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Thielsch A, Francesconi C, Luka Boštjančić L, Leeb C, Theissinger K. The functional role of Daphnia in the host-pathogen interaction of crayfish and the crayfish plague disease agent (Aphanomyces astaci). J Invertebr Pathol 2024; 203:108069. [PMID: 38286329 DOI: 10.1016/j.jip.2024.108069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 01/19/2024] [Accepted: 01/22/2024] [Indexed: 01/31/2024]
Abstract
Pathogen spores have been recognized as prey with implications for resource dynamics, energy transfer and disease transmission. In aquatic ecosystems, filter-feeders are able to consume such motile forms of pathogens that can cause severe disease in susceptible hosts. The interactions between European crayfish and the crayfish plague pathogen Aphanomyces astaci are of particular conservation interest. In this study, we aim to evaluate the ecological interactions between Ap. astaci, its host Astacus astacus and individuals of the genus Daphnia, filter-feeding planktonic crustaceans. Our focus was on the consumption of the motile zoospores by Daphnia individuals, but we also considered the potential of Daphnia as non-target hosts. We conducted a series of infection and life-history experiments with Ap. astaci, three Daphnia species (D. magna, D. galeata, and D. pulex) and the noble crayfish As. astacus. We did not observe any lethal effects in the infection experiments involving Ap. astaci and Daphnia. Only D. pulex showed differences in some life-history traits. The feeding experiment using the motile zoospores of Ap. astaci as alternative food source or as supplement to different amounts of algal food revealed their nutritional value: D. magna individuals survived, grew, and reproduced on a zoospore diet alone. When zoospores were supplemented to the regular algal diet, all life-history parameters have been significantly improved. However, this successful consumption of zoospores did not result in a reduced mortality of the susceptible crayfish As. astacus during the infection experiment. Nevertheless, the pathogen load of Ap. astaci in the tissues of As. astacus was significantly reduced as a consequence of the feeding activity of Daphnia. Our results indicate that an abundant filter-feeding community can reduce the amount of infective zoospores in the water body and thus be beneficial to susceptible crayfish hosts, potentially acting as a general buffer against zoospore-transmitted diseases in lentic waters.
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Affiliation(s)
- Anne Thielsch
- Rhineland-Palatinate Technical University Kaiserslautern Landau, Institute for Environmental Sciences, Department of Molecular Ecology, Fortstr. 7, 76829 Landau, Germany.
| | - Caterina Francesconi
- Rhineland-Palatinate Technical University Kaiserslautern Landau, Institute for Environmental Sciences, Department of Molecular Ecology, Fortstr. 7, 76829 Landau, Germany; LOEWE Centre for Translational Biodiversity Genomics (LOEWE-TBG), Senckenberganlage 25, 60325 Frankfurt, Germany.
| | - Ljudevit Luka Boštjančić
- Rhineland-Palatinate Technical University Kaiserslautern Landau, Institute for Environmental Sciences, Department of Molecular Ecology, Fortstr. 7, 76829 Landau, Germany; LOEWE Centre for Translational Biodiversity Genomics (LOEWE-TBG), Senckenberganlage 25, 60325 Frankfurt, Germany; Department of Computer Science, ICube, UMR 7357, University of Strasbourg, CNRS, Centre de Recherche en Biomédecine de Strasbourg, Rue Eugène Boeckel 1, 67000 Strasbourg, France.
| | - Christoph Leeb
- Austrian Research Centre for Forests, Natural Hazards and Landscape (BFW), Seckendorff-Gudent-Weg 8, 1131 Vienna, Austria.
| | - Kathrin Theissinger
- Rhineland-Palatinate Technical University Kaiserslautern Landau, Institute for Environmental Sciences, Department of Molecular Ecology, Fortstr. 7, 76829 Landau, Germany; LOEWE Centre for Translational Biodiversity Genomics (LOEWE-TBG), Senckenberganlage 25, 60325 Frankfurt, Germany.
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2
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Malinowski CR, Searle CL, Schaber J, Höök TO. Microplastics impact simple aquatic food web dynamics through reduced zooplankton feeding and potentially releasing algae from consumer control. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 904:166691. [PMID: 37659532 DOI: 10.1016/j.scitotenv.2023.166691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 08/25/2023] [Accepted: 08/28/2023] [Indexed: 09/04/2023]
Abstract
Concentrations of microplastics in aquatic environments continue to rise due to industrial production and pollution. While there are various concerns regarding potential deleterious effects of microplastics on ecosystems, several knowledge gaps remain, including the potential for microplastics to directly and indirectly affect biotic interactions and food web dynamics. We explored the effects of environmentally relevant microplastic concentrations on two co-exposed species of herbaceous freshwater crustaceous zooplankton, filter feeding Daphnia dentifera and selective phytoplankton grazers Arctodiaptomus dorsalis. Study organisms were exposed to different concentrations of microplastics (plastic polyethylene microspheres; low = 2.38 × 10-8 mg/L, medium = 0.023 mg/L, high = 162 mg/L), phytoplankton prey, and predator cues, simulating a simple freshwater food web. Microplastic uptake was greater by D. dentifera, but both species were characterized by decreased algal consumption in the highest microplastic concentration treatment. Importantly, aqueous chlorophyll-a concentrations at the conclusion of the experiment were greater for the high microplastic treatment than all controls and other microplastic treatments. Finally, a predator effect was only apparent for D. dentifera, with greater microplastic uptake in the presence of a predator. We conclude that microplastics may adversely impact the ability of zooplankton to feed on algae and potentially release algae from consumptive control by herbivorous zooplankton. SYNOPSIS: This research aimed to better understand the broader food web effects of environmentally relevant microplastic concentrations on aquatic communities.
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Affiliation(s)
- Christopher R Malinowski
- Purdue University, Department of Forestry and Natural Resources, 195 Marsteller St., West Lafayette, IN 47907, USA; Ocean First Institute, 51 Shoreland Drive, Key Largo, FL 33037, USA.
| | - Catherine L Searle
- Purdue University, Department of Biological Sciences, 915 W. State Street, West Lafayette, IN 47907, USA
| | - James Schaber
- Purdue University, Bindley Bioscience Center, 1275 3(rd) St., West Lafayette, IN 47906, USA
| | - Tomas O Höök
- Purdue University, Department of Forestry and Natural Resources, 195 Marsteller St., West Lafayette, IN 47907, USA; Illinois-Indiana Sea Grant College Program, 195 Marsteller St., West Lafayette, IN 47907, USA
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3
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Koprivnikar J, Thieltges DW, Johnson PTJ. Consumption of trematode parasite infectious stages: from conceptual synthesis to future research agenda. J Helminthol 2023; 97:e33. [PMID: 36971341 DOI: 10.1017/s0022149x23000111] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Given their sheer cumulative biomass and ubiquitous presence, parasites are increasingly recognized as essential components of most food webs. Beyond their influence as consumers of host tissue, many parasites also have free-living infectious stages that may be ingested by non-host organisms, with implications for energy and nutrient transfer, as well as for pathogen transmission and infectious disease dynamics. This has been particularly well-documented for the cercaria free-living stage of digenean trematode parasites within the Phylum Platyhelminthes. Here, we aim to synthesize the current state of knowledge regarding cercariae consumption by examining: (a) approaches for studying cercariae consumption; (b) the range of consumers and trematode prey documented thus far; (c) factors influencing the likelihood of cercariae consumption; (d) consequences of cercariae consumption for individual predators (e.g. their viability as a food source); and (e) implications of cercariae consumption for entire communities and ecosystems (e.g. transmission, nutrient cycling and influences on other prey). We detected 121 unique consumer-by-cercaria combinations that spanned 60 species of consumer and 35 trematode species. Meaningful reductions in transmission were seen for 31 of 36 combinations that considered this; however, separate studies with the same cercaria and consumer sometimes showed different results. Along with addressing knowledge gaps and suggesting future research directions, we highlight how the conceptual and empirical approaches discussed here for consumption of cercariae are relevant for the infectious stages of other parasites and pathogens, illustrating the use of cercariae as a model system to help advance our knowledge regarding the general importance of parasite consumption.
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Affiliation(s)
- J Koprivnikar
- Department of Chemistry and Biology, Toronto Metropolitan University, 350 Victoria Street, Toronto, ON, Canada M5B 2K3
| | - D W Thieltges
- Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, Den Burg, The Netherlands
| | - P T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
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4
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Schilliger L, Paillusseau C, François C, Bonwitt J. Major Emerging Fungal Diseases of Reptiles and Amphibians. Pathogens 2023; 12:pathogens12030429. [PMID: 36986351 PMCID: PMC10053826 DOI: 10.3390/pathogens12030429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/16/2023] [Accepted: 03/06/2023] [Indexed: 03/11/2023] Open
Abstract
Emerging infectious diseases (EIDs) are caused by pathogens that have undergone recent changes in terms of geographic spread, increasing incidence, or expanding host range. In this narrative review, we describe three important fungal EIDs with keratin trophism that are relevant to reptile and amphibian conservation and veterinary practice. Nannizziopsis spp. have been mainly described in saurians; infection results in thickened, discolored skin crusting, with eventual progression to deep tissues. Previously only reported in captive populations, it was first described in wild animals in Australia in 2020. Ophidiomyces ophidiicola (formely O. ophiodiicola) is only known to infect snakes; clinical signs include ulcerating lesions in the cranial, ventral, and pericloacal regions. It has been associated with mortality events in wild populations in North America. Batrachochytrium spp. cause ulceration, hyperkeratosis, and erythema in amphibians. They are a major cause of catastrophic amphibian declines worldwide. In general, infection and clinical course are determined by host-related characteristics (e.g., nutritional, metabolic, and immune status), pathogens (e.g., virulence and environmental survival), and environment (e.g., temperature, hygrometry, and water quality). The animal trade is thought to be an important cause of worldwide spread, with global modifications in temperature, hygrometry, and water quality further affecting fungal pathogenicity and host immune response.
