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Hopkins AP, Hoverman JT. Strobilurin fungicide increases the susceptibility of amphibian larvae to trematode infections. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 269:106864. [PMID: 38422928 DOI: 10.1016/j.aquatox.2024.106864] [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: 10/25/2023] [Revised: 02/14/2024] [Accepted: 02/16/2024] [Indexed: 03/02/2024]
Abstract
The global rise in fungal pathogens has driven the increased usage of fungicides, yet our understanding of their ecotoxicity remains largely limited to acute toxicity. While such data is critical for projecting the risk of fungicide exposure to individual species, the contamination of natural systems with fungicides also has the potential to alter species interactions within communities including host-parasite relationships. We examined the effects of the fungicide pyraclostrobin on the susceptibility of larval American bullfrogs (Rana catesbeiana) to trematode (echinostome) infections using a controlled laboratory experiment. Following a 2-wk exposure to 0, 1.0, 5.2, or 8.4 µg/L of pyraclostrobin, tadpoles were then exposed to parasites either in the 1) presence (continued/simultaneous exposure) or 2) absence (fungicide-free water) of pyraclostrobin. We found that when exposed to pyraclostrobin during parasite exposure, meta cercariae counts increased 4 to 8 times compared to control tadpoles. Additionally, parasite loads were approximately 2 times higher in tadpoles with continued fungicide exposures compared to tadpoles that were moved to fresh water following fungicide exposure. This research demonstrates that fungicides at environmentally relevant concentrations can indirectly alter host-parasite interactions, which could elevate disease risk. It also underscores the need for studies that expand beyond traditional toxicity experiments to assess the potential community and ecosystem-level implications of environmental contaminants.
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Affiliation(s)
- Andrew P Hopkins
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN, United States.
| | - Jason T Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN, United States
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2
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Buss N, Hua J. Host exposure to a common pollutant can influence diversity-disease relationships. J Anim Ecol 2023; 92:2151-2162. [PMID: 37587564 DOI: 10.1111/1365-2656.13988] [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: 10/03/2022] [Accepted: 05/15/2023] [Indexed: 08/18/2023]
Abstract
Hosts and parasites are embedded in communities where species richness and composition can influence disease outcomes (diversity-disease relationships). The direction and magnitude of diversity-disease relationships are influenced by variation in competence (ability to support and transmit infections) of hosts in a community. However, host susceptibility to parasites, which mediates host competence, is not static and is influenced by environmental factors, including pollutants. Despite the role that pollutants can play in augmenting host susceptibility, how pollutants influence diversity-disease dynamics is not well understood. Using an amphibian-trematode model, we tested how NaCl influences diversity-disease dynamics. We predicted that NaCl exposure can alter relative susceptibility of host species to trematodes, leading to cascading effects on the diversity-disease relationship. To test these predictions, we exposed hosts to benign or NaCl environments and generated communities that differed in number and composition of host species. We exposed these communities to trematodes and measured disease outcomes at the community (total infections across all hosts within a community) and species levels (average number of infections per host species within a community). Host species differed in their relative susceptibility to trematodes when exposed to NaCl. Consequently, at the community level (total infections across all hosts within a community), we only detected diversity-disease relationships (dilution effects) in communities where hosts were exposed to NaCl. At the species level, disease outcomes (average number of infections/species) and whether multi-species communities supported lower number of infections relative to single-species communities depended on community composition. Notably, however, as with overall community infection, diversity-disease relationships only emerged when hosts were exposed to NaCl. Synthesis. Pollutants are ubiquitous in nature and can influence disease dynamics across a number of host-parasite systems. Here, we show that NaCl exposure can alter the relative susceptibility of host species to parasites, influencing the relationship between biodiversity and disease at both community and species levels. Collectively, our study contributes to the limited knowledge surrounding environmental mediators of host susceptibility and their influence on diversity-disease dynamics.
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Affiliation(s)
- Nicholas Buss
- Department of Biological Sciences, Binghamton University (SUNY), Binghamton, New York, USA
| | - Jessica Hua
- Department of Biological Sciences, Binghamton University (SUNY), Binghamton, New York, USA
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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3
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McGrath-Blaser S, Steffen M, Grafe TU, Torres-Sánchez M, McLeod DS, Muletz-Wolz CR. Early life skin microbial trajectory as a function of vertical and environmental transmission in Bornean foam-nesting frogs. Anim Microbiome 2021; 3:83. [PMID: 34930504 PMCID: PMC8686334 DOI: 10.1186/s42523-021-00147-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 12/07/2021] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND The amphibian skin microbiome is an important mediator of host health and serves as a potential source of undiscovered scientifically significant compounds. However, the underlying modalities of how amphibian hosts obtain their initial skin-associated microbiome remains unclear. Here, we explore microbial transmission patterns in foam-nest breeding tree frogs from Southeast Asia (Genus: Polypedates) whose specialized breeding strategy allows for better delineation between vertically and environmentally derived microbes. To facilitate this, we analyzed samples associated with adult frog pairs taken after mating-including adults of each sex, their foam nests, environments, and tadpoles before and after environmental interaction-for the bacterial communities using DNA metabarcoding data (16S rRNA). Samples were collected from frogs in-situ in Brunei, Borneo, a previously unsampled region for amphibian-related microbial diversity. RESULTS Adult frogs differed in skin bacterial communities among species, but tadpoles did not differ among species. Foam nests had varying bacterial community composition, most notably in the nests' moist interior. Nest interior bacterial communities were discrete for each nest and overall displayed a narrower diversity compared to the nest exteriors. Tadpoles sampled directly from the foam nest displayed a bacterial composition less like the nest interior and more similar to that of the adults and nest exterior. After one week of pond water interaction the tadpole skin microbiome shifted towards the tadpole skin and pond water microbial communities being more tightly coupled than between tadpoles and the internal nest environment, but not to the extent that the skin microbiome mirrored the pond bacterial community. CONCLUSIONS Both vertical influence and environmental interaction play a role in shaping the tadpole cutaneous microbiome. Interestingly, the interior of the foam nest had a distinct bacterial community from the tadpoles suggesting a limited environmental effect on tadpole cutaneous bacterial selection at initial stages of life. The shift in the tadpole microbiome after environmental interaction indicates an interplay between underlying host and ecological mechanisms that drive community formation. This survey serves as a baseline for further research into the ecology of microbial transmission in aquatic animals.
