1
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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2
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Berger L, Skerratt LF, Kosch TA, Brannelly LA, Webb RJ, Waddle AW. Advances in Managing Chytridiomycosis for Australian Frogs: Gradarius Firmus Victoria. Annu Rev Anim Biosci 2024; 12:113-133. [PMID: 38358840 DOI: 10.1146/annurev-animal-021122-100823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
Extensive knowledge gains from research worldwide over the 25 years since the discovery of chytridiomycosis can be used for improved management. Strategies that have saved populations in the short term and/or enabled recovery include captive breeding, translocation into disease refugia, translocation from resistant populations, disease-free exclosures, and preservation of disease refuges with connectivity to previous habitat, while antifungal treatments have reduced mortality rates in the wild. Increasing host resistance is the goal of many strategies under development, including vaccination and targeted genetic interventions. Pathogen-directed strategies may be more challenging but would have broad applicability. While the search for the silver bullet solution continues, we should value targeted local interventions that stop extinction and buy time for evolution of resistance or development of novel solutions. As for most invasive species and infectious diseases, we need to accept that ongoing management is necessary. For species continuing to decline, proactive deployment and assessment of promising interventions are more valid than a hands-off, do-no-harm approach that will likely allow further extinctions.
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Affiliation(s)
- Lee Berger
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia; , , , ,
| | - Lee F Skerratt
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia; , , , ,
| | - Tiffany A Kosch
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia; , , , ,
| | - Laura A Brannelly
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia; , , , ,
| | - Rebecca J Webb
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia; , , , ,
| | - Anthony W Waddle
- One Health Research Group, Melbourne Veterinary School, Faculty of Science, University of Melbourne, Werribee, Victoria, Australia; , , , ,
- Applied Biosciences, Macquarie University, Sydney, New South Wales, Australia;
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3
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Buttimer S, Moura-Campos D, Greenspan SE, Neely WJ, Ferrante L, Toledo LF, Becker CG. Skin microbiome disturbance linked to drought-associated amphibian disease. Ecol Lett 2024; 27:e14372. [PMID: 38288868 DOI: 10.1111/ele.14372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 01/03/2024] [Accepted: 01/08/2024] [Indexed: 02/01/2024]
Abstract
The onset of global climate change has led to abnormal rainfall patterns, disrupting associations between wildlife and their symbiotic microorganisms. We monitored a population of pumpkin toadlets and their skin bacteria in the Brazilian Atlantic Forest during a drought. Given the recognized ability of some amphibian skin bacteria to inhibit the widespread fungal pathogen Batrachochytrium dendrobatidis (Bd), we investigated links between skin microbiome health, susceptibility to Bd and host mortality during a die-off event. We found that rainfall deficit was an indirect predictor of Bd loads through microbiome disruption, while its direct effect on Bd was weak. The microbiome was characterized by fewer putative Bd-inhibitory bacteria following the drought, which points to a one-month lagged effect of drought on the microbiome that may have increased toadlet susceptibility to Bd. Our study underscores the capacity of rainfall variability to disturb complex host-microbiome interactions and alter wildlife disease dynamics.
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Affiliation(s)
- Shannon Buttimer
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
- One Health Microbiome Center, Center for Infectious Disease Dynamics, Ecology Institute, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Diego Moura-Campos
- Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
- Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | - Sasha E Greenspan
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, Alabama, USA
| | - Wesley J Neely
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, Alabama, USA
- Department of Biology, Texas State University, San Marcos, Texas, USA
| | - Lucas Ferrante
- Universidade Federal do Amazonas, Manaus, Amazonas, Brazil
| | - Luís Felipe Toledo
- Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | - C Guilherme Becker
- Department of Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
- One Health Microbiome Center, Center for Infectious Disease Dynamics, Ecology Institute, Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
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Forrest MJ, Halstead BJ, Grear DA, Kleeman PM, Todd BD, Miano OJ, Urquhart KD. KEEPING THE HEAT ON: WEIGHTED SURVEILLANCE FOR CHYTRID FUNGUS (BATRACHOCHYTRIUM DENDROBATIDIS) IN DIXIE VALLEY TOADS (ANAXYRUS [= BUFO] WILLIAMSI). J Wildl Dis 2023; 59:557-568. [PMID: 37486870 DOI: 10.7589/jwd-d-22-00049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 03/09/2023] [Indexed: 07/26/2023]
Abstract
Introduced fungal pathogens have caused declines and extinctions of naïve wildlife populations across vertebrate classes. Consequences of introduced pathogens to hosts with small ranges might be especially severe because of limited redundancy to rescue populations and lower abundance that may limit the resilience of populations to perturbations like disease introduction. As a complement to biosecurity measures to prevent the spread of pathogens, surveillance programs may enable early detection of pathogens, when management actions to limit the effects of pathogens on naïve hosts might be most beneficial. We analyzed surveillance data for the endangered and narrowly endemic Dixie Valley toad (Anaxyrus [= Bufo] williamsi) from two time periods (2011-2014 and 2019-2021) to estimate the minimum detectable prevalence of the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd). We assessed if detection efficiency could be improved by using samples from both Dixie Valley toads and co-occurring introduced American bullfrogs (Lithobates catesbeianus) and literature-derived surveillance weights. We further evaluated a weighted surveillance design to increase the efficiency of surveillance efforts for Bd within the toad's small (<6 km2) range. We found that monitoring adult and larval American bullfrogs would probably detect Bd more efficiently than monitoring Dixie Valley toads alone. Given that no Bd was detected, minimum detectable prevalence of Bd was <3% in 2011-2014, and <5% (Dixie Valley toads only) and <10% (American bullfrogs only) in 2019-2021. Optimal management for Bd depends on the mechanisms underlying its apparent absence from the range of Dixie Valley toads, but a balanced surveillance scheme that includes sampling American bullfrogs to increase the likelihood of detecting Bd, and adult Dixie Valley toads to ensure broad spatial coverage where American bullfrogs do not occur, would probably result in efficient surveillance, which might permit timely management of Bd if it is detected.
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Affiliation(s)
- Matthew J Forrest
- Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
- Co-primary authors
| | - Brian J Halstead
- US Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, USA
- Co-primary authors
| | - Daniel A Grear
- US Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711, USA
| | - Patrick M Kleeman
- US Geological Survey, Western Ecological Research Center, Point Reyes Field Station, 1 Bear Valley Road, Point Reyes Station, California 94956, USA
| | - Brian D Todd
- Department of Wildlife, Fish, and Conservation Biology, University of California-Davis, One Shields Avenue, Davis, California 95616, USA
| | - Oliver J Miano
- Department of Wildlife, Fish, and Conservation Biology, University of California-Davis, One Shields Avenue, Davis, California 95616, USA
| | - Kris D Urquhart
- Nevada Department of Wildlife, 380 West B Street, Fallon, Nevada 89406, USA
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5
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Chen G, Lau A, Wan B, Poon ESK, Fung HS, Lee WH, Sung YH, Sin SYW. OCCURRENCE OF PATHOGENIC CHYTRID FUNGI BATRACHOCHYTRIUM SALAMANDRIVORANS AND BATRACHOCHYTRIUM DENDROBATIDIS IN THE HONG KONG NEWT (PARAMESOTRITON HONGKONGENSIS) AND OTHER WILD AND IMPORTED AMPHIBIANS IN A SUBTROPICAL ASIAN REGION. J Wildl Dis 2023; 59:709-721. [PMID: 37768785 DOI: 10.7589/jwd-d-22-00145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 05/26/2023] [Indexed: 09/30/2023]
Abstract
One of the major threats for the massive loss in global amphibian diversity is chytridiomycosis, caused by chytrid fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal). Following its discovery in 2013, Bsal has emerged as a severe threat to the global survival of urodelans. In 2018, a study reported a high prevalence of Bsal (65.6%) in the Hong Kong newts (Paramesotriton hongkongensis, Near Threatened) of a southern China population adjacent to Hong Kong (HK). Uncertainty regarding the Bsal infection status of P. hongkongensis inhabiting HK raised deep concern over the risk of introducing Bsal from that population. We screened the skin swabs from wild individuals of P. hongkongensis, 15 sympatric amphibian species, and 16 imported amphibian species in HK for chytrids. We found that both Bsal and Bd occur in low prevalences in P. hongkongensis (Bsal 1.7%, 5/293; Bd 0.34%, 1/293), Hong Kong cascade frog, Amolops hongkongensis, family Ranidae (Bsal only, 5.26%, 1/19), and Asian common toad, Duttaphrynus melanostictus, family Bufonidae (Bsal only, 5.88%, 1/17), populations of HK, with infected individuals being asymptomatic, suggesting a potential role of these species as reservoirs of Bsal. Conversely, Bd, but not Bsal, was present on 13.2% (9/68) of imported amphibians, indicating a high chytrid introduction risk posed by international amphibian trade. Long-term surveillance of the presence of Bd and Bsal in wild and captive amphibians would be advisable, and we recommend that import and export of nonnative chytrid carriers should be prevented, especially to those regions with amphibian populations naïve to Bd and Bsal.
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Affiliation(s)
- Guoling Chen
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong, China
| | - Anthony Lau
- Science Unit, Lingnan University, Tuen Mun, Hong Kong, China
| | - Bowen Wan
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong, China
| | - Emily Shui Kei Poon
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong, China
| | - Hon Shing Fung
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong, China
| | - Wing Ho Lee
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong, China
| | - Yik-Hei Sung
- Science Unit, Lingnan University, Tuen Mun, Hong Kong, China
| | - Simon Yung Wa Sin
- School of Biological Sciences, The University of Hong Kong, Pok Fu Lam Road, Hong Kong, China
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6
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Erens J, Preissler K, Speybroeck J, Beukema W, Spitzen-van der Sluijs A, Stark T, Laudelout A, Kinet T, Schmidt BR, Martel A, Steinfartz S, Pasmans F. Divergent population responses following salamander mass mortalities and declines driven by the emerging pathogen Batrachochytrium salamandrivorans. Proc Biol Sci 2023; 290:20230510. [PMID: 37752840 PMCID: PMC10523083 DOI: 10.1098/rspb.2023.0510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 08/31/2023] [Indexed: 09/28/2023] Open
Abstract
Understanding wildlife responses to novel threats is vital in counteracting biodiversity loss. The emerging pathogen Batrachochytrium salamandrivorans (Bsal) causes dramatic declines in European salamander populations, and is considered an imminent threat to global amphibian biodiversity. However, real-life disease outcomes remain largely uncharacterized. We performed a multidisciplinary assessment of the longer-term impacts of Bsal on highly susceptible fire salamander (Salamandra salamandra) populations, by comparing four of the earliest known outbreak sites to uninfected sites. Based on large-scale monitoring efforts, we found population persistence in strongly reduced abundances to over a decade after Bsal invasion, but also the extinction of an initially small-sized population. In turn, we found that host responses varied, and Bsal detection remained low, within surviving populations. Demographic analyses indicated an ongoing scarcity of large reproductive adults with potential for recruitment failure, while spatial comparisons indicated a population remnant persisting within aberrant habitat. Additionally, we detected no early signs of severe genetic deterioration, yet nor of increased host resistance. Beyond offering additional context to Bsal-driven salamander declines, results highlight how the impacts of emerging hypervirulent pathogens can be unpredictable and vary across different levels of biological complexity, and how limited pathogen detectability after population declines may complicate surveillance efforts.
