1
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Waddle AW, Clulow S, Aquilina A, Sauer EL, Kaiser SW, Miller C, Flegg JA, Campbell PT, Gallagher H, Dimovski I, Lambreghts Y, Berger L, Skerratt LF, Shine R. Hotspot shelters stimulate frog resistance to chytridiomycosis. Nature 2024; 631:344-349. [PMID: 38926575 DOI: 10.1038/s41586-024-07582-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 05/17/2024] [Indexed: 06/28/2024]
Abstract
Many threats to biodiversity cannot be eliminated; for example, invasive pathogens may be ubiquitous. Chytridiomycosis is a fungal disease that has spread worldwide, driving at least 90 amphibian species to extinction, and severely affecting hundreds of others1-4. Once the disease spreads to a new environment, it is likely to become a permanent part of that ecosystem. To enable coexistence with chytridiomycosis in the field, we devised an intervention that exploits host defences and pathogen vulnerabilities. Here we show that sunlight-heated artificial refugia attract endangered frogs and enable body temperatures high enough to clear infections, and that having recovered in this way, frogs are subsequently resistant to chytridiomycosis even under cool conditions that are optimal for fungal growth. Our results provide a simple, inexpensive and widely applicable strategy to buffer frogs against chytridiomycosis in nature. The refugia are immediately useful for the endangered species we tested and will have broader utility for amphibian species with similar ecologies. Furthermore, our concept could be applied to other wildlife diseases in which differences in host and pathogen physiologies can be exploited. The refugia are made from cheap and readily available materials and therefore could be rapidly adopted by wildlife managers and the public. In summary, habitat protection alone cannot protect species that are affected by invasive diseases, but simple manipulations to microhabitat structure could spell the difference between the extinction and the persistence of endangered amphibians.
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Affiliation(s)
- Anthony W Waddle
- Melbourne Veterinary School, University of Melbourne, Werribee, Victoria, Australia.
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia.
- Applied BioSciences, Macquarie University, Sydney, New South Wales, Australia.
| | - Simon Clulow
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
- Centre for Conservation Ecology and Genomics, Institute for Applied Ecology, University of Canberra, Bruce, Australian Capital Territory, Australia
| | - Amy Aquilina
- Melbourne Veterinary School, University of Melbourne, Werribee, Victoria, Australia
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Erin L Sauer
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - Shannon W Kaiser
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Claire Miller
- School of Mathematics and Statistics, University of Melbourne, Parkville, Victoria, Australia
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Jennifer A Flegg
- School of Mathematics and Statistics, University of Melbourne, Parkville, Victoria, Australia
| | - Patricia T Campbell
- Department of Infectious Diseases, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Melbourne, Victoria, Australia
| | - Harrison Gallagher
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Ivana Dimovski
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
| | - Yorick Lambreghts
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
- School of Natural Sciences, University of Tasmania, Hobart, Tasmania, Australia
| | - Lee Berger
- Melbourne Veterinary School, University of Melbourne, Werribee, Victoria, Australia
| | - Lee F Skerratt
- Melbourne Veterinary School, University of Melbourne, Werribee, Victoria, Australia
| | - Richard Shine
- School of Natural Sciences, Macquarie University, Sydney, New South Wales, Australia
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2
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Holmes ML, Shine R, Waddle AW. Spontaneous reoccurrence of Batrachochytrium dendrobatidis infections in Australian green tree frogs (Litoria caerulea) following apparently successful heat therapy: Case report. Vet Res Commun 2024:10.1007/s11259-024-10449-2. [PMID: 38951465 DOI: 10.1007/s11259-024-10449-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 06/23/2024] [Indexed: 07/03/2024]
Abstract
Heat therapy has been reported as a safe, effective, and readily available treatment method for heat-tolerant frogs infected with Batrachochytrium dendrobatidis (Bd). We treated wild-caught Australian green tree frogs (Litoria caerulea) infected with Bd using two periods of elevated ambient room temperature (28.2-30.3 °C for 7 weeks followed by 28.9-34.1 °C for 4 weeks). Frogs exhibited persistent and even increasing infection loads in the first treatment period despite prolonged exposure to elevated temperatures, likely due to the presence of cooler microenvironments within their enclosure (25.5-27.0 °C). All frogs eventually returned negative qPCR tests for Bd at the end of the second treatment period, but detectable infections reoccurred one month after frogs were returned to standard housing temperatures (21.2-28.7 °C). Our findings suggest that elevated ambient temperature alone might not eliminate Bd in vivo but can reduce infections loads such that they are undetectable by qPCR analysis of skin swabs. Additional factors, such as cooler microenvironments within enclosures or relative humidity, may influence the success of heat therapy. We recommend further research into the combined effects of temperature and humidity during heat therapy and emphasize the importance of accurate temperature measurements as well as post-treatment monitoring at Bd-permissive temperatures to confirm successful clearance of infections.