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Affiliation(s)
- Lionel Schilliger
- Argos Veterinary Clinic of Paris Auteuil, 35 Rue Leconte de Lisle, 75016 Paris, France
- SpéNac Referral Center, 100 Boulevard de la Tour Maubourg, 75007 Paris, France
- Correspondence: ; Tel.: +33-188-616-831
| | - Clément Paillusseau
- Argos Veterinary Clinic of Paris Auteuil, 35 Rue Leconte de Lisle, 75016 Paris, France
- SpéNac Referral Center, 100 Boulevard de la Tour Maubourg, 75007 Paris, France
| | - Camille François
- Argos Veterinary Clinic of Paris Auteuil, 35 Rue Leconte de Lisle, 75016 Paris, France
- SpéNac Referral Center, 100 Boulevard de la Tour Maubourg, 75007 Paris, France
| | - Jesse Bonwitt
- Department of Anthropology, Durham University, South Rd., Durham DH1 3LE, UK
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Deknock A, Pasmans F, van Leeuwenberg R, Van Praet S, De Troyer N, Goessens T, Lammens L, Bruneel S, Lens L, Martel A, Croubels S, Goethals P. Impact of heavy metal exposure on biological control of a deadly amphibian pathogen by zooplankton. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 823:153800. [PMID: 35150694 DOI: 10.1016/j.scitotenv.2022.153800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 02/07/2022] [Accepted: 02/07/2022] [Indexed: 06/14/2023]
Abstract
Despite devastating effects on global biodiversity, efficient mitigation strategies against amphibian chytridiomycosis are lacking. Since the free-living pathogenic zoospores of Batrachochytrium dendrobatidis (Bd), the infective stage of this disease, can serve as a nutritious food source for components of zooplankton communities, these groups may act as biological control agents by eliminating zoospores from the aquatic environment. Such pathogen-predator interaction is, however, embedded in the aquatic food web structure and is therefore affected by abiotic factors interfering with these networks. Heavy metals, released from both natural and anthropogenic sources, are widespread contaminants of aquatic ecosystems and may interfere with planktonic communities and thus pathogen elimination rates. We investigated the interaction between zooplankton communities and chytridiomycosis infections in a Flemish agricultural region. Moreover, we also investigated the impact of heavy metal contamination, that was previously investigated in the region and presented in recent work, on zooplankton assemblages and chytridiomycosis infections. Finally, we tested the effect of sublethal concentrations of copper and zinc on Bd removal rates by Daphnia magna in a laboratory assay. Although zinc, copper, nickel and chromium were widely abundant pollutants, heavy metals were no driving force for zooplankton assemblages at our study locations. Moreover, our field survey did not reveal indirect effects of zooplankton assemblages on chytridiomycosis infections. However, sampling occasions testing negative for Bd showed a higher degree of copper contamination compared to positive sampling occasions, indicating a potential inhibitory effect of copper on Bd prevalence. Finally, whereas D. magna significantly reduced zoospore densities in its environment, sublethal concentrations of copper and zinc showed no interference with pathogen removal in the laboratory assay. Our results provide perspectives for further research on such a biological control strategy against chytridiomycosis by optimizing environmental conditions for pathogen predation.
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Affiliation(s)
- Arne Deknock
- Department of Animal Sciences and Aquatic Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Building F, B-9000 Ghent, Belgium.
| | - Frank Pasmans
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Robby van Leeuwenberg
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Sarah Van Praet
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Niels De Troyer
- Department of Animal Sciences and Aquatic Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Building F, B-9000 Ghent, Belgium
| | - Tess Goessens
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Leni Lammens
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Stijn Bruneel
- Department of Animal Sciences and Aquatic Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Building F, B-9000 Ghent, Belgium
| | - Luc Lens
- Department of Biology, Faculty of Sciences, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium
| | - An Martel
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Siska Croubels
- Department of Pathobiology, Pharmacology and Zoological Medicine, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, D9, B-9820 Merelbeke, Belgium
| | - Peter Goethals
- Department of Animal Sciences and Aquatic Ecology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, Building F, B-9000 Ghent, Belgium
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6
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Harjoe CC, Buck JC, Rohr JR, Roberts CE, Olson DH, Blaustein AR. Pathogenic fungus causes density‐ and trait‐mediated trophic cascades in an aquatic community. Ecosphere 2022. [DOI: 10.1002/ecs2.4043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Carmen C. Harjoe
- Department of Integrative Biology Oregon State University Corvallis Oregon USA
| | - Julia C. Buck
- Department of Biology and Marine Biology University of North Carolina Wilmington Wilmington North Carolina USA
| | - Jason R. Rohr
- Department of Biological Sciences University of Notre Dame, Eck Institute for Global Health, and Environmental Change Initiative Notre Dame Indiana USA
| | - Claire E. Roberts
- Department of Integrative Biology Oregon State University Corvallis Oregon USA
| | - Deanna H. Olson
- Pacific Northwest Research Station USDA Forest Service Corvallis Oregon USA
| | - Andrew R. Blaustein
- Department of Integrative Biology Oregon State University Corvallis Oregon USA
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7
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Shaw KS, Civitello DJ. Re-emphasizing mechanism in the community ecology of disease. Funct Ecol 2021; 35:2376-2386. [PMID: 37860273 PMCID: PMC10586721 DOI: 10.1111/1365-2435.13892] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/11/2021] [Indexed: 11/29/2022]
Abstract
1. Hosts and their parasites exist within complex ecological communities. However, the role that non-focal community members, species which cannot be infected by a focal pathogen, may play in altering parasite transmission is often only studied in the lens of the "diversity-disease" relationship by focusing on species richness. This approach largely ignores mechanistic species interactions and risks collapsing our understanding of the community ecology of disease down to defining the prominence of "amplification" vs. "dilution" effects. 2. However, non-focal species vary in their traits, densities, and types of interactions with focal hosts and parasites. Therefore, a community ecology approach based on the mechanisms underlying parasite transmission, host harm, and dynamic species interactions may better advance our understanding of parasite transmission in complex communities. 3. Using the concept of the parasite's basic reproductive ratio, R0, as a generalizable framework, we examine several critical mechanisms by which interactions among hosts, parasites, and non-focal species modulate transmission and provide examples from relevant literature. 4. By focusing on the mechanism by which non-focal species impact transmission, we can emphasize the similarities among classic paradigms in the community ecology of disease, gain new insights into parasite invasion and persistence, community traits correlated with disease dilution or amplification, and the feasibility of biocontrol for parasites of conservation, agricultural, or human health concern.
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Affiliation(s)
- KS Shaw
- Department of Biology, Emory University, Atlanta, GA USA 30322
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8
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Rumschlag SL, Roth SA, McMahon TA, Rohr JR, Civitello DJ. Variability in environmental persistence but not per capita transmission rates of the amphibian chytrid fungus leads to differences in host infection prevalence. J Anim Ecol 2021; 91:170-181. [PMID: 34668575 DOI: 10.1111/1365-2656.13612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 09/27/2021] [Indexed: 11/28/2022]
Abstract
Heterogeneities in infections among host populations may arise through differences in environmental conditions through two mechanisms. First, environmental conditions may alter host exposure to pathogens via effects on survival. Second, environmental conditions may alter host susceptibility, making infection more or less likely if contact between a host and pathogen occurs. Further, host susceptibility might be altered through acquired resistance, which hosts can develop, in some systems, through exposure to dead or decaying pathogens and their metabolites. Environmental conditions may alter the rates of pathogen decomposition, influencing the likelihood of hosts developing acquired resistance. The present study primarily tests how environmental context influences the relative contributions of pathogen survival and per capita transmission on host infection prevalence using the amphibian chytrid fungus (Batrachochytrium dendrobatidis; Bd) as a model system. Secondarily, we evaluate how environmental context influences the decomposition of Bd because previous studies have shown that dead Bd and its metabolites can illicit acquired resistance in hosts. We conducted Bd survival and infection experiments and then fit models to discern how Bd mortality, decomposition and per capita transmission rates vary among water sources [e.g. artificial spring water (ASW) or water from three ponds]. We found that infection prevalence differed among water sources, which was driven by differences in mortality rates of Bd, rather than differences in per capita transmission rates. Bd mortality rates varied among pond water treatments and were lower in ASW compared to pond water. These results suggest that variation in Bd infection dynamics could be a function of environmental factors in waterbodies that result in differences in exposure of hosts to live Bd. In contrast to the persistence of live Bd, we found that the rates of decomposition of dead Bd did not vary among water sources, which may suggest that exposure of hosts to dead Bd or its metabolites might not commonly vary among nearby sites. Ultimately, a mechanistic understanding of the environmental dependence of free-living pathogens could lead to a deeper understanding of the patterns of outbreak heterogeneity, which could inform surveillance and management strategies.
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Affiliation(s)
- Samantha L Rumschlag
- Department of Biological Sciences, Environmental Change Initiative, and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA.,Department of Integrative Biology, University of South Florida, Tampa, FL, USA
| | - Sadie A Roth
- Department of Integrative Biology, University of South Florida, Tampa, FL, USA.,Department of Natural Resources Management, Texas Tech University, Lubbock, TX, USA
| | - Taegan A McMahon
- Department of Biology, University of Tampa, Tampa, FL, USA.,Department of Biology, Connecticut College, New London, CT, USA
| | - Jason R Rohr
- Department of Biological Sciences, Environmental Change Initiative, and Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, USA.,Department of Integrative Biology, University of South Florida, Tampa, FL, USA
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9
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De Troyer N, Bruneel S, Lock K, Greener MS, Facq E, Deknock A, Martel A, Pasmans F, Goethals P. Ratio-dependent functional response of two common Cladocera present in farmland ponds to Batrachochytrium dendrobatidis. FUNGAL ECOL 2021. [DOI: 10.1016/j.funeco.2021.101089] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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10
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Deknock A, Pasmans F, van Leeuwenberg R, Van Praet S, Bruneel S, Lens L, Croubels S, Martel A, Goethals P. Alternative food sources interfere with removal of a fungal amphibian pathogen by zooplankton. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.14018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Arne Deknock
- Department of Animal Sciences and Aquatic Ecology Faculty of Bioscience Engineering Ghent University Ghent Belgium
| | - Frank Pasmans
- Department of Pathology, Bacteriology and Poultry Diseases Faculty of Veterinary Medicine Ghent University Merelbeke Belgium
| | - Robby van Leeuwenberg
- Department of Pathology, Bacteriology and Poultry Diseases Faculty of Veterinary Medicine Ghent University Merelbeke Belgium
| | - Sarah Van Praet
- Department of Pathology, Bacteriology and Poultry Diseases Faculty of Veterinary Medicine Ghent University Merelbeke Belgium
| | - Stijn Bruneel
- Department of Animal Sciences and Aquatic Ecology Faculty of Bioscience Engineering Ghent University Ghent Belgium
| | - Luc Lens
- Department of Biology Faculty of Sciences Ghent University Ghent Belgium
| | - Siska Croubels
- Department of Pharmacology Toxicology and Biochemistry Faculty of Veterinary Medicine Ghent University Merelbeke Belgium
| | - An Martel
- Department of Pathology, Bacteriology and Poultry Diseases Faculty of Veterinary Medicine Ghent University Merelbeke Belgium
| | - Peter Goethals
- Department of Animal Sciences and Aquatic Ecology Faculty of Bioscience Engineering Ghent University Ghent Belgium
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11
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McDevitt-Galles T, Carpenter SA, Koprivnikar J, Johnson PTJ. How predator and parasite size interact to determine consumption of infectious stages. Oecologia 2021; 197:551-564. [PMID: 34405300 DOI: 10.1007/s00442-021-05010-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 08/02/2021] [Indexed: 01/02/2023]
Abstract
Parasites are important players in ecological communities that can shape community structure and influence ecosystem energy flow. Yet beyond their effects on hosts, parasites can also function as an important prey resource for predators. Predators that consume infectious stages in the environment can benefit from a nutrient-rich prey item while concurrently reducing transmission to downstream hosts, highlighting the broad importance of this interaction. Less clear, however, are the specific characteristics of parasites and predators that increase the likelihood of consumption. Here, we determine what combination(s) of predator and parasite morphological traits lead to high parasite consumption. We exposed the infectious stages (cercariae) of five trematode (fluke) taxa to aquatic insect predators with varying foraging strategies and morphologies. Across the 19 predator-parasite combinations tested, damselfly predators in the family Coenagrionidae were, on average, the most effective predators of cercariae, consuming between 13 and 55% of administered cercariae. Large-bodied cercariae of Ribeiroia ondatrae had the highest average vulnerability to predation, with 37-48% of cercariae consumed. The interaction between predator head width and cercariae tail size strongly influenced the probability of consumption: small-bodied predators were the most effective consumers, particularly for larger tailed parasites. Thus, the likelihood of parasite consumption depended strongly on the relative size between predator and parasite. Our study helps establish that predation on free-living parasites largely follows a broader predator-prey framework. This will help to identify which predator and parasite combinations will likely have high consumptive interactions, potentially reducing parasite transmission in natural populations.