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Affiliation(s)
- Jesse Erens
- Wildlife Health Ghent, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | | | | | - Wouter Beukema
- Wildlife Health Ghent, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
- Reptile, Amphibian & Fish Conservation Netherlands (RAVON), Nijmegen, the Netherlands
| | - Annemarieke Spitzen-van der Sluijs
- Reptile, Amphibian & Fish Conservation Netherlands (RAVON), Nijmegen, the Netherlands
- Institute for Water and Wetland Research, Animal Ecology and Physiology, Radboud University, Nijmegen, the Netherlands
| | - Tariq Stark
- Reptile, Amphibian & Fish Conservation Netherlands (RAVON), Nijmegen, the Netherlands
| | | | | | - Benedikt R. Schmidt
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Info fauna karch, Neuchâtel, Switzerland
| | - An Martel
- Wildlife Health Ghent, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
| | | | - Frank Pasmans
- Wildlife Health Ghent, Faculty of Veterinary Medicine, Ghent University, Ghent, Belgium
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7
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Pereira KE, Bletz MC, McCartney JA, Woodhams DC, Woodley SK. Effects of exogenous elevation of corticosterone on immunity and the skin microbiome of eastern newts ( Notophthalmus viridescens). Philos Trans R Soc Lond B Biol Sci 2023; 378:20220120. [PMID: 37305906 DOI: 10.1098/rstb.2022.0120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023] Open
Abstract
The amphibian chytrid fungus, Batrachochytrium salamandrivorans (Bsal) threatens salamander biodiversity. The factors underlying Bsal susceptibility may include glucocorticoid hormones (GCs). The effects of GCs on immunity and disease susceptibility are well studied in mammals, but less is known in other groups, including salamanders. We used Notophthalmus viridescens (eastern newts) to test the hypothesis that GCs modulate salamander immunity. We first determined the dose required to elevate corticosterone (CORT; primary GC in amphibians) to physiologically relevant levels. We then measured immunity (neutrophil lymphocyte ratios, plasma bacterial killing ability (BKA), skin microbiome, splenocytes, melanomacrophage centres (MMCs)) and overall health in newts following treatment with CORT or an oil vehicle control. Treatments were repeated for a short (two treatments over 5 days) or long (18 treatments over 26 days) time period. Contrary to our predictions, most immune and health parameters were similar for CORT and oil-treated newts. Surprisingly, differences in BKA, skin microbiome and MMCs were observed between newts subjected to short- and long-term treatments, regardless of treatment type (CORT, oil vehicle). Taken together, CORT does not appear to be a major factor contributing to immunity in eastern newts, although more studies examining additional immune factors are necessary. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Affiliation(s)
- Kenzie E Pereira
- Department of Biology, Duquesne University, Pittsburgh, PA 15282, USA
| | - Molly C Bletz
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Julia A McCartney
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Douglas C Woodhams
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Sarah K Woodley
- Department of Biology, Duquesne University, Pittsburgh, PA 15282, USA
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8
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Miller AJ, Gass J, Jo MC, Bishop L, Petereit J, Woodhams DC, Voyles J. Towards the generation of gnotobiotic larvae as a tool to investigate the influence of the microbiome on the development of the amphibian immune system. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220125. [PMID: 37305911 PMCID: PMC10258664 DOI: 10.1098/rstb.2022.0125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/28/2022] [Indexed: 06/13/2023] Open
Abstract
The immune equilibrium model suggests that exposure to microbes during early life primes immune responses for pathogen exposure later in life. While recent studies using a range of gnotobiotic (germ-free) model organisms offer support for this theory, we currently lack a tractable model system for investigating the influence of the microbiome on immune system development. Here, we used an amphibian species (Xenopus laevis) to investigate the importance of the microbiome in larval development and susceptibility to infectious disease later in life. We found that experimental reductions of the microbiome during embryonic and larval stages effectively reduced microbial richness, diversity and altered community composition in tadpoles prior to metamorphosis. In addition, our antimicrobial treatments resulted in few negative effects on larval development, body condition, or survival to metamorphosis. However, contrary to our predictions, our antimicrobial treatments did not alter susceptibility to the lethal fungal pathogen Batrachochytrium dendrobatidis (Bd) in the adult life stage. While our treatments to reduce the microbiome during early development did not play a critical role in determining susceptibility to disease caused by Bd in X. laevis, they nevertheless indicate that developing a gnotobiotic amphibian model system may be highly useful for future immunological investigations. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Affiliation(s)
| | - Jordan Gass
- Department of Biology, University of Nevada, Reno, NV 89557, USA
| | - Myung Chul Jo
- Environmental Health and Safety, University of Nevada, Reno, NV 89557, USA
| | - Lucas Bishop
- Nevada Bioinformatics Center, University of Nevada, Reno, NV 89557, USA
| | - Juli Petereit
- Nevada Bioinformatics Center, University of Nevada, Reno, NV 89557, USA
| | | | - Jamie Voyles
- Department of Biology, University of Nevada, Reno, NV 89557, USA
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9
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Siomko SA, Greenspan SE, Barnett KM, Neely WJ, Chtarbanova S, Woodhams DC, McMahon TA, Becker CG. Selection of an anti-pathogen skin microbiome following prophylaxis treatment in an amphibian model system. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220126. [PMID: 37305917 DOI: 10.1098/rstb.2022.0126] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023] Open
Abstract
With emerging diseases on the rise, there is an urgent need to identify and understand novel mechanisms of prophylactic protection in vertebrate hosts. Inducing resistance against emerging pathogens through prophylaxis is an ideal management strategy that may impact pathogens and their host-associated microbiome. The host microbiome is recognized as a critical component of immunity, but the effects of prophylactic inoculation on the microbiome are unknown. In this study, we investigate the effects of prophylaxis on host microbiome composition, focusing on the selection of anti-pathogenic microbes contributing to host acquired immunity in a model host-fungal disease system, amphibian chytridiomycosis. We inoculated larval Pseudacris regilla against the fungal pathogen Batrachochytrium dendrobatidis (Bd) with a Bd metabolite-based prophylactic. Increased prophylactic concentration and exposure duration were associated with significant increases in proportions of putatively Bd-inhibitory host-associated bacterial taxa, indicating a protective prophylactic-induced shift towards microbiome members that are antagonistic to Bd. Our findings are in accordance with the adaptive microbiome hypothesis, where exposure to a pathogen alters the microbiome to better cope with subsequent pathogen encounters. Our study advances research on the temporal dynamics of microbiome memory and the role of prophylaxis-induced shifts in microbiomes contributing to prophylaxis effectiveness. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Affiliation(s)
- Samantha A Siomko
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - Sasha E Greenspan
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | - K M Barnett
- Department of Biology, Emory University, Atlanta, GA 30322, USA
| | - Wesley J Neely
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487, USA
| | | | - Douglas C Woodhams
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125, USA
| | - Taegan A McMahon
- Department of Biology, Connecticut College, New London, CT 06320, USA
| | - C Guilherme Becker
- Department of Biology, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
- Center for Infectious Disease Dynamics, One Health Microbiome Center, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA
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10
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Assis VR, Robert J, Titon SCM. Introduction to the special issue Amphibian immunity: stress, disease and ecoimmunology. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220117. [PMID: 37305915 PMCID: PMC10258669 DOI: 10.1098/rstb.2022.0117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Accepted: 05/02/2023] [Indexed: 06/13/2023] Open
Abstract
Amphibian populations have been declining worldwide, with global climate changes and infectious diseases being among the primary causes of this scenario. Infectious diseases are among the primary drivers of amphibian declines, including ranavirosis and chytridiomycosis, which have gained more attention lately. While some amphibian populations are led to extinction, others are disease-resistant. Although the host's immune system plays a major role in disease resistance, little is known about the immune mechanisms underlying amphibian disease resistance and host-pathogen interactions. As ectotherms, amphibians are directly subjected to changes in temperature and rainfall, which modulate stress-related physiology, including immunity and pathogen physiology associated with diseases. In this sense, the contexts of stress, disease and ecoimmunology are essential for a better understanding of amphibian immunity. This issue brings details about the ontogeny of the amphibian immune system, including crucial aspects of innate and adaptive immunity and how ontogeny can influence amphibian disease resistance. In addition, the papers in the issue demonstrate an integrated view of the amphibian immune system associated with the influence of stress on immune-endocrine interactions. The collective body of research presented herein can provide valuable insights into the mechanisms underlying disease outcomes in natural populations, particularly in the context of changing environmental conditions. These findings may ultimately enhance our ability to forecast effective conservation strategies for amphibian populations. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.
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Affiliation(s)
- Vania Regina Assis
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, 05508-900 São Paulo, Brazil
- College of Public Health, University of South Florida, Tampa, FL 33612-9415, USA
| | - Jacques Robert
- Department of Microbiology and Immunology, University of Rochester, Rochester, NY 14642, USA
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11
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Lundsgaard NU, Hird C, Doody KA, Franklin CE, Cramp RL. Carryover effects from environmental change in early life: An overlooked driver of the amphibian extinction crisis? Glob Chang Biol 2023; 29:3857-3868. [PMID: 37310166 DOI: 10.1111/gcb.16726] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Accepted: 03/27/2023] [Indexed: 06/14/2023]
Abstract
Ecological carryover effects, or delayed effects of the environment on an organism's phenotype, are central predictors of individual fitness and a key issue in conservation biology. Climate change imposes increasingly variable environmental conditions that may be challenging to early life-history stages in animals with complex life histories, leading to detrimental physiological and fitness effects in later life. Yet, the latent nature of carryover effects, combined with the long temporal scales over which they can manifest, means that this phenomenon remains understudied and is often overlooked in short-term studies limited to single life-history stages. Herein, we review evidence for the physiological carryover effects induced by elevated ultraviolet radiation (UVR; 280-400 nm) as a potential contributor to recent amphibian population declines. UVR exposure causes a suite of molecular, cellular and physiological consequences known to underpin carryover effects in other taxa, but there is a lack of research linking embryonic and larval UVR exposures to fitness consequences post-metamorphosis in amphibians. We propose that the key impacts of UVR on disease-related amphibian declines are facilitated through carryover effects that bridge embryonic and larval UVR exposure with potential increased disease susceptibility post-metamorphosis. We conclude by identifying a practical direction for the study of ecological carryover effects in amphibians that could guide future ecological research in the broader field of conservation physiology. Only by addressing carryover effects can many of the mechanistic links between environmental change and population declines be elucidated.
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Affiliation(s)
- Niclas U Lundsgaard
- School of Biological Sciences, The University of Queensland, St Lucia, Australia
| | - Coen Hird
- School of Biological Sciences, The University of Queensland, St Lucia, Australia
| | - Kathleen A Doody
- School of Biological Sciences, The University of Queensland, St Lucia, Australia
| | - Craig E Franklin
- School of Biological Sciences, The University of Queensland, St Lucia, Australia
| | - Rebecca L Cramp
- School of Biological Sciences, The University of Queensland, St Lucia, Australia
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12
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Barnett KM, Hilgendorff BA, Civitello DJ, McMahon TA. FUNGAL METABOLITES PROVIDE PRE-EXPOSURE PROTECTION BUT NO POSTEXPOSURE BENEFIT OR HARM AGAINST BATRACHOCHYTRIUM DENDROBATIDIS. J Wildl Dis 2023:492377. [PMID: 37074806 DOI: 10.7589/jwd-d-22-00073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2022] [Accepted: 12/16/2022] [Indexed: 04/20/2023]
Abstract
Disease control tools are needed to mitigate the effect of the fungal pathogen Batrachochytrium dendrobatidis (Bd) on amphibian biodiversity loss. In previous experiments, Bd metabolites (i.e., noninfectious chemicals released by Bd) have been shown to induce partial resistance to Bd when administered before live pathogen exposure and therefore have potential as an intervention strategy to curb Bd outbreaks. In the wild, however, amphibians inhabiting Bd-endemic ecosystems may have already been exposed to or infected with Bd before metabolite administration. It is therefore critical to evaluate the efficacy and safety of Bd metabolites applied postexposure to live Bd. We tested whether Bd metabolites administered postexposure would induce resistance, exacerbate infections, or have no effect. The results confirmed that Bd metabolites applied before pathogen exposure significantly reduced infection intensity, but Bd metabolites applied after pathogen exposure neither protected against nor exacerbated infections. These results reveal the importance of timing the application of Bd metabolite early in the transmission season for Bd-endemic ecosystems and emphasize that Bd metabolite prophylaxis may be a useful tool in captive reintroduction campaigns where Bd threatens the success of re-establishing endangered amphibian populations.
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Affiliation(s)
- K M Barnett
- Department of Biology, Emory University, 1510 Clifton Rd. NE, Atlanta, Georgia 30322, USA
| | - Bridget A Hilgendorff
- Department of Biology, Connecticut College, 270 Mohegan Ave. Pkwy., New London, Connecticut 06320, USA
| | - David J Civitello
- Department of Biology, Emory University, 1510 Clifton Rd. NE, Atlanta, Georgia 30322, USA
| | - Taegan A McMahon
- Department of Biology, Connecticut College, 270 Mohegan Ave. Pkwy., New London, Connecticut 06320, USA
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13
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Plewnia A, Lötters S, Veith M, Peters M, Böning P. Successful Drug-Mediated Host Clearance of Batrachochytrium salamandrivorans. Emerg Infect Dis 2023; 29:411-414. [PMID: 36692470 PMCID: PMC9881767 DOI: 10.3201/eid2902.221162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Skin fungi are among the most dangerous drivers of global amphibian declines, and few mitigation strategies are known. For Batrachochytrium salamandrivorans (Chytridiomycota), available treatments rely on temperature, partially combined with antifungal drugs. We report the clearance of B. salamandrivorans in 2 urodelan species using a solely drug-based approach.
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14
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Barbi A, Goessens T, Strubbe D, Deknock A, Van Leeuwenberg R, De Troyer N, Verbrugghe E, Greener M, De Baere S, Lens L, Goethals P, Martel A, Croubels S, Pasmans F. Widespread triazole pesticide use affects infection dynamics of a global amphibian pathogen. Ecol Lett 2023; 26:313-322. [PMID: 36592335 DOI: 10.1111/ele.14154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 11/08/2022] [Accepted: 11/25/2022] [Indexed: 01/03/2023]
Abstract
The sixth mass extinction is a consequence of complex interplay between multiple stressors with negative impact on biodiversity. We here examine the interaction between two globally widespread anthropogenic drivers of amphibian declines: the fungal disease chytridiomycosis and antifungal use in agriculture. Field monitoring of 26 amphibian ponds in an agricultural landscape shows widespread occurrence of triazole fungicides in the water column throughout the amphibian breeding season, together with a negative correlation between early season application of epoxiconazole and the prevalence of chytrid infections in aquatic newts. While triazole concentrations in the ponds remained below those that inhibit growth of Batrachochytrium dendrobatidis, they bioaccumulated in the newts' skin up to tenfold, resulting in cutaneous growth-suppressing concentrations. As such, a concentration of epoxiconazole, 10 times below that needed to inhibit fungal growth, prevented chytrid infection in anuran tadpoles. The widespread presence of triazoles may thus alter chytrid dynamics in agricultural landscapes.
