1
|
Wilber MQ, DeMarchi JA, Briggs CJ, Streipert S. Rapid Evolution of Resistance and Tolerance Leads to Variable Host Recoveries following Disease-Induced Declines. Am Nat 2024; 203:535-550. [PMID: 38635360 DOI: 10.1086/729437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2024]
Abstract
AbstractRecoveries of populations that have suffered severe disease-induced declines are being observed across disparate taxa. Yet we lack theoretical understanding of the drivers and dynamics of recovery in host populations and communities impacted by infectious disease. Motivated by disease-induced declines and nascent recoveries in amphibians, we developed a model to ask the following question: How does the rapid evolution of different host defense strategies affect the transient recovery trajectories of hosts following pathogen invasion and disease-induced declines? We found that while host life history is predictably a major driver of variability in population recovery trajectories (including declines and recoveries), populations that use different host defense strategies (i.e., tolerance, avoidance resistance, and intensity-reduction resistance) experience notably different recoveries. In single-species host populations, populations evolving tolerance recovered on average four times slower than populations evolving resistance. Moreover, while populations using avoidance resistance strategies had the fastest potential recovery rates, these populations could get trapped in long transient states at low abundance prior to recovery. In contrast, the recovery of populations evolving intensity-reduction resistance strategies were more consistent across ecological contexts. Overall, host defense strategies strongly affect the transient dynamics of population recovery and may affect the ultimate fate of real populations recovering from disease-induced declines.
Collapse
|
2
|
Snyder PW, Ramsay CT, Harjoe CC, Khazan ES, Briggs CJ, Hoverman JT, Johnson PTJ, Preston D, Rohr JR, Blaustein AR. Experimental evidence that host species composition alters host-pathogen dynamics in a ranavirus-amphibian assemblage. Ecology 2023; 104:e3885. [PMID: 36217286 PMCID: PMC9898091 DOI: 10.1002/ecy.3885] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 08/12/2022] [Accepted: 08/19/2022] [Indexed: 02/06/2023]
Abstract
Losses in biodiversity can alter disease risk through changes in host species composition. Host species vary in pathogen susceptibility and competence, yet how changes in diversity alter host-pathogen dynamics remains unclear in many systems, particularly with respect to generalist pathogens. Amphibians are experiencing worldwide population declines linked to generalist pathogens, such as ranavirus, and thus represent an ideal group to investigate how host species composition affects disease risk. We conducted experiments in which amphibian larvae of three native species (Pacific tree frogs, Pseudacris regilla; Cascades frogs, Rana cascadae; and Western toads, Anaxyrus boreas) were exposed to ranavirus individually (in the laboratory) or as assemblages (in outdoor mesocosms). In a laboratory experiment, we observed low survival and high viral loads in P. regilla compared to the other species, suggesting that this species was highly susceptible to the pathogen. In the mesocosm experiment, we observed 41% A. boreas mortality when alone and 98% mortality when maintained with P. regilla and R. cascadae. Our results suggest that the presence of highly susceptible species can alter disease dynamics across multiple species, potentially increasing infection risk and mortality in co-occurring species.
Collapse
Affiliation(s)
- Paul W Snyder
- Integrative Biology, Oregon State University, Corvallis, Oregon, USA
| | - Chloe T Ramsay
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | - Carmen C Harjoe
- Integrative Biology, Oregon State University, Corvallis, Oregon, USA
| | - Emily S Khazan
- School of Natural Resources and Environment, University of Florida, Gainesville, Florida, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Jason Todd Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, Indiana, USA
| | - Pieter T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado, USA
| | - Daniel Preston
- Department of Fish, Wildlife and Conservation Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, Florida, USA
| | | |
Collapse
|
3
|
Wilber MQ, Knapp RA, Smith TC, Briggs CJ. Host density has limited effects on pathogen invasion, disease-induced declines and within-host infection dynamics across a landscape of disease. J Anim Ecol 2022; 91:2451-2464. [PMID: 36285540 DOI: 10.1111/1365-2656.13823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Accepted: 09/20/2022] [Indexed: 12/14/2022]
Abstract
1. Host density is hypothesized to be a major driver of variability in the responses and outcomes of wildlife populations following pathogen invasion. While the effects of host density on pathogen transmission have been extensively studied, these studies are dominated by theoretical analyses and small-scale experiments. This focus leads to an incomplete picture regarding how host density drives observed variability in disease outcomes in the field. 2. Here, we leveraged a dataset of hundreds of replicate amphibian populations that varied by orders of magnitude in host density. We used these data to test the effects of host density on three outcomes following the arrival of the amphibian-killing fungal pathogen Batrachochytrium dendrobatidis (Bd): the probability that Bd successfully invaded a host population and led to a pathogen outbreak, the magnitude of the host population-level decline following an outbreak and within-host infection dynamics that drive population-level outcomes in amphibian-pathogen systems. 3. Based on previous small-scale transmission experiments, we expected that populations with higher densities would be more likely to experience Bd outbreaks and would suffer larger proportional declines following outbreaks. To test these predictions, we developed and fitted a Hidden Markov Model that accounted for imperfectly observed disease outbreak states in the amphibian populations we surveyed. 4. Contrary to our predictions, we found minimal effects of host density on the probability of successful Bd invasion, the magnitude of population decline following Bd invasion and the dynamics of within-host infection intensity. Environmental conditions, such as summer temperature, winter severity and the presence of pathogen reservoirs, were more predictive of variability in disease outcomes. 5. Our results highlight the limitations of extrapolating findings from small-scale transmission experiments to observed disease trajectories in the field and provide strong evidence that variability in host density does not necessarily drive variability in host population responses following pathogen arrival. In an applied context, we show that feedbacks between host density and disease will not necessarily affect the success of reintroduction efforts in amphibian-Bd systems of conservation concern.
Collapse
Affiliation(s)
- Mark Q Wilber
- Department of Forestry, Wildlife, and Fisheries, University of Tennessee Institute of Agriculture, Knoxville, Tennessee, USA
| | - Roland A Knapp
- Earth Research Institute, University of California, Santa Barbara, California, USA.,Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, USA
| | - Thomas C Smith
- Earth Research Institute, University of California, Santa Barbara, California, USA.,Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| |
Collapse
|
4
|
Wilber MQ, Ohmer MEB, Altman KA, Brannelly LA, LaBumbard BC, Le Sage EH, McDonnell NB, Muñiz Torres AY, Nordheim CL, Pfab F, Richards-Zawacki CL, Rollins-Smith LA, Saenz V, Voyles J, Wetzel DP, Woodhams DC, Briggs CJ. Once a reservoir, always a reservoir? Seasonality affects the pathogen maintenance potential of amphibian hosts. Ecology 2022; 103:e3759. [PMID: 35593515 DOI: 10.1002/ecy.3759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 03/18/2022] [Accepted: 03/31/2022] [Indexed: 11/10/2022]
Abstract
Host species that can independently maintain a pathogen in a host community and contribute to infection in other species are important targets for disease management. However, the potential of host species to maintain a pathogen is not fixed over time, and an important challenge is understanding how within- and across-season variability in host maintenance potential affects pathogen persistence over longer time scales relevant for disease management (e.g., years). Here, we sought to understand the causes and consequences of seasonal infection dynamics in leopard frogs (Rana sphenocephala and R. pipiens) infected with the fungal pathogen Batrachochytrium dendrobatidis (Bd). We addressed three questions broadly applicable to seasonal host-parasite systems. First, to what degree are observed seasonal patterns in infection driven by temperature-dependent infection processes compared to seasonal host demographic processes? Second, how does seasonal variation in maintenance potential affect long-term pathogen persistence in multihost communities? Third, does high deterministic maintenance potential relate to the long-term stochastic persistence of pathogens in host populations with seasonal infection dynamics? To answer these questions, we used field data collected over three years on >1400 amphibians across four geographic locations, laboratory and mesocosm experiments, and a novel mathematical model. We found that the mechanisms that drive seasonal prevalence were different than those driving seasonal infection intensity. Seasonal variation in Bd prevalence was driven primarily by changes in host contact rates associated with breeding migrations to and from aquatic habitat. In contrast, seasonal changes in infection intensity were driven by temperature-induced changes in Bd growth rate. Using our model, we found that the maintenance potential of leopard frogs varied significantly throughout the year and that seasonal troughs in infection prevalence made it unlikely that leopard frogs were responsible for long-term Bd persistence in these seasonal amphibian communities, highlighting the importance of alternative pathogen reservoirs for Bd persistence. Our results have broad implications for management in seasonal host-pathogen systems, showing that seasonal changes in host and pathogen vital rates, rather than the depletion of susceptible hosts, can lead to troughs in pathogen prevalence and stochastic pathogen extirpation.
