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Becker CG, Rodriguez D, Toledo LF, Longo AV, Lambertini C, Corrêa DT, Leite DS, Haddad CFB, Zamudio KR. Partitioning the net effect of host diversity on an emerging amphibian pathogen. Proc Biol Sci 2015; 281:rspb.2014.1796. [PMID: 25297867 DOI: 10.1098/rspb.2014.1796] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The 'dilution effect' (DE) hypothesis predicts that diverse host communities will show reduced disease. The underlying causes of pathogen dilution are complex, because they involve non-additive (driven by host interactions and differential habitat use) and additive (controlled by host species composition) mechanisms. Here, we used measures of complementarity and selection traditionally employed in the field of biodiversity-ecosystem function (BEF) to quantify the net effect of host diversity on disease dynamics of the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd). Complementarity occurs when average infection load in diverse host assemblages departs from that of each component species in uniform populations. Selection measures the disproportionate impact of a particular species in diverse assemblages compared with its performance in uniform populations, and therefore has strong additive and non-additive properties. We experimentally infected tropical amphibian species of varying life histories, in single- and multi-host treatments, and measured individual Bd infection loads. Host diversity reduced Bd infection in amphibians through a mechanism analogous to complementarity (sensu BEF), potentially by reducing shared habitat use and transmission among hosts. Additionally, the selection component indicated that one particular terrestrial species showed reduced infection loads in diverse assemblages at the expense of neighbouring aquatic hosts becoming heavily infected. By partitioning components of diversity, our findings underscore the importance of additive and non-additive mechanisms underlying the DE.
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Affiliation(s)
- C Guilherme Becker
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
| | - David Rodriguez
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA Department of Agriculture, Texas State University, San Marcos, TX 78666, USA
| | - L Felipe Toledo
- Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil
| | - Ana V Longo
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
| | - Carolina Lambertini
- Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil
| | - Décio T Corrêa
- Departamento de Biologia Animal, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil Department of Integrative Biology, The University of Texas at Austin, Austin, TX 78712, USA
| | - Domingos S Leite
- Departamento de Genética, Evolução e Bioagentes, Universidade Estadual de Campinas, Campinas, São Paulo 13083-970, Brazil
| | - Célio F B Haddad
- Departamento de Zoologia, Universidade Estadual Paulista, Rio Claro, São Paulo 13506-900, Brazil
| | - Kelly R Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
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Raffel TR, Halstead NT, McMahon TA, Davis AK, Rohr JR. Temperature variability and moisture synergistically interact to exacerbate an epizootic disease. Proc Biol Sci 2015; 282:20142039. [PMID: 25567647 DOI: 10.1098/rspb.2014.2039] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Climate change is altering global patterns of precipitation and temperature variability, with implications for parasitic diseases of humans and wildlife. A recent study confirmed predictions that increased temperature variability could exacerbate disease, because of lags in host acclimation following temperature shifts. However, the generality of these host acclimation effects and the potential for them to interact with other factors have yet to be tested. Here, we report similar effects of host thermal acclimation (constant versus shifted temperatures) on chytridiomycosis in red-spotted newts (Notophthalmus viridescens). Batrachochytrium dendrobatidis (Bd) growth on newts was greater following a shift to a new temperature, relative to newts already acclimated to this temperature (15°C versus 25°C). However, these acclimation effects depended on soil moisture (10, 16 and 21% water) and were only observed at the highest moisture level, which induced greatly increased Bd growth and infection-induced mortality. Acclimation effects were also greater following a decrease rather than an increase in temperature. The results are consistent with previous findings that chytridiomycosis is associated with precipitation, lower temperatures and increased temperature variability. This study highlights host acclimation as a potentially general mediator of climate-disease interactions, and the need to account for context-dependencies when testing for acclimation effects on disease.
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Affiliation(s)
- Thomas R Raffel
- Department of Biology, Oakland University, Rochester, MI, USA
| | - Neal T Halstead
- Department of Integrative Biology, University of South Florida, Tampa, FL, USA
| | | | - Andrew K Davis
- Odum School of Ecology, University of Georgia, Athens, GA, USA
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, FL, USA
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53
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James TY, Toledo LF, Rödder D, da Silva Leite D, Belasen AM, Betancourt-Román CM, Jenkinson TS, Soto-Azat C, Lambertini C, Longo AV, Ruggeri J, Collins JP, Burrowes PA, Lips KR, Zamudio KR, Longcore JE. Disentangling host, pathogen, and environmental determinants of a recently emerged wildlife disease: lessons from the first 15 years of amphibian chytridiomycosis research. Ecol Evol 2015; 5:4079-97. [PMID: 26445660 PMCID: PMC4588650 DOI: 10.1002/ece3.1672] [Citation(s) in RCA: 150] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2015] [Accepted: 07/25/2015] [Indexed: 12/18/2022] Open
Abstract
The amphibian fungal disease chytridiomycosis, which affects species across all continents, recently emerged as one of the greatest threats to biodiversity. Yet, many aspects of the basic biology and epidemiology of the pathogen, Batrachochytrium dendrobatidis (Bd), are still unknown, such as when and from where did Bd emerge and what is its true ecological niche? Here, we review the ecology and evolution of Bd in the Americas and highlight controversies that make this disease so enigmatic. We explore factors associated with variance in severity of epizootics focusing on the disease triangle of host susceptibility, pathogen virulence, and environment. Reevaluating the causes of the panzootic is timely given the wealth of data on Bd prevalence across hosts and communities and the recent discoveries suggesting co-evolutionary potential of hosts and Bd. We generate a new species distribution model for Bd in the Americas based on over 30,000 records and suggest a novel future research agenda. Instead of focusing on pathogen "hot spots," we need to identify pathogen "cold spots" so that we can better understand what limits the pathogen's distribution. Finally, we introduce the concept of "the Ghost of Epizootics Past" to discuss expected patterns in postepizootic host communities.