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Affiliation(s)
- Andrea Barbi
- Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Wildlife Health Ghent, Ghent University, Merelbeke, Belgium
| | - Tess Goessens
- Laboratory of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Ghent University, Merelbeke, Belgium
| | - Diederik Strubbe
- Terrestrial Ecology Unit, Department of Biology, Ghent University, Ghent, Belgium
| | - Arne Deknock
- Aquatic Ecology Unit, Faculty of Bioscience Engineering, Department of Animal Sciences and Aquatic Ecology, Ghent University, Ghent, Belgium
| | - Robby Van Leeuwenberg
- Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Wildlife Health Ghent, Ghent University, Merelbeke, Belgium
| | - Niels De Troyer
- Aquatic Ecology Unit, Faculty of Bioscience Engineering, Department of Animal Sciences and Aquatic Ecology, Ghent University, Ghent, Belgium
| | - Elin Verbrugghe
- Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Wildlife Health Ghent, Ghent University, Merelbeke, Belgium
| | - Mark Greener
- School of Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow, UK
| | - Siegrid De Baere
- Laboratory of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Ghent University, Merelbeke, Belgium
| | - Luc Lens
- Terrestrial Ecology Unit, Department of Biology, Ghent University, Ghent, Belgium
| | - Peter Goethals
- Aquatic Ecology Unit, Faculty of Bioscience Engineering, Department of Animal Sciences and Aquatic Ecology, Ghent University, Ghent, Belgium
| | - An Martel
- Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Wildlife Health Ghent, Ghent University, Merelbeke, Belgium
| | - Siska Croubels
- Laboratory of Pharmacology and Toxicology, Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Ghent University, Merelbeke, Belgium
| | - Frank Pasmans
- Faculty of Veterinary Medicine, Department of Pathobiology, Pharmacology and Zoological Medicine, Wildlife Health Ghent, Ghent University, Merelbeke, Belgium
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15
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Hollanders M, Grogan LF, Nock CJ, McCallum HI, Newell DA. Recovered frog populations coexist with endemic Batrachochytrium dendrobatidis despite load-dependent mortality. Ecol Appl 2023. [PMID: 36054297 DOI: 10.5061/dryad.g1jwstqtb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Novel infectious diseases, particularly those caused by fungal pathogens, pose considerable risks to global biodiversity. The amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) has demonstrated the scale of the threat, having caused the greatest recorded loss of vertebrate biodiversity attributable to a pathogen. Despite catastrophic declines on several continents, many affected species have experienced population recoveries after epidemics. However, the potential ongoing threat of endemic Bd in these recovered or recovering populations is still poorly understood. We investigated the threat of endemic Bd to frog populations that recovered after initial precipitous declines, focusing on the endangered rainforest frog Mixophyes fleayi. We conducted extensive field surveys over 4 years at three independent sites in eastern Australia. First, we compared Bd infection prevalence and infection intensities within frog communities to reveal species-specific infection patterns. Then, we analyzed mark-recapture data of M. fleayi to estimate the impact of Bd infection intensity on apparent mortality rates and Bd infection dynamics. We found that M. fleayi had lower infection intensities than sympatric frogs across the three sites, and cleared infections at higher rates than they gained infections throughout the study period. By incorporating time-varying individual infection intensities, we show that healthy M. fleayi populations persist despite increased apparent mortality associated with infrequent high Bd loads. Infection dynamics were influenced by environmental conditions, with Bd prevalence, infection intensity, and rates of gaining infection associated with lower temperatures and increased rainfall. However, mortality remained constant year-round despite these fluctuations in Bd infections, suggesting major mortality events did not occur over the study period. Together, our results demonstrate that while Bd is still a potential threat to recovered populations of M. fleayi, high rates of clearing infections and generally low average infection loads likely minimize mortality caused by Bd. Our results are consistent with pathogen resistance contributing to the coexistence of M. fleayi with endemic Bd. We emphasize the importance of incorporating infection intensity into disease models rather than infection status alone. Similar population and infection dynamics likely exist within other recovered amphibian-Bd systems around the globe, promising longer-term persistence in the face of endemic chytridiomycosis.
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Affiliation(s)
- Matthijs Hollanders
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia
| | - Laura F Grogan
- Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Gold Coast, Queensland, Australia
| | - Catherine J Nock
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia
| | - Hamish I McCallum
- Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Gold Coast, Queensland, Australia
| | - David A Newell
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia
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16
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Hollanders M, Grogan LF, Nock CJ, McCallum HI, Newell DA. Recovered frog populations coexist with endemic Batrachochytrium dendrobatidis despite load-dependent mortality. Ecol Appl 2023. [PMID: 36054297 DOI: 10.5281/zenodo.6981761] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Novel infectious diseases, particularly those caused by fungal pathogens, pose considerable risks to global biodiversity. The amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) has demonstrated the scale of the threat, having caused the greatest recorded loss of vertebrate biodiversity attributable to a pathogen. Despite catastrophic declines on several continents, many affected species have experienced population recoveries after epidemics. However, the potential ongoing threat of endemic Bd in these recovered or recovering populations is still poorly understood. We investigated the threat of endemic Bd to frog populations that recovered after initial precipitous declines, focusing on the endangered rainforest frog Mixophyes fleayi. We conducted extensive field surveys over 4 years at three independent sites in eastern Australia. First, we compared Bd infection prevalence and infection intensities within frog communities to reveal species-specific infection patterns. Then, we analyzed mark-recapture data of M. fleayi to estimate the impact of Bd infection intensity on apparent mortality rates and Bd infection dynamics. We found that M. fleayi had lower infection intensities than sympatric frogs across the three sites, and cleared infections at higher rates than they gained infections throughout the study period. By incorporating time-varying individual infection intensities, we show that healthy M. fleayi populations persist despite increased apparent mortality associated with infrequent high Bd loads. Infection dynamics were influenced by environmental conditions, with Bd prevalence, infection intensity, and rates of gaining infection associated with lower temperatures and increased rainfall. However, mortality remained constant year-round despite these fluctuations in Bd infections, suggesting major mortality events did not occur over the study period. Together, our results demonstrate that while Bd is still a potential threat to recovered populations of M. fleayi, high rates of clearing infections and generally low average infection loads likely minimize mortality caused by Bd. Our results are consistent with pathogen resistance contributing to the coexistence of M. fleayi with endemic Bd. We emphasize the importance of incorporating infection intensity into disease models rather than infection status alone. Similar population and infection dynamics likely exist within other recovered amphibian-Bd systems around the globe, promising longer-term persistence in the face of endemic chytridiomycosis.
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Affiliation(s)
- Matthijs Hollanders
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia
| | - Laura F Grogan
- Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Gold Coast, Queensland, Australia
| | - Catherine J Nock
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia
| | - Hamish I McCallum
- Centre for Planetary Health and Food Security, School of Environment and Science, Griffith University, Gold Coast, Queensland, Australia
| | - David A Newell
- Faculty of Science and Engineering, Southern Cross University, Lismore, New South Wales, Australia
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17
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Hollanders M, Grogan LF, Nock CJ, McCallum HI, Newell DA. Recovered frog populations coexist with endemic Batrachochytrium dendrobatidis despite load-dependent mortality. Ecol Appl 2023; 33:e2724. [PMID: 36054297 PMCID: PMC10078584 DOI: 10.1002/eap.2724] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 05/15/2022] [Accepted: 06/22/2022] [Indexed: 05/15/2023]
Abstract
Novel infectious diseases, particularly those caused by fungal pathogens, pose considerable risks to global biodiversity. The amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) has demonstrated the scale of the threat, having caused the greatest recorded loss of vertebrate biodiversity attributable to a pathogen. Despite catastrophic declines on several continents, many affected species have experienced population recoveries after epidemics. However, the potential ongoing threat of endemic Bd in these recovered or recovering populations is still poorly understood. We investigated the threat of endemic Bd to frog populations that recovered after initial precipitous declines, focusing on the endangered rainforest frog Mixophyes fleayi. We conducted extensive field surveys over 4 years at three independent sites in eastern Australia. First, we compared Bd infection prevalence and infection intensities within frog communities to reveal species-specific infection patterns. Then, we analyzed mark-recapture data of M. fleayi to estimate the impact of Bd infection intensity on apparent mortality rates and Bd infection dynamics. We found that M. fleayi had lower infection intensities than sympatric frogs across the three sites, and cleared infections at higher rates than they gained infections throughout the study period. By incorporating time-varying individual infection intensities, we show that healthy M. fleayi populations persist despite increased apparent mortality associated with infrequent high Bd loads. Infection dynamics were influenced by environmental conditions, with Bd prevalence, infection intensity, and rates of gaining infection associated with lower temperatures and increased rainfall. However, mortality remained constant year-round despite these fluctuations in Bd infections, suggesting major mortality events did not occur over the study period. Together, our results demonstrate that while Bd is still a potential threat to recovered populations of M. fleayi, high rates of clearing infections and generally low average infection loads likely minimize mortality caused by Bd. Our results are consistent with pathogen resistance contributing to the coexistence of M. fleayi with endemic Bd. We emphasize the importance of incorporating infection intensity into disease models rather than infection status alone. Similar population and infection dynamics likely exist within other recovered amphibian-Bd systems around the globe, promising longer-term persistence in the face of endemic chytridiomycosis.
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Affiliation(s)
- Matthijs Hollanders
- Faculty of Science and EngineeringSouthern Cross UniversityLismoreNew South WalesAustralia
| | - Laura F. Grogan
- Centre for Planetary Health and Food Security, School of Environment and ScienceGriffith UniversityGold CoastQueenslandAustralia
| | - Catherine J. Nock
- Faculty of Science and EngineeringSouthern Cross UniversityLismoreNew South WalesAustralia
| | - Hamish I. McCallum
- Centre for Planetary Health and Food Security, School of Environment and ScienceGriffith UniversityGold CoastQueenslandAustralia
| | - David A. Newell
- Faculty of Science and EngineeringSouthern Cross UniversityLismoreNew South WalesAustralia
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18
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Wilber MQ, Knapp RA, Smith TC, Briggs CJ. Host density has limited effects on pathogen invasion, disease-induced declines and within-host infection dynamics across a landscape of disease. J Anim Ecol 2022; 91:2451-2464. [PMID: 36285540 DOI: 10.1111/1365-2656.13823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 09/20/2022] [Indexed: 12/14/2022]
Abstract
1. Host density is hypothesized to be a major driver of variability in the responses and outcomes of wildlife populations following pathogen invasion. While the effects of host density on pathogen transmission have been extensively studied, these studies are dominated by theoretical analyses and small-scale experiments. This focus leads to an incomplete picture regarding how host density drives observed variability in disease outcomes in the field. 2. Here, we leveraged a dataset of hundreds of replicate amphibian populations that varied by orders of magnitude in host density. We used these data to test the effects of host density on three outcomes following the arrival of the amphibian-killing fungal pathogen Batrachochytrium dendrobatidis (Bd): the probability that Bd successfully invaded a host population and led to a pathogen outbreak, the magnitude of the host population-level decline following an outbreak and within-host infection dynamics that drive population-level outcomes in amphibian-pathogen systems. 3. Based on previous small-scale transmission experiments, we expected that populations with higher densities would be more likely to experience Bd outbreaks and would suffer larger proportional declines following outbreaks. To test these predictions, we developed and fitted a Hidden Markov Model that accounted for imperfectly observed disease outbreak states in the amphibian populations we surveyed. 4. Contrary to our predictions, we found minimal effects of host density on the probability of successful Bd invasion, the magnitude of population decline following Bd invasion and the dynamics of within-host infection intensity. Environmental conditions, such as summer temperature, winter severity and the presence of pathogen reservoirs, were more predictive of variability in disease outcomes. 5. Our results highlight the limitations of extrapolating findings from small-scale transmission experiments to observed disease trajectories in the field and provide strong evidence that variability in host density does not necessarily drive variability in host population responses following pathogen arrival. In an applied context, we show that feedbacks between host density and disease will not necessarily affect the success of reintroduction efforts in amphibian-Bd systems of conservation concern.
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Affiliation(s)
- Mark Q Wilber
- Department of Forestry, Wildlife, and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Roland A Knapp
- Earth Research Institute, University of California, Santa Barbara, California, USA.,Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, USA
| | - Thomas C Smith
- Earth Research Institute, University of California, Santa Barbara, California, USA.,Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
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19
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Castro Monzon F, Rödel MO, Ruland F, Parra-Olea G, Jeschke JM. Batrachochytrium salamandrivorans' Amphibian Host Species and Invasion Range. Ecohealth 2022; 19:475-486. [PMID: 36611108 PMCID: PMC9898388 DOI: 10.1007/s10393-022-01620-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 08/31/2022] [Indexed: 06/17/2023]
Abstract
Batrachochytrium salamandrivorans (Bsal), a species related to the destructive pathogen Batrachochytrium dendrobatidis (Bd), was found and identified in Europe in 2013. Now, a decade later, a large amount of information is available. This includes data from studies in the field, reports of infection in captive amphibians, laboratory studies testing host susceptibility, and data from prospective studies that test for Bsal's presence in a location. We conducted a systematic review of the published literature and compiled a dataset of Bsal tests. We identified 67 species that have been reported positive for Bsal, 20 of which have a threatened conservation status. The distribution of species that have been found with infection encompasses 69 countries, highlighting the potential threat that Bsal poses. We point out where surveillance to detect Bsal have taken place and highlight areas that have not been well monitored. The large number of host species belonging to the families Plethodontidae and Salamandridae suggests a taxonomic pattern of susceptibility. Our results provide insight into the risk posed by Bsal and identifies vulnerable species and areas where surveillance is needed to fill existing knowledge gaps.
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Affiliation(s)
- Federico Castro Monzon
- Institute of Biology, Freie Universität Berlin, Königin-Luise-Str. 1-3, 14195, Berlin, Germany.
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587, Berlin, Germany.
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, Altensteinstr. 34, 14195, Berlin, Germany.