Collapse
Affiliation(s)
- Mark Q Wilber
- Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Institute of Agriculture, Knoxville, TN.,Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA
| | - Michel E B Ohmer
- Living Earth Collaborative, Washington University in St. Louis, St. Louis, MO.,Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Biology, University of Mississippi, Oxford, MS
| | - Karie A Altman
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Department of Biology, St. Bonaventure University, St Bonaventure, NY
| | - Laura A Brannelly
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA.,Melbourne Veterinary School, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Victoria, Australia
| | - Brandon C LaBumbard
- Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Emily H Le Sage
- Department of Pathology Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN
| | - Nina B McDonnell
- Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Aura Y Muñiz Torres
- Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Caitlin L Nordheim
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA.,Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Ferdinand Pfab
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA
| | | | - Louise A Rollins-Smith
- Department of Pathology Microbiology, and Immunology, Vanderbilt University School of Medicine, Nashville, TN
| | - Veronica Saenz
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Jamie Voyles
- Department of Biology, University of Nevada, Reno, Reno, NV
| | - Daniel P Wetzel
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Douglas C Woodhams
- Department of Biology, University of Massachusetts Boston, Boston, Massachusetts, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA
| |
Collapse
|
5
|
Pfab F, Nisbet RM, Briggs CJ. A time-since-infection model for populations with two pathogens. Theor Popul Biol 2022; 144:1-12. [PMID: 35051523 DOI: 10.1016/j.tpb.2022.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Revised: 06/07/2021] [Accepted: 01/04/2022] [Indexed: 10/19/2022]
Abstract
The pioneering work of Kermack and McKendrick (1927, 1932, 1933) is now most known for introducing the SIR model, which divides a population into discrete compartments for susceptible, infected and removed individuals. The SIR model is the archetype of widely used compartmental models for epidemics. It is sometimes forgotten, that Kermack and McKendrick introduced the SIR model as a special case of a more general framework. This general framework distinguishes individuals not only by whether they are susceptible, infected or removed, but additionally tracks the time passed since they got infected. Such time-since-infection models can mechanistically link within-host dynamics to the population level. This allows the models to account for more details of the disease dynamics, such as delays of infectiousness and symptoms during the onset of an infection. Details like this can be vital for interpreting epidemiological data. The time-since-infection framework was originally formulated for a host population with a single pathogen. However, the interactions of multiple pathogens within hosts and within a population can be crucial for understanding the severity and spread of diseases. Current models for multiple pathogens mostly rely on compartmental models. While such models are relatively easy to set up, they do not have the same mechanistic underpinning as time-since-infection models. To approach this gap of connecting within-host dynamics of multiple pathogens to the population level, we here extend the time-since-infection framework of Kermack and McKendrick for two pathogens. We derive formulas for the basic reproduction numbers in the system. Those numbers determine whether a pathogen can invade a population, potentially depending on whether the other pathogen is present or not. We then demonstrate use of the framework by setting up a simple within-host model that we connect to the population model. The example illustrates the context-specific information required for this type of model, and shows how the system can be simulated numerically. We verify that the formulas for the basic reproduction numbers correctly specify the invasibility conditions.
Collapse
Affiliation(s)
- Ferdinand Pfab
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, USA.
| | - Roger M Nisbet
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, USA.
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, USA.
| |
Collapse
|
6
|
Knapp RA, Joseph MB, Smith TC, Hegeman EE, Vredenburg VT, Erdman Jr JE, Boiano DM, Jani AJ, Briggs CJ. Effectiveness of antifungal treatments during chytridiomycosis epizootics in populations of an endangered frog. PeerJ 2022; 10:e12712. [PMID: 35036095 PMCID: PMC8742549 DOI: 10.7717/peerj.12712] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 12/09/2021] [Indexed: 01/07/2023] Open
Abstract
The recently-emerged amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has had an unprecedented impact on global amphibian populations, and highlights the urgent need to develop effective mitigation strategies. We conducted in-situ antifungal treatment experiments in wild populations of the endangered mountain yellow-legged frog during or immediately after Bd-caused mass die-off events. The objective of treatments was to reduce Bd infection intensity ("load") and in doing so alter frog-Bd dynamics and increase the probability of frog population persistence despite ongoing Bd infection. Experiments included treatment of early life stages (tadpoles and subadults) with the antifungal drug itraconazole, treatment of adults with itraconazole, and augmentation of the skin microbiome of subadults with Janthinobacterium lividum, a commensal bacterium with antifungal properties. All itraconazole treatments caused immediate reductions in Bd load, and produced longer-term effects that differed between life stages. In experiments focused on early life stages, Bd load was reduced in the 2 months immediately following treatment and was associated with increased survival of subadults. However, Bd load and frog survival returned to pre-treatment levels in less than 1 year, and treatment had no effect on population persistence. In adults, treatment reduced Bd load and increased frog survival over the entire 3-year post-treatment period, consistent with frogs having developed an effective adaptive immune response against Bd. Despite this protracted period of reduced impacts of Bd on adults, recruitment into the adult population was limited and the population eventually declined to near-extirpation. In the microbiome augmentation experiment, exposure of subadults to a solution of J. lividum increased concentrations of this potentially protective bacterium on frogs. However, concentrations declined to baseline levels within 1 month and did not have a protective effect against Bd infection. Collectively, these results indicate that our mitigation efforts were ineffective in causing long-term changes in frog-Bd dynamics and increasing population persistence, due largely to the inability of early life stages to mount an effective immune response against Bd. This results in repeated recruitment failure and a low probability of population persistence in the face of ongoing Bd infection.
