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Lee F Skerratt - One of the best experts on this subject based on the ideXlab platform.
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response to comment on amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity
Science, 2020Co-Authors: Ben C Scheele, Wouter Beukema, Aldemar A Acevedo, Lee F Skerratt, Lee Berger, An Martel, Frank Pasmans, Patricia A BurrowesAbstract:Lambert et al. question our retrospective and holistic epidemiological assessment of the role of Chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that Chytridiomycosis has affected at least 501 amphibian species.
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Susceptibility of frogs to Chytridiomycosis correlates with increased levels of immunomodulatory serotonin in the skin
Cellular microbiology, 2019Co-Authors: Sieara C. Claytor, Lee F Skerratt, Lee Berger, Rebecca J. Webb, Laura F. Grogan, Joel P. A. Gummer, Laura A. Brannelly, Alexandra A. RobertsAbstract:Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a skin disease responsible for the global decline of amphibians. Frog species and populations can vary in susceptibility, but this phenomenon remains poorly understood. Here, we investigated serotonin in the skin of infected and uninfected frogs. In more susceptible frog populations, skin serotonin rose with increasing infection intensity, but decreased in later stages of the disease. The more resistant population maintained a basal level of skin serotonin. Serotonin inhibited both Bd sporangial growth and Jurkat lymphocyte proliferation in vitro. However, serotonin accumulates in skin granular glands, and this compartmentalisation may prevent inhibition of Bd growth in vivo. We suggest that skin serotonin increases in susceptible frogs due to pathogen excretion of precursor tryptophan, but that resistant frogs are able to control the levels of serotonin. Overall, the immunosuppressive effects of serotonin may contribute to the susceptibility of frogs to Chytridiomycosis.
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amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity
ISSN: 0036-8075, 2019Co-Authors: Ben C Scheele, Wouter Beukema, Aldemar A Acevedo, Lee F Skerratt, Lee Berger, An Martel, Frank Pasmans, Patricia A BurrowesAbstract:Anthropogenic trade and development have broken down dispersal barriers, facilitating the spread of diseases that threaten Earth's biodiversity. We present a global, quantitative assessment of the amphibian Chytridiomycosis panzootic, one of the most impactful examples of disease spread, and demonstrate its role in the decline of at least 501 amphibian species over the past half-century, including 90 presumed extinctions. The effects of Chytridiomycosis have been greatest in large-bodied, range-restricted anurans in wet climates in the Americas and Australia. Declines peaked in the 1980s, and only 12% of declined species show signs of recovery, whereas 39% are experiencing ongoing decline. There is risk of further Chytridiomycosis outbreaks in new areas. The Chytridiomycosis panzootic represents the greatest recorded loss of biodiversity attributable to a disease.
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Review of the amphibian immune response to Chytridiomycosis, and future directions
Frontiers in immunology, 2018Co-Authors: Laura F. Grogan, Ben C Scheele, Lee F Skerratt, Lee Berger, David A. Newell, Jacques Robert, J. Guy Castley, Hamish MccallumAbstract:The fungal skin disease, Chytridiomycosis (caused by Batrachochytrium dendrobatidis and B. salamandrivorans), has caused amphibian declines and extinctions globally since its emergence. Characterizing the host immune response to Chytridiomycosis has been a focus of study with the aim of disease mitigation. However, many aspects of the innate and adaptive arms of this response are still poorly understood, likely due to the wide range of species' responses to infection. In this paper we provide an overview of expected immunological responses (with inference based on amphibian and mammalian immunology), together with a synthesis of current knowledge about these responses for the amphibian-Chytridiomycosis system. We structure our review around four key immune stages: (1) the naive immunocompetent state, (2) immune defenses that are always present (constitutive defenses), (3) mechanisms for recognition of a pathogen threat and innate immune defenses, and (4) adaptive immune responses. We also evaluate the current hot topics of immunosuppression and immunopathology in Chytridiomycosis, and discuss their respective roles in pathogenesis. Our synthesis reveals that susceptibility to Chytridiomycosis is likely to be multifactorial. Susceptible amphibians appear to have ineffective constitutive and innate defenses, and a late-stage response characterized by immunopathology and Bd-induced suppression of lymphocyte responses. Overall, we identify substantial gaps in current knowledge, particularly concerning the entire innate immune response (mechanisms of initial pathogen detection and possible immunoevasion by Bd, degree of activation and efficacy of the innate immune response, the unexpected absence of innate leukocyte infiltration, and the cause and role of late-stage immunopathology in pathogenesis). There are also gaps concerning most of the adaptive immune system (the relative importance of B and T cell responses for pathogen clearance, the capacity and extent of immunological memory, and specific mechanisms of pathogen-induced immunosuppression). Improving our capacity for amphibian immunological research will require selection of an appropriate Bd-susceptible model species, the development of taxon-specific affinity reagents and cell lines for functional assays, and the application of a suite of conventional and emerging immunological methods. Despite current knowledge gaps, immunological research remains a promising avenue for amphibian conservation management.