- Department of Zoology, Institute of Biology, Universidad Nacional Autonoma de Mexico, AP 70-153, 04510, Mexico City, Mexico.
| | - Mark-Oliver Rödel
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, Altensteinstr. 34, 14195, Berlin, Germany
- Museum für Naturkunde-Leibniz Institute for Evolution and Biodiversity Science, Invalidenstr. 43, 10115, Berlin, Germany
| | - Florian Ruland
- Institute of Biology, Freie Universität Berlin, Königin-Luise-Str. 1-3, 14195, Berlin, Germany
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587, Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, Altensteinstr. 34, 14195, Berlin, Germany
| | - Gabriela Parra-Olea
- Department of Zoology, Institute of Biology, Universidad Nacional Autonoma de Mexico, AP 70-153, 04510, Mexico City, Mexico
| | - Jonathan M Jeschke
- Institute of Biology, Freie Universität Berlin, Königin-Luise-Str. 1-3, 14195, Berlin, Germany
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Müggelseedamm 310, 12587, Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, Altensteinstr. 34, 14195, Berlin, Germany
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20
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Venesky MD, DeMarchi J, Hickerson C, Anthony CD. Does the thermal mismatch hypothesis predict disease outcomes in different morphs of a terrestrial salamander? J Exp Zool A Ecol Integr Physiol 2022; 337:467-476. [PMID: 35167180 DOI: 10.1002/jez.2581] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 12/23/2021] [Accepted: 01/19/2022] [Indexed: 06/14/2023]
Abstract
Many aspects of ectotherm physiology are temperature-dependent. The immune system of temperate-dwelling ectothermic host species is no exception and their immune function is often downregulated in cold temperatures. Likewise, species of ectothermic pathogens experience temperature-mediated effects on rates of transmission and/or virulence. Although seemingly straightforward, predicting the outcomes of ectothermic host-pathogen interactions is quite challenging. A recent hypothesis termed the thermal mismatch hypothesis posits that cool-adapted host species should be most susceptible to pathogen infection during warm temperature periods whereas warm-adapted host species should be most susceptible to pathogens during periods of cool temperatures. We explore this hypothesis using two ecologically and physiologically differentiated color morphs of the Eastern Red-backed Salamander (Plethodon cinereus) and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis; hereafter "Bd") using a fully factorial laboratory experiment. At cool temperatures, unstriped salamanders (i.e., those that are tolerant of warm temperatures) had a significantly higher probability of Bd infection compared with cool-tolerant striped salamanders, consistent with the thermal mismatch hypothesis. However, we found no support for this hypothesis when salamanders were exposed to Bd at warm temperatures: the probability of Bd infection in the cool-tolerant striped salamanders was nearly identical in both cool and warm temperatures, opposite the predictions of the thermal mismatch hypothesis. Our results are most consistent with the fact that Bd grows poorly at warm temperatures. Alternatively, our data could indicate that the two color morphs do not differ in their tolerance to warm temperatures but that striped salamanders are more tolerant to cool temperatures than unstriped salamanders.
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Affiliation(s)
- Matthew D Venesky
- Department of Biology, Allegheny College, Meadville, Pennsylvania, USA
| | - Joseph DeMarchi
- Department of Biology, John Carroll University, University Heights, Ohio, USA
| | - Cari Hickerson
- Department of Biology, John Carroll University, University Heights, Ohio, USA
| | - Carl D Anthony
- Department of Biology, John Carroll University, University Heights, Ohio, USA
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21
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McCarthy K, Shinn O, Luna-Reyes R, Mendelson III JR. A redescription of the poorly known Central American toad Inciliustacanensis (Anura, Bufonidae), with a summary of its biology and conservation status. Zookeys 2022; 1102:149-161. [PMID: 36761155 PMCID: PMC9848913 DOI: 10.3897/zookeys.1102.79229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Accepted: 04/18/2022] [Indexed: 11/12/2022] Open
Abstract
Based on examination of most of the existing museum specimens of the rare bufonid frog Inciliustacanensis, we present a redescription and new diagnosis for this species. The species is limited to small region of the Pacific chain of volcanoes in southeastern Chiapas, Mexico, and adjacent areas of Guatemala. The species has not been observed in the wild since 1984 and may have been reduced or eliminated by regional epidemics of chytridiomycosis.
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Affiliation(s)
- Kathryn McCarthy
- School of Biological Sciences, Georgia Institute of Technology, 950 Atlantic Dr NW, Atlanta, Georgia, 30332, USAGeorgia Institute of TechnologyAtlantaUnited States of America
| | - Ollie Shinn
- School of Biological Sciences, Georgia Institute of Technology, 950 Atlantic Dr NW, Atlanta, Georgia, 30332, USAGeorgia Institute of TechnologyAtlantaUnited States of America
| | - Roberto Luna-Reyes
- Dirección de Áreas Naturales y Vida Silvestre, Secretaría de Medio Ambiente e Historia Natural, Calzada de las Personas Ilustres s/n, Colonia Centro, Tuxtla Gutiérrez, 29000, Chiapas, MexicoSecretaría de Medio Ambiente e Historia NaturalTuxtla GutiérrezMexico
| | - Joseph R. Mendelson III
- School of Biological Sciences, Georgia Institute of Technology, 950 Atlantic Dr NW, Atlanta, Georgia, 30332, USAGeorgia Institute of TechnologyAtlantaUnited States of America,Zoo Atlanta, 800 Cherokee Ave SE, Atlanta, Georgia, 30315, USASecretaría de Medio Ambiente e Historia NaturalAtlantaUnited States of America
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22
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Hardy BM, Muths E, Koons DN. Context-dependent variation in persistence of host populations in the face of disease. J Anim Ecol 2022; 91:282-286. [PMID: 35112351 DOI: 10.1111/1365-2656.13654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 12/07/2021] [Indexed: 11/28/2022]
Abstract
Research Highlight: Valenzuela-Sánchez, A., Azat, C., Cunningham, A. A., Delgado, S., Bacigalupe, L. D., Beltrand, J., Serrano, J. M., Sentenac, H., Haddow, N., Toledo, V., Schmidt, B. R., & Cayuela, H. (2022). Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen. Journal of Animal Ecology, 00, 1- 12. https://doi.org/10.1111/1365-2656.13603. Understanding the nuances of population persistence in the face of a stressor can help predict extinction risk and guide conservation actions. However, the exact mechanisms driving population stability may not always be known. In this paper, Valenzuela-Sánchez et al. (2022) integrate long-term mark-recapture data, focal measurements of reproductive effort, a population matrix model and inferences on life-history variation to reveal differences in demographic response to disease in a susceptible frog species (Rhinoderma darwinii). Valenzuela-Sánchez et al. found that demographic compensation via recruitment explained the positive population growth rate in their high disease prevalence population whereas the low disease prevalence population did not compensate and thus had decreasing population growth. Compensatory recruitment was likely due to the high probability of males brooding, and the high number of brooded larvae in the high prevalence population compared to low prevalence and disease-free populations. Valenzuela-Sánchez et al. also document faster generation times in the high prevalence population, which may indicate a faster life history that may be contributing to the population's ability to compensate for reduced survival. Lastly, the authors find a positive relationship between disease prevalence and the proportion of juveniles in a given population that suggest that there may be a threshold for disease prevalence that triggers increased reproductive effort. Altogether, their study provides novel support for increased reproductive effort as the pathway for compensatory recruitment leading to increasing population growth despite strong negative effects of disease on adult survival. Their results also caution the overgeneralization of the effects of stressors (e.g. disease) on population dynamics, where context-dependent responses may differ among host populations of a given species.
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Affiliation(s)
- Bennett M Hardy
- Department of Fish, Wildlife and Conservation Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
| | - Erin Muths
- U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA
| | - David N Koons
- Department of Fish, Wildlife and Conservation Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
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23
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Li Z, Wang Q, Sun K, Feng J. Prevalence of Batrachochytrium dendrobatidis in Amphibians From 2000 to 2021: A Global Systematic Review and Meta-Analysis. Front Vet Sci 2022; 8:791237. [PMID: 34977222 PMCID: PMC8718539 DOI: 10.3389/fvets.2021.791237] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Accepted: 11/26/2021] [Indexed: 11/16/2022] Open
Abstract
Chytridiomycosis is an amphibian fungal disease caused by Batrachochytrium dendrobatidis (Bd), which has caused large-scale death and population declines on several continents around the world. To determine the current status of Bd infection in amphibians, we conducted a global meta-analysis. Using PubMed, ScienceDirect, SpringerLink, China National Knowledge Infrastructure (CNKI) and Wanfang database searches, we retrieved a total of 111 articles from 2000 to 2021. Based on these, we estimated the Bd prevalence to be 18.54% (95% CI: 13.76–20.52) in current extent amphibians. Among these populations, the prevalence of Bd in Asia was the lowest at 7.88% (95% CI: 1.92–8.71). Further, no Bd infection was found in Vietnam. However, the prevalence of Bd in Oceania was the highest at 36.34% (95% CI: 11.31–46.52). The Bd prevalence in Venezuela was as high as 49.77% (95% CI: 45.92–53.62). After 2009, the global Bd prevalence decreased to 18.91% (95% CI: 13.23–21.56). The prevalence of Bd in epizootic populations was significantly higher than enzootic populations. The highest prevalence of Bd was detected with real-time PCR at 20.11% (95% CI: 13.12–21.38). The prevalence of Bd in frogs was the highest at 20.04% (95% CI: 13.52–21.71), and this different host was statistically significant (P < 0.05). At the same time, we analyzed the geographic factors (longitude, latitude, elevation, rainfall and temperature) that impacted the fungal prevalence in amphibians. Our meta-analysis revealed that factors including region, disease dynamic, detection method, host and climate may be sources of the observed heterogeneity. These results indicate that chytridiomycosis was a consistent threat to amphibians from 2000 to 2021. Based on different habitat types and geographical conditions, we recommend formulating corresponding control plans and adopting reasonable and efficient biological or chemical methods to reduce the severity of such diseases.
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Affiliation(s)
- Zhongle Li
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China.,College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
| | - Qi Wang
- College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
| | - Keping Sun
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China.,Key Laboratory of Vegetation Ecology, Ministry of Education, Changchun, China
| | - Jiang Feng
- Jilin Provincial Key Laboratory of Animal Resource Conservation and Utilization, Northeast Normal University, Changchun, China.,College of Animal Science and Technology, Jilin Agricultural University, Changchun, China
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24
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Cowgill M, Zink AG, Sparagon W, Yap TA, Sulaeman H, Koo MS, Vredenburg VT. Social Behavior, Community Composition, Pathogen Strain, and Host Symbionts Influence Fungal Disease Dynamics in Salamanders. Front Vet Sci 2021; 8:742288. [PMID: 34938792 PMCID: PMC8687744 DOI: 10.3389/fvets.2021.742288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 10/06/2021] [Indexed: 11/29/2022] Open
Abstract
The emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), which can cause a fatal disease called chytridiomycosis, is implicated in the collapse of hundreds of host amphibian species. We describe chytridiomycosis dynamics in two co-occurring terrestrial salamander species, the Santa Lucia Mountains slender salamander, Batrachoseps luciae, and the arboreal salamander, Aneides lugubris. We (1) conduct a retrospective Bd-infection survey of specimens collected over the last century, (2) estimate present-day Bd infections in wild populations, (3) use generalized linear models (GLM) to identify biotic and abiotic correlates of infection risk, (4) investigate susceptibility of hosts exposed to Bd in laboratory trials, and (5) examine the ability of host skin bacteria to inhibit Bd in culture. Our historical survey of 2,866 specimens revealed that for most of the early 20th century (~1920–1969), Bd was not detected in either species. By the 1990s the proportion of infected specimens was 29 and 17% (B. luciae and A. lugubris, respectively), and in the 2010s it was 10 and 17%. This was similar to the number of infected samples from contemporary populations (2014–2015) at 10 and 18%. We found that both hosts experience signs of chytridiomycosis and suffered high Bd-caused mortality (88 and 71% for B. luciae and A. lugubris, respectively). Our GLM revealed that Bd-infection probability was positively correlated with intraspecific group size and proximity to heterospecifics but not to abiotic factors such as precipitation, minimum temperature, maximum temperature, mean temperature, and elevation, or to the size of the hosts. Finally, we found that both host species contain symbiotic skin-bacteria that inhibit growth of Bd in laboratory trials. Our results provide new evidence consistent with other studies showing a relatively recent Bd invasion of amphibian host populations in western North America and suggest that the spread of the pathogen may be enabled both through conspecific and heterospecific host interactions. Our results suggest that wildlife disease studies should assess host-pathogen dynamics that consider the interactions and effects of multiple hosts, as well as the historical context of pathogen invasion, establishment, and epizootic to enzootic transitions to better understand and predict disease dynamics.
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Affiliation(s)
- Mae Cowgill
- Department of Biology, San Francisco State University, San Francisco, CA, United States
| | - Andrew G Zink
- Department of Biology, San Francisco State University, San Francisco, CA, United States
| | - Wesley Sparagon
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, Department of Oceanography and Sea Grant College Program, UUniversity of Hawai'i at Mānoa, HI, United States
| | - Tiffany A Yap
- Center for Biological Diversity, Oakland, CA, United States
| | - Hasan Sulaeman
- Department of Biology, San Francisco State University, San Francisco, CA, United States
| | - Michelle S Koo
- Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States
| | - Vance T Vredenburg
- Department of Biology, San Francisco State University, San Francisco, CA, United States.,Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States
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25
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Buttimer S, Hernández-Gómez O, Rosenblum EB. Skin bacterial metacommunities of San Francisco Bay Area salamanders are structured by host genus and habitat quality. FEMS Microbiol Ecol 2021; 97:6464136. [PMID: 34918086 DOI: 10.1093/femsec/fiab162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 12/14/2021] [Indexed: 11/13/2022] Open
Abstract
Host-associated microbial communities can influence physiological processes of macroorganisms, including contributing to infectious disease resistance. For instance, some bacteria that live on amphibian skin produce antifungal compounds that inhibit two lethal fungal pathogens, Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal). Therefore, differences in microbiome composition among host species or populations within a species can contribute to variation in susceptibility to Bd/Bsal. This study applies 16S rRNA sequencing to characterize the skin bacterial microbiomes of three widespread terrestrial salamander genera native to the western United States. Using a metacommunity structure analysis, we identified dispersal barriers for these influential bacteria between salamander families and localities. We also analyzed the effects of habitat characteristics such as percent natural cover and temperature seasonality on the microbiome. We found that certain environmental variables may influence the skin microbial communities of some salamander genera more strongly than others. Each salamander family had a somewhat distinct community of putative anti-Bd skin bacteria, suggesting that salamanders may select for a functional assembly of cutaneous symbionts that could differ in its ability to protect these amphibians from disease. Our observations raise the need to consider host identity and environmental heterogeneity during the selection of probiotics to treat wildlife diseases.