Collapse
Affiliation(s)
- Roland A. Knapp
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, United States
- Earth Research Institute, University of California, Santa Barbara, California, United States
| | | | - Thomas C. Smith
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, United States
- Earth Research Institute, University of California, Santa Barbara, California, United States
| | - Ericka E. Hegeman
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, United States
- Earth Research Institute, University of California, Santa Barbara, California, United States
| | - Vance T. Vredenburg
- Department of Biology, San Francisco State University, San Francisco, California, United States
| | - James E. Erdman Jr
- California Department of Fish and Wildlife, Bishop, California, United States
| | - Daniel M. Boiano
- Sequoia and Kings Canyon National Parks, National Park Service, Three Rivers, California, United States
| | - Andrea J. Jani
- Pacific Biosciences Research Center, University of Hawai’i at Mànoa, Honolulu, Hawai’i, United States
| | - Cheryl J. Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, United States
| |
Collapse
|
7
|
Adams AJ, Peralta-García A, Flores-López CA, Valdez-Villavicencio JH, Briggs CJ. High fungal pathogen loads and prevalence in Baja California amphibian communities: The importance of species, elevation, and historical context. Glob Ecol Conserv 2022. [DOI: 10.1016/j.gecco.2021.e01968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
|
8
|
Wilber MQ, Pfab F, Ohmer ME, Briggs CJ. Integrating Infection Intensity into Within- and Between-Host Pathogen Dynamics: Implications for Invasion and Virulence Evolution. Am Nat 2021; 198:661-677. [PMID: 34762573 DOI: 10.1086/716914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractInfection intensity can dictate disease outcomes but is typically ignored when modeling infection dynamics of microparasites (e.g., bacteria, virus, and fungi). However, for a number of pathogens of wildlife typically categorized as microparasites, accounting for infection intensity and within-host infection processes is critical for predicting population-level responses to pathogen invasion. Here, we develop a modeling framework we refer to as reduced-dimension host-parasite integral projection models (reduced IPMs) that we use to explore how within-host infection processes affect the dynamics of pathogen invasion and virulence evolution. We find that individual-level heterogeneity in pathogen load-a nearly ubiquitous characteristic of host-parasite interactions that is rarely considered in models of microparasites-generally reduces pathogen invasion probability and dampens virulence-transmission trade-offs in host-parasite systems. The latter effect likely contributes to widely predicted virulence-transmission trade-offs being difficult to observe empirically. Moreover, our analyses show that intensity-dependent host mortality does not always induce a virulence-transmission trade-off, and systems with steeper than linear relationships between pathogen intensity and host mortality rate are significantly more likely to exhibit these trade-offs. Overall, reduced IPMs provide a useful framework to expand our theoretical and data-driven understanding of how within-host processes affect population-level disease dynamics.
Collapse
|
9
|
Rothstein AP, Byrne AQ, Knapp RA, Briggs CJ, Voyles J, Richards-Zawacki CL, Rosenblum EB. Divergent regional evolutionary histories of a devastating global amphibian pathogen. Proc Biol Sci 2021; 288:20210782. [PMID: 34157877 PMCID: PMC8220259 DOI: 10.1098/rspb.2021.0782] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Emerging infectious diseases are a pressing threat to global biological diversity. Increased incidence and severity of novel pathogens underscores the need for methodological advances to understand pathogen emergence and spread. Here, we use genetic epidemiology to test, and challenge, key hypotheses about a devastating zoonotic disease impacting amphibians globally. Using an amplicon-based sequencing method and non-invasive samples we retrospectively explore the history of the fungal pathogen Batrachochytrium dendrobatidis (Bd) in two emblematic amphibian systems: the Sierra Nevada of California and Central Panama. The hypothesis in both regions is the hypervirulent Global Panzootic Lineage of Bd (BdGPL) was recently introduced and spread rapidly in a wave-like pattern. Our data challenge this hypothesis by demonstrating similar epizootic signatures can have radically different underlying evolutionary histories. In Central Panama, our genetic data confirm a recent and rapid pathogen spread. However, BdGPL in the Sierra Nevada has remarkable spatial structuring, high genetic diversity and a relatively older history inferred from time-dated phylogenies. Thus, this deadly pathogen lineage may have a longer history in some regions than assumed, providing insights into its origin and spread. Overall, our results highlight the importance of integrating observed wildlife die-offs with genetic data to more accurately reconstruct pathogen outbreaks.
Collapse
Affiliation(s)
- Andrew P Rothstein
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, USA.,Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA, USA
| | - Allison Q Byrne
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, USA.,Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA, USA.,Center for Conservation Genomics, Smithsonian Conservation Biology Institute, National Zoological Park, Washington, DC, USA
| | - Roland A Knapp
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA, USA.,Earth Research Institute, University of California, Santa Barbara, CA, USA
| | - Cheryl J Briggs
- Earth Research Institute, University of California, Santa Barbara, CA, USA.,Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, USA
| | - Jamie Voyles
- Department of Biology, University of Nevada, Reno, NV, USA
| | | | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, USA.,Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA, USA
| |
Collapse
|
10
|
Wilber MQ, Carter ED, Gray MJ, Briggs CJ. Putative resistance and tolerance mechanisms have little impact on disease progression for an emerging salamander pathogen. Funct Ecol 2021. [DOI: 10.1111/1365-2435.13754] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Mark Q. Wilber
- Department of Ecology Evolution and Marine Biology University of California Santa Barbara CA USA
- Center for Wildlife Health Department of Forestry, Wildlife and Fisheries University of Tennessee Institute of Agriculture Knoxville TN USA
| | - Edward Davis Carter
- Center for Wildlife Health Department of Forestry, Wildlife and Fisheries University of Tennessee Institute of Agriculture Knoxville TN USA
| | - Matthew J. Gray
- Center for Wildlife Health Department of Forestry, Wildlife and Fisheries University of Tennessee Institute of Agriculture Knoxville TN USA
| | - Cheryl J. Briggs
- Department of Ecology Evolution and Marine Biology University of California Santa Barbara CA USA
| |
Collapse
|
11
|
Wilber MQ, Briggs CJ, Johnson PTJ. Disease's hidden death toll: Using parasite aggregation patterns to quantify landscape-level host mortality in a wildlife system. J Anim Ecol 2020; 89:2876-2887. [PMID: 32935347 PMCID: PMC9009358 DOI: 10.1111/1365-2656.13343] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 08/06/2020] [Indexed: 12/31/2022]
Abstract
World-wide, infectious diseases represent a major source of mortality in humans and livestock. For wildlife populations, disease-induced mortality is likely even greater, but remains notoriously difficult to estimate-especially for endemic infections. Approaches for quantifying wildlife mortality due to endemic infections have historically been limited by an inability to directly observe wildlife mortality in nature. Here we address a question that can rarely be answered for endemic pathogens of wildlife: what are the population- and landscape-level effects of infection on host mortality? We combined laboratory experiments, extensive field data and novel mathematical models to indirectly estimate the magnitude of mortality induced by an endemic, virulent trematode parasite (Ribeiroia ondatrae) on hundreds of amphibian populations spanning four native species. We developed a flexible statistical model that uses patterns of aggregation in parasite abundance to infer host mortality. Our model improves on previous approaches for inferring host mortality from parasite abundance data by (i) relaxing restrictive assumptions on the timing of host mortality and sampling, (ii) placing all mortality inference within a Bayesian framework to better quantify uncertainty and (iii) accommodating data from laboratory experiments and field sampling to allow for estimates and comparisons of mortality within and among host populations. Applying our approach to 301 amphibian populations, we found that trematode infection was associated with an average of between 13% and 40% population-level mortality. For three of the four amphibian species, our models predicted that some populations experienced >90% mortality due to infection, leading to mortality of thousands of amphibian larvae within a pond. At the landscape scale, the total number of amphibians predicted to succumb to infection was driven by a few high mortality sites, with fewer than 20% of sites contributing to greater than 80% of amphibian mortality on the landscape. The mortality estimates in this study provide a rare glimpse into the magnitude of effects that endemic parasites can have on wildlife populations and our theoretical framework for indirectly inferring parasite-induced mortality can be applied to other host-parasite systems to help reveal the hidden death toll of pathogens on wildlife hosts.
Collapse
Affiliation(s)
- Mark Q. Wilber
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106
| | - Cheryl J. Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, 93106
| | | |
Collapse
|
12
|
Brannelly LA, McCallum HI, Grogan LF, Briggs CJ, Ribas MP, Hollanders M, Sasso T, Familiar López M, Newell DA, Kilpatrick AM. Mechanisms underlying host persistence following amphibian disease emergence determine appropriate management strategies. Ecol Lett 2020; 24:130-148. [PMID: 33067922 DOI: 10.1111/ele.13621] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/18/2020] [Accepted: 09/08/2020] [Indexed: 12/19/2022]
Abstract
Emerging infectious diseases have caused many species declines, changes in communities and even extinctions. There are also many species that persist following devastating declines due to disease. The broad mechanisms that enable host persistence following declines include evolution of resistance or tolerance, changes in immunity and behaviour, compensatory recruitment, pathogen attenuation, environmental refugia, density-dependent transmission and changes in community composition. Here we examine the case of chytridiomycosis, the most important wildlife disease of the past century. We review the full breadth of mechanisms allowing host persistence, and synthesise research on host, pathogen, environmental and community factors driving persistence following chytridiomycosis-related declines and overview the current evidence and the information required to support each mechanism. We found that for most species the mechanisms facilitating persistence have not been identified. We illustrate how the mechanisms that drive long-term host population dynamics determine the most effective conservation management strategies. Therefore, understanding mechanisms of host persistence is important because many species continue to be threatened by disease, some of which will require intervention. The conceptual framework we describe is broadly applicable to other novel disease systems.