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Chytridiomycosis causes catastrophic organism-wide metabolic dysregulation including profound failure of cellular energy pathways.
Scientific reports, 2018Co-Authors: Laura F. Grogan, Lee F Skerratt, Lee Berger, Scott D. Cashins, Robert D. Trengove, Joel P. A. GummerAbstract:Chytridiomycosis is among several recently emerged fungal diseases of wildlife that have caused decline or extinction of naive populations. Despite recent advances in understanding pathogenesis, host response to infection remains poorly understood. Here we modelled a total of 162 metabolites across skin and liver tissues of 61 frogs from four populations (three long-exposed and one naive to the fungus) of the Australian alpine tree frog (Litoria verreauxii alpina) throughout a longitudinal exposure experiment involving both infected and negative control individuals. We found that Chytridiomycosis dramatically altered the organism-wide metabolism of clinically diseased frogs. Chytridiomycosis caused catastrophic failure of normal homeostatic mechanisms (interruption of biosynthetic and degradation metabolic pathways), and pronounced dysregulation of cellular energy metabolism. Key intermediates of the tricarboxylic acid cycle were markedly depleted, including in particular α-ketoglutarate and glutamate that together constitute a key nutrient pathway for immune processes. This study was the first to apply a non-targeted metabolomics approach to a fungal wildlife disease and specifically to dissect the host-pathogen interface of Bd-infected frogs. The patterns of metabolite accumulation we have identified reveal whole-body metabolic dysfunction induced by a fungal skin infection, and these findings have broad relevance for other fungal diseases.
Lee Berger - One of the best experts on this subject based on the ideXlab platform.
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response to comment on amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity
Science, 2020Co-Authors: Ben C Scheele, Wouter Beukema, Aldemar A Acevedo, Lee F Skerratt, Lee Berger, An Martel, Frank Pasmans, Patricia A BurrowesAbstract:Lambert et al. question our retrospective and holistic epidemiological assessment of the role of Chytridiomycosis in amphibian declines. Their alternative assessment is narrow and provides an incomplete evaluation of evidence. Adopting this approach limits understanding of infectious disease impacts and hampers conservation efforts. We reaffirm that our study provides unambiguous evidence that Chytridiomycosis has affected at least 501 amphibian species.
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Susceptibility of frogs to Chytridiomycosis correlates with increased levels of immunomodulatory serotonin in the skin
Cellular microbiology, 2019Co-Authors: Sieara C. Claytor, Lee F Skerratt, Lee Berger, Rebecca J. Webb, Laura F. Grogan, Joel P. A. Gummer, Laura A. Brannelly, Alexandra A. RobertsAbstract:Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a skin disease responsible for the global decline of amphibians. Frog species and populations can vary in susceptibility, but this phenomenon remains poorly understood. Here, we investigated serotonin in the skin of infected and uninfected frogs. In more susceptible frog populations, skin serotonin rose with increasing infection intensity, but decreased in later stages of the disease. The more resistant population maintained a basal level of skin serotonin. Serotonin inhibited both Bd sporangial growth and Jurkat lymphocyte proliferation in vitro. However, serotonin accumulates in skin granular glands, and this compartmentalisation may prevent inhibition of Bd growth in vivo. We suggest that skin serotonin increases in susceptible frogs due to pathogen excretion of precursor tryptophan, but that resistant frogs are able to control the levels of serotonin. Overall, the immunosuppressive effects of serotonin may contribute to the susceptibility of frogs to Chytridiomycosis.