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Affiliation(s)
- Timothy Y James
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109
| | - L Felipe Toledo
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB) Departamento de Biologia Animal Instituto de Biologia Universidade Estadual de Campinas Caixa Postal 6109 Campinas São Paulo CEP 13083-863 Brazil
| | - Dennis Rödder
- Section of Herpetology Zoologisches Forschungsmuseum Alexander Koenig Adenauerallee 160 53113 Bonn Germany
| | - Domingos da Silva Leite
- Laboratório de Antígenos Bacterianos II Departamento de Genética, Evolução e Bioagentes Instituto de Biologia Universidade Estadual de Campinas Caixa Postal 6109 Campinas São Paulo CEP 13083-862 Brazil
| | - Anat M Belasen
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109
| | | | - Thomas S Jenkinson
- Department of Ecology and Evolutionary Biology University of Michigan Ann Arbor Michigan 48109
| | - Claudio Soto-Azat
- Centro de Investigación para la Sustentabilidad Facultad de Ecología y Recursos Naturales, Universidad Andres Bello Santiago Chile
| | - Carolina Lambertini
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB) Departamento de Biologia Animal Instituto de Biologia Universidade Estadual de Campinas Caixa Postal 6109 Campinas São Paulo CEP 13083-863 Brazil
| | - Ana V Longo
- Department of Ecology and Evolutionary Biology Cornell University Ithaca New York 14853
| | - Joice Ruggeri
- Departamento de Zoologia Laboratório de Anfíbios e Répteis Universidade Federal do Rio de Janeiro, Instituto de Biologia Ilha do Fundão, Caixa postal: 68044 Rio de Janeiro RJ CEP 21941-590 Brazil
| | - James P Collins
- School of Life Sciences Arizona State University PO Box 874501 Tempe Arizona 85287-4501
| | | | - Karen R Lips
- Department of Biology University of Maryland College Park Maryland 20901
| | - Kelly R Zamudio
- Department of Ecology and Evolutionary Biology Cornell University Ithaca New York 14853
| | - Joyce E Longcore
- School of Biology and Ecology University of Maine Orono Maine 04469-5722
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Agostini MG, Cortelezzi A, Berkunsky I, Soler G, Burrowes P. First record of Batrachochytrium dendrobatidis infecting threatened populations of Tandilean Red-belly toad (Melanophryniscus aff. montevidensis) in Argentina. REV MEX BIODIVERS 2015. [DOI: 10.1016/j.rmb.2015.07.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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55
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Ruggeri J, Longo AV, Gaiarsa MP, Alencar LRV, Lambertini C, Leite DS, Carvalho-e-Silva SP, Zamudio KR, Toledo LF, Martins M. Seasonal Variation in Population Abundance and Chytrid Infection in Stream-Dwelling Frogs of the Brazilian Atlantic Forest. PLoS One 2015; 10:e0130554. [PMID: 26161777 PMCID: PMC4498819 DOI: 10.1371/journal.pone.0130554] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 05/22/2015] [Indexed: 11/18/2022] Open
Abstract
Enigmatic amphibian declines were first reported in southern and southeastern Brazil in the late 1980s and included several species of stream-dwelling anurans (families Hylodidae and Cycloramphidae). At that time, we were unaware of the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd); therefore, pollution, habitat loss, fragmentation and unusual climatic events were hypothesized as primary causes of these declines. We now know that multiple lineages of Bd have infected amphibians of the Brazilian Atlantic forest for over a century, yet declines have not been associated specifically with Bd outbreaks. Because stream-dwelling anurans occupy an environmental hotspot ideal for disease transmission, we investigated temporal variation in population and infection dynamics of three stream-adapted species (Hylodes asper, H. phyllodes, and Cycloramphus boraceiensis) on the northern coast of São Paulo state, Brazil. We surveyed standardized transects along streams for four years, and show that fluctuations in the number of frogs correlate with specific climatic variables that also increase the likelihood of Bd infections. In addition, we found that Bd infection probability in C. boraceiensis, a nocturnal species, was significantly higher than in Hylodes spp., which are diurnal, suggesting that the nocturnal activity may either facilitate Bd zoospore transmission or increase susceptibility of hosts. Our findings indicate that, despite long-term persistence of Bd in Brazil, some hosts persist with seasonally variable infections, and thus future persistence in the face of climate change will depend on the relative effect of those changes on frog recruitment and pathogen proliferation.