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Affiliation(s)
- Madeleine L Holmes
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia.
| | - Richard Shine
- School of Natural Sciences, Macquarie University, Sydney, NSW, Australia
| | - Anthony W Waddle
- Applied Biosciences, Macquarie University, Sydney, NSW, Australia
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3
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Sauer EL, Venesky MD, McMahon TA, Cohen JM, Bessler S, Brannelly LA, Brem F, Byrne AQ, Halstead N, Hyman O, Johnson PTJ, Richards-Zawacki CL, Rumschlag SL, Sears B, Rohr JR. Are novel or locally adapted pathogens more devastating and why? Resolving opposing hypotheses. Ecol Lett 2024; 27:e14431. [PMID: 38712705 DOI: 10.1111/ele.14431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 05/08/2024]
Abstract
There is a rich literature highlighting that pathogens are generally better adapted to infect local than novel hosts, and a separate seemingly contradictory literature indicating that novel pathogens pose the greatest threat to biodiversity and public health. Here, using Batrachochytrium dendrobatidis, the fungus associated with worldwide amphibian declines, we test the hypothesis that there is enough variance in "novel" (quantified by geographic and phylogenetic distance) host-pathogen outcomes to pose substantial risk of pathogen introductions despite local adaptation being common. Our continental-scale common garden experiment and global-scale meta-analysis demonstrate that local amphibian-fungal interactions result in higher pathogen prevalence, pathogen growth, and host mortality, but novel interactions led to variable consequences with especially virulent host-pathogen combinations still occurring. Thus, while most pathogen introductions are benign, enough variance exists in novel host-pathogen outcomes that moving organisms around the planet greatly increases the chance of pathogen introductions causing profound harm.
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Affiliation(s)
- Erin L Sauer
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - Matthew D Venesky
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
- Department of Biology, Allegheny College, Meadville, Pennsylvania, USA
| | - Taegan A McMahon
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
- Biology Department, Connecticut College, New London, Connecticut, USA
| | - Jeremy M Cohen
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA
| | - Scott Bessler
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - Laura A Brannelly
- Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana, USA
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Melbourne, Victoria, Australia
| | - Forrest Brem
- Biology Department, University of Memphis, Memphis, Tennessee, USA
| | - Allison Q Byrne
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
| | - Neal Halstead
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
- Wildlands Conservation, Tampa, Florida, USA
| | - Oliver Hyman
- Biology Department, James Madison University, Harrisonburg, Virginia, USA
| | - Pieter T J Johnson
- Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA
| | - Corinne L Richards-Zawacki
- Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana, USA
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Samantha L Rumschlag
- Department of Biology, Miami University, Oxford, Ohio, USA
- U.S. Environmental Protection Agency, Office of Research and Development, Center for Computational Toxicology and Exposure, Great Lakes Toxicology and Ecology Division, Duluth, Minnesota, USA
| | - Brittany Sears
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
- Department of Biological Sciences, University of Notre Dame, South Bend, Indiana, USA
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4
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Humphries JE, Lanctôt CM, McCallum HI, Newell DA, Grogan LF. Chytridiomycosis causes high amphibian mortality prior to the completion of metamorphosis. ENVIRONMENTAL RESEARCH 2024; 247:118249. [PMID: 38244972 DOI: 10.1016/j.envres.2024.118249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2023] [Revised: 01/09/2024] [Accepted: 01/17/2024] [Indexed: 01/22/2024]
Abstract