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Affiliation(s)
- Sarah McGrath-Blaser
- Department of Biology, University of Florida, 421 Carr Hall, Gainesville, FL 32611 USA
| | - Morgan Steffen
- Department of Biology, James Madison University, 951 Carrier Dr, Harrisonburg, VA 22807 USA
| | - T. Ulmar Grafe
- Universiti Brunei Darussalam, Tungku Link, Gadong, BE 1410 Brunei
| | - María Torres-Sánchez
- Department of Biology, University of Florida, 421 Carr Hall, Gainesville, FL 32611 USA
| | - David S. McLeod
- Department of Biology, James Madison University, 951 Carrier Dr, Harrisonburg, VA 22807 USA
- North Carolina Museum of Natural Sciences, 11 West Jones Street, Raleigh, NC 27601 USA
| | - Carly R. Muletz-Wolz
- Smithsonian National Zoo and Conservation Biology Institute, Center for Conservation Genomics, 3001 Connecticut Ave., Washington, DC 20008 USA
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4
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Ortega N, Roznik EA, Surbaugh KL, Cano N, Price W, Campbell T, Rohr JR. Parasite spillover to native hosts from more tolerant, supershedding invasive hosts: Implications for management. J Appl Ecol 2021. [DOI: 10.1111/1365-2664.13906] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicole Ortega
- Department of Biology University of Tampa Tampa FL USA
| | - Elizabeth A. Roznik
- North Carolina Zoo Asheboro NC USA
- Department of Integrative Biology University of South Florida Tampa FL USA
| | - Kerri L. Surbaugh
- Department of Integrative Biology University of South Florida Tampa FL USA
| | - Natalia Cano
- Department of Integrative Biology University of South Florida Tampa FL USA
| | - Wayne Price
- Department of Biology University of Tampa Tampa FL USA
| | - Todd Campbell
- Department of Biology University of Tampa Tampa FL USA
| | - Jason R. Rohr
- Department of Biological Sciences University of Notre DameNotre Dame IN USA
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5
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Experimental evidence that host choice by parasites is age-dependent in a fish-monogenean system. Parasitol Res 2021; 121:115-126. [PMID: 34755222 DOI: 10.1007/s00436-021-07356-9] [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: 08/14/2021] [Accepted: 10/19/2021] [Indexed: 10/19/2022]
Abstract
Host age is known to influence the risk of parasite infection, but there is very little experimental evidence on whether parasites show preference towards potential hosts of a specific age. To investigate how host age affects host choice by parasites, we used the Nile tilapia (Oreochromis niloticus) as a fish parasite model and manipulated its gill ectoparasitic monogeneans in mesocosm experiments. Our experimental setting combined three age classes (juvenile, subadult, and adult) of both infected donor hosts and uninfected potential target hosts assigned to each treatment. We predicted that adult target hosts would be more susceptible to parasites than juveniles and adults because they represent high-quality habitat patches. Contrary to our prediction, we found that subadults were more susceptible to parasites than juvenile and adult target hosts. Our models confirmed that variation in target host age influenced parasite choice, suggesting that subadults might represent the most favourable option for parasites regarding a balance between host quality and susceptibility. We provide experimental evidence that host choice by parasites is age-dependent, and that this life-history trait can play a major role in structuring parasite populations.
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6
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Rubenina I, Kirjusina M, Ceirans A, Gravele E, Gavarane I, Pupins M, Krasnov BR. Environmental, anthropogenic, and spatial factors affecting species composition and species associations in helminth communities of water frogs (Pelophylax esculentus complex) in Latvia. Parasitol Res 2021; 120:3461-3474. [PMID: 34476585 DOI: 10.1007/s00436-021-07303-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Accepted: 08/25/2021] [Indexed: 10/20/2022]
Abstract
We investigated factors affecting species composition and patterns of species associations in parasite communities of water frogs (Pelophylax esculentus complex), applying the distance-based redundancy analysis for component communities (assemblages harboured by host populations) and Markov random fields modelling for infracommunities (assemblages harboured by individual hosts), respectively. We asked (a) What are the relative effects of variation in environmental, land use (i.e., anthropogenic), and spatial factors on the variation in the species composition of component communities (i.e., in a locality)? and (b) What is the dominant pattern of species associations in infracommunities (in a host individual), and how do these associations vary along environmental and/or anthropogenic gradients? In component communities, the greatest portion of variation in helminth species composition was explained by the combined effects of space, anthropogenic pressure, and NDVI, with the pure effect of the spatial predictor being much stronger than the effects of the remaining predictors. In infracommunities, the probability of occurrence of some, but not all, helminth species depended on the occurrence of another species, with the numbers of negative and positive co-occurrences being equal. The strength and/or sign of associations of some species pairs were spatially stable, whereas interactions between other species pairs varied along the gradient of the amount of green vegetation, from negative to positive and vice versa. We conclude that the processes in parasite infracommunities and component communities in frogs are intertwined, with both bottom-up and top-down effects acting at different hierarchical scales.
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Affiliation(s)
- Ilze Rubenina
- Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia.
| | - Muza Kirjusina
- Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia
| | - Andris Ceirans
- Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia
| | - Evita Gravele
- Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia
| | - Inese Gavarane
- Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia
| | - Mihails Pupins
- Institute of Life Sciences and Technologies, Daugavpils University, Parades Street 1A, Daugavpils, 5401, Latvia
| | - Boris R Krasnov
- Mitrani Department of Desert Ecology, Swiss Institute for Dryland Environmental and Energy Research, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
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7
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Helminth communities in amphibians from Latvia, with an emphasis on their connection to host ecology. J Helminthol 2021; 95:e48. [PMID: 34429177 DOI: 10.1017/s0022149x2100047x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Helminth infracommunities were studied at 174 sites of Latvia in seven hosts from six amphibian taxa of different taxonomical, ontogenic and ecological groups. They were described using a standard set of parasitological parameters, compared by ecological indices and linear discriminant analysis. Their species associations were identified by Kendall's rank correlation, but relationships with host size and waterbody area were analysed by zero-inflated Poisson and zero-inflated negative binomial regressions. The richest communities (25 species) were found in post-metamorphic semi-aquatic Pelophylax spp. frogs, which were dominated by trematode species of both adult and larval stages. Both larval and terrestrial hosts yielded depauperate trematode communities with accession of aquatic and soil-transmitted nematode species, respectively. Nematode loads peaked in terrestrial Bufo bufo. Helminth infracommunities suggested some differences in host microhabitat or food object selection not detected by their ecology studies. Associations were present in 96% of helminth species (on average, 7.3 associations per species) and dominated positive ones. Species richness and abundances, in most cases, were positively correlated with host size, which could be explained by increasing parasite intake rates over host ontogeny (trematode adult stages) or parasite accumulation (larval Alaria alata). Two larval diplostomid species (Strigea strigis, Tylodelphys excavata) had a negative relationship with host size, which could be caused by parasite-induced host mortality. The adult trematode abundances were higher in larger waterbodies, most likely due to their ecosystem richness, while higher larval abundances in smaller waterbodies could be caused by elevated infection rates under high host densities.