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Affiliation(s)
- Joice Ruggeri
- Instituto de Biologia, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, Brazil
| | - Ana V. Longo
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, United States of America
| | - Marília P. Gaiarsa
- Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Laura R. V. Alencar
- Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Carolina Lambertini
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | - Domingos S. Leite
- Laboratório de Antígenos Bacterianos, Departamento de Genética, Evolução e Bioagentes, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | | | - Kelly R. Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, United States of America
| | - Luís Felipe Toledo
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brazil
| | - Marcio Martins
- Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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56
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Longo AV, Savage AE, Hewson I, Zamudio KR. Seasonal and ontogenetic variation of skin microbial communities and relationships to natural disease dynamics in declining amphibians. ROYAL SOCIETY OPEN SCIENCE 2015; 2:140377. [PMID: 26587253 PMCID: PMC4632566 DOI: 10.1098/rsos.140377] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Accepted: 06/18/2015] [Indexed: 05/09/2023]
Abstract
Recently, microbiologists have focused on characterizing the probiotic role of skin bacteria for amphibians threatened by the fungal disease chytridiomycosis. However, the specific characteristics of microbial diversity required to maintain health or trigger disease are still not well understood in natural populations. We hypothesized that seasonal and developmental transitions affecting susceptibility to chytridiomycosis could also alter the stability of microbial assemblages. To test our hypothesis, we examined patterns of skin bacterial diversity in two species of declining amphibians (Lithobates yavapaiensis and Eleutherodactylus coqui) affected by the pathogenic fungus Batrachochytrium dendrobatidis (Bd). We focused on two important transitions that affect Bd susceptibility: ontogenetic (from juvenile to adult) shifts in E. coqui and seasonal (from summer to winter) shifts in L. yavapaiensis. We used a combination of community-fingerprinting analyses and 16S rRNA amplicon sequencing to quantify changes in bacterial diversity and assemblage composition between seasons and developmental stages, and to investigate the relationship between bacterial diversity and pathogen load. We found that winter-sampled frogs and juveniles, two states associated with increased Bd susceptibility, exhibited higher diversity compared with summer-sampled frogs and adult individuals. Our findings also revealed that hosts harbouring higher bacterial diversity carried lower Bd infections, providing support for the protective role of bacterial communities. Ongoing work to understand skin microbiome resilience after pathogen disturbance has the potential to identify key taxa involved in disease resistance.
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Affiliation(s)
- Ana V. Longo
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
- Author for correspondence: Ana V. Longo e-mail:
| | - Anna E. Savage
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
- Department of Biology, University of Central Florida, Orlando, FL 32816, USA
| | - Ian Hewson
- Department of Microbiology, Cornell University, Ithaca, NY 14853, USA
| | - Kelly R. Zamudio
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853, USA
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57
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Kolby JE, Smith KM, Ramirez SD, Rabemananjara F, Pessier AP, Brunner JL, Goldberg CS, Berger L, Skerratt LF. Rapid Response to Evaluate the Presence of Amphibian Chytrid Fungus (Batrachochytrium dendrobatidis) and Ranavirus in Wild Amphibian Populations in Madagascar. PLoS One 2015; 10:e0125330. [PMID: 26083349 PMCID: PMC4471163 DOI: 10.1371/journal.pone.0125330] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Accepted: 03/11/2015] [Indexed: 12/03/2022] Open
Abstract
We performed a rapid response investigation to evaluate the presence and distribution of amphibian pathogens in Madagascar following our identification of amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) and ranavirus in commercially exported amphibians. This targeted risk-based field surveillance program was conducted from February to April 2014 encompassing 12 regions and 47 survey sites. We simultaneously collected amphibian and environmental samples to increase survey sensitivity and performed sampling both in wilderness areas and commercial amphibian trade facilities. Bd was not detected in any of 508 amphibian skin swabs or 68 water filter samples, suggesting pathogen prevalence was below 0.8%, with 95% confidence during our visit. Ranavirus was detected in 5 of 97 amphibians, including one adult Mantidactylus cowanii and three unidentified larvae from Ranomafana National Park, and one adult Mantidactylus mocquardi from Ankaratra. Ranavirus was also detected in water samples collected from two commercial amphibian export facilities. We also provide the first report of an amphibian mass-mortality event observed in wild amphibians in Madagascar. Although neither Bd nor ranavirus appeared widespread in Madagascar during this investigation, additional health surveys are required to disentangle potential seasonal variations in pathogen abundance and detectability from actual changes in pathogen distribution and rates of spread. Accordingly, our results should be conservatively interpreted until a comparable survey effort during winter months has been performed. It is imperative that biosecurity practices be immediately adopted to limit the unintentional increased spread of disease through the movement of contaminated equipment or direct disposal of contaminated material from wildlife trade facilities. The presence of potentially introduced strains of ranaviruses suggests that Madagascar's reptile species might also be threatened by disease. Standardized population monitoring of key amphibian and reptile species should be established with urgency to enable early detection of potential impacts of disease emergence in this global biodiversity hotspot.
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Affiliation(s)
- Jonathan E. Kolby
- One Health Research Group, College of Public Health, Medical, and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia
- EcoHealth Alliance, New York, New York, United States of America
- * E-mail:
| | | | - Sara D. Ramirez
- Sustainability Studies Program, Ramapo College of New Jersey, Mahwah, New Jersey, United States of America
| | | | - Allan P. Pessier
- Amphibian Disease Laboratory, Institute for Conservation Research, San Diego Zoo Global, San Diego, California, United States of America
| | - Jesse L. Brunner
- School of Biological Sciences, Washington State University, Pullman, Washington, United States of America
| | - Caren S. Goldberg
- School of the Environment, Washington State University, Pullman, Washington, United States of America
| | - Lee Berger
- One Health Research Group, College of Public Health, Medical, and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia
| | - Lee F. Skerratt
- One Health Research Group, College of Public Health, Medical, and Veterinary Sciences, James Cook University, Townsville, Queensland, Australia
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58
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Moriguchi S, Tominaga A, Irwin KJ, Freake MJ, Suzuki K, Goka K. Predicting the potential distribution of the amphibian pathogen Batrachochytrium dendrobatidis in East and Southeast Asia. DISEASES OF AQUATIC ORGANISMS 2015; 113:177-185. [PMID: 25850395 DOI: 10.3354/dao02838] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Batrachochytrium dendrobatidis (Bd) is the pathogen responsible for chytridiomycosis, a disease that is associated with a worldwide amphibian population decline. In this study, we predicted the potential distribution of Bd in East and Southeast Asia based on limited occurrence data. Our goal was to design an effective survey area where efforts to detect the pathogen can be focused. We generated ecological niche models using the maximum-entropy approach, with alleviation of multicollinearity and spatial autocorrelation. We applied eigenvector-based spatial filters as independent variables, in addition to environmental variables, to resolve spatial autocorrelation, and compared the model's accuracy and the degree of spatial autocorrelation with those of a model estimated using only environmental variables. We were able to identify areas of high suitability for Bd with accuracy. Among the environmental variables, factors related to temperature and precipitation were more effective in predicting the potential distribution of Bd than factors related to land use and cover type. Our study successfully predicted the potential distribution of Bd in East and Southeast Asia. This information should now be used to prioritize survey areas and generate a surveillance program to detect the pathogen.