Amphibian populations are undergoing extensive declines globally. The fungal disease chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), is a primary contributor to these declines. The amphibian metamorphic stages (Gosner stages 42-46) are particularly vulnerable to a range of stressors, including Bd. Despite this, studies that explicitly examine host response to chytridiomycosis throughout the metamorphic stages are lacking. We aimed to determine how Bd exposure during the larval stages impacts metamorphic development and infection progression in the endangered Fleay's barred frog (Mixophyes fleayi). We exposed M. fleayi to Bd during pro-metamorphosis (Gosner stages 35-38) and monitored infection dynamics throughout metamorphosis. We took weekly morphological measurements (weight, total body length, snout-vent-length and Gosner stage) and quantified Bd load using qPCR. While we observed minimal impact of Bd infection on animal growth and development, Bd load varied throughout ontogeny, with an infection load plateau during the tadpole stages (Gosner stages 35-41) and temporary infection clearance at Gosner stage 42. Bd load increased exponentially between Gosner stages 42 and 45, with most exposed animals becoming moribund at Gosner stage 45, prior to the completion of metamorphosis. There was variability in infection outcome of exposed individuals, with a subgroup of animals (n = 5/29) apparently clearing their infection while the majority (n = 21/29) became moribund with high infection burdens. This study demonstrates the role that metamorphic restructuring plays in shaping Bd infection dynamics and raises the concern that substantial Bd-associated mortality could be overlooked in the field due to the often cryptic nature of these latter metamorphic stages. We recommend future studies that directly examine the host immune response to Bd infection throughout metamorphosis, incorporating histological and molecular methods to elucidate the mechanisms responsible for the observed trends.
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Affiliation(s)
- Josephine E Humphries
- School of Environment and Science, Griffith University, Southport, Queensland 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland 4222, Australia.
| | - Chantal M Lanctôt
- School of Environment and Science, Griffith University, Southport, Queensland 4222, Australia; Australian Rivers Institute, Griffith University, Southport, Queensland 4222, Australia
| | - Hamish I McCallum
- Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland 4222, Australia
| | - David A Newell
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales 2480, Australia
| | - Laura F Grogan
- School of Environment and Science, Griffith University, Southport, Queensland 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland 4222, Australia
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5
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Chondrelli N, Kuehn E, Meurling S, Cortázar-Chinarro M, Laurila A, Höglund J. Batrachochytrium dendrobatidis strain affects transcriptomic response in liver but not skin in latitudinal populations of the common toad (Bufo bufo). Sci Rep 2024; 14:2495. [PMID: 38291226 PMCID: PMC10828426 DOI: 10.1038/s41598-024-52975-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2023] [Accepted: 01/25/2024] [Indexed: 02/01/2024] Open
Abstract
Batrachochytrium dendrobatidis (Bd) is a fungal pathogen that has decimated amphibian populations worldwide for several decades. We examined the changes in gene expression in response to Bd infection in two populations of the common toad, Bufo bufo, in a laboratory experiment. We collected B. bufo eggs in southern and northern Sweden, and infected the laboratory-raised metamorphs with two strains of the global panzoonotic lineage Bd-GPL. Differential expression analysis showed significant differences between infected and control individuals in both liver and skin. The skin samples showed no discernible differences in gene expression between the two strains used, while liver samples were differentiated by strain, with one of the strains eliciting no immune response from infected toads. Immune system genes were overexpressed in skin samples from surviving infected individuals, while in liver samples the pattern was more diffuse. Splitting samples by population revealed a stronger immune response in northern individuals. Differences in transcriptional regulation between populations are particularly relevant to study in Swedish amphibians, which may have experienced varying exposure to Bd. Earlier exposure to this pathogen and subsequent adaptation or selection pressure may contribute to the survival of some populations over others, while standing genetic diversity in different populations may also affect the infection outcome.