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amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity
ISSN: 0036-8075, 2019Co-Authors: Ben C Scheele, Wouter Beukema, Aldemar A Acevedo, Lee F Skerratt, Lee Berger, An Martel, Frank Pasmans, Patricia A BurrowesAbstract:Anthropogenic trade and development have broken down dispersal barriers, facilitating the spread of diseases that threaten Earth's biodiversity. We present a global, quantitative assessment of the amphibian Chytridiomycosis panzootic, one of the most impactful examples of disease spread, and demonstrate its role in the decline of at least 501 amphibian species over the past half-century, including 90 presumed extinctions. The effects of Chytridiomycosis have been greatest in large-bodied, range-restricted anurans in wet climates in the Americas and Australia. Declines peaked in the 1980s, and only 12% of declined species show signs of recovery, whereas 39% are experiencing ongoing decline. There is risk of further Chytridiomycosis outbreaks in new areas. The Chytridiomycosis panzootic represents the greatest recorded loss of biodiversity attributable to a disease.
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Review of the amphibian immune response to Chytridiomycosis, and future directions
Frontiers in immunology, 2018Co-Authors: Laura F. Grogan, Ben C Scheele, Lee F Skerratt, Lee Berger, David A. Newell, Jacques Robert, J. Guy Castley, Hamish MccallumAbstract:The fungal skin disease, Chytridiomycosis (caused by Batrachochytrium dendrobatidis and B. salamandrivorans), has caused amphibian declines and extinctions globally since its emergence. Characterizing the host immune response to Chytridiomycosis has been a focus of study with the aim of disease mitigation. However, many aspects of the innate and adaptive arms of this response are still poorly understood, likely due to the wide range of species' responses to infection. In this paper we provide an overview of expected immunological responses (with inference based on amphibian and mammalian immunology), together with a synthesis of current knowledge about these responses for the amphibian-Chytridiomycosis system. We structure our review around four key immune stages: (1) the naive immunocompetent state, (2) immune defenses that are always present (constitutive defenses), (3) mechanisms for recognition of a pathogen threat and innate immune defenses, and (4) adaptive immune responses. We also evaluate the current hot topics of immunosuppression and immunopathology in Chytridiomycosis, and discuss their respective roles in pathogenesis. Our synthesis reveals that susceptibility to Chytridiomycosis is likely to be multifactorial. Susceptible amphibians appear to have ineffective constitutive and innate defenses, and a late-stage response characterized by immunopathology and Bd-induced suppression of lymphocyte responses. Overall, we identify substantial gaps in current knowledge, particularly concerning the entire innate immune response (mechanisms of initial pathogen detection and possible immunoevasion by Bd, degree of activation and efficacy of the innate immune response, the unexpected absence of innate leukocyte infiltration, and the cause and role of late-stage immunopathology in pathogenesis). There are also gaps concerning most of the adaptive immune system (the relative importance of B and T cell responses for pathogen clearance, the capacity and extent of immunological memory, and specific mechanisms of pathogen-induced immunosuppression). Improving our capacity for amphibian immunological research will require selection of an appropriate Bd-susceptible model species, the development of taxon-specific affinity reagents and cell lines for functional assays, and the application of a suite of conventional and emerging immunological methods. Despite current knowledge gaps, immunological research remains a promising avenue for amphibian conservation management.
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Chytridiomycosis causes catastrophic organism-wide metabolic dysregulation including profound failure of cellular energy pathways.
Scientific reports, 2018Co-Authors: Laura F. Grogan, Lee F Skerratt, Lee Berger, Scott D. Cashins, Robert D. Trengove, Joel P. A. GummerAbstract:Chytridiomycosis is among several recently emerged fungal diseases of wildlife that have caused decline or extinction of naive populations. Despite recent advances in understanding pathogenesis, host response to infection remains poorly understood. Here we modelled a total of 162 metabolites across skin and liver tissues of 61 frogs from four populations (three long-exposed and one naive to the fungus) of the Australian alpine tree frog (Litoria verreauxii alpina) throughout a longitudinal exposure experiment involving both infected and negative control individuals. We found that Chytridiomycosis dramatically altered the organism-wide metabolism of clinically diseased frogs. Chytridiomycosis caused catastrophic failure of normal homeostatic mechanisms (interruption of biosynthetic and degradation metabolic pathways), and pronounced dysregulation of cellular energy metabolism. Key intermediates of the tricarboxylic acid cycle were markedly depleted, including in particular α-ketoglutarate and glutamate that together constitute a key nutrient pathway for immune processes. This study was the first to apply a non-targeted metabolomics approach to a fungal wildlife disease and specifically to dissect the host-pathogen interface of Bd-infected frogs. The patterns of metabolite accumulation we have identified reveal whole-body metabolic dysfunction induced by a fungal skin infection, and these findings have broad relevance for other fungal diseases.