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Affiliation(s)
| | - Sara A Carpenter
- Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
- Department of Integrative Biology, Oregon State University, Corvallis, OR, USA
| | - Janet Koprivnikar
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
| | - Pieter T J Johnson
- Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
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12
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Fisher MC, Pasmans F, Martel A. Virulence and Pathogenicity of Chytrid Fungi Causing Amphibian Extinctions. Annu Rev Microbiol 2021; 75:673-693. [PMID: 34351790 DOI: 10.1146/annurev-micro-052621-124212] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ancient enzootic associations between wildlife and their infections allow evolution to innovate mechanisms of pathogenicity that are counterbalanced by host responses. However, erosion of barriers to pathogen dispersal by globalization leads to the infection of hosts that have not evolved effective resistance and the emergence of highly virulent infections. Global amphibian declines driven by the rise of chytrid fungi and chytridiomycosis are emblematic of emerging infections. Here, we review how modern biological methods have been used to understand the adaptations and counteradaptations that these fungi and their amphibian hosts have evolved. We explore the interplay of biotic and abiotic factors that modify the virulence of these infections and dissect the complexity of this disease system. We highlight progress that has led to insights into how we might in the future lessen the impact of these emerging infections. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Matthew C Fisher
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial School of Public Health, Imperial College London, London W2 1PG, United Kingdom;
| | - Frank Pasmans
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, B-9820 Merelbeke, Belgium
| | - An Martel
- Wildlife Health Ghent, Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, B-9820 Merelbeke, Belgium
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13
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Mechanisms by which predators mediate host-parasite interactions in aquatic systems. Trends Parasitol 2021; 37:890-906. [PMID: 34281798 DOI: 10.1016/j.pt.2021.06.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 06/21/2021] [Accepted: 06/28/2021] [Indexed: 02/08/2023]
Abstract
It is often assumed that predators reduce disease prevalence and transmission by lowering prey population density and/or by selectively feeding on infected individuals. However, recent studies, many of which come from aquatic systems, suggest numerous alternative mechanisms by which predators can influence disease dynamics in their prey. Here, we review the mechanisms by which predators can mediate host-parasite interactions in aquatic prey. We highlight how life histories of aquatic hosts and parasites influence transmission pathways and describe how such pathways intersect with predation to shape disease dynamics. We also provide recommendations for future studies; experiments that account for multiple effects of predators on host-parasite interactions, and that examine how predator-host-parasite interactions shift under changing environmental conditions, are particularly needed.
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HIGHER INFECTION PREVALENCE IN AMPHIBIANS INHABITING HUMAN-MADE COMPARED TO NATURAL WETLANDS. J Wildl Dis 2021; 56:823-836. [PMID: 33600598 DOI: 10.7589/2019-09-220] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [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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15
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Schomaker RA, Dudycha JL. De novo transcriptome assembly of the green alga Ankistrodesmus falcatus. PLoS One 2021; 16:e0251668. [PMID: 33989339 PMCID: PMC8121315 DOI: 10.1371/journal.pone.0251668] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 04/30/2021] [Indexed: 01/11/2023] Open
Abstract
Ankistrodesmus falcatus is a globally distributed freshwater chlorophyte that is a candidate for biofuel production, is used to study the effects of toxins on aquatic communities, and is used as food in zooplankton research. Each of these research fields is transitioning to genomic tools. We created a reference transcriptome for of A. falcatus using NextGen sequencing and de novo assembly methods including Trinity, Velvet-Oases, and EvidentialGene. The assembled transcriptome has a total of 17,997 contigs, an N50 value of 2,462, and a GC content of 64.8%. BUSCO analysis recovered 83.3% of total chlorophyte BUSCOs and 82.5% of the eukaryotic BUSCOs. A portion (7.9%) of these supposedly single-copy genes were found to have transcriptionally active, distinct duplicates. We annotated the assembly using the dammit annotation pipeline, resulting in putative functional annotation for 68.89% of the assembly. Using available rbcL sequences from 16 strains (10 species) of Ankistrodesmus, we constructed a neighbor-joining phylogeny to illustrate genetic distances of our A. falcatus strain to other members of the genus. This assembly will be valuable for researchers seeking to identify Ankistrodesmus sequences in metatranscriptomic and metagenomic field studies and in experiments where separating expression responses of zooplankton and their algal food sources through bioinformatics is important.
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Affiliation(s)
- Rachel A Schomaker
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States of America
| | - Jeffry L Dudycha
- Department of Biological Sciences, University of South Carolina, Columbia, SC, United States of America
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16
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Farthing HN, Jiang J, Henwood AJ, Fenton A, Garner TWJ, Daversa DR, Fisher MC, Montagnes DJS. Microbial Grazers May Aid in Controlling Infections Caused by the Aquatic Zoosporic Fungus Batrachochytrium dendrobatidis. Front Microbiol 2021; 11:592286. [PMID: 33552011 PMCID: PMC7858660 DOI: 10.3389/fmicb.2020.592286] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/16/2020] [Indexed: 11/13/2022] Open
Abstract
Free-living eukaryotic microbes may reduce animal diseases. We evaluated the dynamics by which micrograzers (primarily protozoa) apply top-down control on the chytrid Batrachochytrium dendrobatidis (Bd) a devastating, panzootic pathogen of amphibians. Although micrograzers consumed zoospores (∼3 μm), the dispersal stage of chytrids, not all species grew monoxenically on zoospores. However, the ubiquitous ciliate Tetrahymena pyriformis, which likely co-occurs with Bd, grew at near its maximum rate (r = 1.7 d-1). A functional response (ingestion vs. prey abundance) for T. pyriformis, measured using spore-surrogates (microspheres) revealed maximum ingestion (I max ) of 1.63 × 103 zoospores d-1, with a half saturation constant (k) of 5.75 × 103 zoospores ml-1. Using these growth and grazing data we developed and assessed a population model that incorporated chytrid-host and micrograzer dynamics. Simulations using our data and realistic parameters obtained from the literature suggested that micrograzers could control Bd and potentially prevent chytridiomycosis (defined as 104 sporangia host-1). However, simulated inferior micrograzers (0.7 × I max and 1.5 × k) did not prevent chytridiomycosis, although they ultimately reduced pathogen abundance to below levels resulting in disease. These findings indicate how micrograzer responses can be applied when modeling disease dynamics for Bd and other zoosporic fungi.
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Affiliation(s)
- Hazel N. Farthing
- Shanghai Universities Key Laboratory of Marine Animal Taxonomy and Evolution, Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
- Department of Evolution, Ecology and Behaviour, Biosciences Building, University of Liverpool, Liverpool, United Kingdom
| | - Jiamei Jiang
- Shanghai Universities Key Laboratory of Marine Animal Taxonomy and Evolution, Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
| | - Alexandra J. Henwood
- Department of Evolution, Ecology and Behaviour, Biosciences Building, University of Liverpool, Liverpool, United Kingdom
| | - Andy Fenton
- Department of Evolution, Ecology and Behaviour, Biosciences Building, University of Liverpool, Liverpool, United Kingdom
| | - Trent W. J. Garner
- Institute of Zoology, Zoological Society of London, London, United Kingdom
| | - David R. Daversa
- MRC Centre for Global Infectious Disease Analysis, Imperial College London, London, United Kingdom
| | - Matthew C. Fisher
- Department of Evolution, Ecology and Behaviour, Biosciences Building, University of Liverpool, Liverpool, United Kingdom
- Institute of Zoology, Zoological Society of London, London, United Kingdom
| | - David J. S. Montagnes
- Department of Evolution, Ecology and Behaviour, Biosciences Building, University of Liverpool, Liverpool, United Kingdom
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17
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Towards a food web based control strategy to mitigate an amphibian panzootic in agricultural landscapes. Glob Ecol Conserv 2020. [DOI: 10.1016/j.gecco.2020.e01314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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18
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Dzyuba EV, Kondratov IG, Maikova OO, Nebesnykh IA, Khanaev IV, Denikina NN. Water Molds of the Order Saprolegniales (Oomycota) in Association with Fish and Sponge Species from Lake Baikal. BIOL BULL+ 2020. [DOI: 10.1134/s1062359020040056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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19
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Ismail NS, Olive M, Fernandez-Cassi X, Bachmann V, Kohn T. Viral Transfer and Inactivation through Zooplankton Trophic Interactions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:9418-9426. [PMID: 32662638 DOI: 10.1021/acs.est.0c02545] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Waterborne viruses are responsible for numerous diseases and are abundant in aquatic systems. Understanding the fate of viruses in natural systems has important implications for human health. This research quantifies the uptake of the bacteriophage T4 and the enteric virus echovirus 11 when exposed to the filter feeders Tetrahymena pyriformis and Daphnia magna, and also examines the potential of viral transfer due to trophic interactions. Experiments co-incubating each species with the viruses over 72-96 h showed up to a 4 log virus removal for T. pyriformis, while direct viral uptake by D. magna was not observed. However, viral uptake by D. magna occurred indirectly by viral transfer from prey to predator, through D. magna feeding on virus-loaded T. pyriformis. This prey-predator interaction resulted in a 1 log additional virus removal compared to removal by T. pyriformis alone. Incomplete viral inactivation by D. magna was observed through recovery of infective viruses from the daphnid tissue. This research furthers our understanding of the impacts of zooplankton filter feeding on viral inactivation and shows the potential for viral transfer through the food chain. The viral-zooplankton interactions observed in these studies indicate that zooplankton may improve water quality through viral uptake or may serve as vectors for infection by accumulating viruses.