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Affiliation(s)
- Shannon Buttimer
- Department of Environmental Science, Policy, and Management - The University of California, Berkeley, Berkeley, CA, U.S.A.,Department of Biological Sciences - The University of Alabama, Tuscaloosa, AL, U.S.A
| | - Obed Hernández-Gómez
- Department of Environmental Science, Policy, and Management - The University of California, Berkeley, Berkeley, CA, U.S.A.,School of Health and Natural Sciences - Dominican University of California, San Rafael, CA, U.S.A
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management - The University of California, Berkeley, Berkeley, CA, U.S.A
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26
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Koo MS, Vredenburg VT, Deck JB, Olson DH, Ronnenberg KL, Wake DB. Tracking, Synthesizing, and Sharing Global Batrachochytrium Data at AmphibianDisease.org. Front Vet Sci 2021; 8:728232. [PMID: 34692807 PMCID: PMC8527349 DOI: 10.3389/fvets.2021.728232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 09/02/2021] [Indexed: 11/13/2022] Open
Abstract
Emerging infectious diseases have been especially devastating to amphibians, the most endangered class of vertebrates. For amphibians, the greatest disease threat is chytridiomycosis, caused by one of two chytridiomycete fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). Research over the last two decades has shown that susceptibility to this disease varies greatly with respect to a suite of host and pathogen factors such as phylogeny, geography (including abiotic factors), host community composition, and historical exposure to pathogens; yet, despite a growing body of research, a comprehensive understanding of global chytridiomycosis incidence remains elusive. In a large collaborative effort, Bd-Maps was launched in 2007 to increase multidisciplinary investigations and understanding using compiled global Bd occurrence data (Bsal was not discovered until 2013). As its database functions aged and became unsustainable, we sought to address critical needs utilizing new technologies to meet the challenges of aggregating data to facilitate research on both Bd and Bsal. Here, we introduce an advanced central online repository to archive, aggregate, and share Bd and Bsal data collected from around the world. The Amphibian Disease Portal (https://amphibiandisease.org) addresses several critical community needs while also helping to build basic biological knowledge of chytridiomycosis. This portal could be useful for other amphibian diseases and could also be replicated for uses with other wildlife diseases. We show how the Amphibian Disease Portal provides: (1) a new repository for the legacy Bd-Maps data; (2) a repository for sample-level data to archive datasets and host published data with permanent DOIs; (3) a flexible framework to adapt to advances in field, laboratory, and informatics technologies; and (4) a global aggregation of Bd and Bsal infection data to enable and accelerate research and conservation. The new framework for this project is built using biodiversity informatics best practices and metadata standards to ensure scientific reproducibility and linkages across other biological and biodiversity repositories.
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Affiliation(s)
- Michelle S Koo
- Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States
| | - Vance T Vredenburg
- Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States.,Department of Biology, San Francisco State University, San Francisco, CA, United States
| | - John B Deck
- Berkeley Natural History Museums, University of California, Berkeley, Berkeley, CA, United States
| | - Deanna H Olson
- US Department of Agriculture, Forest Service, Pacific Northwest Research Station, Corvallis, OR, United States
| | - Kathryn L Ronnenberg
- US Department of Agriculture, Forest Service, Pacific Northwest Research Station, Corvallis, OR, United States
| | - David B Wake
- Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States
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27
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Valenzuela-Sánchez A, Azat C, Cunningham AA, Delgado S, Bacigalupe LD, Beltrand J, Serrano JM, Sentenac H, Haddow N, Toledo V, Schmidt BR, Cayuela H. Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen. J Anim Ecol 2021; 91:308-319. [PMID: 34704260 DOI: 10.1111/1365-2656.13603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 10/04/2021] [Indexed: 11/28/2022]
Abstract
Compensatory recruitment is a key demographic mechanism that has allowed the coexistence of populations of susceptible amphibians with Batrachochytrium dendrobatidis (Bd), a fungus causing one of the most devastating emerging infectious disease ever recorded among vertebrates. However, the underlying processes (e.g. density-dependent increase in survival at early life stages, change in reproductive traits) as well as the level of interpopulation variation in this response are poorly known. We explore potential mechanisms of compensatory recruitment in response to Bd infection by taking advantage of an amphibian system where male reproductive traits are easy to quantify in free-living populations. The Southern Darwin's frog Rhinoderma darwinii is a vocal sac-brooding species that exhibits a high susceptibility to lethal Bd infection. Using a 7-year capture-recapture study at four populations with contrasting Bd infection status (one high prevalence, one low prevalence and two Bd-free populations), we evaluated whether Bd-positive populations exhibited a higher adult recruitment and a higher male reproductive effort than Bd-negative populations. We also estimated population growth rates to explore whether recruitment compensated for the negative impacts of Bd on the survival of adults. In addition, we evaluated a potential demographic signal of compensatory recruitment (i.e. positive relationship between the proportion of juveniles and Bd prevalence) in response to Bd infection using raw count data from 13 R. darwinii populations. The high Bd prevalence population exhibited the highest male reproductive effort and the highest recruitment among the four monitored populations. This led to a growing population during the study period despite high mortality of adult hosts. In contrast, males from the population with low Bd prevalence had a low reproductive effort and this population, which had the lowest adult recruitment, was declining during the study period despite adults having a higher survival in comparison to the high Bd prevalence population. We also found a demographic signal of compensatory recruitment in response to Bd infection in our broader analysis of 13 R. darwinii populations. Our study underlines the importance of interpopulation variation in life-history strategies on the fate of host populations after infectious disease emergence. Our results also suggest that an increase in reproductive effort can be one of the processes underlying compensatory recruitment in populations of Bd-susceptible amphibians.
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Affiliation(s)
- Andrés Valenzuela-Sánchez
- ONG Ranita de Darwin, Valdivia, Chile.,Instituto de Conservación, Biodiversidad y Territorio, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile, Valdivia, Chile.,Sustainability Research Centre & PhD in Conservation Medicine, Life Sciences Faculty, Universidad Andres Bello, Santiago, Chile
| | - Claudio Azat
- Sustainability Research Centre & PhD in Conservation Medicine, Life Sciences Faculty, Universidad Andres Bello, Santiago, Chile
| | | | | | - Leonardo D Bacigalupe
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | | | - José M Serrano
- ONG Ranita de Darwin, Valdivia, Chile.,Museo de Zoología 'Alfonso L. Herrera', Departamento Biología Evolutiva, Facultad de Ciencias, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Hugo Sentenac
- Institute of Zoology, Zoological Society of London, London, UK.,Royal Veterinary College, University of London, London, UK
| | - Natashja Haddow
- Sustainability Research Centre & PhD in Conservation Medicine, Life Sciences Faculty, Universidad Andres Bello, Santiago, Chile.,Institute of Zoology, Zoological Society of London, London, UK.,Royal Veterinary College, University of London, London, UK
| | | | - Benedikt R Schmidt
- Info fauna karch, Neuchâtel, Switzerland.,Institut für Evolutionsbiologie und Umweltwissenschaften, Universität Zürich, Zürich, Switzerland
| | - Hugo Cayuela
- Department of Ecology and Evolution, Biophore, University of Lausanne, Lausanne, Switzerland
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28
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Bosch J, Martel A, Sopniewski J, Thumsová B, Ayres C, Scheele BC, Velo-Antón G, Pasmans F. Batrachochytrium salamandrivorans Threat to the Iberian Urodele Hotspot. J Fungi (Basel) 2021; 7:jof7080644. [PMID: 34436183 PMCID: PMC8400424 DOI: 10.3390/jof7080644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/02/2021] [Accepted: 08/05/2021] [Indexed: 12/17/2022] Open
Abstract
The recent introduction of the chytrid fungus Batrachochytrium salamandrivorans into northeastern Spain threatens salamander diversity on the Iberian Peninsula. We assessed the current epidemiological situation with extensive field sampling of urodele populations. We then sought to delineate priority regions and identify conservation units for the Iberian Peninsula by estimating the susceptibility of Iberian urodeles using laboratory experiments, evidence from mortality events in nature and captivity and inference from phylogeny. None of the 1395 field samples, collected between 2015 and 2021 were positive for Bsal and no Bsal-associated mortality events were recorded, in contrast to the confirmed occurrence of Bsal outbreak previously described in 2018. We classified five of eleven Iberian urodele species as highly susceptible, predicting elevated mortality and population declines following potential Bsal emergence in the wild, five species as intermediately susceptible with variable disease outcomes and one species as resistant to disease and mortality. We identified the six conservation units (i.e., species or lineages within species) at highest risk and propose priority areas for active disease surveillance and field biosecurity measures. The magnitude of the disease threat identified here emphasizes the need for region-tailored disease abatement plans that couple active disease surveillance to rapid and drastic actions.
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Affiliation(s)
- Jaime Bosch
- Biodiversity Research Institute (IMIB), University of Oviedo-Principality of Asturias-CSIC, 33600 Mieres, Spain;
- Museo Nacional de Ciencias Naturales-CSIC, 28006 Madrid, Spain
- Correspondence: ; Tel.: +34-6-777-724-02
| | - An Martel
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Poultry Diseases, Ghent University, B9820 Merelbeke, Belgium; (A.M.); (F.P.)
| | - Jarrod Sopniewski
- Fenner School of Environment and Society, Australian National University, Canberra 2601, Australia; (J.S.); (B.C.S.)
| | - Barbora Thumsová
- Biodiversity Research Institute (IMIB), University of Oviedo-Principality of Asturias-CSIC, 33600 Mieres, Spain;
- Museo Nacional de Ciencias Naturales-CSIC, 28006 Madrid, Spain
- Asociación Herpetologica Española, 28006 Madrid, Spain;
| | - Cesar Ayres
- Asociación Herpetologica Española, 28006 Madrid, Spain;
| | - Ben C. Scheele
- Fenner School of Environment and Society, Australian National University, Canberra 2601, Australia; (J.S.); (B.C.S.)
| | - Guillermo Velo-Antón
- CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, 4485-661 Vairão, Portugal;
- Grupo GEA, Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36310 Vigo, Spain
| | - Frank Pasmans
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Poultry Diseases, Ghent University, B9820 Merelbeke, Belgium; (A.M.); (F.P.)
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29
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Siddons SR, Searle CL. Exposure to a fungal pathogen increases the critical thermal minimum of two frog species. Ecol Evol 2021; 11:9589-9598. [PMID: 34306645 PMCID: PMC8293773 DOI: 10.1002/ece3.7779] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 05/14/2021] [Accepted: 05/19/2021] [Indexed: 11/12/2022] Open
Abstract
The ability of an organism to tolerate seasonal temperature changes, such as extremely cold temperatures during the winter, can be influenced by their pathogens. We tested how exposure to a virulent fungal pathogen, Batrachochytrium dendrobatidis (Bd), affected the critical thermal minimum (CTmin) of two frog species, Hyla versicolor (gray treefrog) and Lithobates palustris (pickerel frog). The CTmin is the minimum thermal performance point of an organism, which we estimated via righting response trials. For both frog species, we compared the righting response of Bd-exposed and Bd-unexposed individuals in either a constant (15ºC) environment or with decreasing temperatures (-1°C/2.5 min) starting from 15°C. The CTmin for both species was higher for Bd-exposed frogs than unexposed frogs, and the CTmin of H. versicolor was higher than L. palustris. We also found that Bd-exposed frogs of both species righted themselves significantly fewer times in both decreasing and constant temperature trials. Our findings show that pathogen exposure can reduce cold tolerance and limit the thermal performance range of hosts, which may lead to increased overwintering mortality.
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30
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Sheets CN, Schmidt DR, Hurtado PJ, Byrne AQ, Rosenblum EB, Richards-Zawacki CL, Voyles J. Thermal Performance Curves of Multiple Isolates of Batrachochytrium dendrobatidis, a Lethal Pathogen of Amphibians. Front Vet Sci 2021; 8:687084. [PMID: 34239916 PMCID: PMC8258153 DOI: 10.3389/fvets.2021.687084] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 05/20/2021] [Indexed: 11/13/2022] Open
Abstract
Emerging infectious disease is a key factor in the loss of amphibian diversity. In particular, the disease chytridiomycosis has caused severe declines around the world. The lethal fungal pathogen that causes chytridiomycosis, Batrachochytrium dendrobatidis (Bd), has affected amphibians in many different environments. One primary question for researchers grappling with disease-induced losses of amphibian biodiversity is what abiotic factors drive Bd pathogenicity in different environments. To study environmental influences on Bd pathogenicity, we quantified responses of Bd phenotypic traits (e.g., viability, zoospore densities, growth rates, and carrying capacities) over a range of environmental temperatures to generate thermal performance curves. We selected multiple Bd isolates that belong to a single genetic lineage but that were collected across a latitudinal gradient. For the population viability, we found that the isolates had similar thermal optima at 21°C, but there was considerable variation among the isolates in maximum viability at that temperature. Additionally, we found the densities of infectious zoospores varied among isolates across all temperatures. Our results suggest that temperatures across geographic point of origin (latitude) may explain some of the variation in Bd viability through vertical shifts in maximal performance. However, the same pattern was not evident for other reproductive parameters (zoospore densities, growth rates, fecundity), underscoring the importance of measuring multiple traits to understand variation in pathogen responses to environmental conditions. We suggest that variation among Bd genetic variants due to environmental factors may be an important determinant of disease dynamics for amphibians across a range of diverse environments.