Collapse
Affiliation(s)
- Laura A Brannelly
- Veterinary BioSciences, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Werribee, Vic, 3030, Australia
| | - Hamish I McCallum
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Nathan, Qld., 4111, Australia
| | - Laura F Grogan
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Nathan, Qld., 4111, Australia.,Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Maria P Ribas
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia.,Wildlife Conservation Medicine Research Group, Departament de Medicina i Cirurgia Animals, Universitat Autònoma de Barcelona, Bellaterra, 08193, Spain
| | - Matthijs Hollanders
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Thais Sasso
- Environmental Futures Research Institute and School of Environment and Science, Griffith University, Nathan, Qld., 4111, Australia
| | - Mariel Familiar López
- School of Environment and Sciences, Griffith University, Gold Coast, Qld., 4215, Australia
| | - David A Newell
- Forest Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, 2480, Australia
| | - Auston M Kilpatrick
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
| |
Collapse
|
13
|
Rothstein AP, Knapp RA, Bradburd GS, Boiano DM, Briggs CJ, Rosenblum EB. Stepping into the past to conserve the future: Archived skin swabs from extant and extirpated populations inform genetic management of an endangered amphibian. Mol Ecol 2020; 29:2598-2611. [PMID: 32573039 DOI: 10.1111/mec.15515] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 05/21/2020] [Accepted: 06/05/2020] [Indexed: 12/20/2022]
Abstract
Moving animals on a landscape through translocations and reintroductions is an important management tool used in the recovery of endangered species, particularly for the maintenance of population genetic diversity and structure. Management of imperiled amphibian species rely heavily on translocations and reintroductions, especially for species that have been brought to the brink of extinction by habitat loss, introduced species, and disease. One striking example of amphibian declines and associated management efforts is in California's Sequoia and Kings Canyon National Parks with the mountain yellow-legged frog species complex (Rana sierrae/muscosa). Mountain yellow-legged frogs have been extirpated from more than 93% of their historic range, and limited knowledge of their population genetics has made long-term conservation planning difficult. To address this, we used 598 archived skin swabs from both extant and extirpated populations across 48 lake basins to generate a robust Illumina-based nuclear amplicon data set. We found that samples grouped into three main genetic clusters, concordant with watershed boundaries. We also found evidence for historical gene flow across watershed boundaries with a north-to-south axis of migration. Finally, our results indicate that genetic diversity is not significantly different between populations with different disease histories. Our study offers specific management recommendations for imperiled mountain yellow-legged frogs and, more broadly, provides a population genetic framework for leveraging minimally invasive samples for the conservation of threatened species.
Collapse
Affiliation(s)
- Andrew P Rothstein
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, USA.,Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA, USA
| | - Roland A Knapp
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA, USA
| | - Gideon S Bradburd
- Department of Integrative Biology, Michigan State University, East Lansing, MI, USA
| | - Daniel M Boiano
- Sequoia and Kings Canyon National Parks, Three Rivers, CA, USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, CA, USA
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California Berkeley, Berkeley, CA, USA.,Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, CA, USA
| |
Collapse
|
14
|
Wilber MQ, Johnson PTJ, Briggs CJ. Disease hotspots or hot species? Infection dynamics in multi-host metacommunities controlled by species identity, not source location. Ecol Lett 2020; 23:1201-1211. [PMID: 32357383 DOI: 10.1111/ele.13518] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/29/2020] [Accepted: 03/25/2020] [Indexed: 01/12/2023]
Abstract
Pathogen persistence in host communities is influenced by processes operating at the individual host to landscape-level scale, but isolating the relative contributions of these processes is challenging. We developed theory to partition the influence of host species, habitat patches and landscape connectivity on pathogen persistence within metacommunities of hosts and pathogens. We used this framework to quantify the contributions of host species composition and habitat patch identity on the persistence of an amphibian pathogen across the landscape. By sampling over 11 000 hosts of six amphibian species, we found that a single host species could maintain the pathogen in 91% of observed metacommunities. Moreover, this dominant maintenance species contributed, on average, twice as much to landscape-level pathogen persistence compared to the most influential source patch in a metacommunity. Our analysis demonstrates substantial inequality in how species and patches contribute to pathogen persistence, with important implications for targeted disease management.
Collapse
Affiliation(s)
- Mark Q Wilber
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
| | - Pieter T J Johnson
- Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, 80309, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
| |
Collapse
|
15
|
DiRenzo GV, Chen R, Ibsen K, Toothman M, Miller AJ, Gershman A, Mitragotri S, Briggs CJ. Investigating the potential use of an ionic liquid (1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) as an anti-fungal treatment against the amphibian chytrid fungus, Batrachochytrium dendrobatidis. PLoS One 2020; 15:e0231811. [PMID: 32302369 PMCID: PMC7164615 DOI: 10.1371/journal.pone.0231811] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Accepted: 04/01/2020] [Indexed: 11/19/2022] Open
Abstract
The disease chytridiomycosis, caused by the pathogenic chytrid fungus, Batrachochytrium dendrobatidis (Bd), has contributed to global amphibian declines. Bd infects the keratinized epidermal tissue in amphibians and causes hyperkeratosis and excessive skin shedding. In individuals of susceptible species, the regulatory function of the amphibian’s skin is disrupted resulting in an electrolyte depletion, osmotic imbalance, and eventually death. Safe and effective treatments for chytridiomycosis are urgently needed to control chytrid fungal infections and stabilize populations of endangered amphibian species in captivity and in the wild. Currently, the most widely used anti-Bd treatment is itraconazole. Preparations of itraconazole formulated for amphibian use has proved effective, but treatment involves short baths over seven to ten days, a process which is logistically challenging, stressful, and causes long-term health effects. Here, we explore a novel anti-fungal therapeutic using a single application of the ionic liquid, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-NTf2), for the treatment of chytridiomycosis. BMP-NTf2 was found be effective at killing Bd in vitro at low concentrations (1:1000 dilution). We tested BMP-NTf2 in vivo on two amphibian species, one that is relatively tolerant of chytridiomycosis (Pseudacris regilla) and one that is highly susceptible (Dendrobates tinctorius). A toxicity trial revealed a surprising interaction between Bd infection status and the impact of BMP-NTf2 on D. tinctorius survival. Uninfected D. tinctorius tolerated BMP-NTf2 (mean ± SE; 96.01 ± 9.00 μl/g), such that only 1 out of 30 frogs died following treatment (at a dose of 156.95 μL/g), whereas, a lower dose (mean ± SE; 97.45 ± 3.52 μL/g) was not tolerated by Bd-infected D. tinctorius, where 15 of 23 frogs died shortly upon BMP-NTf2 application. Those that tolerated the BMP-NTf2 application did not exhibit Bd clearance. Thus, BMP-NTf2 application, under the conditions tested here, is not a suitable option for clearing Bd infection in D. tinctorius. However, different results were obtained for P. regilla. Two topical applications of BMP-NTf2 on Bd-infected P. regilla (using a lower BMP-NTf2 dose than on D. tinctorius, mean ± SE; 9.42 ± 1.43 μL/g) reduced Bd growth, although the effect was lower than that obtained by daily doses of itracanozole (50% frogs exhibited complete clearance on day 16 vs. 100% for itracanozole). Our findings suggest that BMP-NTf2 has the potential to treat Bd infection, however the effect depends on several parameters. Further optimization of dose and schedule are needed before BMP-NTf2 can be considered as a safe and effective alternative to more conventional antifungal agents, such as itraconazole.