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8
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Brown SR, Flynn RW, Hoverman JT. Perfluoroalkyl Substances Increase Susceptibility of Northern Leopard Frog Tadpoles to Trematode Infection. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2021; 40:689-694. [PMID: 31995841 DOI: 10.1002/etc.4678] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 10/23/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
Per/polyfluoroalkyl substances (PFAS) are contaminants of emerging concern that can impair immune function, yet few studies have tested whether exposure increases infection risk. Using laboratory experiments, we found that exposure to 10 ppb of perfluorohexanesulfonic acid increased trematode (Echinoparyphium lineage 3) infections in larval northern leopard frogs (Lithobates pipiens). However, there was no effect of perfluorooctanesulfonic acid. Our results demonstrate that PFAS can potentially enhance infection risk in natural systems. Environ Toxicol Chem 2021;40:689-694. © 2020 SETAC.
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Affiliation(s)
- Sophia R Brown
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, USA
| | - R Wesley Flynn
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, USA
| | - Jason T Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, USA
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9
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Pathirana N, Meegaskumbura M, Rajakaruna R. Host resistance and tolerance to parasitism: development-dependent fitness consequences in Common Hourglass Tree Frog (Polypedates cruciger) tadpoles exposed to two larval trematodes. CAN J ZOOL 2019. [DOI: 10.1139/cjz-2018-0126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Tolerance and resistance to parasites are defense strategies of host organisms. Here, we tested the development-dependent tolerance and resistance of Polypedates cruciger Blyth, 1852 tadpoles to trematode infection. We exposed the tadpoles at Gosner stages 27, 28–29, and 30–31 to two types of cercariae (furcocercous and pleurolophocercous cercariae of Acanthostomum burminis (Bhalerao, 1926)) under laboratory conditions. To determine tolerance (the ability of a host to limit health effects of a given parasite load), we exposed the tadpoles until all cercariae penetrated the host. As a measure of determining resistance, we exposed tadpoles to cercariae for a limited time and counted the number of cercariae penetrating the tadpoles. The survival of tadpoles exposed at early stages was significantly lower than that of tadpoles exposed at later stages (mixed-effect model, p < 0.05), suggesting an age-dependent tolerance to parasitism. Tadpoles exposed at early stages were also smaller, took longer to metamorphosis, showed lower resistance to parasitism (ANOVA, p < 0.001), and developed axial malformations. In the resistance experiment, fewer parasites penetrated later stage tadpoles than early stage tadpoles. Tadpoles of P. cruciger showed a development-dependent tolerance and resistance to parasitism, resulting in greater survival and fewer malformations when parasitism occurs at late stages.
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Affiliation(s)
- N.U.K. Pathirana
- Department of Zoology, University of Peradeniya, Peradeniya 20400, Sri Lanka
- Postgraduate Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
- Freshwater Fish Group and Fish Health Unit, Centre for Sustainable Aquatic Ecosystems, School of Veterinary and Life Sciences, Murdoch University, Murdoch, Western Australia 6150, Australia
| | - M. Meegaskumbura
- Guangxi Key Laboratory of Forest Ecology and Conservation, College of Forestry, Guangxi University, Nanning, Guangxi 530004, People’s Republic of China
- Department of Molecular Biology and Biotechnology, University of Peradeniya, Peradeniya 20400, Sri Lanka
| | - R.S. Rajakaruna
- Department of Zoology, University of Peradeniya, Peradeniya 20400, Sri Lanka
- Postgraduate Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka
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10
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Wersebe M, Blackwood P, Guo YT, Jaeger J, May D, Meindl G, Ryan SN, Wong V, Hua J. The effects of different cold-temperature regimes on development, growth, and susceptibility to an abiotic and biotic stressor. Ecol Evol 2019; 9:3355-3366. [PMID: 30962897 PMCID: PMC6434568 DOI: 10.1002/ece3.4957] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/19/2018] [Accepted: 01/08/2019] [Indexed: 11/05/2022] Open
Abstract
Global climate change is expected to both increase average temperatures as well as temperature variability.Increased average temperatures have led to earlier breeding in many spring-breeding organisms. However, individuals breeding earlier will also face increased temperature fluctuations, including exposure to potentially harmful cold-temperature regimes during early developmental stages.Using a model spring-breeding amphibian, we investigated how embryonic exposure to different cold-temperature regimes (control, cold-pulse, and cold-press) affected (a) compensatory larval development and growth, (b) larval susceptibility to a common contaminant, and (c) larval susceptibility to parasites.We found: (a) no evidence of compensatory development or growth, (b) larvae exposed to the cold-press treatment were more susceptible to NaCl at 4-days post-hatching but recovered by 17-days post-hatching, and (c) larvae exposed to both cold treatments were less susceptible to parasites.These results demonstrate that variation in cold-temperature regimes can lead to unique direct and indirect effects on larval growth, development, and response to stressors. This underscores the importance of considering cold-temperature variability and not just increased average temperatures when examining the impacts of climate disruption.
