, Butcher L, Simpson K, Cameron A, Marcus AD, Higgins DP. Developing Immune Profiles of Endangered Australian Sea Lion ( Neophoca cinerea) Pups Within the Context of Endemic Hookworm ( Uncinaria sanguinis) Infection. Front Vet Sci 2022; 9:824584. [PMID: 35529837 PMCID: PMC9069138 DOI: 10.3389/fvets.2022.824584] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 03/28/2022] [Indexed: 11/13/2022] Open
Abstract
As a top predator, the endangered Australian sea lion (Neophoca cinerea) is a sentinel of ecosystem change, where population trends can reflect broader shifts in the marine environment. The population of this endemic pinniped was historically diminished by commercial sealing, and recovery has been slowed by fishery interactions, disease and, potentially, pollutants. Hookworm infects 100% of neonatal pups and has been identified as a contributor to population decline. Here, a multivariable approach using traditional serological and novel molecular tools such as qPCR and ddPCR was used to examine immune phenotypes of developing Australian sea lion pups infected with the endemic hookworm (Uncinaria sanguinis) from two South Australian colonies. Results show changing immunophenotypes throughout the patent period of infection represented by pro-inflammatory cytokines (IL-6), IgG and acute-phase proteins. Although cytokines may prove useful as markers of resistance, in this study, IL-6 is determined to be an early biomarker of inflammation in Australian sea lion pups, excluding the alternative hypothesis. Additionally, immunological differences between animals from high- and low-intensity hookworm seasons, as well as ivermectin-treated animals, indicate hookworm infection modulation of the host immune response, as evidenced by a lower IL-6 mRNA expression in the non-treated groups. This study of the Australian sea lion is an example of an ecoimmunological approach to disease investigation, which can be applied to evaluate the impact of environmental and anthropogenic factors on susceptibility to infectious diseases in free-ranging species
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Affiliation(s)
- María-Ignacia Meza Cerda
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Rachael Gray
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Peter C Thomson
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Loreena Butcher
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Kelly Simpson
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Abby Cameron
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Alan D Marcus
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
| | - Damien P Higgins
- Faculty of Science, Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW, Australia
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Lindsay SA, Caraguel CG, Gray R. Topical ivermectin is a highly effective seal 'spot-on': A randomised trial of hookworm and lice treatment in the endangered Australian sea lion ( Neophoca cinerea). Int J Parasitol Parasites Wildl 2021; 16:275-284. [PMID: 34877253 PMCID: PMC8633868 DOI: 10.1016/j.ijppaw.2021.11.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/10/2021] [Accepted: 11/10/2021] [Indexed: 12/03/2022]
Abstract
The Australian sea lion (Neophoca cinerea) is an endangered and declining otariid species, with a high rate of pup mortality associated with endemic hookworm (Uncinaria sanguinis) infection a suspected contributor to this decline. Injected ivermectin is an effective treatment for Uncinaria sp. in otariids, with optimal outcomes achieved by the early treatment of pups prior to disease development. This randomised controlled trial evaluated the effectiveness of the novel use of a topical ivermectin formulation against hookworm infection and lice (Antarctophthirus microchir) infestation, in comparison with injected ivermectin. During the 2017 breeding season at Dangerous Reef, South Australia, pups ≤ 70 cm in standard length (≤ 2 weeks of age; n = 85) were randomised to single dose topical (500 μg/kg spot-on; n = 27) or injected (200 μg/kg subcutaneous; n = 29) ivermectin treatment groups, or to an untreated control group (n = 29). Topical ivermectin was highly effective for U. sanguinis elimination, and not significantly different to the injected formulation (estimated effectiveness 96.4% and 96.8%, respectively; P > 0.05). Its application resulted in an 81.6% reduction and 62.7% additional clearance for A. microchir infestation by 15-24 days post-treatment, compared with untreated control pups (also not significantly different to injected ivermectin; 83.1% and 59.4%, respectively; P > 0.05). Treatment with either ivermectin formulation significantly ameliorated increases in inflammatory markers detected in the blood of untreated control pups - peripheral blood eosinophil counts (persisting to 36-41 days post-recruitment P < 0.05) and increased plasma protein concentrations (15-24 days post-recruitment; P < 0.05). Further, an initial short-term decrease in body condition in the control group was not observed in either of the treatment groups. This study demonstrates that topical ivermectin is an effective antiparasitic treatment in N. cinerea. It offers an alternative administration method for ivermectin delivery to a young pup cohort in this species, and an alternative, minimally invasive management tool for species conservation.
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Affiliation(s)
- Scott A. Lindsay
- Sydney School of Veterinary Science, The University of Sydney, Camperdown, New South Wales, Australia
- School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia
| | - Charles G.B. Caraguel
- School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia
| | - Rachael Gray
- Sydney School of Veterinary Science, The University of Sydney, Camperdown, New South Wales, Australia
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Bilgmann K, Armansin N, Ferchaud A, Normandeau E, Bernatchez L, Harcourt R, Ahonen H, Lowther A, Goldsworthy S, Stow A. Low effective population size in the genetically bottlenecked Australian sea lion is insufficient to maintain genetic variation. Anim Conserv 2021. [DOI: 10.1111/acv.12688] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- K. Bilgmann
- Department of Biological Sciences Macquarie University Sydney Australia
| | - N. Armansin
- Department of Biological Sciences Macquarie University Sydney Australia
| | - A.L. Ferchaud
- Département de Biologie Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - E. Normandeau
- Département de Biologie Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - L. Bernatchez
- Département de Biologie Institut de Biologie Intégrative et des Systèmes (IBIS) Université Laval Québec QC Canada
| | - R. Harcourt
- Department of Biological Sciences Macquarie University Sydney Australia
| | - H. Ahonen
- Department of Biological Sciences Macquarie University Sydney Australia
- Norwegian Polar Institute Tromsø Norway
| | | | - S.D. Goldsworthy
- South Australian Research and Development Institute Adelaide South Australia
| | - A. Stow
- Department of Biological Sciences Macquarie University Sydney Australia
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Small localized breeding populations in a widely distributed coastal shark species. CONSERV GENET 2021. [DOI: 10.1007/s10592-021-01398-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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