Ross A. Alford - One of the best experts on this subject based on the ideXlab platform.
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Infection dynamics, dispersal, and adaptation: understanding the lack of recovery in a remnant frog population following a disease outbreak
Heredity, 2020Co-Authors: Donald T. Mcknight, Ross A. Alford, Deborah S. Bower, Leah J. Carr, Lin Schwarzkopf, Kyall R. ZengerAbstract:Emerging infectious diseases can cause dramatic declines in wildlife populations. Sometimes, these declines are followed by recovery, but many populations do not recover. Studying differential recovery patterns may yield important information for managing disease-afflicted populations and facilitating population recoveries. In the late 1980s, a Chytridiomycosis outbreak caused multiple frog species in Australia’s Wet Tropics to decline. Populations of some species (e.g., Litoria nannotis ) subsequently recovered, while others (e.g., Litoria dayi ) did not. We examined the population genetics and current infection status of L. dayi , to test several hypotheses regarding the failure of its populations to recover: (1) a lack of individual dispersal abilities has prevented recolonization of previously occupied locations, (2) a loss of genetic variation has resulted in limited adaptive potential, and (3) L. dayi is currently adapting to Chytridiomycosis. We found moderate-to-high levels of gene flow and diversity ( Fst range:
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Seasonal, annual and decadal change in tadpole populations in tropical Australian streams: supplementary material
2019Co-Authors: Katrin Schmidt, Stephen Richards, Richard G. Pearson, Ross A. Alford, Robert PuschendorfAbstract:Declines due to fungal disease (Chytridiomycosis) have affected many stream-dwelling frog species, especially in the tropics, leading to reduced abundance and diversity of their tadpoles. Studies in the Australian Wet Tropics have demonstrated that some frog species have declined or disappeared, while others have persisted. To assess the occurrence of stream-breeding frogs, we monitored tadpole populations of five frog species in Wet Tropics streams in the early 1990s (uplands, before chytridomycosis emergence), and in 2011–2013 (uplands and lowlands, after Chytridiomycosis emergence), and investigated environmental factors that might influence tadpole abundance. Riffle-dwelling tadpoles of two frog species disappeared from the upland stream site during the 1990s, reflecting reported losses of adult populations. Tadpoles of one upland pool species initially declined but had recovered by 2011–2013. Samples from the lowlands in 2011 to 2013 indicated no similar loss. Chytridiomycosis was the likely cause of changes in tadpole abundances between the two survey periods, given its known occurrence and documented effects on adult frogs in these systems; however, we did not measure its prevalence in this study. Tadpole populations fluctuated seasonally, with abundances highest in spring and summer, reflecting the timing of frog reproduction. The most important biophysical influence on the assemblages that we measured was current velocity. Tadpole peak abundances suggest that they make a substantial contribution at the consumer level of food webs, and that their loss has altered food webs substantially in upland streams
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behaviour of australian rainforest stream frogs may affect the transmission of Chytridiomycosis
Diseases of Aquatic Organisms, 2007Co-Authors: Jodi J. L. Rowley, Ross A. AlfordAbstract:The amphibian disease Chytridiomycosis, caused by the pathogen Batrachochytrium dendrobatidis, has been implicated in mass mortalities, population declines and extinctions of amphibians around the world. In almost all cases, amphibian species that have disappeared or declined due to Chytridiomycosis coexist with non-declining species. One reason why some species decline from Chytridiomycosis and others do not may be interspecific differences in behaviour. Host behaviour could either facilitate or hinder pathogen transmission, and transmission rates in the field are likely to vary among species according the frequency of factors such as physical contact between frogs, contact with infected water and contact with environmental substrates containing B. dendrobatidis. We tracked 117 frogs (28 Litoria nannotis, 27 L. genimaculata and 62 L. lesueuri) at 5 sites where B. dendrobatidis is endemic in the rainforest of tropical northern Queensland and recorded the frequency of frog-to-frog contact and the frequency of contact with stream water and environmental substrates. Frequency of contact with other frogs and with water were highest in L. nannotis, intermediate in L. genimaculata and lowest in L. lesueueri. Environmental substrate use also differed among species. These species-specific opportunities for disease transmission were correlated with conservation status: L. nannotis is the species most susceptible to Chytridiomycosis-related declines and L. lesueuri is the least susceptible. Interspecific variation in transmission probability may, therefore, play a large role in determining why Chytridiomycosis drives some populations to extinction and not others.