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Affiliation(s)
- Sachiko Moriguchi
- Invasive Alien Species Research Team, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
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59
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Short term minimum water temperatures determine levels of infection by the amphibian chytrid fungus in Alytes obstetricans tadpoles. PLoS One 2015; 10:e0120237. [PMID: 25793985 PMCID: PMC4368698 DOI: 10.1371/journal.pone.0120237] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 02/04/2015] [Indexed: 11/19/2022] Open
Abstract
Amphibians are one of the groups of wildlife most seriously threatened by emerging infectious disease. In particular, chytridiomycosis, caused by the aquatic fungus Batrachochytrium dendrobatidis, is responsible for amphibian species declines on a worldwide scale. Population-level outcomes following the introduction of the pathogen are context dependent and mediated by a large suite of abiotic and biotic variables. In particular, studies have shown that temperature has a key role in determining infection dynamics owing to the ectothermic nature of the amphibian host and temperature-dependency of pathogen growth rates. To assess the temperature-dependent seasonality of infectious burdens in a susceptible host species, we monitored lowland populations of larval midwife toads, Alytes obstetricians, in Central Spain throughout the year. We found that infections were highly seasonal, and inversely correlated against water temperature, with the highest burdens of infection seen during the colder months. Short-term impacts of water-temperature were found, with the minimum temperatures occurring before sampling being more highly predictive of infectious burdens than were longer-term spans of temperature. Our results will be useful for selecting the optimal time for disease surveys and, more broadly, for determining the key periods to undertake disease mitigation.
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60
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Mendoza-Almeralla C, Burrowes P, Parra-Olea G. La quitridiomicosis en los anfibios de México: una revisión. REV MEX BIODIVERS 2015. [DOI: 10.7550/rmb.42588] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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61
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Rollins-Smith LA, Reinert LK, Burrowes PA. Coqui frogs persist with the deadly chytrid fungus despite a lack of defensive antimicrobial peptides. DISEASES OF AQUATIC ORGANISMS 2015; 113:81-83. [PMID: 25667340 DOI: 10.3354/dao02823] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The amphibian skin fungus Batrachochytrium dendrobatidis (Bd) occurs widely in Puerto Rico and is thought to be responsible for the apparent extinction of 3 species of endemic frogs in the genus Eleutherodactylus, known as coquis. To examine immune defenses which may protect surviving species, we induced secretion of skin peptides from adult common coqui frogs E. coqui collected from upland forests at El Yunque. By matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, we were unable to detect peptide signals suggestive of antimicrobial peptides, and enriched peptides showed no capacity to inhibit growth of Bd. Thus, it appears that E. coqui depend on other skin defenses to survive in the presence of this deadly fungus.
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Affiliation(s)
- Louise A Rollins-Smith
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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62
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Korfel CA, Hetherington TE. Temperature alone does not explain patterns of Batrachochytrium dendrobatidis infections in the green frog Lithobates clamitans. DISEASES OF AQUATIC ORGANISMS 2014; 109:177-185. [PMID: 24991844 DOI: 10.3354/dao02749] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Batrachochytrium dendrobatidis (Bd) is an invasive, waterborne fungal pathogen that has caused significant declines and extinctions of amphibian species worldwide. Temperature is a major factor impacting the growth and spread of Bd, but little is known regarding the associated patterns in natural habitats. This study analyzed the temperature-associated trends, as correlated with season and microhabitat, of Bd prevalence and infection intensity in green frogs Lithobates clamitans in a temperate environment (central Ohio, USA). Bd was widely distributed at the study sites and found in more than half of the frogs sampled. Bd prevalence was significantly higher in the spring and in forested stream habitats compared to emergent wetland habitats. In contrast, Bd infection intensities tended to be higher in summer. Given the known temperature sensitivity of Bd as demonstrated in laboratory studies, these findings suggest that temperature may be an important factor determining Bd prevalence in green frogs at our study sites, but that factors other than temperature are more important in determining infection intensity. Our findings suggest that future monitoring of Bd among vulnerable species in regions experiencing seasonal temperature variation should study a range of environmental variables to better understand the dynamic relationship between Bd and its amphibian hosts.