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Affiliation(s)
- Niki Chondrelli
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
| | - Emily Kuehn
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Sara Meurling
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Maria Cortázar-Chinarro
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
- MEMEG/Department of Biology, Faculty of Science, Lund University, Lund, Sweden
| | - Anssi Laurila
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
| | - Jacob Höglund
- Animal Ecology/Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden
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6
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Belasen AM, Peek RA, Adams AJ, Russell ID, De León ME, Adams MJ, Bettaso J, Breedveld KGH, Catenazzi A, Dillingham CP, Grear DA, Halstead BJ, Johnson PG, Kleeman PM, Koo MS, Koppl CW, Lauder JD, Padgett-Flohr G, Piovia-Scott J, Pope KL, Vredenburg V, Westphal M, Wiseman K, Kupferberg SJ. Chytrid infections exhibit historical spread and contemporary seasonality in a declining stream-breeding frog. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231270. [PMID: 38298390 PMCID: PMC10827429 DOI: 10.1098/rsos.231270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 12/18/2023] [Indexed: 02/02/2024]
Abstract
Species with extensive geographical ranges pose special challenges to assessing drivers of wildlife disease, necessitating collaborative and large-scale analyses. The imperilled foothill yellow-legged frog (Rana boylii) inhabits a wide geographical range and variable conditions in rivers of California and Oregon (USA), and is considered threatened by the pathogen Batrachochytrium dendrobatidis (Bd). To assess drivers of Bd infections over time and space, we compiled over 2000 datapoints from R. boylii museum specimens (collected 1897-2005) and field samples (2005-2021) spanning 9° of latitude. We observed a south-to-north spread of Bd detections beginning in the 1940s and increase in prevalence from the 1940s to 1970s, coinciding with extirpation from southern latitudes. We detected eight high-prevalence geographical clusters through time that span the species' geographical range. Field-sampled male R. boylii exhibited the highest prevalence, and juveniles sampled in autumn exhibited the highest loads. Bd infection risk was highest in lower elevation rain-dominated watersheds, and with cool temperatures and low stream-flow conditions at the end of the dry season. Through a holistic assessment of relationships between infection risk, geographical context and time, we identify the locations and time periods where Bd mitigation and monitoring will be critical for conservation of this imperilled species.
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Affiliation(s)
- A. M. Belasen
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, USA
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA
| | - R. A. Peek
- California Department of Fish and Wildlife, West Sacramento, CA, USA
| | - A. J. Adams
- Earth Research Institute, University of California, Santa Barbara, CA, USA
| | - I. D. Russell
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
| | - M. E. De León
- Genome Center, University of California, Davis, CA, USA
| | - M. J. Adams
- U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, USA
| | - J. Bettaso
- Six Rivers National Forest, Lower Trinity Ranger District, USDA Forest Service, P.O. Box 68, Willow Creek, CA, USA
| | | | - A. Catenazzi
- Department of Biological Sciences, Florida International University, Miami, FL, USA
| | | | - D. A. Grear
- U.S. Geological Survey, National Wildlife Health Center, Madison, WI, USA
| | - B. J. Halstead
- Point Reyes Field Station, U.S. Geological Survey, Western Ecological Research Center, Point Reyes Station, CA, USA
| | - P. G. Johnson
- Pinnacles National Park, National Park Service, Paicines, CA, USA
| | - P. M. Kleeman
- Point Reyes Field Station, U.S. Geological Survey, Western Ecological Research Center, Point Reyes Station, CA, USA
| | - M. S. Koo
- Museum of Vertebrate Zoology, University of California, Berkeley, CA
| | - C. W. Koppl
- Plumas National Forest, USDA Forest Service, Quincy, CA, USA
| | | | | | - J. Piovia-Scott
- School of Biological Sciences, Washington State University, Vancouver, WA, USA
| | - K. L. Pope
- Pacific Southwest Research Station, USDA Forest Service, Arcata, CA, USA
| | - V. Vredenburg
- Department of Biology, San Francisco State University, San Francisco, CA, USA
| | - M. Westphal
- Central Coast Field Office, United States Bureau of Land Management, Marina, CA, USA
| | - K. Wiseman
- Department of Herpetology, California Academy of Sciences, San Francisco, CA, USA
| | - S. J. Kupferberg
- Department of Integrative Biology, University of California, Berkeley, CA, USA
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7
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Hollanders M, Grogan LF, McCallum HI, Brannelly LA, Newell DA. Limited impact of chytridiomycosis on juvenile frogs in a recovered species. Oecologia 2023:10.1007/s00442-023-05406-w. [PMID: 37349661 DOI: 10.1007/s00442-023-05406-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 06/12/2023] [Indexed: 06/24/2023]