Collapse
Affiliation(s)
- Graziella V. DiRenzo
- Department of Ecology, Evolution, & Marine Biology, University of California, Santa Barbara, CA, United States of America
- * E-mail:
| | - Renwei Chen
- Center for Bioengineering, University of California, Santa Barbara, CA, United States of America
| | - Kelly Ibsen
- Center for Bioengineering, University of California, Santa Barbara, CA, United States of America
- Department of Chemical Engineering, University of California, Santa Barbara, CA, United States of America
- School of Engineering and Applied Sciences, Harvard University Cambridge, Cambridge, MA, United States of America
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, United States of America
| | - Mary Toothman
- Department of Ecology, Evolution, & Marine Biology, University of California, Santa Barbara, CA, United States of America
| | - Abigail J. Miller
- Department of Ecology, Evolution, & Marine Biology, University of California, Santa Barbara, CA, United States of America
| | - Ariel Gershman
- Department of Ecology, Evolution, & Marine Biology, University of California, Santa Barbara, CA, United States of America
| | - Samir Mitragotri
- Center for Bioengineering, University of California, Santa Barbara, CA, United States of America
- Department of Chemical Engineering, University of California, Santa Barbara, CA, United States of America
- School of Engineering and Applied Sciences, Harvard University Cambridge, Cambridge, MA, United States of America
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, United States of America
| | - Cheryl J. Briggs
- Department of Ecology, Evolution, & Marine Biology, University of California, Santa Barbara, CA, United States of America
| |
Collapse
|
16
|
Woodhams DC, Rollins-Smith LA, Reinert LK, Lam BA, Harris RN, Briggs CJ, Vredenburg VT, Patel BT, Caprioli RM, Chaurand P, Hunziker P, Bigler L. Probiotics Modulate a Novel Amphibian Skin Defense Peptide That Is Antifungal and Facilitates Growth of Antifungal Bacteria. Microb Ecol 2020; 79:192-202. [PMID: 31093727 DOI: 10.1007/s00248-019-01385-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 04/25/2019] [Indexed: 06/09/2023]
Abstract
Probiotics can ameliorate diseases of humans and wildlife, but the mechanisms remain unclear. Host responses to interventions that change their microbiota are largely uncharacterized. We applied a consortium of four natural antifungal bacteria to the skin of endangered Sierra Nevada yellow-legged frogs, Rana sierrae, before experimental exposure to the pathogenic fungus Batrachochytrium dendrobatidis (Bd). The probiotic microbes did not persist, nor did they protect hosts, and skin peptide sampling indicated immune modulation. We characterized a novel skin defense peptide brevinin-1Ma (FLPILAGLAANLVPKLICSITKKC) that was downregulated by the probiotic treatment. Brevinin-1Ma was tested against a range of amphibian skin cultures and found to inhibit growth of fungal pathogens Bd and B. salamandrivorans, but enhanced the growth of probiotic bacteria including Janthinobacterium lividum, Chryseobacterium ureilyticum, Serratia grimesii, and Pseudomonas sp. While commonly thought of as antimicrobial peptides, here brevinin-1Ma showed promicrobial function, facilitating microbial growth. Thus, skin exposure to probiotic bacterial cultures induced a shift in skin defense peptide profiles that appeared to act as an immune response functioning to regulate the microbiome. In addition to direct microbial antagonism, probiotic-host interactions may be a critical mechanism affecting disease resistance.
Collapse
Affiliation(s)
- Douglas C Woodhams
- Department of Biology, University of Massachusetts Boston, Boston, MA, 02125, USA.
| | - Louise A Rollins-Smith
- Departments of Pathology, Microbiology and Immunology and Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
- Department of Biological Science, Vanderbilt University School of Medicine, Nashville, TN, 37235, USA
| | - Laura K Reinert
- Departments of Pathology, Microbiology and Immunology and Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, 37232, USA
| | - Briana A Lam
- Department of Biology, James Madison University, Harrisonburg, VA, 22807, USA
| | - Reid N Harris
- Department of Biology, James Madison University, Harrisonburg, VA, 22807, USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA, 93106-9610, USA
| | - Vance T Vredenburg
- Department of Biology, San Francisco State University, San Francisco, CA, 94132-1722, USA
| | - Bhumi T Patel
- Department of Biology, University of Massachusetts Boston, Boston, MA, 02125, USA
| | - Richard M Caprioli
- Mass Spectrometry Research Center and Department of Biochemistry, Vanderbilt University, Nashville, TN, 37232-8575, USA
| | - Pierre Chaurand
- Department of Chemistry, Université de Montréal, Montreal, QC, H3T 1J4, Canada
| | - Peter Hunziker
- Functional Genomics Center Zurich, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| | - Laurent Bigler
- Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057, Zurich, Switzerland
| |
Collapse
|
17
|
Canessa S, Spitzen‐van der Sluijs A, Stark T, Allen BE, Bishop PJ, Bletz M, Briggs CJ, Daversa DR, Gray MJ, Griffiths RA, Harris RN, Harrison XA, Hoverman JT, Jervis P, Muths E, Olson DH, Price SJ, Richards‐Zawacki CL, Robert J, Rosa GM, Scheele BC, Schmidt BR, Garner TWJ. Conservation decisions under pressure: Lessons from an exercise in rapid response to wildlife disease. Conservat Sci and Prac 2019. [DOI: 10.1111/csp2.141] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Affiliation(s)
- Stefano Canessa
- Wildlife Health Ghent, Faculty of Veterinary MedicineGhent University Merelbeke Belgium
| | | | - Tariq Stark
- Reptile, Amphibian & Fish Conservation Netherlands (RAVON) Nijmegen The Netherlands
| | - Bryony E. Allen
- Institute of ZoologyZoological Society of London, Regents Park London UK
- Institute for Integrative BiologyUniversity of Liverpool Liverpool UK
| | - Phillip J. Bishop
- Department of ZoologyUniversity of Otago Dunedin New Zealand
- Amphibian Survival Alliance London UK
| | - Molly Bletz
- Biology DepartmentUniversity of Massachusetts Boston Massachusetts
| | - Cheryl J. Briggs
- Department of Ecology, Evolution and Marine BiologyUniversity of California Santa Barbara California
| | - David R. Daversa
- Institute of ZoologyZoological Society of London, Regents Park London UK
- Institute for Integrative BiologyUniversity of Liverpool Liverpool UK
| | - Matthew J. Gray
- Center for Wildlife HealthUniversity of Tennessee Institute of Agriculture Knoxville Tennessee
| | - Richard A. Griffiths
- Durrell Institute of Conservation and Ecology, School of Anthropology and ConservationUniversity of Kent Kent UK
| | - Reid N. Harris
- Amphibian Survival Alliance London UK
- Department of BiologyJames Madison University Harrisonburg Virginia
| | | | - Jason T. Hoverman
- Department of Forestry and Natural ResourcesPurdue University West Lafayette Indiana
| | - Phillip Jervis
- Institute of ZoologyZoological Society of London, Regents Park London UK
- Faculty of Medicine, School of Public HealthImperial College London UK
| | - Erin Muths
- United States Geological Survey Fort Collins Colorado
| | - Deanna H. Olson
- Pacific Northwest Research Station, US Forest Service Corvallis Oregon
| | | | | | - Jacques Robert
- Department of Microbiology & ImmunologyUniversity of Rochester Rochester New York
| | - Gonçalo M. Rosa
- Institute of ZoologyZoological Society of London, Regents Park London UK
- Centre for Ecology, Evolution and Environmental Changes (CE3C), Faculdade de Ciências da Universidade de Lisboa Lisbon Portugal
| | - Ben C. Scheele
- Fenner School of Environment and SocietyThe Australian National University Canberra Australian Capital Territory Australia
| | - Benedikt R. Schmidt
- Institut für Evolutionsbiologie und Umweltwissenschaften, Universität Zürich Zürich Switzerland
- Info Fauna Karch Neuchâtel Switzerland
| | | |
Collapse
|
18
|
Wilber MQ, Jani AJ, Mihaljevic JR, Briggs CJ. Fungal infection alters the selection, dispersal and drift processes structuring the amphibian skin microbiome. Ecol Lett 2019; 23:88-98. [PMID: 31637835 DOI: 10.1111/ele.13414] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/17/2019] [Accepted: 09/29/2019] [Indexed: 12/23/2022]
Abstract
Symbiotic microbial communities are important for host health, but the processes shaping these communities are poorly understood. Understanding how community assembly processes jointly affect microbial community composition is limited because inflexible community models rely on rejecting dispersal and drift before considering selection. We developed a flexible community assembly model based on neutral theory to ask: How do dispersal, drift and selection concurrently affect the microbiome across environmental gradients? We applied this approach to examine how a fungal pathogen affected the assembly processes structuring the amphibian skin microbiome. We found that the rejection of neutrality for the amphibian microbiome across a fungal gradient was not strictly due to selection processes, but was also a result of species-specific changes in dispersal and drift. Our modelling framework brings the qualitative recognition that niche and neutral processes jointly structure microbiomes into quantitative focus, allowing for improved predictions of microbial community turnover across environmental gradients.