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Affiliation(s)
- Chelsea A Korfel
- The Ohio State University, Museum of Biological Diversity, 1315 Kinnear Rd, Columbus, OH 43212, USA
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63
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Daskin JH, Bell SC, Schwarzkopf L, Alford RA. Cool temperatures reduce antifungal activity of symbiotic bacteria of threatened amphibians--implications for disease management and patterns of decline. PLoS One 2014; 9:e100378. [PMID: 24941262 PMCID: PMC4062522 DOI: 10.1371/journal.pone.0100378] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 05/27/2014] [Indexed: 11/18/2022] Open
Abstract
Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), is a widespread disease of amphibians responsible for population declines and extinctions. Some bacteria from amphibians' skins produce antimicrobial substances active against Bd. Supplementing populations of these cutaneous antifungal bacteria might help manage chytridiomycosis in wild amphibians. However, the activity of protective bacteria may depend upon environmental conditions. Biocontrol of Bd in nature thus requires knowledge of how environmental conditions affect their anti-Bd activity. For example, Bd-driven amphibian declines have often occurred at temperatures below Bd's optimum range. It is possible these declines occurred due to reduced anti-Bd activity of bacterial symbionts at cool temperatures. Better understanding of the effects of temperature on chytridiomycosis development could also improve risk evaluation for amphibian populations yet to encounter Bd. We characterized, at a range of temperatures approximating natural seasonal variation, the anti-Bd activity of bacterial symbionts from the skins of three species of rainforest tree frogs (Litoria nannotis, Litoria rheocola, and Litoria serrata). All three species declined during chytridiomycosis outbreaks in the late 1980s and early 1990s and have subsequently recovered to differing extents. We collected anti-Bd bacterial symbionts from frogs and cultured the bacteria at constant temperatures from 8 °C to 33 °C. Using a spectrophotometric assay, we monitored Bd growth in cell-free supernatants (CFSs) from each temperature treatment. CFSs from 11 of 24 bacteria showed reduced anti-Bd activity in vitro when they were produced at cool temperatures similar to those encountered by the host species during population declines. Reduced anti-Bd activity of metabolites produced at low temperatures may, therefore, partially explain the association between Bd-driven declines and cool temperatures. We show that to avoid inconsistent antifungal activity, bacteria evaluated for use in chytridiomycosis biocontrol should be tested over a range of environmental temperatures spanning those likely to be encountered in the field.
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Affiliation(s)
- Joshua H. Daskin
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
- * E-mail:
| | - Sara C. Bell
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
| | - Lin Schwarzkopf
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
| | - Ross A. Alford
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland, Australia
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64
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Susceptibility to the amphibian chytrid fungus varies with ontogeny in the direct-developing frog, Eleutherodactylus coqui. J Wildl Dis 2014; 50:438-46. [PMID: 24807186 DOI: 10.7589/2013-10-268] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Age-related differences in susceptibility to infectious disease are known from a wide variety of plant and animal taxonomic groups. For example, the immature immune systems of young vertebrates, along with limited prior exposure to pathogens and behavioral factors, can place juveniles at greater risk of acquiring and succumbing to a pathogen. We studied the ontogenetic susceptibility of terrestrial direct-developing frogs (Eleutherodactylus coqui) to the fungal pathogen, Batrachochytrium dendrobatidis (Bd), which is responsible for the decline of amphibian species worldwide. By exposing juvenile and adult frogs to the same dose and strain of Bd, we uncovered ontogenetic differences in susceptibility. Froglets exposed to the pathogen had significantly lower survival rates compared with control froglets, while adult frogs largely cleared infection and had survival rates indistinguishable from control frogs, even when exposed to a much higher dose of Bd. The high disease-induced mortality rate of juveniles may explain ongoing population declines in eastern Puerto Rico, where Bd is endemic and juveniles experience higher prevalence and infection intensity compared to adults. Our results have important implications for understanding and modeling the decline, possibly to extinction, of amphibian populations and species.
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65
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Langhammer PF, Lips KR, Burrowes PA, Tunstall T, Palmer CM, Collins JP. A fungal pathogen of amphibians, Batrachochytrium dendrobatidis, attenuates in pathogenicity with in vitro passages. PLoS One 2013; 8:e77630. [PMID: 24130895 PMCID: PMC3795048 DOI: 10.1371/journal.pone.0077630] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 09/04/2013] [Indexed: 11/19/2022] Open
Abstract
Laboratory investigations into the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), have accelerated recently, given the pathogen's role in causing the global decline and extinction of amphibians. Studies in which host animals were exposed to Bd have largely assumed that lab-maintained pathogen cultures retained the infective and pathogenic properties of wild isolates. Attenuated pathogenicity is common in artificially maintained cultures of other pathogenic fungi, but to date, it is unknown whether, and to what degree, Bd might change in culture. We compared zoospore production over time in two samples of a single Bd isolate having different passage histories: one maintained in artificial media for more than six years (JEL427-P39), and one recently thawed from cryopreserved stock (JEL427-P9). In a common garden experiment, we then exposed two different amphibian species, Eleutherodactylus coqui and Atelopus zeteki, to both cultures to test whether Bd attenuates in pathogenicity with in vitro passages. The culture with the shorter passage history, JEL427-P9, had significantly greater zoospore densities over time compared to JEL427-P39. This difference in zoospore production was associated with a difference in pathogenicity for a susceptible amphibian species, indicating that fecundity may be an important virulence factor for Bd. In the 130-day experiment, Atelopus zeteki frogs exposed to the JEL427-P9 culture experienced higher average infection intensity and 100% mortality, compared with 60% mortality for frogs exposed to JEL427-P39. This effect was not observed with Eleutherodactylus coqui, which was able to clear infection. We hypothesize that the differences in phenotypic performance observed with Atelopus zeteki are rooted in changes of the Bd genome. Future investigations enabled by this study will focus on the underlying mechanisms of Bd pathogenicity.