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Affiliation(s)
- Niveen S Ismail
- Picker Engineering Program, Smith College, Northampton, Massachusetts 01063, United States
| | - Margot Olive
- Laboratory of Environmental Chemistry, School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Xavier Fernandez-Cassi
- Laboratory of Environmental Chemistry, School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Virginie Bachmann
- Laboratory of Environmental Chemistry, School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Tamar Kohn
- Laboratory of Environmental Chemistry, School of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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20
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Frenken T, Miki T, Kagami M, Van de Waal DB, Van Donk E, Rohrlack T, Gsell AS. The potential of zooplankton in constraining chytrid epidemics in phytoplankton hosts. Ecology 2019; 101:e02900. [PMID: 31544240 PMCID: PMC7003484 DOI: 10.1002/ecy.2900] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 07/18/2019] [Accepted: 08/26/2019] [Indexed: 11/10/2022]
Abstract
Fungal diseases threaten natural and man‐made ecosystems. Chytridiomycota (chytrids) infect a wide host range, including phytoplankton species that form the basis of aquatic food webs and produce roughly half of Earth's oxygen. However, blooms of large or toxic phytoplankton form trophic bottlenecks, as they are inedible to zooplankton. Chytrids infecting inedible phytoplankton provide a trophic link to zooplankton by producing edible zoospores of high nutritional quality. By grazing chytrid zoospores, zooplankton may induce a trophic cascade, as a decreased zoospore density will reduce new infections. Conversely, fewer infections will not produce enough zoospores to sustain long‐term zooplankton growth and reproduction. This intricate balance between zoospore density necessary for zooplankton energetic demands (growth/survival), and the loss in new infections (and thus new zoospores) because of grazing was tested empirically. To this end, we exposed a cyanobacterial host (Planktothrix rubescens) infected by a chytrid (Rizophydium megarrhizum) to a grazer density gradient (the rotifer Keratella cf. cochlearis). Rotifers survived and reproduced on a zoospore diet, but the Keratella population growth was limited by the amount of zoospores provided by chytrid infections, resulting in a situation where zooplankton survived but were restricted in their ability to control disease in the cyanobacterial host. We subsequently developed and parameterized a dynamical food‐chain model using an allometric relationship for clearance rate to assess theoretically the potential of different‐sized zooplankton groups to restrict disease in phytoplankton hosts. Our model suggests that smaller‐sized zooplankton may have a high potential to reduce chytrid infections on inedible phytoplankton. Together, our results point out the complexity of three‐way interactions between hosts, parasites, and grazers and highlight that trophic cascades are not always sustainable and may depend on the grazer's energetic demand.
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Affiliation(s)
- Thijs Frenken
- Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6708 PB, The Netherlands.,Department of Ecosystem Research, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 301, Berlin, 12587, Germany
| | - Takeshi Miki
- Department of Environmental Solution Technology, Faculty of Science and Technology, Ryukoku University, 1-5 Yokotani, Seta Oe-cho, Otsu, 520-2194, Japan.,Institute of Oceanography, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei, 107, Taiwan
| | - Maiko Kagami
- Graduate School of Environment and Information Sciences, Yokohama National University, 79-7, Tokiwadai, Hodogaya-ku, 240-8501, Japan
| | - Dedmer B Van de Waal
- Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6708 PB, The Netherlands
| | - Ellen Van Donk
- Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6708 PB, The Netherlands.,Institute of Environmental Biology, University of Utrecht, P.O. Box 80.056, Utrecht, 3508 TB, The Netherlands
| | - Thomas Rohrlack
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, Ås, NO-1432, Norway
| | - Alena S Gsell
- Department of Aquatic Ecology, Netherlands Institute of Ecology (NIOO-KNAW), P.O. Box 50, Wageningen, 6708 PB, The Netherlands
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21
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Hettyey A, Ujszegi J, Herczeg D, Holly D, Vörös J, Schmidt BR, Bosch J. Mitigating Disease Impacts in Amphibian Populations: Capitalizing on the Thermal Optimum Mismatch Between a Pathogen and Its Host. Front Ecol Evol 2019. [DOI: 10.3389/fevo.2019.00254] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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22
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Frenken T, Agha R, Schmeller DS, van West P, Wolinska J. Biological Concepts for the Control of Aquatic Zoosporic Diseases. Trends Parasitol 2019; 35:571-582. [PMID: 31076352 DOI: 10.1016/j.pt.2019.04.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Revised: 04/04/2019] [Accepted: 04/06/2019] [Indexed: 12/26/2022]
Abstract
Aquatic zoosporic diseases are threatening global biodiversity and ecosystem services, as well as economic activities. Current means of controlling zoosporic diseases are restricted primarily to chemical treatments, which are usually harmful or likely to be ineffective in the long term. Furthermore, some of these chemicals have been banned due to adverse effects. As a result, there is a need for alternative methods with minimal side-effects on the ecosystem or environment. Here, we integrate existing knowledge of three poorly interconnected areas of disease research - amphibian conservation, aquaculture, and plankton ecology - and arrange it into seven biological concepts to control zoosporic diseases. These strategies may be less harmful and more sustainable than chemical approaches. However, more research is needed before safe application is possible.
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Affiliation(s)
- Thijs Frenken
- Department of Ecosystem Research, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany.
| | - Ramsy Agha
- Department of Ecosystem Research, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
| | - Dirk S Schmeller
- ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse, France
| | - Pieter van West
- Aberdeen Oomycete Laboratory, College of Life Sciences and Medicine, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Justyna Wolinska
- Department of Ecosystem Research, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany; Institute of Biology, Freie Universität Berlin, Berlin, Germany
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23
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Zumbado‐Ulate H, García‐Rodríguez A, Vredenburg VT, Searle C. Infection with Batrachochytrium dendrobatidis is common in tropical lowland habitats: Implications for amphibian conservation. Ecol Evol 2019; 9:4917-4930. [PMID: 31031954 PMCID: PMC6476760 DOI: 10.1002/ece3.5098] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 02/25/2019] [Accepted: 02/28/2019] [Indexed: 11/24/2022] Open
Abstract
Numerous species of amphibians declined in Central America during the 1980s and 1990s. These declines mostly affected highland stream amphibians and have been primarily linked to chytridiomycosis, a deadly disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Since then, the majority of field studies on Bd in the Tropics have been conducted in midland and highland environments (>800 m) mainly because the environmental conditions of mountain ranges match the range of ideal abiotic conditions for Bd in the laboratory. This unbalanced sampling has led researchers to largely overlook host-pathogen dynamics in lowlands, where other amphibian species declined during the same period. We conducted a survey testing for Bd in 47 species (n = 348) in four lowland sites in Costa Rica to identify local host-pathogen dynamics and to describe the abiotic environment of these sites. We detected Bd in three sampling sites and 70% of the surveyed species. We found evidence that lowland study sites exhibit enzootic dynamics with low infection intensity and moderate to high prevalence (55% overall prevalence). Additionally, we found evidence that every study site represents an independent climatic zone, where local climatic differences may explain variations in Bd disease dynamics. We recommend more detection surveys across lowlands and other sites that have been historically considered unsuitable for Bd occurrence. These data can be used to identify sites for potential disease outbreaks and amphibian rediscoveries.
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Affiliation(s)
| | - Adrián García‐Rodríguez
- Departamento de Zoología, Instituto de BiologíaUniversidad Nacional Autónoma de México (UNAM)Ciudad de MéxicoMéxico
- Escuela de BiologíaUniversidad de Costa RicaSan JoséCosta Rica
- Departamento de EcologiaUniversidade Federal do Rio Grande do NorteNatalBrazil
| | | | - Catherine Searle
- Department of Biological SciencesPurdue UniversityWest LafayetteIndiana
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24
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Campbell L, Bower DS, Clulow S, Stockwell M, Clulow J, Mahony M. Interaction between temperature and sublethal infection with the amphibian chytrid fungus impacts a susceptible frog species. Sci Rep 2019; 9:83. [PMID: 30643160 PMCID: PMC6331562 DOI: 10.1038/s41598-018-35874-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/07/2018] [Indexed: 11/09/2022] Open
Abstract
The amphibian chytrid fungus Batrachochytrium dendrobatidis is an emerging infectious pathogen present on every continent except Antarctica. It causes the disease chytridiomycosis in a subset of species but does not always result in disease or death for every host. Ambient temperature influences both amphibian metabolism and chytrid pathogenicity, however the interactive effects on host physiology is not well understood. We investigated the sublethal effect of B. dendrobatidis infection on a susceptible host, Litoria aurea to test (1) whether the infection load, metabolic activity, body fat and gonad size differed in L. aurea at either 24 °C or 12 °C ambient temperatures and (2) whether previous Bd infection caused long-term changes to body fat and gonad size. Litoria aurea in 12 °C treatments had higher infection loads of B. dendrobatidis and lower survivorship. Metabolic rate was higher and fat mass was lower in infected individuals and in animals in 24 °C treatments. Male L. aurea previously infected with B. dendrobatidis had smaller testes 5 months-post clearance of infection, an effect likely to translate to fitness costs in wild populations. These experiments demonstrate a physiological cost to sublethal B. dendrobatidis infection, which suggests a reduction in host fitness mediated by temperature in the host's environment regardless of whether infection leads to mortality.