Abstract
The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has caused catastrophic frog declines on several continents, but disease outcome is mediated by a number of factors. Host life stage is an important consideration and many studies have highlighted the vulnerability of recently metamorphosed or juvenile frogs compared to adults. The majority of these studies have taken place in a laboratory setting, and there is a general paucity of longitudinal field studies investigating the influence of life stage on disease outcome. In this study, we assessed the effect of endemic Bd on juvenile Mixophyes fleayi (Fleay's barred frog) in subtropical eastern Australian rainforest. Using photographic mark-recapture, we made 386 captures of 116 individuals and investigated the effect of Bd infection intensity on the apparent mortality rates of frogs using a multievent model correcting for infection state misclassification. We found that neither Bd infection status nor infection intensity predicted mortality in juvenile frogs, counter to the expectation that early life stages are more vulnerable to disease, despite average high infection prevalence (0.35, 95% HDPI [0.14, 0.52]). Additionally, we found that observed infection prevalence and intensity were somewhat lower for juveniles than adults. Our results indicate that in this Bd-recovered species, the realized impacts of chytridiomycosis on juveniles were apparently low, likely resulting in high recruitment contributing to population stability. We highlight the importance of investigating factors relating to disease outcome in a field setting and make recommendations for future studies.
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Affiliation(s)
- Matthijs Hollanders
- Faculty of Science and Engineering, Southern Cross University, Lismore, NSW, Australia.
| | - Laura F Grogan
- Centre for Planetary Health and Food Security, and School of Environment and Science, Griffith University, Southport, QLD, Australia
| | - Hamish I McCallum
- Centre for Planetary Health and Food Security, and School of Environment and Science, Griffith University, Southport, QLD, Australia
| | - Laura A Brannelly
- Veterinary BioSciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, VIC, Australia
| | - David A Newell
- Faculty of Science and Engineering, Southern Cross University, Lismore, NSW, Australia
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8
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Adams AJ, Bushell J, Grasso RL. To treat or not to treat? Experimental pathogen exposure, treatment, and release of a threatened amphibian. Ecosphere 2022. [DOI: 10.1002/ecs2.4294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Affiliation(s)
- Andrea J. Adams
- Resources Management and Science Division Yosemite National Park El Portal California USA
- Earth Research Institute University of California Santa Barbara California USA
| | | | - Robert L. Grasso
- Resources Management and Science Division Yosemite National Park El Portal California USA
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9
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Humphries JE, Lanctôt CM, Robert J, McCallum HI, Newell DA, Grogan LF. Do immune system changes at metamorphosis predict vulnerability to chytridiomycosis? An update. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2022; 136:104510. [PMID: 35985564 DOI: 10.1016/j.dci.2022.104510] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 06/20/2022] [Accepted: 07/15/2022] [Indexed: 06/15/2023]
Abstract
Amphibians are among the vertebrate groups suffering great losses of biodiversity due to a variety of causes including diseases, such as chytridiomycosis (caused by the fungal pathogens Batrachochytrium dendrobatidis and B. salamandrivorans). The amphibian metamorphic period has been identified as being particularly vulnerable to chytridiomycosis, with dramatic physiological and immunological reorganisation likely contributing to this vulnerability. Here, we overview the processes behind these changes at metamorphosis and then perform a systematic literature review to capture the breadth of empirical research performed over the last two decades on the metamorphic immune response. We found that few studies focused specifically on the immune response during the peri-metamorphic stages of amphibian development and fewer still on the implications of their findings with respect to chytridiomycosis. We recommend future studies consider components of the immune system that are currently under-represented in the literature on amphibian metamorphosis, particularly pathogen recognition pathways. Although logistically challenging, we suggest varying the timing of exposure to Bd across metamorphosis to examine the relative importance of pathogen evasion, suppression or dysregulation of the immune system. We also suggest elucidating the underlying mechanisms of the increased susceptibility to chytridiomycosis at metamorphosis and the associated implications for population persistence. For species that overlap a distribution where Bd/Bsal are now endemic, we recommend a greater focus on management strategies that consider the important peri-metamorphic period.