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Affiliation(s)
- Matthew Wersebe
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Paradyse Blackwood
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Ying Tong Guo
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Jared Jaeger
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Dyllan May
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - George Meindl
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Sean N. Ryan
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Vivian Wong
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
| | - Jessica Hua
- Biological Sciences DepartmentBinghamton University (SUNY)BinghamtonNew York
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11
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Johnson PTJ, Wilber MQ. Biological and statistical processes jointly drive population aggregation: using host-parasite interactions to understand Taylor's power law. Proc Biol Sci 2018; 284:rspb.2017.1388. [PMID: 28931738 DOI: 10.1098/rspb.2017.1388] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Accepted: 08/10/2017] [Indexed: 12/25/2022] Open
Abstract
The macroecological pattern known as Taylor's power law (TPL) represents the pervasive tendency of the variance in population density to increase as a power function of the mean. Despite empirical illustrations in systems ranging from viruses to vertebrates, the biological significance of this relationship continues to be debated. Here we combined collection of a unique dataset involving 11 987 amphibian hosts and 332 684 trematode parasites with experimental measurements of core epidemiological outcomes to explicitly test the contributions of hypothesized biological processes in driving aggregation. After using feasible set theory to account for mechanisms acting indirectly on aggregation and statistical constraints inherent to the data, we detected strongly consistent influences of host and parasite species identity over 7 years of sampling. Incorporation of field-based measurements of host body size, its variance and spatial heterogeneity in host density accounted for host identity effects, while experimental quantification of infection competence (and especially virulence from the 20 most common host-parasite combinations) revealed the role of species-by-environment interactions. By uniting constraint-based theory, controlled experiments and community-based field surveys, we illustrate the joint influences of biological and statistical processes on parasite aggregation and emphasize their importance for understanding population regulation and ecological stability across a range of systems, both infectious and free-living.
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Affiliation(s)
- Pieter T J Johnson
- Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - Mark Q Wilber
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
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12
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Budischak SA, O'Neal D, Jolles AE, Ezenwa VO. Differential host responses to parasitism shape divergent fitness costs of infection. Funct Ecol 2017. [DOI: 10.1111/1365-2435.12951] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Sarah A. Budischak
- Odum School of EcologyUniversity of Georgia Athens GA USA
- Department of Ecology and Evolutionary Biology Princeton NJ USA
| | - Dawn O'Neal
- Odum School of EcologyUniversity of Georgia Athens GA USA
- Huyck Preserve & Biological Research Station Rensselaerville NY USA
| | - Anna E. Jolles
- Department of Biomedical Sciences and Department of Integrative BiologyOregon State University Corvallis OR USA
| | - Vanessa O. Ezenwa
- Odum School of EcologyUniversity of Georgia Athens GA USA
- Department of Infectious DiseasesUniversity of Georgia Athens GA USA
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13
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Koprivnikar J, Riepe TB, Calhoun DM, Johnson PTJ. Whether larval amphibians school does not affect the parasite aggregation rule: testing the effects of host spatial heterogeneity in field and experimental studies. OIKOS 2017. [DOI: 10.1111/oik.04249] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Janet Koprivnikar
- Dept of Chemistry and Biology; Ryerson Univ., 350 Victoria Street; Toronto ON, M5B 2K3 Canada
| | - Tawni B. Riepe
- Dept of Ecology and Evolutionary Biology; Univ. of Colorado; Boulder CO USA
| | - Dana M. Calhoun
- Dept of Ecology and Evolutionary Biology; Univ. of Colorado; Boulder CO USA
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14
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Wilber MQ, Johnson PTJ, Briggs CJ. When can we infer mechanism from parasite aggregation? A constraint-based approach to disease ecology. Ecology 2017; 98:688-702. [PMID: 27935638 DOI: 10.1002/ecy.1675] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 10/05/2016] [Accepted: 11/29/2016] [Indexed: 11/09/2022]
Abstract
Few hosts have many parasites while many hosts have few parasites. This axiom of macroparasite aggregation is so pervasive it is considered a general law in disease ecology, with important implications for the dynamics of host-parasite systems. Because of these dynamical implications, a significant amount of work has explored both the various mechanisms leading to parasite aggregation patterns and how to infer mechanism from these patterns. However, as many disease mechanisms can produce similar aggregation patterns, it is not clear whether aggregation itself provides any additional information about mechanism. Here we apply a "constraint-based" approach developed in macroecology that allows us to explore whether parasite aggregation contains any additional information beyond what is provided by mean parasite load. We tested two constraint-based null models, both of which were constrained on the total number of parasites P and hosts H found in a sample, using data from 842 observed amphibian host-trematode parasite distributions. We found that constraint-based models captured ~85% of the observed variation in host-parasite distributions, suggesting that the constraints P and H contain much of the information about the shape of the host-parasite distribution. However, we also found that extending the constraint-based null models can identify the potential role of known aggregating mechanisms (such as host heterogeneity) and disaggregating mechanisms (such as parasite-induced host mortality) in constraining host-parasite distributions. Thus, by providing robust null models, constraint-based approaches can help guide investigations aimed at detecting biological processes that directly affect parasite aggregation above and beyond those that indirectly affect aggregation through P and H.
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Affiliation(s)
- Mark Q Wilber
- University of California, Santa Barbara, Santa Barbara, California, 93106, USA
| | | | - Cheryl J Briggs
- University of California, Santa Barbara, Santa Barbara, California, 93106, USA
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15
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The distribution of echinostome parasites in ponds and implications for larval anuran survival. Parasitology 2017; 144:801-811. [DOI: 10.1017/s0031182016002547] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
SUMMARYParasites can influence host population dynamics, community composition and evolution. Prediction of these effects, however, requires an understanding of the influence of ecological context on parasite distributions and the consequences of infection for host fitness. We address these issues with an amphibian – trematode (Digenea: Echinostomatidae) host–parasite system. We initially performed a field survey of trematode infection in first (snail) and second (larval green frog, Rana clamitans) intermediate hosts over 5 years across a landscape of 23 ponds in southeastern Michigan. We then combined this study with a tadpole enclosure experiment in eight ponds. We found echinostomes in all ponds during the survey, although infection levels in both snails and amphibians differed across ponds and years. Echinostome prevalence (proportion of hosts infected) in snails also changed seasonally depending on host species, and abundance (parasites per host) in tadpoles depended on host size and prevalence in snails. The enclosure experiment demonstrated that infection varied at sites within ponds, and tadpole survival was lower in enclosures with higher echinostome abundance. The observed effects enhance our ability to predict when and where host–parasite interactions will occur and the potential fitness consequences of infection, with implications for population and community dynamics, evolution and conservation.