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Affiliation(s)
- Penny F. Langhammer
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - Karen R. Lips
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
| | - Patricia A. Burrowes
- Department of Biology, University of Puerto Rico, San Juan, Puerto Rico, United States of America
| | - Tate Tunstall
- Department of Biology, University of Maryland, College Park, Maryland, United States of America
| | - Crystal M. Palmer
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | - James P. Collins
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
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66
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Pasmans F, Van Rooij P, Blooi M, Tessa G, Bogaerts S, Sotgiu G, Garner TWJ, Fisher MC, Schmidt BR, Woeltjes T, Beukema W, Bovero S, Adriaensen C, Oneto F, Ottonello D, Martel A, Salvidio S. Resistance to chytridiomycosis in European plethodontid salamanders of the genus Speleomantes. PLoS One 2013; 8:e63639. [PMID: 23703511 PMCID: PMC3659026 DOI: 10.1371/journal.pone.0063639] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 04/04/2013] [Indexed: 11/18/2022] Open
Abstract
North America and the neotropics harbor nearly all species of plethodontid salamanders. In contrast, this family of caudate amphibians is represented in Europe and Asia by two genera, Speleomantes and Karsenia, which are confined to small geographic ranges. Compared to neotropical and North American plethodontids, mortality attributed to chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd) has not been reported for European plethodontids, despite the established presence of Bd in their geographic distribution. We determined the extent to which Bd is present in populations of all eight species of European Speleomantes and show that Bd was undetectable in 921 skin swabs. We then compared the susceptibility of one of these species, Speleomantes strinatii, to experimental infection with a highly virulent isolate of Bd (BdGPL), and compared this to the susceptible species Alytes muletensis. Whereas the inoculated A. muletensis developed increasing Bd-loads over a 4-week period, none of five exposed S. strinatii were colonized by Bd beyond 2 weeks post inoculation. Finally, we determined the extent to which skin secretions of Speleomantes species are capable of killing Bd. Skin secretions of seven Speleomantes species showed pronounced killing activity against Bd over 24 hours. In conclusion, the absence of Bd in Speleomantes combined with resistance to experimental chytridiomycosis and highly efficient skin defenses indicate that the genus Speleomantes is a taxon unlikely to decline due to Bd.
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Affiliation(s)
- Frank Pasmans
- Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
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67
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Moeller KT, Butler MW, Denardo DF. The effect of hydration state and energy balance on innate immunity of a desert reptile. Front Zool 2013; 10:23. [PMID: 23642164 PMCID: PMC3660207 DOI: 10.1186/1742-9994-10-23] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Accepted: 04/24/2013] [Indexed: 11/24/2022] Open
Abstract
Introduction Immune function is a vital physiological process that is often suppressed during times of resource scarcity due to investments in other physiological systems. While energy is the typical currency that has been examined in such trade-offs, limitations of other resources may similarly lead to trade-offs that affect immune function. Specifically, water is a critical resource with profound implications for organismal ecology, yet its availability can fluctuate at local, regional, and even global levels. Despite this, the effect of osmotic state on immune function has received little attention. Results Using agglutination and lysis assays as measures of an organism’s plasma concentration of natural antibodies and capacity for foreign cell destruction, respectively, we tested the independent effects of osmotic state, digestive state, and energy balance on innate immune function in free-ranging and laboratory populations of the Gila monster, Heloderma suspectum. This desert-dwelling lizard experiences dehydration and energy resource fluctuations on a seasonal basis. Dehydration was expected to decrease innate immune function, yet we found that dehydration increased lysis and agglutination abilities in both lab and field studies, a relationship that was not simply an effect of an increased concentration of immune molecules. Laboratory-based differences in digestive state were not associated with lysis or agglutination metrics, although in our field population, a loss of fat stores was correlated with an increase in lysis. Conclusions Depending on the life history of an organism, osmotic state may have a greater influence on immune function than energy availability. Thus, consideration of osmotic state as a factor influencing immune function will likely improve our understanding of ecoimmunology and the disease dynamics of a wide range of species.
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Affiliation(s)
- Karla T Moeller
- School of Life Sciences, Arizona State University, Tempe, AZ, USA.
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68
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Riley K, Berry OF, Roberts JD. Do global models predicting environmental suitability for the amphibian fungus,Batrachochytrium dendrobatidis, have local value to conservation managers? J Appl Ecol 2013. [DOI: 10.1111/1365-2664.12091] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Karen Riley
- School of Animal Biology M092; University of Western Australia; 35 Stirling Highway; Crawley; WA; 6009; Australia
| | - Oliver F. Berry
- School of Animal Biology M092; University of Western Australia; 35 Stirling Highway; Crawley; WA; 6009; Australia
| | - J. Dale Roberts
- School of Animal Biology; Centre for Evolutionary Biology and Centre of Excellence in Natural Resource Management; University of Western Australia; PO Box 5771; Albany; WA; 6330; Australia
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69
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Becker CG, Rodriguez D, Longo AV, Talaba AL, Zamudio KR. Disease risk in temperate amphibian populations is higher at closed-canopy sites. PLoS One 2012; 7:e48205. [PMID: 23118953 PMCID: PMC3485156 DOI: 10.1371/journal.pone.0048205] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 09/20/2012] [Indexed: 01/11/2023] Open
Abstract
Habitat loss and chytridiomycosis (a disease caused by the chytrid fungus Batrachochytrium dendrobatidis - Bd) are major drivers of amphibian declines worldwide. Habitat loss regulates host-pathogen interactions by altering biotic and abiotic factors directly linked to both host and pathogen fitness. Therefore, studies investigating the links between natural vegetation and chytridiomycosis require integrative approaches to control for the multitude of possible interactions of biological and environmental variables in spatial epidemiology. In this study, we quantified Bd infection dynamics across a gradient of natural vegetation and microclimates, looking for causal associations between vegetation cover, multiple microclimatic variables, and pathogen prevalence and infection intensity. To minimize the effects of host diversity in our analyses, we sampled amphibian populations in the Adirondack Mountains of New York State, a region with relatively high single-host dominance. We sampled permanent ponds for anurans, focusing on populations of the habitat generalist frog Lithobates clamitans, and recorded various biotic and abiotic factors that potentially affect host-pathogen interactions: natural vegetation, canopy density, water temperature, and host population and community attributes. We screened for important explanatory variables of Bd infections and used path analyses to statistically test for the strength of cascading effects linking vegetation cover, microclimate, and Bd parameters. We found that canopy density, natural vegetation, and daily average water temperature were the best predictors of Bd. High canopy density resulted in lower water temperature, which in turn predicted higher Bd prevalence and infection intensity. Our results confirm that microclimatic shifts arising from changes in natural vegetation play an important role in Bd spatial epidemiology, with areas of closed canopy favoring Bd. Given increasing rates of anthropogenic habitat modification and the resulting declines in temperate and tropical frogs, understanding how vegetation cover and disease interact is critical for predicting Bd spread and developing appropriate management tools for wild populations.