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Affiliation(s)
- Lachlan Campbell
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, 2300, NSW, Australia.
| | - Deborah S Bower
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, 2300, NSW, Australia.,James Cook University, Townsville, 4811, Qld, Australia
| | - Simon Clulow
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, 2300, NSW, Australia.,Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Michelle Stockwell
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, 2300, NSW, Australia
| | - John Clulow
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, 2300, NSW, Australia
| | - Michael Mahony
- School of Environmental and Life Sciences, University of Newcastle, Callaghan, Newcastle, 2300, NSW, Australia
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25
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Effects of Emerging Infectious Diseases on Amphibians: A Review of Experimental Studies. DIVERSITY-BASEL 2018. [DOI: 10.3390/d10030081] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Numerous factors are contributing to the loss of biodiversity. These include complex effects of multiple abiotic and biotic stressors that may drive population losses. These losses are especially illustrated by amphibians, whose populations are declining worldwide. The causes of amphibian population declines are multifaceted and context-dependent. One major factor affecting amphibian populations is emerging infectious disease. Several pathogens and their associated diseases are especially significant contributors to amphibian population declines. These include the fungi Batrachochytrium dendrobatidis and B. salamandrivorans, and ranaviruses. In this review, we assess the effects of these three pathogens on amphibian hosts as found through experimental studies. Such studies offer valuable insights to the causal factors underpinning broad patterns reported through observational studies. We summarize key findings from experimental studies in the laboratory, in mesocosms, and from the field. We also summarize experiments that explore the interactive effects of these pathogens with other contributors of amphibian population declines. Though well-designed experimental studies are critical for understanding the impacts of disease, inconsistencies in experimental methodologies limit our ability to form comparisons and conclusions. Studies of the three pathogens we focus on show that host susceptibility varies with such factors as species, host age, life history stage, population and biotic (e.g., presence of competitors, predators) and abiotic conditions (e.g., temperature, presence of contaminants), as well as the strain and dose of the pathogen, to which hosts are exposed. Our findings suggest the importance of implementing standard protocols and reporting for experimental studies of amphibian disease.
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26
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Mosher BA, Bailey LL, Muths E, Huyvaert KP. Host-pathogen metapopulation dynamics suggest high elevation refugia for boreal toads. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2018; 28:926-937. [PMID: 29430754 DOI: 10.1002/eap.1699] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 12/18/2017] [Accepted: 01/02/2018] [Indexed: 06/08/2023]
Abstract
Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads (Anaxyrus boreas boreas) in the southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic data set, we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be suboptimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian-Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.
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Affiliation(s)
- Brittany A Mosher
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Larissa L Bailey
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
| | - Erin Muths
- U.S. Geological Survey, Fort Collins Science Center, 2150 Centre Avenue, Building C, Fort Collins, Colorado, 80526, USA
| | - Kathryn P Huyvaert
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, Colorado, 80523, USA
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27
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Drawert B, Griesemer M, Petzold LR, Briggs CJ. Using stochastic epidemiological models to evaluate conservation strategies for endangered amphibians. J R Soc Interface 2018; 14:rsif.2017.0480. [PMID: 28855388 PMCID: PMC5582134 DOI: 10.1098/rsif.2017.0480] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 08/07/2017] [Indexed: 01/02/2023] Open
Abstract
Recent outbreaks of chytridiomycosis, the disease of amphibians caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), have contributed to population declines of numerous amphibian species worldwide. The devastating impacts of this disease have led researchers to attempt drastic conservation measures to prevent further extinctions and loss of biodiversity. The conservation measures can be labour-intensive or expensive, and in many cases have been unsuccessful. We developed a mathematical model of Bd outbreaks that includes the effects of demographic stochasticity and within-host fungal load dynamics. We investigated the impacts of one-time treatment conservation strategies during the disease outbreak that occurs following the initial arrival of Bd into a previously uninfected frog population. We found that for all versions of the model, for a large fraction of parameter space, none of the one-time treatment strategies are effective at preventing disease-induced extinction of the amphibian population. Of the strategies considered, treating frogs with antifungal agents to reduce their fungal load had the greatest likelihood of a beneficial outcome and the lowest risk of decreasing the persistence of the frog population, suggesting that this disease mitigation strategy should be prioritized over disinfecting the environment or reducing host density.
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Affiliation(s)
- Brian Drawert
- Department of Computer Science, University of North Carolina Asheville, Asheville, NC 28804, USA
| | - Marc Griesemer
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA 94551, USA
| | - Linda R Petzold
- Department of Computer Science, University of California, Santa Barbara, CA 93106, USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA 93106, USA
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Jani AJ, Briggs CJ. Host and Aquatic Environment Shape the Amphibian Skin Microbiome but Effects on Downstream Resistance to the Pathogen Batrachochytrium dendrobatidis Are Variable. Front Microbiol 2018; 9:487. [PMID: 29619014 PMCID: PMC5871691 DOI: 10.3389/fmicb.2018.00487] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 03/01/2018] [Indexed: 01/01/2023] Open
Abstract
Symbiotic microbial communities play key roles in the health and development of their multicellular hosts. Understanding why microbial communities vary among different host species or individuals is an important step toward understanding the diversity and function of the microbiome. The amphibian skin microbiome may affect resistance to the fungal pathogen Batrachochytrium dendrobatidis (Bd). Still, the factors that determine the diversity and composition of the amphibian skin microbiome, and therefore may ultimately contribute to disease resistance, are not well understood. We conducted a two-phase experiment to first test how host and environment shape the amphibian skin microbiome, and then test if the microbiome affects or is affected by Bd infection. Most lab experiments testing assembly of the amphibian skin microbiome so far have compared sterile to non-sterile environments or heavily augmented to non-augmented frogs. A goal of this study was to evaluate, in an experimental setting, realistic potential drivers of microbiome assembly that would be relevant to patterns observed in nature. We tested effects of frog genetic background (2 source populations) and 6 natural lake water sources in shaping the microbiome of the frog Rana sierrae. Water in which frogs were housed affected the microbiome in a manner that partially mimicked patterns observed in natural populations. In particular, frogs housed in water from disease-resistant populations had greater bacterial richness than frogs housed in water from populations that died out due to Bd. However, in the experiment this difference in microbiomes did not lead to differences in host mortality or rates of pathogen load increase. Frog source population also affected the microbiome and, although none of the frogs in this study showed true resistance to infection, host source population had a small effect on the rate of pathogen load increase. This difference in infection trajectories could be due to the observed differences in the microbiome, but could also be due to other traits that differ between frogs from the two populations. In addition to examining effects of the microbiome on Bd, we tested the effect of Bd infection severity on the microbiome. Specifically, we studied a time series of the microbiome over the course of infection to test if the effects of Bd on the microbiome are dependent on Bd infection severity. Although limited to a small subset of frogs, time series analysis suggested that relative abundances of several bacterial phylotypes changed as Bd loads increased through time, indicating that Bd-induced disturbance of the R. sierrae microbiome is not a binary effect but instead is dependent on infection severity. We conclude that both host and aquatic environment help shape the R. sierrae skin microbiome, with links to small changes in disease resistance in some cases, but in this study the effect of Bd on the microbiome was greater than the effect of the microbiome on Bd. Assessment of the microbiome differences between more distantly related populations than those studied here is needed to fully understand the role of the microbiome in resistance to Bd.
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Affiliation(s)
- Andrea J Jani
- Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI, United States
| | - Cheryl J Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
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Wilson EA, Briggs CJ, Dudley TL. Invasive African clawed frogs in California: A reservoir for or predator against the chytrid fungus? PLoS One 2018; 13:e0191537. [PMID: 29444096 PMCID: PMC5812569 DOI: 10.1371/journal.pone.0191537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/05/2018] [Indexed: 11/18/2022] Open
Abstract
Amphibian species are experiencing population declines due to infection by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). The African clawed frog (Xenopus laevis), an asymptomatic carrier of Bd, has been implicated in the spread of this pathogen through global trade and established invasive populations on several continents. However, research has not explored the relationships of both life stages of this amphibian with Bd. While the post-metamorphic individuals may act as a reservoir, spreading the infection to susceptible species, the filter-feeding larvae may consume the motile Bd zoospores from the water column, potentially reducing pathogen abundance and thus the likelihood of infection. We explore these contrasting processes by assessing Bd prevalence and infection intensities in field populations of post-metamorphic individuals, and performing laboratory experiments to determine if larval X. laevis preyed upon Bd zoospores. The water flea, Daphnia magna, was included in the Bd consumption trials to compare consumption rates and to explore whether intraguild predation between the larval X. laevis and Daphnia may occur, potentially interfering with control of Bd zoospores by Daphnia. Field surveys of three X. laevis populations in southern California, in which 70 post-metamorphic individuals were tested for Bd, found 10% infection prevalence. All infected individuals had very low infection loads (all Bd loads were below 5 zoospore equivalents). Laboratory experiments found that larval X. laevis consume Bd zoospores and therefore may reduce Bd abundance and transmission between amphibians. However, metamorphic and juvenile X. laevis exhibited intraguild predation by consuming Daphnia, which also prey upon Bd zoospores. The results suggest that X laevis is not a large reservoir for Bd and its larval stage may offer some reduction of Bd transmission through direct predation.
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Affiliation(s)
- Emily A. Wilson
- Marine Science Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
| | - Cheryl J. Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| | - Tom L. Dudley
- Marine Science Institute, University of California Santa Barbara, Santa Barbara, California, United States of America
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Hite JL, Bosch J, Fernández-Beaskoetxea S, Medina D, Hall SR. Joint effects of habitat, zooplankton, host stage structure and diversity on amphibian chytrid. Proc Biol Sci 2017; 283:rspb.2016.0832. [PMID: 27466456 DOI: 10.1098/rspb.2016.0832] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 07/05/2016] [Indexed: 11/12/2022] Open
Abstract
Why does the severity of parasite infection differ dramatically across habitats? This question remains challenging to answer because multiple correlated pathways drive disease. Here, we examined habitat-disease links through direct effects on parasites and indirect effects on parasite predators (zooplankton), host diversity and key life stages of hosts. We used a case study of amphibian hosts and the chytrid fungus, Batrachochytrium dendrobatidis, in a set of permanent and ephemeral alpine ponds. A field experiment showed that ultraviolet radiation (UVR) killed the free-living infectious stage of the parasite. Yet, permanent ponds with more UVR exposure had higher infection prevalence. Two habitat-related indirect effects worked together to counteract parasite losses from UVR: (i) UVR reduced the density of parasite predators and (ii) permanent sites fostered multi-season host larvae that fuelled parasite production. Host diversity was unlinked to hydroperiod or UVR but counteracted parasite gains; sites with higher diversity of host species had lower prevalence of infection. Thus, while habitat structure explained considerable variation in infection prevalence through two indirect pathways, it could not account for everything. This study demonstrates the importance of creating mechanistic, food web-based links between multiple habitat dimensions and disease.