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Resistance to Chytridiomycosis varies among amphibian species and is correlated with skin peptide defenses
Animal Conservation, 2007Co-Authors: Douglas C. Woodhams, Ross A. Alford, Laura K. Reinert, Gerry Marantelli, K. Ardipradja, Louise A. Rollins-smithAbstract:Innate immune mechanisms of defense are especially important to ectothermic vertebrates in which adaptive immune responses may be slow to develop. One innate defense in amphibian skin is the release of abundant quantities of antimicrobial peptides. Chytridiomycosis is an emerging infectious disease of amphibians caused by the skin fungus, Batrachochytrium dendrobatidis. Susceptibility to Chytridiomycosis varies among species, and mechanisms of disease resistance are not well understood. Previously, we have shown that Australian and Panamanian amphibian species that possess skin peptides that effectively inhibit the growth of B. dendrobatidis in vitro tend to survive better in the wild or are predicted to survive the first encounter with this lethal pathogen. For most species, it has been difficult to experimentally infect individuals with B. dendrobatidis and directly evaluate both survival and antimicrobial peptide defenses. Here, we demonstrate differences in susceptibility to Chytridiomycosis among four Australian species (Litoria caerulea, Litoria chloris, Mixophyes fasciolatus and Limnodynastes tasmaniensis) after experimental infection with B. dendrobatidis, and show that the survival rate increases with the in vitro effectiveness of the skin peptides. We also observed that circulating granulocyte, but not lymphocyte, counts differed between infected and uninfected Lit. chloris. This suggests that innate granulocyte defenses may be activated by pathogen exposure. Taken together, our data suggest that multiple innate defense mechanisms are involved in resistance to Chytridiomycosis, and the efficacy of these defenses varies by amphibian species.
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Methodology for investigating the distribution and determinants of Chytridiomycosis
2006Co-Authors: Andrea D. Phillott, Lee F Skerratt, Lee Berger, Ross A. Alford, Keith R. Mcdonald, Diana Mendez, Richard Speare, Scott D. Cashins, Harry Hines, Jodi J. L. RowleyAbstract:Chytridiomycosis is an important emerging pandemic infectious disease of amphibians. Investigating this disease has been challenging due to a lack of knowledge and expertise in studying disease in amphibians in general, and because of the novel nature of the pathogen, Batrachochytrium dendrobatidis (Bd), which is the first chytrid fungus known to cause disease in vertebrates. Bd is difficult to isolate and has a diverse and wide host range, and frog population sizes are largely unknown and the ability to find frogs varies with climatic conditions. We have adapted veterinary and zoological methods and expertise to examine the distribution and determinants of Chytridiomycosis. Our studies of the determinants of Chytridiomycosis have involved research at multiple levels. We have examined correlations of disease prevalence with environmental, climatic and host variables. Within populations, we use mark-recapture methods to estimate incidence and mortality rates and relate these to possible determinants. At the level of the individual host, we use radio telemetry to examine the effects of host behaviour and microenvironment on infection and transmission mechanisms. In the laboratory, experimental infections are used to test and demonstrate relationships between determinants and Chytridiomycosis. It is expected that understanding the epidemiology of this disease will lead to better management of Chytridiomycosis and improved conservation for frogs.
Laura F. Grogan - One of the best experts on this subject based on the ideXlab platform.
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Immunological Aspects of Chytridiomycosis
Journal of fungi (Basel Switzerland), 2020Co-Authors: Laura F. Grogan, David A. Newell, Jacques Robert, Josephine E. Humphries, Chantal M. Lanctôt, Catherine J Nock, Hamish MccallumAbstract:Amphibians are currently the most threatened vertebrate class, with the disease Chytridiomycosis being a major contributor to their global declines. Chytridiomycosis is a frequently fatal skin disease caused by the fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). The severity and extent of the impact of the infection caused by these pathogens across modern Amphibia are unprecedented in the history of vertebrate infectious diseases. The immune system of amphibians is thought to be largely similar to that of other jawed vertebrates, such as mammals. However, amphibian hosts are both ectothermic and water-dependent, which are characteristics favouring fungal proliferation. Although amphibians possess robust constitutive host defences, Bd/Bsal replicate within host cells once these defences have been breached. Intracellular fungal localisation may contribute to evasion of the induced innate immune response. Increasing evidence suggests that once the innate defences are surpassed, fungal virulence factors suppress the targeted adaptive immune responses whilst promoting an ineffectual inflammatory cascade, resulting in immunopathology and systemic metabolic disruption. Thus, although infections are contained within the integument, crucial homeostatic processes become compromised, leading to mortality. In this paper, we present an integrated synthesis of amphibian post-metamorphic immunological responses and the corresponding outcomes of infection with Bd, focusing on recent developments within the field and highlighting future directions.