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Affiliation(s)
- Ciara N Sheets
- Department of Biology, University of Nevada, Reno, NV, United States
| | - Deena R Schmidt
- Department of Mathematics and Statistics, University of Nevada, Reno, NV, United States
| | - Paul J Hurtado
- Department of Mathematics and Statistics, University of Nevada, Reno, NV, United States
| | - Allison Q Byrne
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, United States.,Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, CA, United States.,Museum of Vertebrate Zoology, University of California, Berkeley, Berkeley, CA, United States
| | | | - Jamie Voyles
- Department of Biology, University of Nevada, Reno, NV, United States
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31
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Siddons SR, Bray MC, Searle CL. HIGHER INFECTION PREVALENCE IN AMPHIBIANS INHABITING HUMAN-MADE COMPARED TO NATURAL WETLANDS. J Wildl Dis 2020; 56:823-36. [PMID: 33600598 DOI: 10.7589/2019-09-220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 02/21/2020] [Indexed: 11/20/2022]
Abstract
It is unclear how suitable human-made wetlands are for supporting wildlife and how they impact wildlife disease risk. Natural wetlands (those that were created without human actions) can support more diverse and resilient communities that are at lower risk of disease outbreaks. We compared frog community composition and infection with the pathogenic fungus Batrachochytrium dendrobatidis (Bd) between human-made and natural wetlands in Tippecanoe County, Indiana, US. We conducted visual encounter surveys of frog communities and quantified Bd infection prevalence at four natural and five human-made wetlands. Water parameters associated with human practices (e.g., pH, salinity) and surrounding land use were also compared across sites. We found higher Bd infection prevalence at human-made sites than at natural sites, with monthly differences showing highest infection in spring and fall, and decreasing infection with increasing water temperature. However, we found no differences between human-made and natural sites regarding amphibian community composition, water quality, or surrounding land use. Further, we found frog density increased with distance to nearest roads among both human-made and natural sites. These findings might suggest that human-made wetlands can support frog communities similar to natural wetlands, but pose a greater risk of Bd infection.
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Medina D, Greenspan SE, Carvalho T, Becker CG, Toledo LF. Co-infecting pathogen lineages have additive effects on host bacterial communities. FEMS Microbiol Ecol 2021; 97:6134751. [PMID: 33580951 DOI: 10.1093/femsec/fiab030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 02/11/2021] [Indexed: 01/08/2023] Open
Abstract
Amphibian skin bacteria may confer protection against the fungus Batrachochytrium dendrobatidis (Bd), but responses of skin bacteria to different Bd lineages are poorly understood. The global panzootic lineage (Bd-GPL) has caused amphibian declines and extinctions globally. However, other lineages are enzootic (Bd-Asia-2/Brazil). Increased contact rates between Bd-GPL and enzootic lineages via globalization pose unknown consequences for host-microbiome-pathogen dynamics. We conducted a laboratory experiment and used 16S rRNA amplicon-sequencing to assess: (i) whether two lineages (Bd-Asia-2/Brazil and Bd-GPL) and their recombinant, in single and mixed infections, differentially affect amphibian skin bacteria; (ii) and the changes associated with the transition to laboratory conditions. We determined no clear differences in bacterial diversity among Bd treatments, despite differences in infection intensity. However, we observed an additive effect of mixed infections on bacterial alpha diversity and a potentially antagonistic interaction between Bd genotypes. Additionally, observed changes in community composition suggest a higher ability of Bd-GPL to alter skin bacteria. Lastly, we observed a drastic reduction in bacterial diversity and a change in community structure in laboratory conditions. We provide evidence for complex interactions between Bd genotypes and amphibian skin bacteria during coinfections, and expand on the implications of experimental conditions in ecological studies.
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Affiliation(s)
- Daniel Medina
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Instituto de Biologia, Universidade Estadual de Campinas, R. Monteiro Lobato, 255 - CEP 13083-862, Campinas, São Paulo, Brazil.,Sistema Nacional de Investigación, SENACYT, Building 205, City of Knowledge, Clayton, Panama, Republic of Panama
| | - Sasha E Greenspan
- Department of Biological Sciences, The University of Alabama, 1339 Science and Engineering Complex, Tuscaloosa 35487, Alabama, USA
| | - Tamilie Carvalho
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Instituto de Biologia, Universidade Estadual de Campinas, R. Monteiro Lobato, 255 - CEP 13083-862, Campinas, São Paulo, Brazil
| | - C Guilherme Becker
- Department of Biological Sciences, The University of Alabama, 1339 Science and Engineering Complex, Tuscaloosa 35487, Alabama, USA
| | - Luís Felipe Toledo
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Instituto de Biologia, Universidade Estadual de Campinas, R. Monteiro Lobato, 255 - CEP 13083-862, Campinas, São Paulo, Brazil
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Lastra González D, Baláž V, Vojar J, Chajma P. Dual Detection of the Chytrid Fungi Batrachochytrium spp. with an Enhanced Environmental DNA Approach. J Fungi (Basel) 2021; 7:258. [PMID: 33808405 DOI: 10.3390/jof7040258] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 03/23/2021] [Accepted: 03/26/2021] [Indexed: 01/24/2023] Open
Abstract
Environmental DNA (eDNA) is becoming an indispensable tool in biodiversity monitoring, including the monitoring of invasive species and pathogens. Aquatic chytrid fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal) are major threats to amphibians. However, the use of eDNA for detecting these pathogens has not yet become widespread, due to technological and economic obstacles. Using the enhanced eDNA approach (a simple and cheap sampling protocol) and the universally accepted qPCR assay, we confirmed the presence of Bsal and Bd in previously identified sites in Spain, including four sites that were new for Bsal. The new approach was successfully tested in laboratory conditions using manufactured gene fragments (gBlocks) of the targeted DNA sequence. A comparison of storage methods showed that samples kept in ethanol had the best DNA yield. Our results showed that the number of DNA copies in the Internal Transcribed Spacer region was 120 copies per Bsal cell. Eradication of emerging diseases requires quick and cost-effective solutions. We therefore performed cost-efficiency analyses of standard animal swabbing, a previous eDNA approach, and our own approach. The procedure presented here was evaluated as the most cost-efficient. Our findings will help to disseminate information about efforts to prevent the spread of chytrid fungi.
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Azat C. Not just a pathogen: The importance of recognizing genetic variability to mitigate a wildlife pandemic. Mol Ecol Resour 2021; 21:1410-1412. [PMID: 33559328 DOI: 10.1111/1755-0998.13348] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/02/2021] [Indexed: 11/29/2022]
Abstract
Emerging infectious diseases (EIDs) are increasingly recognized as a threat to both biodiversity and human health (Scheele et al., 2019; Wells et al., 2020). But pathogens cannot been seen as unique entities; their intraspecific genetic variability represented in variants, strains, antigenic types or genetic lineages may cause different impacts at the population level (Nelson and Holmes, 2007; Greenspan et al., 2018). The global spread of pathogens has been largely facilitated by globalization of transport, which particularly intensified during the last century (O'Hanlon et al., 2018). As seen with SARS-CoV-2, air travel can rapidly spread a pathogen globally (Wells et al., 2020). Furthermore, after initial introduction subsequent translocations of a pathogen may cause the contact of different variants facilitating the rise of novel genotypes that may have higher pathogenicity or transmissibility (Nelson and Holmes, 2007; Greenspan et al., 2018). Chytridiomycosis is an EID caused by the fungus Batrachochytrium dendrobatidis (Bd), that infects amphibian skin causing population declines to extinction in susceptible species. Now a wildlife pandemic, Bd has been recognized as the single pathogen causing the greatest loss of biodiversity on Earth (Scheele et al., 2019). Recent advances in genetics have made novel tools for pathogen detection and characterization more accessible and reliable (Boyle et al., 2004; Byrne et al., 2019). In this issue of Molecular Ecology Resources, Ghosh et al. (2021) report the development of a new genotyping qPCR assay targeting mitochondrial DNA (mtDNA) of Bd, and based on noninvasive swab samples (Figure 1), discriminate between the two most globally widespread and pathogenic genetic lineages of Bd. Having a better understanding of how the genetic diversity of a pathogen is distributed is crucial to understand their spread patterns and develop timely mitigation strategies.
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Affiliation(s)
- Claudio Azat
- Sustainability Research Centre & PhD in Conservation Medicine Program, Life Sciences Faculty, Universidad Andres Bello, Santiago, Chile
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35
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Jervis P, Pintanel P, Hopkins K, Wierzbicki C, Shelton JMG, Skelly E, Rosa GM, Almeida-Reinoso D, Eugenia-Ordoñez M, Ron S, Harrison X, Merino-Viteri A, Fisher MC. Post-epizootic microbiome associations across communities of neotropical amphibians. Mol Ecol 2021; 30:1322-1335. [PMID: 33411382 DOI: 10.1111/mec.15789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 12/31/2022]
Abstract
Microbiome-pathogen interactions are increasingly recognized as an important element of host immunity. While these host-level interactions will have consequences for community disease dynamics, the factors which influence host microbiomes at larger scales are poorly understood. We here describe landscape-scale pathogen-microbiome associations within the context of post-epizootic amphibian chytridiomycosis, a disease caused by the panzootic chytrid fungus Batrachochytrium dendrobatidis. We undertook a survey of Neotropical amphibians across altitudinal gradients in Ecuador ~30 years following the observed amphibian declines and collected skin swab-samples which were metabarcoded using both fungal (ITS-2) and bacterial (r16S) amplicons. The data revealed marked variation in patterns of both B. dendrobatidis infection and microbiome structure that are associated with host life history. Stream breeding amphibians were most likely to be infected with B. dendrobatidis. This increased probability of infection was further associated with increased abundance and diversity of non-Batrachochytrium chytrid fungi in the skin and environmental microbiome. We also show that increased alpha diversity and the relative abundance of fungi are lower in the skin microbiome of adult stream amphibians compared to adult pond-breeding amphibians, an association not seen for bacteria. Finally, stream tadpoles exhibit lower proportions of predicted protective microbial taxa than pond tadpoles, suggesting reduced biotic resistance. Our analyses show that host breeding ecology strongly shapes pathogen-microbiome associations at a landscape scale, a trait that may influence resilience in the face of emerging infectious diseases.
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Affiliation(s)
- Phillip Jervis
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College, London, UK.,Institute of Zoology, Zoological Society of London, London, UK.,Department of Chemistry, UCL, London, UK.,Laboratorio de Ecofisiología and Museo de Zoología (QCAZ), Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Quito, Ecuador
| | - Pol Pintanel
- Laboratorio de Ecofisiología and Museo de Zoología (QCAZ), Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Quito, Ecuador.,Department of Evolutionary Ecology, Estación Biológica de Doñana, CSIC, Sevilla, Spain
| | - Kevin Hopkins
- Institute of Zoology, Zoological Society of London, London, UK
| | - Claudia Wierzbicki
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College, London, UK.,Institute of Zoology, Zoological Society of London, London, UK
| | - Jennifer M G Shelton
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College, London, UK
| | - Emily Skelly
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College, London, UK.,Institute of Zoology, Zoological Society of London, London, UK
| | - Gonçalo M Rosa
- Institute of Zoology, Zoological Society of London, London, UK.,Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências da Universidade de Lisboa, Lisboa, Portugal
| | - Diego Almeida-Reinoso
- Museo de Zoologίa (QCAZ), Escuela de Ciencias Biológicas, Pontificia Universidad Catόlica del Ecuador, Quito, Ecuador.,SARgrillo: Ex situ Management Program of Endangered Amphibians and Insect Breeding program, Quito, Ecuador
| | - Maria Eugenia-Ordoñez
- Fungario QCAM, Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Quito, Ecuador
| | - Santiago Ron
- Museo de Zoologίa (QCAZ), Escuela de Ciencias Biológicas, Pontificia Universidad Catόlica del Ecuador, Quito, Ecuador
| | - Xavier Harrison
- Centre for Ecology and Conservation, University of Exeter, Penryn, UK
| | - Andrés Merino-Viteri
- Laboratorio de Ecofisiología and Museo de Zoología (QCAZ), Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador, Quito, Ecuador
| | - Matthew C Fisher
- MRC Centre for Global Infectious Disease Analysis, School of Public Health, Imperial College, London, UK
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Abstract
AbstractAnimals challenged with disease may select specific habitat conditions that help prevent or reduce infection. Whereas preinfection avoidance of habitats with a high risk of disease exposure has been documented in both captive and free-ranging animals, evidence of switching habitats after infection to support the clearing of the infection is limited to laboratory experiments. The extent to which wild animals proximately modify habitat choices in response to infection status thus remains unclear. We investigated preinfection behavioral avoidance and postinfection habitat switching using wild, radio-tracked boreal toads (Anaxyrus boreas boreas) in a population challenged with Batrachochytrium dendrobatidis (Bd), a pathogenic fungus responsible for a catastrophic panzootic affecting hundreds of amphibian species worldwide. Boreal toads did not preemptively avoid microhabitats with conditions conducive to Bd growth. Infected individuals, however, selected warmer, more open habitats, which were associated with elevated body temperature and the subsequent clearing of infection. Our results suggest that disease can comprise an important selective pressure on animal habitat and space use. Habitat selection models, therefore, may be greatly improved by including variables that quantify infection risk and/or the infection status of individuals through time.