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Calhoun DM, Woodhams D, Howard C, LaFonte BE, Gregory JR, Johnson PTJ. Role of Antimicrobial Peptides in Amphibian Defense Against Trematode Infection. ECOHEALTH 2016; 13:383-91. [PMID: 26911920 PMCID: PMC4996749 DOI: 10.1007/s10393-016-1102-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/11/2016] [Accepted: 01/13/2016] [Indexed: 05/18/2023]
Abstract
Antimicrobial peptides (AMPs) contribute to the immune defenses of many vertebrates, including amphibians. As larvae, amphibians are often exposed to the infectious stages of trematode parasites, many of which must penetrate the host's skin, potentially interacting with host AMPs. We tested the effects of the natural AMPs repertoires on both the survival of trematode infectious stages as well as their ability to infect larval amphibians. All five trematode species exhibited decreased survival of cercariae in response to higher concentrations of adult bullfrog AMPs, but no effect when exposed to AMPs from larval bullfrogs. Similarly, the use of norepinephrine to remove AMPs from larval bullfrogs, Pacific chorus frogs, and gray treefrogs had only weak (gray treefrogs) or non-significant (other tested species) effects on infection success by Ribeiroia ondatrae. We nonetheless observed strong differences in parasite infection as a function of both host stage (first- versus second-year bullfrogs) and host species (Pacific chorus frogs versus gray treefrogs) that were apparently unrelated to AMPs. Taken together, our results suggest that AMPs do not play a significant role in defending larval amphibians against trematode cercariae, but that they could be one mechanism helping to prevent infection of post-metamorphic amphibians, particularly for highly aquatic species.
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Affiliation(s)
- Dana M Calhoun
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Ramaley N122 CB334, Boulder, CO, 80309, USA.
| | - Doug Woodhams
- Department of Biology, University of Massachusetts Boston, 100 Morrissey Blvd., Boston, MA, 02125, USA
| | - Cierra Howard
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Ramaley N122 CB334, Boulder, CO, 80309, USA
| | - Bryan E LaFonte
- George Washington University Law School, George Washington University, 2000 H St NW, Washington, DC, 20052, USA
| | - Jacklyn R Gregory
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Ramaley N122 CB334, Boulder, CO, 80309, USA
| | - Pieter T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Ramaley N122 CB334, Boulder, CO, 80309, USA
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17
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Interspecific variation in larval anuran anti-parasite behavior: a test of the adaptive plasticity hypothesis. Evol Ecol 2016. [DOI: 10.1007/s10682-016-9831-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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18
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Eisenlord ME, Groner ML, Yoshioka RM, Elliott J, Maynard J, Fradkin S, Turner M, Pyne K, Rivlin N, van Hooidonk R, Harvell CD. Ochre star mortality during the 2014 wasting disease epizootic: role of population size structure and temperature. Philos Trans R Soc Lond B Biol Sci 2016; 371:20150212. [PMID: 26880844 PMCID: PMC4760142 DOI: 10.1098/rstb.2015.0212] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/15/2015] [Indexed: 11/18/2022] Open
Abstract
Over 20 species of asteroids were devastated by a sea star wasting disease (SSWD) epizootic, linked to a densovirus, from Mexico to Alaska in 2013 and 2014. For Pisaster ochraceus from the San Juan Islands, South Puget Sound and Washington outer coast, time-series monitoring showed rapid disease spread, high mortality rates in 2014, and continuing levels of wasting in the survivors in 2015. Peak prevalence of disease at 16 sites ranged to 100%, with an overall mean of 61%. Analysis of longitudinal data showed disease risk was correlated with both size and temperature and resulted in shifts in population size structure; adult populations fell to one quarter of pre-outbreak abundances. In laboratory experiments, time between development of disease signs and death was influenced by temperature in adults but not juveniles and adult mortality was 18% higher in the 19 °C treatment compared to the lower temperature treatments. While larger ochre stars developed disease signs sooner than juveniles, diseased juveniles died more quickly than diseased adults. Unusual 2-3 °C warm temperature anomalies were coincident with the summer 2014 mortalities. We suggest these warm waters could have increased the disease progression and mortality rates of SSWD in Washington State.
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Affiliation(s)
- Morgan E Eisenlord
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14850, USA
| | - Maya L Groner
- Department of Health Management, University of Prince Edward Island, Atlantic Veterinary College, Charlottetown, Prince Edward Island, Canada C1A 4P3
| | - Reyn M Yoshioka
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14850, USA
| | - Joel Elliott
- Department of Biology, University of Puget Sound, Tacoma, WA 98416, USA
| | - Jeffrey Maynard
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14850, USA Laboratoire d'Excellence «CORAIL» USR 3278 CNRS-EPHE, CRIOBE, Papetoai, Moorea, Polynésie Française
| | - Steven Fradkin
- Lake Crescent Laboratory, Olympic National Park, Port Angeles, WA 98362, USA
| | - Margaret Turner
- Marine Science Center, Northeastern University, Nahant, MA 01908, USA
| | - Katie Pyne
- Department of Biology, University of Puget Sound, Tacoma, WA 98416, USA
| | - Natalie Rivlin
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14850, USA
| | - Ruben van Hooidonk
- Atlantic Oceanographic and Meteorological Laboratory, NOAA, 4301 Rickenbacker Causeway, Miami, FL 33149, USA Cooperative Institute for Marine and Atmospheric Studies, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA
| | - C Drew Harvell
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14850, USA
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Ortega N, Price W, Campbell T, Rohr J. Acquired and introduced macroparasites of the invasive Cuban treefrog, Osteopilus septentrionalis. INTERNATIONAL JOURNAL FOR PARASITOLOGY-PARASITES AND WILDLIFE 2015; 4:379-84. [PMID: 26759792 PMCID: PMC4683551 DOI: 10.1016/j.ijppaw.2015.10.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 10/02/2015] [Accepted: 10/07/2015] [Indexed: 11/28/2022]
Abstract
Because shifts in host–parasite relationships can alter host populations, attention should be given to the parasites that introduced species take with them or acquire in their introduced range. The Cuban treefrog, Osteopilus septentrionalis, is a successful invasive species in Florida with its parasites in the native range being well-documented, but there is a void in the literature regarding what parasites were lost or introduced in its expansion. We necropsied 330 O. septentrionalis from Tampa, FL and compared their macroparasites to those of O. septentrionalis in their native range and to the parasites of anurans native to the Tampa, FL area to determine the species O. septentrionalis likely introduced or acquired in Florida. At least nine parasite species (Aplectana sp., Oswaldocruzia lenteixeirai, Cylindrotaenia americana, Physaloptera sp., Rhabdias sp., Centrorhynchus sp., unidentified trematode metacercariae, unidentified larval acuariids, and unidentified pentastomids) were isolated. We found no differences in parasite communities of adult male and female frogs, which averaged 19.36 parasite individuals and 1.39 parasite species per adult frog, and had an overall prevalence of 77.52%. Acuariid larvae were likely acquired by O. septentrionalis in FL because they are not found in their native range. O. lenteixeirai was likely introduced because it is commonly reported in O. septentrionalis' native range but has never been reported in FL-native anurans. Aplectana sp. is also likely introduced because it has been reported in several anurans in Cuba but only reported once in Florida. O. septentrionalis tended to harbor fewer of its native parasites in the introduced range, which is consistent with the enemy release hypothesis and potentially creates an immunological advantage for this invasive host. Because native populations can be threatened by introduced parasites, there is a need to further explore the frequency and rate at which non-native hosts introduce parasites. We found at least six new host records of parasites in the Cuban treefrog. Host type significantly affected parasite mean abundance and mean intensity. Hosts were infected with fewer species of parasites than in their native range. Introduced parasite prevalence is eight-fifteen times higher in its native range.