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Affiliation(s)
- Josephine E Humphries
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland, 4222, Australia; Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, 2480, Australia.
| | - Chantal M Lanctôt
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Australian Rivers Institute, Griffith University, Southport, Queensland, 4222, Australia
| | - Jacques Robert
- Department of Microbiology and Immunology, University of Rochester Medical Center, 14642, Rochester, NY, United States
| | - Hamish I McCallum
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland, 4222, Australia
| | - David A Newell
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, 2480, Australia
| | - Laura F Grogan
- School of Environment and Science, Griffith University, Southport, Queensland, 4222, Australia; Centre for Planetary Health and Food Security, Griffith University, Southport, Queensland, 4222, Australia
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10
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Byrne AQ, Waddle AW, Saenz V, Ohmer M, Jaeger JR, Richards-Zawacki CL, Voyles J, Rosenblum EB. Host species is linked to pathogen genotype for the amphibian chytrid fungus (Batrachochytrium dendrobatidis). PLoS One 2022; 17:e0261047. [PMID: 35286323 PMCID: PMC8920232 DOI: 10.1371/journal.pone.0261047] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 03/01/2022] [Indexed: 11/21/2022] Open
Abstract
Host-pathogen specificity can arise from certain selective environments mediated by both the host and pathogen. Therefore, understanding the degree to which host species identity is correlated with pathogen genotype can help reveal historical host-pathogen dynamics. One animal disease of particular concern is chytridiomycosis, typically caused by the global panzootic lineage of the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd), termed Bd-GPL. This pathogen lineage has caused devastating declines in amphibian communities around the world. However, the site of origin for the common ancestor of modern Bd-GPL and the fine-scale transmission dynamics of this lineage have remained a mystery. This is especially the case in North America where Bd-GPL is widespread, but disease outbreaks occur sporadically. Herein, we use Bd genetic data collected throughout the United States from amphibian skin swabs and cultured isolate samples to investigate Bd genetic patterns. We highlight two case studies in Pennsylvania and Nevada where Bd-GPL genotypes are strongly correlated with host species identity. Specifically, in some localities bullfrogs (Rana catesbeiana) are infected with Bd-GPL lineages that are distinct from those infecting other sympatric amphibian species. Overall, we reveal a previously unknown association of Bd genotype with host species and identify the eastern United States as a Bd diversity hotspot and potential site of origin for Bd-GPL.
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Affiliation(s)
- Allison Q. Byrne
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, California, United States of America
- * E-mail:
| | - Anthony W. Waddle
- One Health Research Group, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Victoria, Australia
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
| | - Veronica Saenz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Michel Ohmer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- Department of Biology, University of Mississippi, Oxford, Mississippi, United States of America
| | - Jef R. Jaeger
- School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, Nevada, United States of America
| | - Corinne L. Richards-Zawacki
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Jamie Voyles
- Department of Biology, University of Nevada Reno, Reno, Nevada, United States of America
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, California, United States of America
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11
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Belasen AM, Russell ID, Zamudio KR, Bletz MC. Endemic Lineages of Batrachochytrium dendrobatidis Are Associated With Reduced Chytridiomycosis-Induced Mortality in Amphibians: Evidence From a Meta-Analysis of Experimental Infection Studies. Front Vet Sci 2022; 9:756686. [PMID: 35310410 PMCID: PMC8931402 DOI: 10.3389/fvets.2022.756686] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 02/08/2022] [Indexed: 01/13/2023] Open
Abstract