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Friday B, Holzheuser C, Lips KR, Longo AV. Preparing for invasion: Assessing risk of infection by chytrid fungi in southeastern plethodontid salamanders. J Exp Zool A Ecol Integr Physiol 2020; 333:829-840. [PMID: 33174393 DOI: 10.1002/jez.2427] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 09/30/2020] [Accepted: 10/23/2020] [Indexed: 12/31/2022]
Abstract
Understanding the responses of naïve communities to the invasion of multihost pathogens requires accurate estimates of susceptibility across taxa. In the Americas, the likely emergence of a second amphibian pathogenic fungus (Batrachochytrium salamandrivorans, Bsal) calls for new ways of prioritizing disease mitigation among species due to the high diversity of naïve hosts with prior B. dendrobatidis (Bd) infections. Here, we applied the concept of pathogenic potential to quantify the virulence of chytrid fungi on naïve amphibians and evaluate species for conservation efforts in the event of an outbreak. The benefit of this measure is that it combines and summarizes the variation in disease effects into a single numerical index, allowing for comparisons across species, populations or groups of individuals that may inherently exhibit differences in susceptibility. As a proof of concept, we obtained standardized responses of disease severity by performing experimental infections with Bsal on five plethodontid salamanders from southeastern United States. Four out of five species carried natural infections of Bd at the start of the experiments. We showed that Bsal exhibited its highest value of pathogenic potential in a species that is already declining (Desmognathus auriculatus). We find that this index provides additional information beyond the standard measures of disease prevalence, intensity, and mortality, because it leveraged these disease parameters within each categorical group. Scientists and practitioners could use this measure to justify research, funding, trade, or conservation measures.
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Affiliation(s)
- Brenna Friday
- Department of Biology, University of Maryland, College Park, Maryland, USA.,Department of Biological Sciences, Wayne State University, Detroit, Michigan, USA
| | - Chace Holzheuser
- Department of Biology, University of Maryland, College Park, Maryland, USA.,Department of Biological Science, Florida State University, Tallahassee, Florida, USA
| | - Karen R Lips
- Department of Biology, University of Maryland, College Park, Maryland, USA
| | - Ana V Longo
- Department of Biology, University of Florida, Gainesville, Florida, USA
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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: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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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Rodriguez KM, Voyles J. The amphibian complement system and chytridiomycosis. J Exp Zool A Ecol Integr Physiol 2020; 333:706-719. [PMID: 33052039 PMCID: PMC7821119 DOI: 10.1002/jez.2419] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 08/26/2020] [Accepted: 09/24/2020] [Indexed: 12/26/2022]
Abstract
Understanding host immune function and ecoimmunology is increasingly important at a time when emerging infectious diseases (EIDs) threaten wildlife. One EID that has emerged and spread widely in recent years is chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), which is implicated unprecedented amphibian declines around the world. The impacts of Bd have been severe for many amphibian species, but some populations have exhibited signs of persistence, and even recovery, in some regions. Many mechanisms may underpin this pattern and amphibian immune responses are likely one key component. Although we have made great strides in understanding amphibian immunity, the complement system remains poorly understood. The complement system is a nonspecific, innate immune defense that is known to enhance other immune responses. Complement activation can occur by three different biochemical pathways and result in protective mechanisms, such as inflammation, opsonization, and pathogen lysis, thereby providing protection to the host. We currently lack an understanding of complement pathway activation for chytridiomycosis, but several studies have suggested that it may be a key part of an early and robust immune response that confers host resistance. Here, we review the available research on the complement system in general as well as amphibian complement responses to Bd infection. Additionally, we propose future research directions that will increase our understanding of the amphibian complement system and other immune responses to Bd. Finally, we suggest how a deeper understanding of amphibian immunity could enhance the conservation and management of amphibian species that are threatened by chytridiomycosis.
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Affiliation(s)
| | - Jamie Voyles
- Department of Biology, University of Nevada-Reno, Reno, Nevada, USA
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40
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Beukema W, Pasmans F, Van Praet S, Ferri-Yáñez F, Kelly M, Laking AE, Erens J, Speybroeck J, Verheyen K, Lens L, Martel A. Microclimate limits thermal behaviour favourable to disease control in a nocturnal amphibian. Ecol Lett 2020; 24:27-37. [PMID: 33022129 DOI: 10.1111/ele.13616] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 07/15/2020] [Accepted: 09/07/2020] [Indexed: 11/28/2022]
Abstract
While epizootics increasingly affect wildlife, it remains poorly understood how the environment shapes most host-pathogen systems. Here, we employ a three-step framework to study microclimate influence on ectotherm host thermal behaviour, focusing on amphibian chytridiomycosis in fire salamanders (Salamandra salamandra) infected with the fungal pathogen Batrachochytrium salamandrivorans (Bsal). Laboratory trials reveal that innate variation in thermal preference, rather than behavioural fever, can inhibit infection and facilitate salamander recovery under humidity-saturated conditions. Yet, a 3-year field study and a mesocosm experiment close to the invasive Bsal range show that microclimate constraints suppress host thermal behaviour favourable to disease control. A final mechanistic model, that estimates range-wide, year-round host body temperature relative to microclimate, suggests that these constraints are rule rather than exception. Our results demonstrate how innate host defences against epizootics may remain constrained in the wild, which predisposes to range-wide disease outbreaks and population declines.
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Affiliation(s)
- Wouter Beukema
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
| | - Frank Pasmans
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
| | - Sarah Van Praet
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
| | - Francisco Ferri-Yáñez
- Department of Community Ecology, Helmholtz Centre for Environmental Research (UFZ), Theodor-Lieser-Strasse 4, Halle, 06120, Germany
| | - Moira Kelly
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
| | - Alexandra E Laking
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
| | - Jesse Erens
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
| | - Jeroen Speybroeck
- Research Institute for Nature and Forest - INBO, Havenlaan 88 bus 73, Brussels, 1000, Belgium
| | - Kris Verheyen
- Forest & Nature Lab, Department of Forest and Water Management, Ghent University, Geraardsbergsesteenweg 267, Gontrode, 9090, Belgium
| | - Luc Lens
- Terrestrial Ecology Unit, Ghent University, K. L, Ledeganckstraat 35, Ghent, 9000, Belgium
| | - An Martel
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Ghent University, Salisburylaan 133, Merelbeke, 9820, Belgium
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Bell SC, Heard GW, Berger L, Skerratt LF. Connectivity over a disease risk gradient enables recovery of rainforest frogs. Ecol Appl 2020; 30:e02152. [PMID: 32343856 DOI: 10.1002/eap.2152] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 02/14/2020] [Accepted: 03/30/2020] [Indexed: 06/11/2023]
Abstract
Chytridiomycosis has been a key driver of global frog declines and extinctions, particularly for high-altitude populations across Australia and the Americas. While recent evidence shows some species are recovering, the extent of such recoveries and the mechanisms underpinning them remain poorly resolved. We surveyed the historical latitudinal and elevational range of four Australian rainforest frogs that disappeared from upland sites between 1989 and 1994 to establish their contemporary distribution and elevational limits, and investigate factors affecting population recovery. Five rainforest streams were surveyed from mountain-base to summit (30 sites in total), with swabs collected from the target species (Litoria dayi, L. nannotis, L. rheocola, and L. serrata) to determine their infection status, and data loggers deployed to measure microclimatic variation across the elevational gradient. Infection probability increased with elevation and canopy cover as it was tightly and inversely correlated with stream-side air temperature. Occupancy patterns suggest varying responses to this disease threat gradient. Two species, L. rheocola and L. serrata, were found over their full historical elevational range (≥1,000 m above sea level [asl]), while L. dayi was not detected above 400 m (formerly known up to 900 m asl) and L. nannotis was not detected above 800 m (formerly known up to 1,200 m asl). Site occupancy probability was negatively related to predicted infection prevalence for L. dayi, L. nannotis, and L. rheocola, but not L. serrata, which appears to now tolerate high fungal burdens. This study highlights the importance of environmental refuges and connectivity across disease risk gradients for the persistence and natural recovery of frogs susceptible to chytridiomycosis. Likewise, in documenting both interspecific variation in recovery rates and intraspecific differences between sites, this study suggests interactions between disease threats and host selection exist that could be manipulated. For example, translocations may be warranted where connectivity is poor or the increase in disease risk is too steep to allow recolonization, combined with assisted selection or use of founders from populations that have already undergone natural selection.
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Affiliation(s)
- Sara C Bell
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Townsville, Queensland, 4811, Australia
- One Health Research Group, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, 3030, Australia
| | - Geoffrey W Heard
- Institute of Land, Water and Society, Charles Sturt University, Albury, New South Wales, 2640, Australia
- Victorian Department of Environment, Land, Water and Planning, Arthur Rylah Institute for Environmental Research, Heidelberg, Victoria, 3084, Australia
| | - Lee Berger
- One Health Research Group, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, 3030, Australia
| | - Lee F Skerratt
- One Health Research Group, Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, 3030, Australia
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Burrowes PA, James TY, Jenkinson TS, De la Riva I. Genetic analysis of post-epizootic amphibian chytrid strains in Bolivia: Adding a piece to the puzzle. Transbound Emerg Dis 2020; 67:2163-2171. [PMID: 32277592 DOI: 10.1111/tbed.13568] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 02/11/2020] [Accepted: 03/14/2020] [Indexed: 12/26/2022]
Abstract
The evolutionary history and dispersal pattern of Batrachochytrium dendrobatidis (Bd), an emergent fungal pathogen responsible for the decline and extinctions of many species of amphibians worldwide, is still not well understood. In South America, the tropical Andes are known as an important site for amphibian diversification, but also for being a place where hosts are at greater risk of chytridiomycosis. In an attempt to understand the history and the geographic pattern of Bd-associated amphibian declines in Bolivia, we isolated Bd from hosts at two locations that differ in their chronology of Bd prevalence and host survival outcome, the cloud forests of the Amazonian slopes of the Andes and Lake Titicaca in the altiplano. We genotyped Bd from both locations and sequenced the genome from the cloud forest isolate and then compared them to reference sequences of other Bd strains across the world. We found that the Bolivian chytrid isolates were nearly genotypically identical and that they belong to the global panzootic lineage (Bd-GPL). The Bolivian Bd strain grouped with other tropical New World strains but was closest to those from the Brazilian Atlantic Forest. Our results extend the presence of Bd-GPL to the central Andes in South America and report this hypervirulent strain at Lago Titicaca, where Bd has been detected since 1863, without evidence of amphibian declines. These findings suggest a more complex evolutionary history for this pathogen in Bolivia and may point to the existence of an old lineage of Bd that has since been extirpated following the arrival of the panzootic Bd-GPL or that the timing of Bd-GPL emergence is earlier than generally acknowledged.
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Affiliation(s)
| | - Timothy Y James
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Thomas S Jenkinson
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
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Morison SA, Cramp RL, Alton LA, Franklin CE. Cooler temperatures slow the repair of DNA damage in tadpoles exposed to ultraviolet radiation: Implications for amphibian declines at high altitude. Glob Chang Biol 2020; 26:1225-1234. [PMID: 31518484 DOI: 10.1111/gcb.14837] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 08/16/2019] [Indexed: 05/25/2023]
Abstract
Ultraviolet B radiation (UVBR) damages the DNA of exposed cells, causing dimers to form between adjacent pyrimidine nucleotides. These dimers block DNA replication, causing mutations and apoptosis. Most organisms utilize biochemical or biophysical DNA repair strategies to restore DNA structure; however, as with most biological reactions, these processes are likely to be thermally sensitive. Tadpoles exposed to elevated UVBR at low environmental temperatures have significantly higher rates of mortality and developmental deformities compared with tadpoles exposed to the same levels of UVBR at higher environmental temperatures. We hypothesized that low environmental temperatures impair the primary enzymatic (photolyase) DNA repair pathway in amphibians, leading to the accumulation of DNA damage. To test this hypothesis, we compared DNA repair rates and photolyase gene expression patterns in Limnodynastes peronii. Tadpoles were acutely exposed to UVBR for 1 hr at either 20 or 30°C, and we measured DNA damage and photolyase expression levels at intervals following this exposure. Temperature had a significant effect on the rate of DNA repair, with repair at 30°C occurring twice as fast as repair at 20°C. Photolyase gene expression (6-4 PP and CPD) was significantly upregulated by UVBR exposure, with expression levels increasing within 6 hr of UVBR exposure. CPD expression levels were not significantly affected by temperature, but 6-4 PP expression was significantly higher in tadpoles in the 30°C treatment within 12 hr of UVBR exposure. These data support the hypothesis that DNA repair rates are thermally sensitive in tadpoles and may explain why enigmatic amphibian declines are higher in montane regions where UVBR levels are naturally elevated and environmental temperatures are lower.