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Affiliation(s)
- Nicole Ortega
- Department of Integrative Biology, University of South Florida, 4202 E. Fowler Ave - SCA 110, Tampa, FL 33620-5150, United States
| | - Wayne Price
- Department of Biology, 401 W. Kennedy Blvd., University of Tampa, Tampa, FL 33606, United States
| | - Todd Campbell
- Department of Biology, 401 W. Kennedy Blvd., University of Tampa, Tampa, FL 33606, United States
| | - Jason Rohr
- Department of Integrative Biology, University of South Florida, 4202 E. Fowler Ave - SCA 110, Tampa, FL 33620-5150, United States
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20
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Lott MJ, Hose GC, Power ML. Parasitic nematode communities of the red kangaroo, Macropus rufus: richness and structuring in captive systems. Parasitol Res 2015; 114:2925-32. [PMID: 25916465 DOI: 10.1007/s00436-015-4494-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 04/20/2015] [Indexed: 11/25/2022]
Abstract
Captive management practices have the potential to drastically alter pre-existing host-parasite relationships. This can have profound implications for the health and productivity of threatened species in captivity, even in the absence of clinical symptoms of disease. Maximising the success of captive breeding programmes requires a detailed knowledge of anthropogenic influences on the structure of parasite assemblages in captive systems. In this study, we employed two high-throughput molecular techniques to characterise the parasitic nematode (suborder Strongylida) communities of the red kangaroo, Macropus rufus, across seven captive sites. The first was terminal restriction fragment length polymorphism (T-RFLP) analysis of a region of rDNA encompassing the internal transcribed spacers 1 (ITS1), the 5.8S rRNA gene and the internal transcribed spacer 2 (ITS2). The second was Illumina MiSeq next-generation sequencing of the ITS2 region. The prevalence, intensity of infection, taxonomic composition and comparative structure of strongylid nematode assemblages was assessed at each location. Prevalence (P = <0.001) and mean infection intensity (df = 6, F = 17.494, P = <0.001) differed significantly between the seven captive sites. Significant levels of parasite community structure were observed (ANOSIM, P = 0.01), with most of the variation being distributed within, rather than between, captive sites. The range of nematode taxa that occurred in captive red kangaroos appeared to differ from that of wild conspecifics, with representatives of the genus Cloacina, a dominant nematode parasite of the macropodid forestomach, being detected at only two of the seven study sites. This study also provides the first evidence for the presence of the genus Trichostrongylus in a macropodid marsupial. Our results demonstrate that contemporary species management practices may exert a profound influence on the structure of parasite communities in captive systems.
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Affiliation(s)
- M J Lott
- Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia,
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21
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A Skeletochronological Assessment of Age–Parasitism Relationships in Wood Frogs (Lithobates sylvaticus). J HERPETOL 2015. [DOI: 10.1670/13-118] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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22
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Sears BF, Snyder PW, Rohr JR. Host life history and host-parasite syntopy predict behavioural resistance and tolerance of parasites. J Anim Ecol 2015; 84:625-636. [PMID: 25583069 DOI: 10.1111/1365-2656.12333] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 12/07/2014] [Indexed: 11/27/2022]
Abstract
There is growing interest in the role that life-history traits of hosts, such as their 'pace-of-life', play in the evolution of resistance and tolerance to parasites. Theory suggests that, relative to host species that have high syntopy (local spatial and temporal overlap) with parasites, host species with low syntopy should have lower selection pressures for more constitutive (always present) and costly defences, such as tolerance, and greater reliance on more inducible and cheaper defences, such as behaviour. Consequently, we postulated that the degree of host-parasite syntopy, which is negatively correlated with host pace-of-life (an axis reflecting the developmental rate of tadpoles and the inverse of their size at metamorphosis) in our tadpole-parasitic cercarial (trematode) system, would be a negative and positive predictor of behavioural resistance and tolerance, respectively. To test these hypotheses, we exposed seven tadpole species to a range of parasite (cercarial) doses crossed with anaesthesia treatments that controlled for anti-parasite behaviour. We quantified host behaviour, successful and unsuccessful infections, and each species' reaction norm for behavioural resistance and tolerance, defined as the slope between cercarial exposure (or attempted infections) and anti-cercarial behaviours and mass change, respectively. Hence, tolerance is capturing any cost of parasite exposure. As hypothesized, tadpole pace-of-life was a significant positive predictor of behavioural resistance and negative predictor of tolerance, a result that is consistent with a trade-off between behavioural resistance and tolerance across species that warrants further investigation. Moreover, these results were robust to considerations of phylogeny, all possible re-orderings of the three fastest or slowest paced species, and various measurements of tolerance. These results suggest that host pace-of-life and host-parasite syntopy are powerful drivers of both the strength and type of host defence strategies against parasites. Future research should evaluate how often and how strongly host pace-of-life and host-parasite syntopy are correlated and which is the better predictor of the strength and type of host investments in anti-parasite defences.
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Affiliation(s)
- Brittany F Sears
- Department of Integrative Biology, University of South Florida, Tampa, FL, 33620, USA
| | | | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, FL, 33620, USA
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23
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Civitello DJ, Rohr JR. Disentangling the effects of exposure and susceptibility on transmission of the zoonotic parasite Schistosoma mansoni. J Anim Ecol 2014; 83:1379-86. [PMID: 24702134 DOI: 10.1111/1365-2656.12222] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 03/24/2014] [Indexed: 11/27/2022]
Abstract
For all parasites, transmission is composed of two processes: host contact with parasites ('exposure') and risk of infection given such contact ('susceptibility'). Classic models, such as mass action (density-dependent) transmission, lump these processes together. However, separating these processes could enhance predictions for disease dynamics, especially for free-living parasites. Here, we outline three transmission models that partition exposure and susceptibility. Using data from a study of Schistosoma mansoni (trematode) infections in Biomphalaria glabrata snails, we competed these three models against four alternative models, including the mass action model (which lumps exposure and susceptibility). The models that separately accounted for exposure and susceptibility best predicted prevalence across the density gradients of hosts and parasites, outperforming all other models based on Akaike information criterion. When embedded into a dynamic epidemiological model, the exposure-explicit models all predicted lower equilibrium densities of infected snails and human-infectious cercariae. Thus, population-level epidemiological models that utilize the classic mass action transmission model might overestimate human risk of schistosomiasis. More generally, the presented approach for disentangling exposure and susceptibility can distinguish between behavioural and immunological resistance, identify mechanisms of 'disease dilution' and provide a more complete dissection of drivers of parasite transmission.