Collapse
Affiliation(s)
- Mark Q Wilber
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
| | - Andrea J Jani
- Department of Oceanography, University of Hawai'i at Manoa, Honolulu, HI, 96822, USA
| | - Joseph R Mihaljevic
- School of Informatics, Computing, and Cyber Systems, Northern Arizona University, Flagstaff, AZ, 86011, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
| |
Collapse
|
19
|
Byrne AQ, Vredenburg VT, Martel A, Pasmans F, Bell RC, Blackburn DC, Bletz MC, Bosch J, Briggs CJ, Brown RM, Catenazzi A, Familiar López M, Figueroa-Valenzuela R, Ghose SL, Jaeger JR, Jani AJ, Jirku M, Knapp RA, Muñoz A, Portik DM, Richards-Zawacki CL, Rockney H, Rovito SM, Stark T, Sulaeman H, Tao NT, Voyles J, Waddle AW, Yuan Z, Rosenblum EB. Cryptic diversity of a widespread global pathogen reveals expanded threats to amphibian conservation. Proc Natl Acad Sci U S A 2019; 116:20382-20387. [PMID: 31548391 PMCID: PMC6789904 DOI: 10.1073/pnas.1908289116] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Biodiversity loss is one major outcome of human-mediated ecosystem disturbance. One way that humans have triggered wildlife declines is by transporting disease-causing agents to remote areas of the world. Amphibians have been hit particularly hard by disease due in part to a globally distributed pathogenic chytrid fungus (Batrachochytrium dendrobatidis [Bd]). Prior research has revealed important insights into the biology and distribution of Bd; however, there are still many outstanding questions in this system. Although we know that there are multiple divergent lineages of Bd that differ in pathogenicity, we know little about how these lineages are distributed around the world and where lineages may be coming into contact. Here, we implement a custom genotyping method for a global set of Bd samples. This method is optimized to amplify and sequence degraded DNA from noninvasive skin swab samples. We describe a divergent lineage of Bd, which we call BdASIA3, that appears to be widespread in Southeast Asia. This lineage co-occurs with the global panzootic lineage (BdGPL) in multiple localities. Additionally, we shed light on the global distribution of BdGPL and highlight the expanded range of another lineage, BdCAPE. Finally, we argue that more monitoring needs to take place where Bd lineages are coming into contact and where we know little about Bd lineage diversity. Monitoring need not use expensive or difficult field techniques but can use archived swab samples to further explore the history-and predict the future impacts-of this devastating pathogen.
Collapse
Affiliation(s)
- Allison Q Byrne
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720
| | - Vance T Vredenburg
- Department of Biology, San Francisco State University, San Francisco, CA 94132
| | - An Martel
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University, 9820 Merelbeke, Belgium
| | - Frank Pasmans
- Department of Pathology, Bacteriology and Avian Diseases, Ghent University, 9820 Merelbeke, Belgium
| | - Rayna C Bell
- Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington DC 20560
- Department of Herpetology, California Academy of Sciences, San Francisco, CA 94118
| | - David C Blackburn
- Florida Museum of Natural History, University of Florida, Gainesville, FL 32601
| | - Molly C Bletz
- Department of Biology, University of Massachusetts Boston, Boston, MA 02125
| | - Jaime Bosch
- Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Cientificas (CSIC), 28006 Madrid, Spain
- Research Unit of Biodiversity, CSIC-Universidad de Oviedo-Gobierno del Principado de Asturias, E-33600 Mieres, Spain
| | - Cheryl J Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106
| | - Rafe M Brown
- University of Kansas Biodiversity Institute, University of Kansas, Lawrence, KS 66045
- Department of Ecology and Evolution, University of Kansas, Lawrence, KS 66045
| | - Alessandro Catenazzi
- Department of Biological Sciences, Florida International University, Miami, FL 33199
| | - Mariel Familiar López
- School of Environment and Sciences, Griffith University, Gold Coast, QLD 4215, Australia
| | | | - Sonia L Ghose
- Department of Evolution and Ecology, University of California, Davis, CA 95616
| | - Jef R Jaeger
- School of Life Sciences, University of Nevada, Las Vegas, NV 89154
| | - Andrea J Jani
- Department of Oceanography, University of Hawai'i at Manoa, Honolulu, HI 96822
| | - Miloslav Jirku
- Institute of Parasitology, Czech Academy of Sciences, 370 05 Ceske Budejovice, Czech Republic
| | - Roland A Knapp
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA 93546
| | - Antonio Muñoz
- Department of Biodiversity Conservation, El Colegio de la Frontera Sur, San Cristobal de las Casas, Chiapas 29290, México
| | - Daniel M Portik
- Department of Ecology and Evolution, University of Arizona, Tucson, AZ 85721
| | | | - Heidi Rockney
- Environmental Sciences Graduate Program, Oregon State University, Corvallis, OR 97331
| | - Sean M Rovito
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato CP36824, México
| | - Tariq Stark
- Reptile, Amphibian and Fish Conservation, 6525 ED Nijmegen, The Netherlands
| | - Hasan Sulaeman
- Department of Biology, San Francisco State University, San Francisco, CA 94132
| | - Nguyen Thien Tao
- Vietnam National Museum of Nature, Vietnam Academy of Science and Technology, Hanoi, Vietnam
| | - Jamie Voyles
- Department of Biology, University of Nevada, Reno, NV 89557
| | - Anthony W Waddle
- School of Life Sciences, University of Nevada, Las Vegas, NV 89154
- One Health Research Group, The University of Melbourne, Werribee, VIC 3030, Australia
| | - Zhiyong Yuan
- College of Forestry, Southwest Forestry University, Kunming 650224, Yunnan, China
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720;
- Museum of Vertebrate Zoology, University of California, Berkeley, CA 94720
| |
Collapse
|
20
|
Vredenburg VT, McNally SVG, Sulaeman H, Butler HM, Yap T, Koo MS, Schmeller DS, Dodge C, Cheng T, Lau G, Briggs CJ. Pathogen invasion history elucidates contemporary host pathogen dynamics. PLoS One 2019; 14:e0219981. [PMID: 31536501 PMCID: PMC6752790 DOI: 10.1371/journal.pone.0219981] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 07/05/2019] [Indexed: 01/23/2023] Open
Abstract
Amphibians, the most threatened group of vertebrates, are seen as indicators of the sixth mass extinction on earth. Thousands of species are threatened with extinction and many have been affected by an emerging infectious disease, chytridiomycosis, caused by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). However, amphibians exhibit different responses to the pathogen, such as survival and population persistence with infection, or mortality of individuals and complete population collapse after pathogen invasion. Multiple factors can affect host pathogen dynamics, yet few studies have provided a temporal view that encompasses both the epizootic phase (i.e. pathogen invasion and host collapse), and the transition to a more stable co-existence (i.e. recovery of infected host populations). In the Sierra Nevada mountains of California, USA, conspecific populations of frogs currently exhibit dramatically different host/ Bd-pathogen dynamics. To provide a temporal context by which present day dynamics may be better understood, we use a Bd qPCR assay to test 1165 amphibian specimens collected between 1900 and 2005. Our historical analyses reveal a pattern of pathogen invasion and eventual spread across the Sierra Nevada over the last century. Although we found a small number of Bd-infections prior to 1970, these showed no sign of spread or increase in infection prevalence over multiple decades. After the late 1970s, when mass die offs were first noted, our data show Bd as much more prevalent and more spatially spread out, suggesting epizootic spread. However, across the ~400km2 area, we found no evidence of a wave-like pattern, but instead discovered multiple, nearly-simultaneous invasions within regions. We found that Bd invaded and spread in the central Sierra Nevada (Yosemite National Park area) about four decades before it invaded and spread in the southern Sierra Nevada (Sequoia and Kings Canyon National Parks area), and suggest that the temporal pattern of pathogen invasion may help explain divergent contemporary host pathogen dynamics.