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Affiliation(s)
- Jessica L Hite
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Jaime Bosch
- Museo Nacional de Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain Centro de Investigación, Seguimiento y Evaluación, Parque Nacional de la Sierra de Guadarrama, Cta. M-604, Km. 27.6, 28740 Rascafría, Spain
| | | | - Daniel Medina
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, USA
| | - Spencer R Hall
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Al-Shorbaji F, Roche B, Britton R, Andreou D, Gozlan R. Influence of predation on community resilience to disease. J Anim Ecol 2017; 86:1147-1158. [PMID: 28758196 DOI: 10.1111/1365-2656.12722] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 06/01/2017] [Indexed: 02/05/2023]
Abstract
Outbreaks of generalist pathogens are influenced by host community structure, including population density and species diversity. Within host communities predation can influence pathogen transmission rates, prevalence and impacts. However, the influence of predation on community resilience to outbreaks of generalist pathogens is not fully understood. The role of predation on host community resilience to disease was assessed using an epidemiological multi-host susceptible-exposed-infectious-recovered model. Sphaerothecum destruens, an emerging fungal-like generalist pathogen, was used as a model pathogen. Six cyprinid and salmonid fishes, including an asymptomatic carrier, were selected as model hosts that are known to be impacted by S. destruens, and they were used within a model host community. Pathogen release into the host community was via introduction of the asymptomatic carrier. Mortality from infection, pathogen incubation rate, and host recovery rate were set to a range of evidence-based values in each species and were varied in secondary consumers to predict top-down effects of infection on the resilience of a host community. Predation pressure within the fish community was varied to test its effects on infection prevalence and host survival in the community. Model predictions suggested that predation of the asymptomatic hosts by fishes in the host community was insufficient to eliminate S. destruens. Sphaerothecum destruens persisted in the community due to its rapid transmission from the asymptomatic host to susceptible host fishes. Following transmission, pathogen prevalence in the community was driven by transmission within and between susceptible host fishes, indicating low host community resilience. However, introducing low densities of a highly specific piscivorous fish into the community to pre-date asymptomatic hosts could limit pathogen prevalence in the host community, thus increasing resilience. The model predictions indicate that whilst resilience to this generalist pathogen in the host community was low, this could be increased using management interventions. The results suggest that this model has high utility for predicting community resilience to disease and thus can be applied to other generalist parasites to determine risks of disease emergence.
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Affiliation(s)
- Farah Al-Shorbaji
- Bournemouth University, Faculty of Science and Technology, Dorset, UK
| | - Benjamin Roche
- Unit for Mathematical and Computer Modelling of Complex Systems, Institute of Research for Development, Montpellier, France.,Institut de Recherche pour le Développement UMR MIVEGEC IRD-CNRS-Université de Montpellier, Centre IRD de Montpellier, Montpellier, France
| | - Robert Britton
- Bournemouth University, Faculty of Science and Technology, Dorset, UK
| | - Demetra Andreou
- Bournemouth University, Faculty of Science and Technology, Dorset, UK
| | - Rodolphe Gozlan
- Institut de Recherche pour le Développement UMR MIVEGEC IRD-CNRS-Université de Montpellier, Centre IRD de Montpellier, Montpellier, France.,Institut de Recherche pour le Développement UMR BOREA IRD-MNHN-Université Pierre et Marie Curie, Muséum National d'Histoire Naturelle, Paris Cedex 5, France
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The Emerging Amphibian Fungal Disease, Chytridiomycosis: A Key Example of the Global Phenomenon of Wildlife Emerging Infectious Diseases. Microbiol Spectr 2017; 4. [PMID: 27337484 DOI: 10.1128/microbiolspec.ei10-0004-2015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The spread of amphibian chytrid fungus, Batrachochytrium dendrobatidis, is associated with the emerging infectious wildlife disease chytridiomycosis. This fungus poses an overwhelming threat to global amphibian biodiversity and is contributing toward population declines and extinctions worldwide. Extremely low host-species specificity potentially threatens thousands of the 7,000+ amphibian species with infection, and hosts in additional classes of organisms have now also been identified, including crayfish and nematode worms.Soon after the discovery of B. dendrobatidis in 1999, it became apparent that this pathogen was already pandemic; dozens of countries and hundreds of amphibian species had already been exposed. The timeline of B. dendrobatidis's global emergence still remains a mystery, as does its point of origin. The reason why B. dendrobatidis seems to have only recently increased in virulence to catalyze this global disease event remains unknown, and despite 15 years of investigation, this wildlife pandemic continues primarily uncontrolled. Some disease treatments are effective on animals held in captivity, but there is currently no proven method to eradicate B. dendrobatidis from an affected habitat, nor have we been able to protect new regions from exposure despite knowledge of an approaching "wave" of B. dendrobatidis and ensuing disease.International spread of B. dendrobatidis is largely facilitated by the commercial trade in live amphibians. Chytridiomycosis was recently listed as a globally notifiable disease by the World Organization for Animal Health, but few countries, if any, have formally adopted recommended measures to control its spread. Wildlife diseases continue to emerge as a consequence of globalization, and greater effort is urgently needed to protect global health.
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Rethinking the role of invertebrate hosts in the life cycle of the amphibian chytridiomycosis pathogen. Parasitology 2016; 143:1723-1729. [PMID: 27573338 DOI: 10.1017/s0031182016001360] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The amphibian pathogen Batrachochytrium dendrobatidis (Bd) has recently emerged as a primary factor behind declining global amphibian populations. Much about the basic biology of the pathogen is unknown, however, such as its true ecological niche and life cycle. Here we evaluated invertebrates as infection models by inoculating host species that had previously been suggested to be parasitized in laboratory settings: crayfish (Procambarus alleni) and nematodes (Caenorhabditis elegans). We found neither negative effects on either host nor evidence of persistent infection despite using higher inoculum loads and more pathogen genotypes than tested in previous studies. In contrast, addition of Bd to C. elegans cultures had a slight positive effect on host growth. Bd DNA was detected on the carapace of 2/34 crayfish 7 weeks post-inoculation, suggesting some means of persistence in the mesocosm. These results question the role of invertebrates as alternative hosts of Bd and their ability to modulate disease dynamics.
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34
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Whitfield SM, Lips KR, Donnelly MA. Amphibian Decline and Conservation in Central America. COPEIA 2016. [DOI: 10.1643/ch-15-300] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Evaluation of Daphnid Grazing on Microscopic Zoosporic Fungi by Using Comparative Threshold Cycle Quantitative PCR. Appl Environ Microbiol 2016; 82:3868-3874. [PMID: 27107112 DOI: 10.1128/aem.00087-16] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 04/14/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Lethal parasitism of large phytoplankton by chytrids (microscopic zoosporic fungi) may play an important role in organic matter and nutrient cycling in aquatic environments by shunting carbon away from hosts and into much smaller zoospores, which are more readily consumed by zooplankton. This pathway provides a mechanism to more efficiently retain carbon within food webs and reduce export losses. However, challenges in accurate identification and quantification of chytrids have prevented a robust assessment of the relative importance of parasitism for carbon and energy flows within aquatic systems. The use of molecular techniques has greatly advanced our ability to detect small, nondescript microorganisms in aquatic environments in recent years, including chytrids. We used quantitative PCR (qPCR) to quantify the consumption of zoospores by Daphnia in laboratory experiments using a culture-based comparative threshold cycle (CT) method. We successfully quantified the reduction of zoospores in water samples during Daphnia grazing and confirmed the presence of chytrid DNA inside the daphnid gut. We demonstrate that comparative CT qPCR is a robust and effective method to quantify zoospores and evaluate zoospore grazing by zooplankton and will aid in better understanding how chytrids contribute to organic matter cycling and trophic energy transfer within food webs. IMPORTANCE The study of aquatic fungi is often complicated by the fact that they possess complex life cycles that include a variety of morphological forms. Studies that rely on morphological characteristics to quantify the abundances of all stages of the fungal life cycle face the challenge of correctly identifying and enumerating the nondescript zoospores. These zoospores, however, provide an important trophic link between large colonial phytoplankton and zooplankton: that is, once the carbon is liberated from phytoplankton into the parasitic zoospores, the latter are consumed by zooplankton and carbon is retained in the aquatic food web rather than exported from the system. This study provides a tool to quantify zoospores and evaluate the consumption of zoospores by zooplankton in order to further our understanding of their role in food web dynamics.
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Al-Shorbaji F, Roche B, Gozlan R, Britton R, Andreou D. The consequences of reservoir host eradication on disease epidemiology in animal communities. Emerg Microbes Infect 2016; 5:e46. [PMID: 27165562 PMCID: PMC4893545 DOI: 10.1038/emi.2016.46] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 01/19/2016] [Accepted: 01/25/2016] [Indexed: 11/09/2022]
Abstract
Non-native species have often been linked with introduction of novel pathogens that spill over into native communities, and the amplification of the prevalence of native parasites. In the case of introduced generalist pathogens, their disease epidemiology in the extant communities remains poorly understood. Here, Sphaerothecum destruens, a generalist fungal-like fish pathogen with bi-modal transmission (direct and environmental) was used to characterise the biological drivers responsible for disease emergence in temperate fish communities. A range of biotic factors relating to both the pathogen and the surrounding host communities were used in a novel susceptible-exposed-infectious-recovered (SEIR) model to test how these factors affected disease epidemiology. These included: (i) pathogen prevalence in an introduced reservoir host (Pseudorasbora parva); (ii) the impact of reservoir host eradication and its timing and (iii) the density of potential hosts in surrounding communities and their connectedness. These were modelled across 23 combinations and indicated that the spill-over of pathogen propagules via environmental transmission resulted in rapid establishment in adjacent fish communities (<1 year). Although disease dynamics were initially driven by environmental transmission in these communities, once sufficient numbers of native hosts were infected, the disease dynamics were driven by intra-species transmission. Subsequent eradication of the introduced host, irrespective of its timing (after one, two or three years), had limited impact on the long-term disease dynamics among local fish communities. These outputs reinforced the importance of rapid detection and eradication of non-native species, in particular when such species are identified as healthy reservoirs of a generalist pathogen.