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Affiliation(s)
- David J Civitello
- Department of Integrative Biology, University of South Florida, 4202 E Fowler Ave, Tampa, FL, 33620, USA
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, 4202 E Fowler Ave, Tampa, FL, 33620, USA
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24
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Johnson PTJ, Hoverman JT. Heterogeneous hosts: how variation in host size, behaviour and immunity affects parasite aggregation. J Anim Ecol 2014; 83:1103-12. [DOI: 10.1111/1365-2656.12215] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 02/10/2014] [Indexed: 11/28/2022]
Affiliation(s)
| | - Jason T. Hoverman
- Department of Forestry and Natural Resources; Purdue University; West Lafayette IN 47907 USA
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25
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Groner ML, Burge CA, Couch CS, Kim CJS, Siegmund GF, Singhal S, Smoot SC, Jarrell A, Gaydos JK, Harvell CD, Wyllie-Echeverria S. Host demography influences the prevalence and severity of eelgrass wasting disease. DISEASES OF AQUATIC ORGANISMS 2014; 108:165-175. [PMID: 24553421 DOI: 10.3354/dao02709] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Many marine pathogens are opportunists, present in the environment, but causing disease only under certain conditions such as immunosuppression due to environmental stress or host factors such as age. In the temperate eelgrass Zostera marina, the opportunistic labyrinthulomycete pathogen Labyrinthula zosterae is present in many populations and occasionally causes severe epidemics of wasting disease; however, risk factors associated with these epidemics are unknown. We conducted both field surveys and experimental manipulations to examine the effect of leaf age (inferred from leaf size) on wasting disease prevalence and severity in Z. marina across sites in the San Juan Archipelago, Washington, USA. We confirmed that lesions observed in the field were caused by active Labyrinthula infections both by identifying the etiologic agent through histology and by performing inoculations with cultures of Labyrinthula spp. isolated from observed lesions. We found that disease prevalence increased at shallower depths and with greater leaf size at all sites, and this effect was more pronounced at declining sites. Experimental inoculations with 2 strains of L. zosterae confirmed an increased susceptibility of older leaves to infection. Overall, this pattern suggests that mature beds and shallow beds of eelgrass may be especially susceptible to outbreaks of wasting disease. The study highlights the importance of considering host and environmental factors when evaluating risk of disease from opportunistic pathogens.
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Affiliation(s)
- Maya L Groner
- Centre for Veterinary and Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, 550 University Ave., Charlottetown, Prince Edward Island, Canada
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26
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Marino JA, Holland MP, Middlemis Maher J. Predators and trematode parasites jointly affect larval anuran functional traits and corticosterone levels. OIKOS 2013. [DOI: 10.1111/j.1600-0706.2013.00896.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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27
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Patanasatienkul T, Sanchez J, Rees EE, Krkosek M, Jones SRM, Revie CW. Sea lice infestations on juvenile chum and pink salmon in the Broughton Archipelago, Canada, from 2003 to 2012. DISEASES OF AQUATIC ORGANISMS 2013; 105:149-161. [PMID: 23872858 DOI: 10.3354/dao02616] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta were sampled by beach or purse seine to assess levels of sea lice infestation in the Knight Inlet and Broughton Archipelago regions of coastal British Columbia, Canada, during the months of March to July from 2003 to 2012. Beach seine data were analyzed for sea lice infestation that was described in terms of prevalence, abundance, intensity, and intensity per unit length. The median annual prevalence for chum was 30%, ranging from 14% (in 2008 and 2009) to 73% (in 2004), while for pink salmon, the median was 27% and ranged from 10% (in 2011) to 68% (in 2004). Annual abundance varied from 0.2 to 5 sea lice per fish with a median of 0.47 for chum and from 0.1 to 3 lice (median 0.42) for pink salmon. Annual infestation followed broadly similar trends for both chum and pink salmon. However, the abundance and intensity of Lepeophtheirus salmonis and Caligus clemensi, the 2 main sea lice species of interest, were significantly greater on chum than on pink salmon in around half of the years studied. Logistic regression with random effect was used to model prevalence of sea lice infestation for the combined beach and purse seine data. The model suggested inter-annual variation as well as a spatial clustering effect on the prevalence of sea lice infestation in both chum and pink salmon. Fish length had an effect on prevalence, although the nature of this effect differed according to host species.
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Affiliation(s)
- Thitiwan Patanasatienkul
- Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada.
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28
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Do parasitic trematode cercariae demonstrate a preference for susceptible host species? PLoS One 2012; 7:e51012. [PMID: 23272084 PMCID: PMC3525650 DOI: 10.1371/journal.pone.0051012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 10/31/2012] [Indexed: 11/23/2022] Open
Abstract
Many parasites are motile and exhibit behavioural preferences for certain host species. Because hosts can vary in their susceptibility to infections, parasites might benefit from preferentially detecting and infecting the most susceptible host, but this mechanistic hypothesis for host-choice has rarely been tested. We evaluated whether cercariae (larval trematode parasites) prefer the most susceptible host species by simultaneously presenting cercariae with four species of tadpole hosts. Cercariae consistently preferred hosts in the following order: Anaxyrus ( = Bufo) terrestris (southern toad), Hyla squirella (squirrel tree frog), Lithobates ( = Rana) sphenocephala (southern leopard frog), and Osteopilus septentrionalis (Cuban tree frog). These host species varied in susceptibility to cercariae in an order similar to their attractiveness with a correlation that approached significance. Host attractiveness to parasites also varied consistently and significantly among individuals within a host species. If heritable, this individual-level host variation would represent the raw material upon which selection could act, which could promote a Red Queen “arms race” between host cues and parasite detection of those cues. If, in general, motile parasites prefer to infect the most susceptible host species, this phenomenon could explain aggregated distributions of parasites among hosts and contribute to parasite transmission rates and the evolution of virulence. Parasite preferences for hosts belie the common assumption of disease models that parasites seek and infect hosts at random.