Collapse
Affiliation(s)
- Vance T. Vredenburg
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, California, United States of America
- * E-mail:
| | - Samuel V. G. McNally
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
| | - Hasan Sulaeman
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
| | - Helen M. Butler
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
| | - Tiffany Yap
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, California, United States of America
- Center for Biological Diversity, Oakland, California, United States of America
| | - Michelle S. Koo
- Museum of Vertebrate Zoology, University of California Berkeley, Berkeley, California, United States of America
| | | | - Celeste Dodge
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
| | - Tina Cheng
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
| | - Gordon Lau
- Department of Biology, San Francisco State University, San Francisco, California, United States of America
| | - Cheryl J. Briggs
- Department of Ecology Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California, United States of America
| |
Collapse
|
21
|
Briggs CJ, Adam TC, Holbrook SJ, Schmitt RJ. Macroalgae size refuge from herbivory promotes alternative stable states on coral reefs. PLoS One 2018; 13:e0202273. [PMID: 30226879 PMCID: PMC6143192 DOI: 10.1371/journal.pone.0202273] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 07/03/2018] [Indexed: 11/20/2022] Open
Abstract
Coral reef systems can undergo rapid transitions from coral-dominated to macroalgae-dominated states following disturbances, and models indicate that these may sometimes represent shifts between alternative stable states. While several mechanisms may lead to alternate stable states on coral reefs, only a few have been investigated theoretically. We explore a model that illustrates that reduced vulnerability of macroalgae to herbivory as macroalgae grow and mature could be an important mechanism: when macroalgae are palatable to herbivores as juveniles, but resistant as adults, coral-dominated and algae-dominated states are bistable across a wide range of parameter space. We compare two approaches to global sensitivity analysis to rank the relative importance of the model parameters in determining the presence and magnitude of alternative stable states, and find that the two most influential parameters are the death rate of coral and the rate of maturation of algae out of the vulnerable stage. The Random Forest approach for global sensitivity analysis, recently adopted by ecologists, provides a more efficient method for ranking the relative importance of parameters than a variance-based approach that has been used frequently by computer scientists and engineers. Our results suggest that managing reefs to reduce chronic stressors that cause coral mortality and/or enhance the growth rates of algae can help prevent reefs from becoming locked in a macroalgae-dominated state.
Collapse
Affiliation(s)
- Cheryl J. Briggs
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, United States of America
- * E-mail:
| | - Thomas C. Adam
- Marine Science Institute, University of California, Santa Barbara, CA, United States of America
| | - Sally J. Holbrook
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, United States of America
- Marine Science Institute, University of California, Santa Barbara, CA, United States of America
| | - Russell J. Schmitt
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, United States of America
- Marine Science Institute, University of California, Santa Barbara, CA, United States of America
| |
Collapse
|
22
|
Tornabene BJ, Blaustein AR, Briggs CJ, Calhoun DM, Johnson PTJ, McDevitt-Galles T, Rohr JR, Hoverman JT. The influence of landscape and environmental factors on ranavirus epidemiology in a California amphibian assemblage. Freshw Biol 2018; 63:639-651. [PMID: 30127540 PMCID: PMC6097636 DOI: 10.1111/fwb.13100] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/16/2018] [Indexed: 06/08/2023]
Abstract
A fundamental goal of disease ecology is to determine the landscape and environmental processes that drive disease dynamics at different biological levels to guide management and conservation. Although ranaviruses (family Iridoviridae) are emerging amphibian pathogens, few studies have conducted comprehensive field surveys to assess potential drivers of ranavirus disease dynamics.We examined the factors underlying patterns in site-level ranavirus presence and individual-level ranavirus infection in 76 ponds and 1,088 individuals representing 5 amphibian species within the East Bay region of California.Based on a competing-model approach followed by variance partitioning, landscape and biotic variables explained the most variation in site-level presence. However, biotic and individual-level variables explained the most variation in individual-level infection.Distance to nearest ranavirus-infected pond (the landscape factor) was more important than biotic factors at the site-level; however, biotic factors were most influential at the individual-level. At the site level, the probability of ranavirus presence correlated negatively with distance to nearest ranavirus-positive pond, suggesting that the movement of water or mobile taxa (e.g., adult amphibians, birds, reptiles) may facilitate the movement of ranavirus between ponds and across the landscape.Taxonomic richness associated positively with ranavirus presence at the site-level, but vertebrate richness associated negatively with infection prevalence in the host population. This might reflect the contrasting influences of diversity on pathogen colonization versus transmission among hosts.Amphibian host species differed in their likelihood of ranavirus infection: American bullfrogs (Rana catesbeiana) had the weakest association with infection while rough-skinned newts (Taricha granulosa) had the strongest. After accounting for host species effects, hosts with greater snout-vent length had a lower probability of infection.Our study demonstrates the array of landscape, environmental, and individual-level factors associated with ranavirus epidemiology. Moreover, our study helps illustrate that the importance of these factors varies with biological level.
Collapse
Affiliation(s)
- Brian J Tornabene
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907-2061
| | - Andrew R Blaustein
- Integrative Biology, 3029 Cordley Hall, Oregon State University, Corvallis, OR 97331-2914
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610
| | - Dana M Calhoun
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309-0334
| | - Pieter T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309-0334
| | - Travis McDevitt-Galles
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309-0334
| | - Jason R Rohr
- Department of Integrative Biology, University of South Florida, Tampa, FL 33620
| | - Jason T Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907-2061
| |
Collapse
|
23
|
MacDonald AJ, Hyon DW, McDaniels A, O'Connor KE, Swei A, Briggs CJ. Risk of vector tick exposure initially increases, then declines through time in response to wildfire in California. Ecosphere 2018. [DOI: 10.1002/ecs2.2227] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Andrew J. MacDonald
- Department of Ecology, Evolution and Marine Biology University of California Santa Barbara California 93106 USA
- Department of Biology Stanford University Stanford California 94305 USA
- Earth Research Institute University of California Santa Barbara California 93106 USA
| | - David W. Hyon
- Department of Ecology, Evolution and Marine Biology University of California Santa Barbara California 93106 USA
| | - Akira McDaniels
- Department of Ecology, Evolution and Marine Biology University of California Santa Barbara California 93106 USA
| | - Kerry E. O'Connor
- Department of Biology San Francisco State University San Francisco California 94132 USA
| | - Andrea Swei
- Department of Biology San Francisco State University San Francisco California 94132 USA
| | - Cheryl J. Briggs
- Department of Ecology, Evolution and Marine Biology University of California Santa Barbara California 93106 USA
| |
Collapse
|
24
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 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.