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Affiliation(s)
- Farah Al-Shorbaji
- Faculty of Science and Technology, Bournemouth University, Fern Barrow, Talbot Campus, Poole, Dorset, BH12 5BB, UK
| | - Benjamin Roche
- Unit for Mathematical and Computer Modelling of Complex Systems, Institute of Research for Development, 34394 Montpellier, France
- Pierre and Marie Curie University, 75005 Paris, France
| | - Rodolphe Gozlan
- Pierre and Marie Curie University, 75005 Paris, France
- Biology of Aquatic Organisms and Ecosystems Research Unit, Institute of Research for Development, 34394 Montpellier, France
- National Museum of Natural History, 75231 Paris, France
| | - Robert Britton
- Faculty of Science and Technology, Bournemouth University, Fern Barrow, Talbot Campus, Poole, Dorset, BH12 5BB, UK
| | - Demetra Andreou
- Faculty of Science and Technology, Bournemouth University, Fern Barrow, Talbot Campus, Poole, Dorset, BH12 5BB, UK
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Grossart HP, Wurzbacher C, James TY, Kagami M. Discovery of dark matter fungi in aquatic ecosystems demands a reappraisal of the phylogeny and ecology of zoosporic fungi. FUNGAL ECOL 2016. [DOI: 10.1016/j.funeco.2015.06.004] [Citation(s) in RCA: 139] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Buck JC, Rohr JR, Blaustein AR. Effects of nutrient supplementation on host-pathogen dynamics of the amphibian chytrid fungus: a community approach. FRESHWATER BIOLOGY 2016; 61:110-120. [PMID: 28956554 PMCID: PMC4857202 DOI: 10.1111/fwb.12685] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Anthropogenic stressors may influence hosts and their pathogens directly or may alter host-pathogen dynamics indirectly through interactions with other species. For example, in aquatic ecosystems, eutrophication may be associated with increased or decreased disease risk. Conversely, pathogens can influence community structure and function and are increasingly recognised as important members of the ecological communities in which they exist.In outdoor mesocosms, we experimentally manipulated nutrients (nitrogen and phosphorus) and the presence of a fungal pathogen, Batrachochytrium dendrobatidis (Bd), and examined the effects on Bd abundance on larval amphibian hosts (Pseudacris regilla: Hylidae), amphibian traits and community dynamics. We predicted that resource supplementation would mitigate negative effects of Bd on tadpole growth and development and that indirect effects of treatments would propagate through the community.Nutrient additions caused changes in algal growth, which benefitted tadpoles through increased mass, development and survival. Bd-exposed tadpoles metamorphosed sooner than unexposed individuals, but their mass at metamorphosis was not affected by Bd exposure. We detected additive rather than interactive effects of nutrient supplementation and Bd in this experiment.Nutrient supplementation was not a significant predictor of infection load of larval amphibians. However, a structural equation model revealed that resource supplementation and exposure of amphibians to Bd altered the structure of the aquatic community. This is the first demonstration that sublethal effects of Bd on amphibians can alter aquatic community dynamics.
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Affiliation(s)
- Julia C Buck
- Texas Research Institute for Environmental Studies, Sam Houston State University, Huntsville, TX, U.S.A
- Department of Integrative Biology, Oregon State University, Corvallis, OR, U.S.A
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, FL, U.S.A
| | - Andrew R Blaustein
- Department of Integrative Biology, Oregon State University, Corvallis, OR, U.S.A
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Van Rooij P, Martel A, Haesebrouck F, Pasmans F. Amphibian chytridiomycosis: a review with focus on fungus-host interactions. Vet Res 2015; 46:137. [PMID: 26607488 PMCID: PMC4660679 DOI: 10.1186/s13567-015-0266-0] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Accepted: 10/05/2015] [Indexed: 01/30/2023] Open
Abstract
Amphibian declines and extinctions are emblematic for the current sixth mass extinction event. Infectious drivers of these declines include the recently emerged fungal pathogens Batrachochytrium dendrobatidis and Batrachochytrium salamandrivorans (Chytridiomycota). The skin disease caused by these fungi is named chytridiomycosis and affects the vital function of amphibian skin. Not all amphibians respond equally to infection and host responses might range from resistant, over tolerant to susceptible. The clinical outcome of infection is highly dependent on the amphibian host, the fungal virulence and environmental determinants. B. dendrobatidis infects the skin of a large range of anurans, urodeles and caecilians, whereas to date the host range of B. salamandrivorans seems limited to urodeles. So far, the epidemic of B. dendrobatidis is mainly limited to Australian, neotropical, South European and West American amphibians, while for B. salamandrivorans it is limited to European salamanders. Other striking differences between both fungi include gross pathology and thermal preferences. With this review we aim to provide the reader with a state-of-the art of host-pathogen interactions for both fungi, in which new data pertaining to the interaction of B. dendrobatidis and B. salamandrivorans with the host’s skin are integrated. Furthermore, we pinpoint areas in which more detailed studies are necessary or which have not received the attention they merit.
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Affiliation(s)
- Pascale Van Rooij
- Laboratory of Veterinary Bacteriology and Mycology, Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - An Martel
- Laboratory of Veterinary Bacteriology and Mycology, Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Freddy Haesebrouck
- Laboratory of Veterinary Bacteriology and Mycology, Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
| | - Frank Pasmans
- Laboratory of Veterinary Bacteriology and Mycology, Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
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Zhang T, Chaturvedi V, Chaturvedi S. Novel Trichoderma polysporum Strain for the Biocontrol of Pseudogymnoascus destructans, the Fungal Etiologic Agent of Bat White Nose Syndrome. PLoS One 2015; 10:e0141316. [PMID: 26509269 PMCID: PMC4624962 DOI: 10.1371/journal.pone.0141316] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 10/07/2015] [Indexed: 01/01/2023] Open
Abstract
White-nose syndrome (WNS), an emerging disease of hibernating bats, has rapidly spread across eastern North America killing millions of bats. Pseudogymnoascus destructans (Pd), the sole etiologic agent of WNS, is widespread and persistent in bat hibernacula. Control of Pd in the affected sites is urgently needed to break the transmission cycle while minimizing any adverse impact on the native organisms. We isolated a novel strain of Trichoderma polysporum (Tp) from one of the caves at the epicenter of WNS zoonotic. Detailed experimental studies revealed: (1) Tp WPM 39143 was highly adapted to grow at temperatures simulating the cave environment (6°C-15°C), (2) Tp WPM 39143 restricted Pd colony growth in dual culture challenges, (3) Tp WPM 39143 caused four logs reduction of Pd colony forming units and genome copies in autoclaved soil samples from one of the WNS affected caves, (4) Tp WPM 39143 extract showed specific fungicidal activity against Pd in disk diffusion assay, but not against closely related fungus P. pannorum (Pp), (5) Tp WPM 39143 extract retained inhibitory activity after exposure to high temperatures, light and proteinase K, and (6) Inhibitory metabolites in Tp WPM 39143 extract comprised of water-soluble, high polarity compounds. These results suggest that Tp WPM 39143 is a promising candidate for further evaluation as a biocontrol agent of Pd in WNS affected sites.
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Affiliation(s)
- Tao Zhang
- Mycology Laboratory, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
| | - Vishnu Chaturvedi
- Mycology Laboratory, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America
| | - Sudha Chaturvedi
- Mycology Laboratory, Wadsworth Center, New York State Department of Health, Albany, New York, United States of America
- Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, New York, United States of America
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Hanlon SM, Lynch KJ, Kerby JL, Parris MJ. The effects of a fungicide and chytrid fungus on anuran larvae in aquatic mesocosms. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:12929-12940. [PMID: 25913318 DOI: 10.1007/s11356-015-4566-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 04/19/2015] [Indexed: 06/04/2023]
Abstract
The amphibian disease chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), has been linked to significant amphibian declines over the past three decades. The most severe effects of the pathogen have been primarily observed in relatively pristine areas that are not affected by many anthropogenic factors.One hypothesis concerning improved amphibian persistence with Bd in disturbed landscapes is that contaminants may abate the effects of Bd on amphibians. Recent laboratory studies have shown that pesticides, specifically the fungicide thiophanate-methyl (TM), can kill Bd outside of hosts and clear Bd infections within hosts. Using aquatic mesocosms, we tested the hypothesis that TM (0.43 mg/L) would alter growth and development of Lithobates sphenocephalus (southern leopard frog) tadpoles and Bd-infection loads in infected individuals. We hypothesized that the scope of such alterations and infection clearing would be affected by aquatic community variables, specifically zooplankton. TM altered zooplankton diversity (reduced cladoceran and increased copepod and ostracod abundances) and caused mortality to all tadpoles in TM-exposed tanks. In TM-free tanks, Bd-exposed tadpoles in high-density treatments metamorphosed smaller than Bd-unexposed, effects that were reversed in low-density treatments. Our study demonstrates the potential adverse effects of a fungicide and Bd on tadpoles and aquatic systems.
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Affiliation(s)
- Shane M Hanlon
- Department of Biological Sciences, University of Memphis, Memphis, TN, 38152, USA,
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Han BA, Kerby JL, Searle CL, Storfer A, Blaustein AR. Host species composition influences infection severity among amphibians in the absence of spillover transmission. Ecol Evol 2015; 5:1432-9. [PMID: 25897383 PMCID: PMC4395173 DOI: 10.1002/ece3.1385] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 12/02/2014] [Accepted: 12/03/2014] [Indexed: 11/23/2022] Open
Abstract
Wildlife epidemiological outcomes can depend strongly on the composition of an ecological community, particularly when multiple host species are affected by the same pathogen. However, the relationship between host species richness and disease risk can vary with community context and with the degree of spillover transmission that occurs among co-occurring host species. We examined the degree to which host species composition influences infection by Batrachochytrium dendrobatidis (Bd), a widespread fungal pathogen associated with amphibian population declines around the world, and whether transmission occurs from one highly susceptible host species to other co-occurring host species. By manipulating larval assemblages of three sympatric amphibian species in the laboratory, we characterized the relationship between host species richness and infection severity, whether infection mediates growth and survivorship differently across various combinations of host species, and whether Bd is transmitted from experimentally inoculated tadpoles to uninfected tadpoles. We found evidence of a dilution effect where Bd infection severity was dramatically reduced in the most susceptible of the three host species (Anaxyrus boreas). Infection also mediated survival and growth of all three host species such that the presence of multiple host species had both positive (e.g., infection reduction) and negative (e.g., mortality) effects on focal species. However, we found no evidence that Bd infection is transmitted by this species. While these results demonstrate that host species richness as well as species identity underpin infection dynamics in this system, dilution is not the product of reduced transmission via fewer infectious individuals of a susceptible host species. We discuss various mechanisms, including encounter reduction and antagonistic interactions such as competition and opportunistic cannibalism that may act in concert to mediate patterns of infection severity, growth, and mortality observed in multihost communities.