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Affiliation(s)
- C Guilherme Becker
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA.
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70
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Hauselberger KF, Alford RA. Prevalence of Batrachochytrium dendrobatidis infection is extremely low in direct-developing Australian microhylids. DISEASES OF AQUATIC ORGANISMS 2012; 100:191-200. [PMID: 22968787 DOI: 10.3354/dao02494] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The emerging infectious disease chytridiomycosis has been implicated in declines and disappearances of amphibian populations around the world. However, susceptibility to infection and the extent of pathological effects of infection vary among hosts, and species with life histories that include parental care of direct-developing terrestrial eggs may tend to be less susceptible. We examined samples from a total of 595 individuals of 9 species of direct-developing Australian frogs in the family Microhylidae for the presence of infection by Batrachochytrium dendrobatidis (Bd). Between 1995 and 2004, 336 samples were collected; 102 of these were analysed histologically and 234 were tissues stored in alcohol, which were examined using diagnostic quantitative PCR (qPCR). Swab samples were collected from 259 frogs from 2005 to 2008 and were examined using qPCR. None of the 595 samples showed evidence of infection by Bd. If these data are regarded as a single sample representative of Australian microhylids, the upper 95% binomial confidence limit for the prevalence of infection in frogs of this family is 0.0062 (<1%). Even if only the data from the more powerful diagnostic qPCR tests are used, the upper 95% confidence limit for prevalence is 0.0075 (<1%). Our data suggest that Australian microhylids have a very low prevalence of infection by Bd in nature, and thus are either not susceptible, or are only slightly susceptible, to chytridiomycosis. This could be due solely to, or in combination with, low rates of transmission and to factors that promote resistance to infection, including ecological or behavioural characteristics, innate immune functions such as antimicrobial skin peptides, or antimicrobial symbionts in skin flora.
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Affiliation(s)
- Kim F Hauselberger
- School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia.
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Whitfield SM, Kerby J, Gentry LR, Donnelly MA. Temporal Variation in Infection Prevalence by the Amphibian Chytrid Fungus in Three Species of Frogs at La Selva, Costa Rica. Biotropica 2012. [DOI: 10.1111/j.1744-7429.2012.00872.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- Steven M. Whitfield
- Biology Department; University of South Dakota; Vermillion; South Dakota; U.S.A
| | - Jacob Kerby
- Biology Department; University of South Dakota; Vermillion; South Dakota; U.S.A
| | - Lydia R. Gentry
- College of Veterinary Medicine; Washington State University; Pullman; Washington; U.S.A
| | - Maureen A. Donnelly
- Department of Biological Sciences; Florida International University; UP Campus, OE 167; Miami; Florida; U.S.A
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Gründler MC, Toledo LF, Parra-Olea G, Haddad CFB, Giasson LOM, Sawaya RJ, Prado CPA, Araujo OGS, Zara FJ, Centeno FC, Zamudio KR. Interaction between breeding habitat and elevation affects prevalence but not infection intensity of Batrachochytrium dendrobatidis in Brazilian anuran assemblages. DISEASES OF AQUATIC ORGANISMS 2012; 97:173-84. [PMID: 22422088 DOI: 10.3354/dao02413] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Chytridiomycosis, an infectious disease of amphibians, is caused by the fungus Batrachochytrium dendrobatidis (Bd) and has been linked to declining amphibian populations worldwide. The susceptibility of amphibians to chytridiomycosis-induced population declines is potentially influenced by many factors, including environmental characteristics, differences among host species and the growth of the pathogen itself. We investigated the effects of elevation and breeding habitat on Bd prevalence and individual infection intensity (zoospore loads) in 3 anuran assemblages of the Atlantic Coastal Forest of Brazil. Bd infection intensity was strongly influenced by elevation and breeding habitat, but we found no evidence of an interaction between those 2 variables in explaining the number of zoospores sampled from individual frogs. In contrast, Bd infection odds were predicted by elevation and by an interaction between elevation and breeding habitat, such that frogs had a higher probability of Bd infection in lotic habitats at low elevations. Our results indicate that Bd persists across a wide variety of habitats and elevations in the Atlantic Coastal Forest. Prevalence and infection intensity of Bd are highest at high elevations where overall environmental conditions for Bd are most favorable. In addition, at low elevations amphibian host habitat choice is also an important determinant of infection. Our study highlights the need to investigate interacting variables of host ecology and the environment simultaneously.