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Hoverman JT, Mihaljevic JR, Richgels KLD, Kerby JL, Johnson PTJ. Widespread co-occurrence of virulent pathogens within California amphibian communities. ECOHEALTH 2012; 9:288-292. [PMID: 22766887 DOI: 10.1007/s10393-012-0778-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 05/23/2012] [Accepted: 05/26/2012] [Indexed: 06/01/2023]
Abstract
The chytrid fungus Batrachochytrium dendrobatidis, ranaviruses, and trematodes (Ribeiroia ondatrae and echinostomes) are highly virulent pathogens known to infect amphibians, yet the extent to which they co-occur within amphibian communities remains poorly understood. Using field surveillance of 85 wetlands in the East Bay region of California, USA, we found that 68% of wetlands had ≥2 pathogens and 36% had ≥3 pathogens. Wetlands with high pathogen species richness also tended to cluster spatially. Our results underscore the need for greater integration of multiple pathogens and their interactions into amphibian disease research and conservation efforts.
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Affiliation(s)
- Jason T Hoverman
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA.
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30
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Koprivnikar J, Marcogliese DJ, Rohr JR, Orlofske SA, Raffel TR, Johnson PTJ. Macroparasite infections of amphibians: what can they tell us? ECOHEALTH 2012; 9:342-360. [PMID: 22810498 DOI: 10.1007/s10393-012-0785-3] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 06/25/2012] [Accepted: 07/01/2012] [Indexed: 06/01/2023]
Abstract
Understanding linkages between environmental changes and disease emergence in human and wildlife populations represents one of the greatest challenges to ecologists and parasitologists. While there is considerable interest in drivers of amphibian microparasite infections and the resulting consequences, comparatively little research has addressed such questions for amphibian macroparasites. What work has been done in this area has largely focused on nematodes of the genus Rhabdias and on two genera of trematodes (Ribeiroia and Echinostoma). Here, we provide a synopsis of amphibian macroparasites, explore how macroparasites may affect amphibian hosts and populations, and evaluate the significance of these parasites in larger community and ecosystem contexts. In addition, we consider environmental influences on amphibian-macroparasite interactions by exploring contemporary ecological factors known or hypothesized to affect patterns of infection. While some macroparasites of amphibians have direct negative effects on individual hosts, no studies have explicitly examined whether such infections can affect amphibian populations. Moreover, due to their complex life cycles and varying degrees of host specificity, amphibian macroparasites have rich potential as bioindicators of environmental modifications, especially providing insights into changes in food webs. Because of their documented pathologies and value as bioindicators, we emphasize the need for broader investigation of this understudied group, noting that ecological drivers affecting these parasites may also influence disease patterns in other aquatic fauna.
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31
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Tinsley R, Stott L, York J, Everard A, Chapple S, Jackson J, Viney M, Tinsley MC. Acquired immunity protects against helminth infection in a natural host population: long-term field and laboratory evidence. Int J Parasitol 2012; 42:931-8. [PMID: 22906507 DOI: 10.1016/j.ijpara.2012.07.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 07/23/2012] [Accepted: 07/24/2012] [Indexed: 11/25/2022]
Abstract
Long-term records of parasite infection are rare for individuals in wild host populations. This study, on an introduced population of Xenopus laevis in Wales, demonstrates powerful control by acquired immunity of the monogenean, Protopolystoma xenopodis. Field evidence was based on a 10 year dataset for 619 individually-marked hosts screened at each capture for patent (egg-producing) infection. The adult parasite population occurred predominantly in juvenile hosts. Invasion began rapidly 'post-birth' (in early tadpoles). Longitudinal records for animals aged ≥15 years showed that, after loss of this primary infection, most hosts had strong resistance to re-infection. For ca. 80% of the population, no infections were recorded during adult life; for ca. 15%, there were isolated brief episodes of patent infection; for ca. 5%, parasites persisted as repeated short-term or chronic long-term infections. Acquired immunity was confirmed by laboratory challenge infection of wild-caught X. laevis: in 30/32 exposures, no parasites survived to maturity; in the two infected, development was retarded. Parasite persistence depends principally on host recruitment generating naïve young (as in human measles). In some hosts, retarded parasite development delays reproduction for several years: these infections show 'Typhoid Mary' characteristics, persisting in 'latent' form with potential to initiate epidemics in naïve cohorts.
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Affiliation(s)
- Richard Tinsley
- School of Biological Sciences, University of Bristol, Bristol, UK.
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Raffel TR, Michel PJ, Sites EW, Rohr JR. What drives chytrid infections in newt populations? Associations with substrate, temperature, and shade. ECOHEALTH 2010; 7:526-536. [PMID: 21125308 DOI: 10.1007/s10393-010-0358-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 11/01/2010] [Accepted: 11/09/2010] [Indexed: 05/30/2023]
Abstract
The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) is considered responsible for the population declines and extinctions of hundreds of amphibian species worldwide. The panzootic was likely triggered by human-assisted spread, but once the pathogen becomes established in a given region, its distribution is probably determined by local drivers. To assess the relative importance of potential drivers of infection in red-spotted newts (Notophthalmus viridescens), we measured Bd levels in 16 populations throughout central Pennsylvania. Infected individuals were detected in all but four populations, indicating that Bd is widespread in this region. We quantified local factors hypothesized to influence Bd, and found that infection levels were best predicted by the proportion of the pond substrate consisting of leaf litter or vegetation, along with a significant effect of water temperature. Bd infection in amphibians is temperature-dependent, and one possible explanation of the apparent substrate effect is that tree cover and vegetation provide shade, reducing the availability of shallow, warm-water patches in which newts might reduce or clear Bd infections. Alternatively, leaf litter and emergent vegetation might increase Bd infection more directly, perhaps by providing substrates for environmental growth of the fungus. We also observed a curvilinear relationship between Bd load and snout-vent length (a proxy for age), hinting that newts might develop acquired resistance to Bd infection. Though correlational, these results add to a growing body of evidence suggesting that environmental temperature is an important driver of Bd infection dynamics.
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Affiliation(s)
- Thomas R Raffel
- Department of Integrative Biology, University of South Florida, 4202 E. Fowler Avenue, SCA 110, Tampa, FL 33620, USA.
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