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Susceptibility of frogs to Chytridiomycosis correlates with increased levels of immunomodulatory serotonin in the skin
Cellular microbiology, 2019Co-Authors: Sieara C. Claytor, Lee F Skerratt, Lee Berger, Rebecca J. Webb, Laura F. Grogan, Joel P. A. Gummer, Laura A. Brannelly, Alexandra A. RobertsAbstract:Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a skin disease responsible for the global decline of amphibians. Frog species and populations can vary in susceptibility, but this phenomenon remains poorly understood. Here, we investigated serotonin in the skin of infected and uninfected frogs. In more susceptible frog populations, skin serotonin rose with increasing infection intensity, but decreased in later stages of the disease. The more resistant population maintained a basal level of skin serotonin. Serotonin inhibited both Bd sporangial growth and Jurkat lymphocyte proliferation in vitro. However, serotonin accumulates in skin granular glands, and this compartmentalisation may prevent inhibition of Bd growth in vivo. We suggest that skin serotonin increases in susceptible frogs due to pathogen excretion of precursor tryptophan, but that resistant frogs are able to control the levels of serotonin. Overall, the immunosuppressive effects of serotonin may contribute to the susceptibility of frogs to Chytridiomycosis.
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Review of the amphibian immune response to Chytridiomycosis, and future directions
Frontiers in immunology, 2018Co-Authors: Laura F. Grogan, Ben C Scheele, Lee F Skerratt, Lee Berger, David A. Newell, Jacques Robert, J. Guy Castley, Hamish MccallumAbstract:The fungal skin disease, Chytridiomycosis (caused by Batrachochytrium dendrobatidis and B. salamandrivorans), has caused amphibian declines and extinctions globally since its emergence. Characterizing the host immune response to Chytridiomycosis has been a focus of study with the aim of disease mitigation. However, many aspects of the innate and adaptive arms of this response are still poorly understood, likely due to the wide range of species' responses to infection. In this paper we provide an overview of expected immunological responses (with inference based on amphibian and mammalian immunology), together with a synthesis of current knowledge about these responses for the amphibian-Chytridiomycosis system. We structure our review around four key immune stages: (1) the naive immunocompetent state, (2) immune defenses that are always present (constitutive defenses), (3) mechanisms for recognition of a pathogen threat and innate immune defenses, and (4) adaptive immune responses. We also evaluate the current hot topics of immunosuppression and immunopathology in Chytridiomycosis, and discuss their respective roles in pathogenesis. Our synthesis reveals that susceptibility to Chytridiomycosis is likely to be multifactorial. Susceptible amphibians appear to have ineffective constitutive and innate defenses, and a late-stage response characterized by immunopathology and Bd-induced suppression of lymphocyte responses. Overall, we identify substantial gaps in current knowledge, particularly concerning the entire innate immune response (mechanisms of initial pathogen detection and possible immunoevasion by Bd, degree of activation and efficacy of the innate immune response, the unexpected absence of innate leukocyte infiltration, and the cause and role of late-stage immunopathology in pathogenesis). There are also gaps concerning most of the adaptive immune system (the relative importance of B and T cell responses for pathogen clearance, the capacity and extent of immunological memory, and specific mechanisms of pathogen-induced immunosuppression). Improving our capacity for amphibian immunological research will require selection of an appropriate Bd-susceptible model species, the development of taxon-specific affinity reagents and cell lines for functional assays, and the application of a suite of conventional and emerging immunological methods. Despite current knowledge gaps, immunological research remains a promising avenue for amphibian conservation management.
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Chytridiomycosis causes catastrophic organism-wide metabolic dysregulation including profound failure of cellular energy pathways.