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Affiliation(s)
- Michael C Gründler
- Cornell University, Department of Ecology and Evolutionary Biology, Ithaca, New York 14853-2701, USA
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Lannoo MJ, Petersen C, Lovich RE, Nanjappa P, Phillips C, Mitchell JC, Macallister I. Do frogs get their kicks on Route 66? Continental U.S. transect reveals spatial and temporal patterns of Batrachochytrium dendrobatidis infection. PLoS One 2011; 6:e22211. [PMID: 21811576 PMCID: PMC3141021 DOI: 10.1371/journal.pone.0022211] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 06/17/2011] [Indexed: 11/19/2022] Open
Abstract
The chytrid fungus Batrachochytrium dendrobatidis (Bd) has been devastating amphibians globally. Two general scenarios have been proposed for the nature and spread of this pathogen: Bd is an epidemic, spreading as a wave and wiping out individuals, populations, and species in its path; and Bd is endemic, widespread throughout many geographic regions on every continent except Antarctica. To explore these hypotheses, we conducted a transcontinental transect of United States Department of Defense (DoD) installations along U.S. Highway 66 from California to central Illinois, and continuing eastward to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia). We addressed the following questions: 1) Does Bd occur in amphibian populations on protected DoD environments? 2) Is there a temporal pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In these limited human-traffic areas, is Bd acting as an epidemic (i.e., with evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (present without clinical signs of disease)? Bd was detected on 13 of the 15 bases sampled. Samples from 30 amphibian species were collected (10% of known United States' species); half (15) tested Bd positive. There was a strong temporal (seasonal) component; in total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period. There was also a strong spatial component--the eleven temperate DoD installations had higher prevalences of Bd infection (20.8%) than the four arid (<60 mm annual precipitation) bases (8.5%). These data support the conclusion that Bd is now widespread, and promote the idea that Bd can today be considered endemic across much of North America, extending from coast-to-coast, with the exception of remote pockets of naïve populations.
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Affiliation(s)
- Michael J Lannoo
- Indiana University School of Medicine, Terre Haute, Indiana, United States of America.
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Tropical amphibian populations experience higher disease risk in natural habitats. Proc Natl Acad Sci U S A 2011; 108:9893-8. [PMID: 21628560 DOI: 10.1073/pnas.1014497108] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Habitat loss and disease are main drivers of global amphibian declines, yet the interaction between them remains largely unexplored. Here we show that paradoxically, habitat loss is negatively associated with occurrence, prevalence, and infection intensity of the chytrid fungus Batrachochytrium dendrobatidis (Bd) in amphibian populations in the tropics. At a large spatial scale, increased habitat loss predicted lower disease risk in amphibian populations across Costa Rica and eastern Australia, even after jointly considering the effect of potential biotic and abiotic correlates. Lower host-species richness and suboptimal microclimates for Bd in disturbed habitats are potential mechanisms underlying this pattern. Furthermore, we found that anthropogenic deforestation practices biased to lowlands and natural vegetation remaining in inaccessible highlands explain increased Bd occurrence at higher elevations. At a smaller spatial scale, holding constant elevation, latitude, and macroclimate, we also found a negative relationship between habitat loss, and both Bd prevalence and infection intensity in frog populations in two landscapes of the Brazilian Atlantic Forest. Our results indicate that amphibians will be disproportionately affected by emerging diseases in pristine environments, and that, paradoxically, disturbed habitats may act as shelters from disease, but only for the very few species that can tolerate deforestation. Thus, tropical amphibian faunas are threatened both by destruction of natural habitats as well as increased disease in pristine forests. To curb further extinctions and develop effective mitigation and restoration programs we must look to interactions between habitat loss and disease, the two main factors at the root of global amphibian declines.
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75
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Coincident mass extirpation of neotropical amphibians with the emergence of the infectious fungal pathogen Batrachochytrium dendrobatidis. Proc Natl Acad Sci U S A 2011; 108:9502-7. [PMID: 21543713 DOI: 10.1073/pnas.1105538108] [Citation(s) in RCA: 191] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Amphibians highlight the global biodiversity crisis because ∼40% of all amphibian species are currently in decline. Species have disappeared even in protected habitats (e.g., the enigmatic extinction of the golden toad, Bufo periglenes, from Costa Rica). The emergence of a fungal pathogen, Batrachochytrium dendrobatidis (Bd), has been implicated in a number of declines that have occurred in the last decade, but few studies have been able to test retroactively whether Bd emergence was linked to earlier declines and extinctions. We describe a noninvasive PCR sampling technique that detects Bd in formalin-preserved museum specimens. We detected Bd by PCR in 83-90% (n = 38) of samples that were identified as positive by histology. We examined specimens collected before, during, and after major amphibian decline events at established study sites in southern Mexico, Guatemala, and Costa Rica. A pattern of Bd emergence coincident with decline at these localities is revealed-the absence of Bd over multiple years at all localities followed by the concurrent emergence of Bd in various species at each locality during a period of population decline. The geographical and chronological emergence of Bd at these localities also indicates a southbound spread from southern Mexico in the early 1970s to western Guatemala in the 1980s/1990s and to Monteverde, Costa Rica by 1987. We find evidence of a historical "Bd epidemic wave" that began in Mexico and subsequently spread to Central America. We describe a technique that can be used to screen museum specimens from other amphibian decline sites around the world.
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76
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BUSTAMANTE HM, LIVO LJ, CAREY C. Effects of temperature and hydric environment on survival of the Panamanian Golden Frog infected with a pathogenic chytrid fungus. Integr Zool 2010; 5:143-153. [DOI: 10.1111/j.1749-4877.2010.00197.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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