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      Beyond the disease: Is Toxoplasma gondii infection causing population declines in the eastern quoll ( Dasyurus viverrinus)?

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          Abstract

          Highlights

          • Seroprevalence of Toxoplasma gondii was investigated in eastern quolls.

          • Seroprevalence of IgG antibodies was higher at sites where quolls were declining.

          • T. gondii infection did not reduce quoll survival or reproduction.

          • Higher seroprevalence signals higher exposure to feral cats at declining sites.

          Abstract

          Disease is often considered a key threat to species of conservation significance. For some, it has resulted in localised extinctions and declines in range and abundance. However, for some species, the assertion that a disease poses a significant threat of extinction is based solely on correlative or anecdotal evidence, often inferred from individual clinical case reports. While a species’ susceptibility to a disease may be demonstrated in a number of individuals, investigations rarely extend to measuring the impact of disease at the population level and its contribution, if any, to population declines. The eastern quoll ( Dasyurus viverrinus) is a medium-sized Australian marsupial carnivore that is undergoing severe and rapid decline in Tasmania, its last refuge. Reasons for the decline are currently not understood. Feral cats ( Felis catus) may be undergoing competitive release following the ongoing decline of the Tasmanian devil ( Sarcophilus harrisii), with cats suppressing eastern quolls through increased predation, competition, exclusion or exposure to diseases such as toxoplasmosis. To investigate the effects of Toxoplasma gondii infection, eastern quoll populations at four sites were regularly screened for the seroprevalence of T. gondii-specific IgG antibodies. Seroprevalence was approximately five times higher at sites with declining quoll populations, and there was a negative association between seroprevalence and quoll abundance. However, T. gondii infection did not reduce quoll survival or reproduction. Despite a high susceptibility to T. gondii infection, eastern quoll populations do not appear to be limited by the parasite or its resultant disease. Significantly higher seroprevalence is a signal of greater exposure to feral cats at sites where eastern quolls are declining, suggesting that increased predation, competition or exclusion by feral cats may be precipitating population declines.

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          Directions in Conservation Biology

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            Evidence for the role of infectious disease in species extinction and endangerment.

            Infectious disease is listed among the top five causes of global species extinctions. However, the majority of available data supporting this contention is largely anecdotal. We used the IUCN Red List of Threatened and Endangered Species and literature indexed in the ISI Web of Science to assess the role of infectious disease in global species loss. Infectious disease was listed as a contributing factor in <4% of species extinctions known to have occurred since 1500 (833 plants and animals) and as contributing to a species' status as critically endangered in <8% of cases (2,852 critically endangered plants and animals). Although infectious diseases appear to play a minor role in global species loss, our findings underscore two important limitations in the available evidence: uncertainty surrounding the threats to species survival and a temporal bias in the data. Several initiatives could help overcome these obstacles, including rigorous scientific tests to determine which infectious diseases present a significant threat at the species level, recognition of the limitations associated with the lack of baseline data for the role of infectious disease in species extinctions, combining data with theory to discern the circumstances under which infectious disease is most likely to serve as an agent of extinction, and improving surveillance programs for the detection of infectious disease. An evidence-based understanding of the role of infectious disease in species extinction and endangerment will help prioritize conservation initiatives and protect global biodiversity.
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              Detecting disease and parasite threats to endangered species and ecosystems.

              Ecologists have recently begun to acknowledge the importance of disease and parasites in the dynamics of populations. Diseases and parasites have probably been responsible for a number of extinctions on islands and on large land masses, but the problem has only been identified in retrospect. In contrast, endemic pathogens and parasites may operate as keystone species, playing a crucial role in maintaining the diversity of ecological communities and ecosystems. Will recent advances in the understanding of parasite population biology allow us to predict threats to endangered species and communities?
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                Author and article information

                Contributors
                Journal
                Int J Parasitol Parasites Wildl
                Int J Parasitol Parasites Wildl
                International Journal for Parasitology: Parasites and Wildlife
                Elsevier
                2213-2244
                29 May 2014
                29 May 2014
                August 2014
                : 3
                : 2
                : 102-112
                Affiliations
                School of Biological Sciences, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia
                Author notes
                [* ]Corresponding author. Tel.: +61 417 980 340; fax: +61 362 262 698. Bronwyn.Fancourt@ 123456utas.edu.au
                Article
                S2213-2244(14)00014-5
                10.1016/j.ijppaw.2014.05.001
                4142269
                25161908
                72985032-7152-424e-af44-49ba49bf26c4
                © 2014 The Authors

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

                Categories
                Article

                toxoplasmosis,epidemiology,feral cat,felis catus,population decline

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