Scientific reports, 2018Co-Authors: Laura F. Grogan, Lee F Skerratt, Lee Berger, Scott D. Cashins, Robert D. Trengove, Joel P. A. GummerAbstract:Chytridiomycosis is among several recently emerged fungal diseases of wildlife that have caused decline or extinction of naive populations. Despite recent advances in understanding pathogenesis, host response to infection remains poorly understood. Here we modelled a total of 162 metabolites across skin and liver tissues of 61 frogs from four populations (three long-exposed and one naive to the fungus) of the Australian alpine tree frog (Litoria verreauxii alpina) throughout a longitudinal exposure experiment involving both infected and negative control individuals. We found that Chytridiomycosis dramatically altered the organism-wide metabolism of clinically diseased frogs. Chytridiomycosis caused catastrophic failure of normal homeostatic mechanisms (interruption of biosynthetic and degradation metabolic pathways), and pronounced dysregulation of cellular energy metabolism. Key intermediates of the tricarboxylic acid cycle were markedly depleted, including in particular α-ketoglutarate and glutamate that together constitute a key nutrient pathway for immune processes. This study was the first to apply a non-targeted metabolomics approach to a fungal wildlife disease and specifically to dissect the host-pathogen interface of Bd-infected frogs. The patterns of metabolite accumulation we have identified reveal whole-body metabolic dysfunction induced by a fungal skin infection, and these findings have broad relevance for other fungal diseases.
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Survival, gene and metabolite responses of Litoria verreauxii alpina frogs to fungal disease Chytridiomycosis.
Scientific data, 2018Co-Authors: Laura F. Grogan, Ben C Scheele, Lee Berger, Scott D. Cashins, Michael Mcfadden, Jason Mulvenna, Joel P. A. Gummer, Peter S. Harlow, David A. Hunter, Robert D. TrengoveAbstract:The fungal skin disease Chytridiomycosis has caused the devastating decline and extinction of hundreds of amphibian species globally, yet the potential for evolving resistance, and the underlying pathophysiological mechanisms remain poorly understood. We exposed 406 naive, captive-raised alpine tree frogs (Litoria verreauxii alpina) from multiple populations (one evolutionarily naive to Chytridiomycosis) to the aetiological agent Batrachochytrium dendrobatidis in two concurrent and controlled infection experiments. We investigated (A) survival outcomes and clinical pathogen burdens between populations and clutches, and (B) individual host tissue responses to Chytridiomycosis. Here we present multiple interrelated datasets associated with these exposure experiments, including animal signalment, survival and pathogen burden of 355 animals from Experiment A, and the following datasets related to 61 animals from Experiment B: animal signalment and pathogen burden; raw RNA-Seq reads from skin, liver and spleen tissues; de novo assembled transcriptomes for each tissue type; raw gene expression data; annotation data for each gene; and raw metabolite expression data from skin and liver tissues. These data provide an extensive baseline for future analyses.
Richard Speare - One of the best experts on this subject based on the ideXlab platform.
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Amphibian Chytridiomycosis.
Diseases of aquatic organisms, 2010Co-Authors: Alex D. Hyatt, Andrew A. Cunningham, Richard Speare, Cynthia CareyAbstract:Amphibian Chytridiomycosis is a fungal disease caused by the chytrid fungus Batrachochytrium dendrobatidis. It is arguably the most significant recorded infectious disease of any vertebrate class. The disease is reducing amphibian biodiversity across most continents and regions of the world, affecting the resilience of surviving populations and driving multiple species to extinction. It is now recognised by the World Organisation for Animal Health (OIE) as an internationally notifiable disease. Collaborative research in areas including the development of diagnostic assays, distribution and impact of the disease, and management (treatment and policy) has assisted in leading a paradigm shift in accepting infectious disease as a major factor influencing wildlife population stability and biodiversity.
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Two amphibian diseases, Chytridiomycosis and ranaviral disease, are now globally notifiable to the World Organization for Animal Health (OIE): an assessment.
Diseases of aquatic organisms, 2010Co-Authors: Lisa M Schloegel, Peter Daszak, Andrew A. Cunningham, Richard Speare, Barry HillAbstract:The global trade in amphibians entails the transport of tens of millions of live animals each year. In addition to the impact harvesting wild animals can have on amphibian populations, there is mounting evidence that the emerging pathogens Batrachochytrium dendrobatidis and ranaviruses, the aetiological agents of Chytridiomycosis and ranaviral disease, respectively, are spread through this trade. The link between these pathogens and amphibian declines and extinctions suggests that the epidemiological impact of the trade is significant and may negatively affect conservation and trade economics. Here we present a brief assessment of the volume of the global trade in live amphibians, the risk of individuals harboring infection, and information on the recent listing by the World Organization for Animal Health (OIE) of Chytridiomycosis and ranaviral disease in the OIE Aquatic Animal Health Code. This listing made Chytridiomycosis and ranaviral disease internationally notifiable diseases and thus subject to OIE standards, which aim to assure the sanitary safety of international trade in live amphibians and their products.