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Affiliation(s)
- Samuel A Morison
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Rebecca L Cramp
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia
| | - Lesley A Alton
- School of Biological Sciences, Monash University, Melbourne, VIC, Australia
| | - Craig E Franklin
- School of Biological Sciences, The University of Queensland, Brisbane, QLD, Australia
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44
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Sauer EL, Cohen JM, Lajeunesse MJ, McMahon TA, Civitello DJ, Knutie SA, Nguyen K, Roznik EA, Sears BF, Bessler S, Delius BK, Halstead N, Ortega N, Venesky MD, Young S, Rohr JR. A meta-analysis reveals temperature, dose, life stage, and taxonomy influence host susceptibility to a fungal parasite. Ecology 2020; 101:e02979. [PMID: 31960949 DOI: 10.1002/ecy.2979] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 10/25/2019] [Accepted: 12/05/2019] [Indexed: 12/22/2022]
Abstract
Complex ecological relationships, such as host-parasite interactions, are often modeled with laboratory experiments. However, some experimental laboratory conditions, such as temperature or infection dose, are regularly chosen based on convenience or convention, and it is unclear how these decisions systematically affect experimental outcomes. Here, we conducted a meta-analysis of 58 laboratory studies that exposed amphibians to the pathogenic fungus Batrachochytrium dendrobatidis (Bd) to understand better how laboratory temperature, host life stage, infection dose, and host species affect host mortality. We found that host mortality was driven by thermal mismatches: hosts native to cooler environments experienced greater Bd-induced mortality at relatively warm experimental temperatures and vice versa. We also found that Bd dose positively predicted Bd-induced host mortality and that the superfamilies Bufonoidea and Hyloidea were especially susceptible to Bd. Finally, the effect of Bd on host mortality varied across host life stages, with larval amphibians experiencing lower risk of Bd-induced mortality than adults or metamorphs. Metamorphs were especially susceptible and experienced mortality when inoculated with much smaller Bd doses than the average dose used by researchers. Our results suggest that when designing experiments on species interactions, researchers should carefully consider the experimental temperature, inoculum dose, and life stage, and taxonomy of the host species.
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Affiliation(s)
- Erin L Sauer
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA.,Department of Forest and Wildlife Ecology, University of Wisconsin, 1630 Linden Dr., Madison, 53706, Wisconsin, USA
| | - Jeremy M Cohen
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA.,Department of Forest and Wildlife Ecology, University of Wisconsin, 1630 Linden Dr., Madison, 53706, Wisconsin, USA
| | - Marc J Lajeunesse
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA
| | - Taegan A McMahon
- Department of Biology, University of Tampa, 401 W. Kennedy Blvd., Tampa, 33606, Florida, USA
| | - David J Civitello
- Department of Biology, Emory University, 201 Dowman Dr., Atlanta, 30322, Georgia, USA
| | - Sarah A Knutie
- Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Road, Storrs, 06269, Connecticut, USA
| | - Karena Nguyen
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA
| | - Elizabeth A Roznik
- Department of Research and Conservation, Memphis Zoo, 2000 Prentiss Place, Memphis, 38112, Tennessee, USA
| | | | - Scott Bessler
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA
| | - Bryan K Delius
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA
| | - Neal Halstead
- Wildlands Conservation, 15310 Amberly Dr., Suite 250, Tampa, 33647, Florida, USA
| | - Nicole Ortega
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA
| | - Matthew D Venesky
- Department of Biology, Allegheny College, 520 N Main St., Meadville, 16335, Pennsylvania, USA
| | - Suzanne Young
- Environmental Engineering Institute, Ecole polytechnique fédérale de Lausanne (EPFL), Route Cantonale, 1015, Lausanne, Switzerland
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Ave, Tampa, 33620, Florida, USA.,Department of Biological Science, University of Notre Dame, 100 Galvin Life Science Center, Notre Dame, 46656, Indiana, USA
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45
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Ohmer MEB, Cramp RL, White CR, Harlow PS, McFadden MS, Merino-Viteri A, Pessier AP, Wu NC, Bishop PJ, Franklin CE. Phylogenetic investigation of skin sloughing rates in frogs: relationships with skin characteristics and disease-driven declines. Proc Biol Sci 2020; 286:20182378. [PMID: 30963925 DOI: 10.1098/rspb.2018.2378] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Amphibian skin is highly variable in structure and function across anurans, and plays an important role in physiological homeostasis and immune defence. For example, skin sloughing has been shown to reduce pathogen loads on the skin, such as the lethal fungus Batrachochytrium dendrobatidis ( Bd), but interspecific variation in sloughing frequency is largely unknown. Using phylogenetic linear mixed models, we assessed the relationship between skin turnover rate, skin morphology, ecological traits and overall evidence of Bd-driven declines. We examined skin sloughing rates in 21 frog species from three continents, as well as structural skin characteristics measured from preserved specimens. We found that sloughing rate varies significantly with phylogenetic group, but was not associated with evidence of Bd-driven declines, or other skin characteristics examined. This is the first comparison of sloughing rate across a wide range of amphibian species, and creates the first database of amphibian sloughing behaviour. Given the strong phylogenetic signal observed in sloughing rate, approximate sloughing rates of related species may be predicted based on phylogenetic position. While not related to available evidence of declines, understanding variation in sloughing rate may help explain differences in the severity of infection in genera with relatively slow skin turnover rates (e.g. Atelopus).
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Affiliation(s)
- Michel E B Ohmer
- 1 School of Biological Sciences, The University of Queensland , St Lucia, Queensland 4072 , Australia.,2 Department of Biological Sciences, University of Pittsburgh , Pittsburgh, PA 15260 , USA
| | - Rebecca L Cramp
- 1 School of Biological Sciences, The University of Queensland , St Lucia, Queensland 4072 , Australia
| | - Craig R White
- 3 School of Biological Sciences, Monash University, Centre for Geometric Biology , Victoria 3800 , Australia
| | - Peter S Harlow
- 4 Taronga Conservation Society Australia, Herpetofauna Division , Mosman, New South Wales , Australia
| | - Michael S McFadden
- 4 Taronga Conservation Society Australia, Herpetofauna Division , Mosman, New South Wales , Australia
| | - Andrés Merino-Viteri
- 5 Laboratorio de Ecofisiología/Museo de Zoología (QCAZ), Escuela de Ciencias Biológicas, Pontificia Universidad Católica del Ecuador , Quito , Ecuador
| | - Allan P Pessier
- 6 Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University , Pullman, WA 99164 , USA
| | - Nicholas C Wu
- 1 School of Biological Sciences, The University of Queensland , St Lucia, Queensland 4072 , Australia
| | - Phillip J Bishop
- 7 Department of Zoology, University of Otago , Dunedin , New Zealand
| | - Craig E Franklin
- 1 School of Biological Sciences, The University of Queensland , St Lucia, Queensland 4072 , Australia
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Weitzman CL, Kaestli M, Gibb K, Brown GP, Shine R, Christian K. Disease Exposure and Antifungal Bacteria on Skin of Invasive Cane Toads, Australia. Emerg Infect Dis 2020; 25:1770-1771. [PMID: 31441753 PMCID: PMC6711215 DOI: 10.3201/eid2509.190386] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Cane toads, an invasive species in Australia, are resistant to fungal pathogens affecting frogs worldwide (Batrachochytrium dendrobatidis). From toad skin swabs, we detected higher proportions of bacteria with antifungal properties in Queensland, where toad and pathogen distributions overlap, than in other sites. This finding suggests that site-specific pathogen pressures help shape skin microbial communities.
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Barnhart KL, Bletz MC, LaBumbard BC, Tokash-Peters AG, Gabor CR, Woodhams DC. Batrachochytrium salamandrivorans ELICITS ACUTE STRESS RESPONSE IN SPOTTED SALAMANDERS BUT NOT INFECTION OR MORTALITY. Anim Conserv 2020; 23:533-546. [PMID: 33071596 DOI: 10.1111/acv.12565] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The emerging fungal pathogen Batrachochytrium salamandrivorans (Bsal) is a major threat to amphibian species worldwide with potential to infect many species if it invades salamander biodiversity hotspots in the Americas. Bsal can cause the disease chytridiomycosis, and it is important to assess the risk of Bsal-induced chytridiomycosis to species in North America. We evaluated the susceptibility to Bsal of the common and widespread spotted salamander, Ambystoma maculatum, across life history stages and monitored the effect of Bsal exposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant to Bsal because they showed no indication of disease or infection, and experienced minor effects on growth upon exposure. While we focused on a single population for this study, results were consistent across conditions of exposure including high or repeated doses of Bsal, life-stage at exposure, environmental conditions including two temperatures and two substrates, and promoting pathogen infectivity by conditioning Bsal cultures with thyroid hormone. Exposure to high levels of Bsal elicited an acute but not chronic increase in corticosterone in spotted salamanders, and reduced growth. We hypothesize that the early acute increase in corticosterone facilitated mounting an immune response to the pathogen, perhaps through immunoredistribution to the skin, but further study is needed to determine immune responses to Bsal. These results will contribute to development of appropriate Bsal management plans to conserve species at risk of emerging disease.
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Affiliation(s)
- Kelly L Barnhart
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Molly C Bletz
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Brandon C LaBumbard
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Amanda G Tokash-Peters
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
| | - Caitlin R Gabor
- Texas State University, Department of Biology, 601 University Drive, San Marcos, TX 78666
| | - Douglas C Woodhams
- University of Massachusetts Boston, Department of Biology, 100 William T Morrissey Blvd, Boston, MA 02125
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48
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Lundsgaard NU, Cramp RL, Franklin CE. Effects of ultraviolet-B radiation on physiology, immune function and survival is dependent on temperature: implications for amphibian declines. Conserv Physiol 2020; 8:coaa002. [PMID: 32467758 PMCID: PMC7245394 DOI: 10.1093/conphys/coaa002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 12/11/2019] [Accepted: 01/17/2020] [Indexed: 05/10/2023]
Abstract
Multiple environmental changes are thought to be contributing to the widespread decline of amphibians in montane regions, but interactions between drivers of decline are not well understood. It has been proposed previously that elevated ultraviolet-B radiation (UBVR) and low temperatures may interact in their negative effects on health, immune function and disease susceptibility in exposed amphibians. In the present study, we chronically exposed larvae of the striped-marsh frog (Limnodynastes peronii) to a factorial combination of high and low UVBR and high and low temperature to assess interactive effects on growth, survival and indices of immune function. The high UVBR treatment reduced growth and survival of larvae compared to the low UVBR treatment at both temperatures, but the effects were significantly enhanced at low temperature. High UVBR exposure also induced a chronic inflammatory response as evidenced by an increase in the leucocyte proportion of total cells and altered the ratio of neutrophils to lymphocytes in the blood, highlighting a potential mechanistic basis for increased disease susceptibility in amphibians living at high altitudes. Our findings stress the importance of investigating environmental factors in combination when assessing their effects and highlight the mechanistic basis for how key environmental drivers in montane regions affect amphibian health. Continuation of this work is necessary for the development of targeted conservation strategies that tackle the root causes of montane amphibian declines.
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Affiliation(s)
- Niclas U Lundsgaard
- School of Biological Sciences, The University of Queensland, Goddard Building (8), St Lucia, Queensland 4072, Australia
| | - Rebecca L Cramp
- School of Biological Sciences, The University of Queensland, Goddard Building (8), St Lucia, Queensland 4072, Australia
| | - Craig E Franklin
- Corresponding author: School of Biological Sciences, The University of Queensland, Brisbane 4072, Australia. Tel: +61 416 801 116;
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49
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Lastra González D, Baláž V, Solský M, Thumsová B, Kolenda K, Najbar A, Najbar B, Kautman M, Chajma P, Balogová M, Vojar J. Recent Findings of Potentially Lethal Salamander Fungus Batrachochytrium salamandrivorans. Emerg Infect Dis 2019; 25:1416-1418. [PMID: 31211934 PMCID: PMC6590763 DOI: 10.3201/eid2507.181001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The distribution of the chytrid fungus Batrachochytrium salamandrivorans continues to expand in Europe. During 2014-2018, we collected 1,135 samples from salamanders and newts in 6 countries in Europe. We identified 5 cases of B. salamandrivorans in a wild population in Spain but none in central Europe or the Balkan Peninsula.
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50
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Rumschlag SL, Boone MD. LETHAL AND SUBLETHAL AMPHIBIAN HOST RESPONSES TO BATRACHOCHYTRIUM DENDROBATIDIS EXPOSURE ARE DETERMINED BY THE ADDITIVE INFLUENCE OF HOST RESOURCE AVAILABILITY. J Wildl Dis 2020; 56:338-49. [PMID: 31769713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Host species may differ in their responses to pathogen exposures based on host energy reserves, which could be important for long-term trends in host population growth. Batrachochytrium dendrobatidis (BD) is a pathogen associated with amphibian population declines but also occurs without causing mass mortalities. The impact of BD in populations without associated declines is not well understood, and food abundance could play a role in determining the magnitude of its effects. We exposed American toad (Anaxyrus americanus), northern leopard frog (Lithobates pipiens), and cricket frog (Acris blanchardi) metamorphs to BD under low or high food treatments. Overall, anuran species responded differently to BD exposure and the combined effect of BD exposure and food abundance was additive. American toad survival was lowered by BD exposure and low food availability. Based on these results, we developed a population model for American toads to estimate how reductions in survival could influence population growth. We found that BD could reduce population growth by 14% with high food availability and 21% with low food availability. In contrast, survival of northern leopard frogs was high across all treatments, but their growth was negatively impacted by the additive effects of BD exposure and low food availability. Cricket frog growth and survival were unaffected by BD exposure, suggesting that this species is not sensitive to the effects of this pathogen in terms of growth and survival across environments of different quality in the time period examined. Our results showed that low food availability additively increased the species-specific lethal and sublethal impacts of BD on hosts, which could have implications for long-term host population dynamics.
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