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Affiliation(s)
- Barbara A Han
- Cary Institute of Ecosystem Studies Millbrook, New York, 12545
| | - Jacob L Kerby
- Biology Department, University of South Dakota 414 E. Clark St., Vermillion, South Dakota, 57069
| | - Catherine L Searle
- Department of Ecology and Evolutionary Biology, University of Michigan Ann Arbor, Michigan, 48109
| | - Andrew Storfer
- School of Biological Sciences, Washington State University Pullman, Washington, 99164
| | - Andrew R Blaustein
- Department of Zoology, Oregon State University 3029 Cordley Hall, Corvallis, Oregon, 97331
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Buck JC, Scholz KI, Rohr JR, Blaustein AR. Trophic dynamics in an aquatic community: interactions among primary producers, grazers, and a pathogenic fungus. Oecologia 2014; 178:239-48. [PMID: 25432573 DOI: 10.1007/s00442-014-3165-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 11/14/2014] [Indexed: 10/24/2022]
Abstract
Free-living stages of parasites are consumed by a variety of predators, which might have important consequences for predators, parasites, and hosts. For example, zooplankton prey on the infectious stage of the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), a pathogen responsible for amphibian population declines and extinctions worldwide. Predation on parasites is predicted to influence community structure and function, and affect disease risk, but relatively few studies have explored its consequences empirically. We investigated interactions among Rana cascadae tadpoles, zooplankton, and Bd in a fully factorial experiment in outdoor mesocosms. We measured growth, development, survival, and infection of amphibians and took weekly measurements of the abundance of zooplankton, phytoplankton (suspended algae), and periphyton (attached algae). We hypothesized that zooplankton might have positive indirect effects on tadpoles by consuming Bd zoospores and by consuming phytoplankton, thus reducing the shading of a major tadpole resource, periphyton. We also hypothesized that zooplankton would have negative effects on tadpoles, mediated by competition for algal resources. Mixed-effects models, repeated-measures ANOVAs, and a structural equation model revealed that zooplankton significantly reduced phytoplankton but had no detectable effects on Bd or periphyton. Hence, the indirect positive effects of zooplankton on tadpoles were negligible when compared to the indirect negative effect mediated by competition for phytoplankton. We conclude that examination of host-pathogen dynamics within a community context may be necessary to elucidate complex community dynamics.
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Affiliation(s)
- Julia C Buck
- Department of Integrative Biology, Oregon State University, Corvallis, OR, 97331, USA,
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Stevenson LA, Roznik EA, Alford RA, Pike DA. Host-specific thermal profiles affect fitness of a widespread pathogen. Ecol Evol 2014; 4:4053-64. [PMID: 25505533 PMCID: PMC4242559 DOI: 10.1002/ece3.1271] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Revised: 09/11/2014] [Accepted: 09/12/2014] [Indexed: 12/02/2022] Open
Abstract
Host behavior can interact with environmental context to influence outcomes of pathogen exposure and the impact of disease on species and populations. Determining whether the thermal behaviors of individual species influence susceptibility to disease can help enhance our ability to explain and predict how and when disease outbreaks are likely to occur. The widespread disease chytridiomycosis (caused by the fungal pathogen Batrachochytrium dendrobatidis, Bd) often has species-specific impacts on amphibian communities; some host species are asymptomatic, whereas others experience mass mortalities and population extirpation. We determined whether the average natural thermal regimes experienced by sympatric frog species in nature, in and of themselves, can account for differences in vulnerability to disease. We did this by growing Bd under temperatures mimicking those experienced by frogs in the wild. At low and high elevations, the rainforest frogs Litoria nannotis, L. rheocola, and L. serrata maintained mean thermal regimes within the optimal range for pathogen growth (15-25°C). Thermal regimes for L. serrata, which has recovered from Bd-related declines, resulted in slower pathogen growth than the cooler and less variable thermal regimes for the other two species, which have experienced more long-lasting declines. For L. rheocola and L. serrata, pathogen growth was faster in thermal regimes corresponding to high elevations than in those corresponding to low elevations, where temperatures were warmer. For L. nannotis, which prefers moist and thermally stable microenvironments, pathogen growth was fastest for low-elevation thermal regimes. All of the thermal regimes we tested resulted in pathogen growth rates equivalent to, or significantly faster than, rates expected from constant-temperature experiments. The effects of host body temperature on Bd can explain many of the broad ecological patterns of population declines in our focal species, via direct effects on pathogen fitness. Understanding the functional response of pathogens to conditions experienced by the host is important for determining the ecological drivers of disease outbreaks.
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Affiliation(s)
- Lisa A Stevenson
- School of Marine and Tropical Biology, James Cook University Townsville, Queensland, Australia
| | - Elizabeth A Roznik
- 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
| | - David A Pike
- School of Marine and Tropical Biology, James Cook University Townsville, Queensland, Australia
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Johnson AF, Brunner JL. Persistence of an amphibian ranavirus in aquatic communities. DISEASES OF AQUATIC ORGANISMS 2014; 111:129-138. [PMID: 25266900 DOI: 10.3354/dao02774] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Host-parasite dynamics can be strongly influenced by interactions with other members of the biotic community, particularly when the parasite spends some fraction of its life in the environment unprotected by its host. Ranaviruses-often lethal viruses of cold-blooded vertebrate hosts transmitted by direct contact, and via water and fomites-offer an interesting system for understanding these community influences. Previous laboratory studies have shown that ranaviruses can persist for anywhere from days to years, depending on the conditions, with much longer times under sterile conditions. To address the role of the biotic community and particulate matter on ranavirus persistence, we experimentally inoculated filter-sterilized, UV-treated, and unmanipulated pond water with a Frog virus 3 (FV3)-like Ranavirus and took samples over 78 d, quantifying viral titers with real-time quantitative PCR and plaque assays. Viral counts dropped quickly in all treatments, by an order of magnitude in under a day in unmanipulated pond water and in 8 d in filter-sterilized pond water. In a second experiment, we measured viral titers over 24 h in virus-spiked spring water with Daphnia pulex. Presence of D. pulex reduced the concentration of infectious ranavirus, but not viral DNA, by an order of magnitude in 24 h. D. pulex themselves did not accumulate the virus. We conclude that both microbial and zooplanktonic communities can play an important role in ranavirus epidemiology, rapidly inactivating ranavirus in the water and thereby minimizing environmental transmission. We suspect that interactions with the biotic community will be important for most pathogens with environmental resting or transmission stages.
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Affiliation(s)
- A F Johnson
- School of Biological Sciences, Washington State University, Pullman, Washington 99164, USA
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Chestnut T, Anderson C, Popa R, Blaustein AR, Voytek M, Olson DH, Kirshtein J. Heterogeneous occupancy and density estimates of the pathogenic fungus Batrachochytrium dendrobatidis in waters of North America. PLoS One 2014; 9:e106790. [PMID: 25222122 PMCID: PMC4164359 DOI: 10.1371/journal.pone.0106790] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Accepted: 08/06/2014] [Indexed: 01/15/2023] Open
Abstract
Biodiversity losses are occurring worldwide due to a combination of stressors. For example, by one estimate, 40% of amphibian species are vulnerable to extinction, and disease is one threat to amphibian populations. The emerging infectious disease chytridiomycosis, caused by the aquatic fungus Batrachochytrium dendrobatidis (Bd), is a contributor to amphibian declines worldwide. Bd research has focused on the dynamics of the pathogen in its amphibian hosts, with little emphasis on investigating the dynamics of free-living Bd. Therefore, we investigated patterns of Bd occupancy and density in amphibian habitats using occupancy models, powerful tools for estimating site occupancy and detection probability. Occupancy models have been used to investigate diseases where the focus was on pathogen occurrence in the host. We applied occupancy models to investigate free-living Bd in North American surface waters to determine Bd seasonality, relationships between Bd site occupancy and habitat attributes, and probability of detection from water samples as a function of the number of samples, sample volume, and water quality. We also report on the temporal patterns of Bd density from a 4-year case study of a Bd-positive wetland. We provide evidence that Bd occurs in the environment year-round. Bd exhibited temporal and spatial heterogeneity in density, but did not exhibit seasonality in occupancy. Bd was detected in all months, typically at less than 100 zoospores L(-1). The highest density observed was ∼3 million zoospores L(-1). We detected Bd in 47% of sites sampled, but estimated that Bd occupied 61% of sites, highlighting the importance of accounting for imperfect detection. When Bd was present, there was a 95% chance of detecting it with four samples of 600 ml of water or five samples of 60 mL. Our findings provide important baseline information to advance the study of Bd disease ecology, and advance our understanding of amphibian exposure to free-living Bd in aquatic habitats over time.
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Affiliation(s)
- Tara Chestnut
- Oregon State University, Environmental Science Graduate Program, Corvallis, Oregon, United States of America
- US Geological Survey, Oregon Water Science Center, Portland, Oregon, United States of America
| | - Chauncey Anderson
- US Geological Survey, Oregon Water Science Center, Portland, Oregon, United States of America
| | - Radu Popa
- Biological Sciences, University of Southern California, Los Angeles, California, United States of America
| | - Andrew R. Blaustein
- Oregon State University, Department of Integrative Biology, Corvallis, Oregon, United States of America
| | - Mary Voytek
- Astrobiology Program, National Aeronautics and Space Administration Headquarters, Washington DC, United States of America
| | - Deanna H. Olson
- US Forest Service, Pacific Northwest Research Station, Corvallis, Oregon, United States of America
| | - Julie Kirshtein
- US Geological Survey, National Research Program, Reston, Virginia, United States of America
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Kagami M, Miki T, Takimoto G. Mycoloop: chytrids in aquatic food webs. Front Microbiol 2014; 5:166. [PMID: 24795703 PMCID: PMC4001071 DOI: 10.3389/fmicb.2014.00166] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 03/27/2014] [Indexed: 11/13/2022] Open
Abstract
Parasites are ecologically significant in various ecosystems through their role in shaping food web structure, facilitating energy transfer, and controlling disease. Here in this review, we mainly focus on parasitic chytrids, the dominant parasites in aquatic ecosystems, and explain their roles in aquatic food webs, particularly as prey for zooplankton. Chytrids have a free-living zoosporic stage, during which they actively search for new hosts. Zoospores are excellent food for zooplankton in terms of size, shape, and nutritional quality. In the field, densities of chytrids can be high, ranging from 10(1) to 10(9) spores L(-1). When large inedible phytoplankton species are infected by chytrids, nutrients within host cells are transferred to zooplankton via the zoospores of parasitic chytrids. This new pathway, the "mycoloop," may play an important role in shaping aquatic ecosystems, by altering sinking fluxes or determining system stability. The grazing of zoospores by zooplankton may also suppress outbreaks of parasitic chytrids. A food web model demonstrated that the contribution of the mycoloop to zooplankton production increased with nutrient availability and was also dependent on the stability of the system. Further studies with advanced molecular tools are likely to discover greater chytrid diversity and evidence of additional mycoloops in lakes and oceans.
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Affiliation(s)
- Maiko Kagami
- Faculty of Science, Toho University Funabashi, Japan
| | - Takeshi Miki
- Institute of Oceanography, National Taiwan University Taipei, Taiwan
| | - Gaku Takimoto
- Faculty of Science, Toho University Funabashi, Japan
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