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impact and dynamics of disease in species threatened by the amphibian chytrid fungus batrachochytrium dendrobatidis
Conservation Biology, 2009Co-Authors: Kris A Murray, Lee F Skerratt, Richard Speare, Hamish MccallumAbstract:Estimating disease-associated mortality and transmission processes is difficult in free-ranging wildlife but important for understanding disease impacts and dynamics and for informing management decisions. In a capture–mark–recapture study, we used a PCR-based diagnostic test in combination with multistate models to provide the first estimates of disease-associated mortality and detection, infection, and recovery rates for frogs endemically infected with the chytrid fungus Batrachochytrium dendrobatidis (Bd), which causes the pandemic amphibian disease Chytridiomycosis. We found that endemic Chytridiomycosis was associated with a substantial reduction (approximately 38%) in apparent monthly survival of the threat- ened rainforest treefrog Litoria pearsoniana despite a long period of coexistence (approximately 30 years); detection rate was not influenced by disease status; improved recovery and reduced infection rates corre- lated with decreased prevalence, which occurred when temperatures increased; and incorporating changes in individuals’ infection status through time with multistate models increased effect size and support (98.6% vs. 71% of total support) for the presence of disease-associated mortality when compared with a Cormack– Jolly–Seber model in which infection status was restricted to the time of first capture. Our results indicate that amphibian populations can face significant ongoing pressure from Chytridiomycosis long after epidemics associated with initial Bd invasions subside, an important consideration for the long-term conservation of many amphibian species worldwide. Our findings also improve confidence in estimates of disease prevalence in wild amphibians and provide a general framework for estimating parameters in epidemiological models for Chytridiomycosis, an important step toward better understanding and management of this disease.
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Case report of Chytridiomycosis in an exotic frog species, Litoria caerulea in South Korea
2009Co-Authors: Hyo Jin Yang, Richard Speare, Chang Park, Youngjun Kim, Hang Lee, Mi-sook MinAbstract:Chytridiomycosis, a disease caused by the chytrid fungus Balrachochytrium dendrob1tidis (Bd), is one of the most serious causes of amphibian decline in the world. We report the infection of an exotic frog (White's tree frog Litoria caerulea) imported as a pet to South Korea from the United States. The frog displayed typical signs of Chytridiomycosis and eventually died. Bd-specific polymerase chain reaction assay, histopathological and immunohistopathological examinations using Bd-specific polyclonal antibody proved that the frog was infected with Bd. This is the first report in Korea of an imported amphibian that was suspected to have died from Chytridiomycosis. The case demonstrates that Bd can enter Korea on imported amphibians. All imported amphibians should be regarded as infected with Bd and isolated until they are proven negative by PCR testing. The impact of imported Bd on wild populations of Korean amphibians is unknown and requires investigation.
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Electrolyte depletion and osmotic imbalance in amphibians with Chytridiomycosis.
Diseases of aquatic organisms, 2007Co-Authors: Jamie Voyles, Lee Berger, Richard Speare, Sam Young, Rebecca J. Webb, Jeffrey H. Warner, Donna Rudd, R. Campbell, Lee F SkerrattAbstract:Mounting evidence implicates the disease Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, in global amphibian declines and extinctions. While the virulence of this disease has been clearly demonstrated, there is, as yet, no mechanistic explanation for how B. dendrobatidis kills amphibians. To investigate the pathology of Chytridiomycosis, blood samples were collected from uninfected, aclinically infected and clinically diseased amphibians and analyzed for a wide range of biochemical and hematological parameters. Here, we show that green tree frogs Litoria caerulea with severe Chytridiomycosis had reduced plasma osmolality, sodium, potassium, magnesium and chloride concentrations. Stable plasma albumin, hematocrit and urea levels indicated that hydration status was unaffected, signifying depletion of electrolytes from circulation rather than dilution due to increased water uptake. We suggest that B. dendrobatidis kills amphibians by disrupting normal epidermal functioning, leading to osmotic imbalance through loss of electrolytes. Determining how B. dendrobatidis kills amphibians is fundamental to understanding the host– pathogen relationship and thus the population declines attributed to B. dendrobatidis. Understanding the mechanisms of mortality may also explain interspecific variation in susceptibility to Chytridiomycosis.