Emerging infectious wildlife diseases have caused devastating declines, particularly when pathogens have been introduced in naïve host populations. The outcome of disease emergence in any host population will be dictated by a series of factors including pathogen virulence, host susceptibility, and prior opportunity for coevolution between hosts and pathogens. Historical coevolution can lead to increased resistance in hosts and/or reduced virulence in endemic pathogens that allows stable persistence of host and pathogen populations. Adaptive coevolution may also occur on relatively short time scales following introduction of a novel pathogen. Here, we performed a meta-analysis of multi-strain Batrachochytrium dendrobatidis (Bd) infection experiments to test whether: (1) amphibian hosts exhibit lower mortality rates when infected with strains belonging to endemic Bd lineages relative to the Global Panzootic Lineage (Bd-GPL), hypothetically owing to long co-evolutionary histories between endemic Bd lineages and their amphibian hosts; and (2) amphibians exhibit lower mortality rates when infected with local Bd-GPL strains compared with non-local Bd-GPL strains, hypothetically owing to recent selection for tolerance or resistance to local Bd-GPL strains. We found that in a majority of cases, amphibians in endemic Bd treatments experienced reduced mortality relative to those in Bd-GPL treatments. Hosts presumed to have historically coexisted with endemic Bd did not show reduced mortality to Bd-GPL compared with hosts that have not historically coexisted with endemic Bd. Finally, we detected no overall difference in amphibian mortality between local and non-local Bd-GPL treatments. Taken together, our results suggest that long-term historical coexistence is associated with less disease-induced mortality potentially due to hypovirulence in endemic Bd lineages, and that more recent coexistence between amphibians and Bd-GPL has not yet resulted in reduced host susceptibility or pathogen virulence. This corroborates previous findings that Bd-GPL introduced via the global amphibian trade has a high capacity for causing disease-induced mortality.
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Affiliation(s)
- Anat M. Belasen
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States
- Society for Conservation Biology, Washington, DC, United States
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States
| | - Imani D. Russell
- Department of Ecology, Evolution, and Marine Biology, University of California-Santa Barbara, Santa Barbara, CA, United States
| | - Kelly R. Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States
- Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States
| | - Molly C. Bletz
- Department of Biology, University of Massachusetts-Boston, Boston, MA, United States
- *Correspondence: Molly C. Bletz
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12
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Garnham JI, Bower DS, Stockwell MP, Pickett EJ, Pollard CJ, Clulow J, Mahony MJ. Seasonal variation in the prevalence of a fungal pathogen and unexpected clearance from infection in a susceptible frog species. DISEASES OF AQUATIC ORGANISMS 2022; 148:1-11. [PMID: 35142293 DOI: 10.3354/dao03628] [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] [Indexed: 06/14/2023]
Abstract
The amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) causes the disease chytridiomycosis, which is a primary driver for amphibian population declines and extinctions worldwide. For highly susceptible species, such as the green and golden bell frog Litoria aurea, large numbers of Bd-related mortalities are thought to occur during the colder season (winter), when low temperatures favour the growth of the pathogen. However, extant L. aurea populations are persisting with Bd. We measured Bd prevalence and infection levels of wild L. aurea using capture-mark-recapture and radio-tracking methods. Using this information, we sought to determine host and environmental correlates of Bd prevalence and infection load. Mean ± SE infection load was higher in frogs sampled in autumn (431.5 ± 310.4 genomic equivalents; GE) and winter (1147.5 ± 735.8 GE), compared to spring (21.8 ± 19.3 GE) and summer (0.9 ± 0.8 GE). Furthermore, prevalence of Bd infection in L. aurea was highest in winter (43.6%; 95% CI 33.1-54.7%) and lowest in summer (11.2%; 95% CI 6.8-17.9%). Both prevalence and infection load decreased with increasing temperature. Seven frogs cleared their fungal infection during the coolest months when Bd prevalence was highest; however, these clearances were not permanent, as 5 frogs became infected again. Understanding the factors that allow amphibians to clear their Bd infections when temperatures are optimal for Bd growth presents the potential for manipulating such factors and provides an important step in future research.
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Affiliation(s)
- James I Garnham
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, New South Wales 2308, Australia
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13
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Bakewell L, Kelehear C, Graham S. Impacts of temperature on immune performance in a desert anuran (
Anaxyrus punctatus
). J Zool (1987) 2021. [DOI: 10.1111/jzo.12891] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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14
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Waddle AW, Rivera R, Rice H, Keenan EC, Rezaei G, Levy JE, Vasquez YS, Sai M, Hill J, Zmuda A, Lambreghts Y, Jaeger JR. Amphibian resistance to chytridiomycosis increases following low‐virulence chytrid fungal infection or drug‐mediated clearance. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.13974] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Anthony W. Waddle
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
- One Health Research Group Faculty of Veterinary and Agricultural Sciences University of Melbourne Werribee Vic. Australia
| | - Rebeca Rivera
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Hannah Rice
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Emma C. Keenan
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Ghazal Rezaei
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Joshua E. Levy
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Yesenia S. Vasquez
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Marlai Sai
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Jessica Hill
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Alexandra Zmuda
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
| | - Yorick Lambreghts
- School of Biological Sciences University of Tasmania Hobart TAS Australia
| | - Jef R. Jaeger
- School of Life Sciences University of Nevada, Las Vegas Las Vegas NV USA
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15
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Adams AJ, Pessier A, Cranston P, Grasso RL. Chytridiomycosis-induced mortality in a threatened anuran. PLoS One 2020; 15:e0241119. [PMID: 33156870 PMCID: PMC7647137 DOI: 10.1371/journal.pone.0241119] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 08/26/2020] [Indexed: 11/20/2022] Open
Abstract
Effectively planning conservation introductions involves assessing the
suitability of both donor and recipient populations, including the landscape of
disease risk. Chytridiomycosis, caused by the fungal pathogen
Batrachochytrium dendrobatidis (Bd), has caused extensive
amphibian declines globally and may hamper reintroduction attempts. To determine
Bd dynamics in potential source populations for conservation translocations of
the threatened California red-legged frog (Rana draytonii) to
Yosemite National Park, we conducted Bd sampling in two populations in the
foothills of the Sierra Nevada Mountains, California, U.S.A. At one of two
sites, we observed lethally high Bd loads in early post-metamorphic life stages
and confirmed one chytridiomycosis-induced mortality, the first such report for
this species. These results informed source population site selection for
subsequent R. draytonii conservation
translocations. Conservation efforts aimed at establishing new populations of
R. draytonii in a landscape where Bd is
ubiquitous can benefit from an improved understanding of risk through disease
monitoring and ex situ infection studies.
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Affiliation(s)
- Andrea J. Adams
- Yosemite National Park, El Portal, California, United States of
America
- Earth Research Institute, University of California Santa Barbara, Santa
Barbara, California, United States of America
- * E-mail:
| | - Allan Pessier
- Department of Veterinary Microbiology and Pathology, College of
Veterinary Medicine, Washington State University, Pullman, Washington, United
States of America
| | - Peggy Cranston
- Mother Lode Field Office, U.S. Bureau of Land Management, Fair Oaks,
California, United States of America
| | - Robert L. Grasso
- Yosemite National Park, El Portal, California, United States of
America
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16
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Grogan LF, Humphries JE, Robert J, Lanctôt CM, Nock CJ, Newell DA, McCallum HI. Immunological Aspects of Chytridiomycosis. J Fungi (Basel) 2020; 6:jof6040234. [PMID: 33086692 PMCID: PMC7712659 DOI: 10.3390/jof6040234] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/14/2020] [Accepted: 10/15/2020] [Indexed: 12/27/2022] Open
Abstract
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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Affiliation(s)
- Laura F. Grogan
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Southport, QLD 4222, Australia;
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia; (J.E.H.); (D.A.N.)
- Correspondence:
| | - Josephine E. Humphries
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia; (J.E.H.); (D.A.N.)
| | - Jacques Robert
- University of Rochester Medical Center, Rochester, NY 14642, USA;
| | - Chantal M. Lanctôt
- Australian Rivers Institute, Griffith University, Southport, QLD 4222, Australia;
| | - Catherine J. Nock
- Southern Cross Plant Science, Southern Cross University, Lismore, NSW 2480, Australia;
| | - David A. Newell
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia; (J.E.H.); (D.A.N.)
| | - Hamish I. McCallum
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Southport, QLD 4222, Australia;
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