Collapse
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
| |
Collapse
|
25
|
Stutz WE, Blaustein AR, Briggs CJ, Hoverman JT, Rohr JR, Johnson PTJ. Using multi-response models to investigate pathogen coinfections across scales: insights from emerging diseases of amphibians. Methods Ecol Evol 2018; 9:1109-1120. [PMID: 29861885 PMCID: PMC5978769 DOI: 10.1111/2041-210x.12938] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Associations among parasites affect many aspects of host-parasite dynamics, but a lack of analytical tools has limited investigations of parasite correlations in observational data that are often nested across spatial and biological scales.Here we illustrate how hierarchical, multiresponse modeling can characterize parasite associations by allowing for hierarchical structuring, offering estimates of uncertainty, and incorporating correlational model structures. After introducing the general approach, we apply this framework to investigate coinfections among four amphibian parasites (the trematodes Ribeiroia ondatrae and Echinostoma spp., the chytrid fungus Batrachochytrium dendrobatidis, and ranaviruses) and among >2000 individual hosts, 90 study sites, and five amphibian host species.Ninety-two percent of sites and 80% of hosts supported two or more pathogen species. Our results revealed strong correlations between parasite pairs that varied by scale (from among hosts to among sites) and classification (microparasite versus macroparasite), but were broadly consistent across taxonomically diverse host species. At the host-scale, infection by the trematode R. ondatrae correlated positively with the microparasites, B. dendrobatidis and ranavirus, which were themselves positively associated. However, infection by a second trematode (Echinostoma spp.) correlated negatively with B. dendrobatidis and ranavirus, both at the host- and site-level scales, highlighting the importance of differential relationships between micro- and macroparasites.Given the extensive number of coinfecting symbiont combinations inherent to natural systems, particularly across multiple host species, multiresponse modeling of cross-sectional field data offers a valuable tool to identify a tractable number of hypothesized interactions for experimental testing while accounting for uncertainty and potential sources of co-exposure. For amphibians specifically, the high frequency of co-occurrence and coinfection among these pathogens - each of which is known to impair host fitness or survival - highlights the urgency of understanding parasite associations for conservation and disease management.
Collapse
Affiliation(s)
- William E. Stutz
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309-0334
| | - Andrew R. Blaustein
- Integrative Biology, 3029 Cordley Hall, Oregon State University, Corvallis, OR 97331-2914
| | - Cheryl J. Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610
| | - Jason T. Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN 47907-2061
| | - Jason R. Rohr
- Department of Integrative Biology, University of South Florida, 4202 East Fowler Avenue, SCA 110, Tampa, FL 33620
| | - Pieter T. J. Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO 80309-0334
| |
Collapse
|
26
|
Johnson PTJ, Calhoun DM, Stokes AN, Susbilla CB, McDevitt-Galles T, Briggs CJ, Hoverman JT, Tkach VV, de Roode JC. Of poisons and parasites-the defensive role of tetrodotoxin against infections in newts. J Anim Ecol 2018; 87:1192-1204. [PMID: 29476541 DOI: 10.1111/1365-2656.12816] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 01/17/2018] [Indexed: 11/29/2022]
Abstract
Classical research on animal toxicity has focused on the role of toxins in protection against predators, but recent studies suggest these same compounds can offer a powerful defense against parasites and infectious diseases. Newts in the genus Taricha are brightly coloured and contain the potent neurotoxin, tetrodotoxin (TTX), which is hypothesized to have evolved as a defense against vertebrate predators such as garter snakes. However, newt populations often vary dramatically in toxicity, which is only partially explained by predation pressure. The primary aim of this study was to evaluate the relationships between TTX concentration and infection by parasites. By systematically assessing micro- and macroparasite infections among 345 adult newts (sympatric populations of Taricha granulosa and T. torosa), we detected 18 unique taxa of helminths, fungi, viruses and protozoans. For both newt species, per-host concentrations of TTX, which varied from undetectable to >60 μg/cm2 skin, negatively predicted overall parasite richness as well as the likelihood of infection by the chytrid fungus, Batrachochytrium dendrobatidis, and ranavirus. No such effect was found on infection load among infected hosts. Despite commonly occurring at the same wetlands, T. torosa supported higher parasite richness and average infection load than T. granulosa. Host body size and sex (females > males) tended to positively predict infection levels in both species. For hosts in which we quantified leucocyte profiles, total white blood cell count correlated positively with both parasite richness and total infection load. By coupling data on host toxicity and infection by a broad range of micro- and macroparasites, these results suggest that-alongside its effects on predators-tetrodotoxin may help protect newts against parasitic infections, highlighting the importance of integrative research on animal chemistry, immunological defenses and natural enemy ecology.
Collapse
Affiliation(s)
- Pieter T J Johnson
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO, USA
| | - Dana M Calhoun
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO, USA
| | - Amber N Stokes
- Department of Biology, California State University, Bakersfield, CA, USA
| | - Calvin B Susbilla
- Department of Biology, California State University, Bakersfield, CA, USA
| | - Travis McDevitt-Galles
- Department of Ecology and Evolutionary Biology, University of Colorado at Boulder, Boulder, CO, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, USA
| | - Jason T Hoverman
- Department of Forestry and Natural Resources, Purdue University, West Lafayette, IN, USA
| | - Vasyl V Tkach
- Department of Biology, University of North Dakota, Grand Forks, ND, USA
| | | |
Collapse
|
27
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [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.
Collapse
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
| |
Collapse
|
28
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
29
|
Abstract
Infectious diseases have serious impacts on human and wildlife populations, but the effects of a disease can vary, even among individuals or populations of the same host species. Identifying the reasons for this variation is key to understanding disease dynamics and mitigating infectious disease impacts, but disentangling cause and correlation during natural outbreaks is extremely challenging. This study aims to understand associations between symbiotic bacterial communities and an infectious disease, and examines multiple host populations before or after pathogen invasion to infer likely causal links. The results show that symbiotic bacteria are linked to fundamentally different outcomes of pathogen infection: host-pathogen coexistence (endemic infection) or host population extirpation (epidemic infection). Diversity and composition of skin-associated bacteria differed between populations of the frog, Rana sierrae, that coexist with or were extirpated by the fungal pathogen, Batrachochytrium dendrobatidis (Bd). Data from multiple populations sampled before or after pathogen invasion were used to infer cause and effect in the relationship between the fungal pathogen and symbiotic bacteria. Among host populations, variation in the composition of the skin microbiome was most strongly predicted by pathogen infection severity, even in analyses where the outcome of infection did not vary. This result suggests that pathogen infection shapes variation in the skin microbiome across host populations that coexist with or are driven to extirpation by the pathogen. By contrast, microbiome richness was largely unaffected by pathogen infection intensity, but was strongly predicted by geographical region of the host population, indicating the importance of environmental or host genetic factors in shaping microbiome richness. Thus, while both richness and composition of the microbiome differed between endemic and epidemic host populations, the underlying causes are most likely different: pathogen infection appears to shape microbiome composition, while microbiome richness was less sensitive to pathogen-induced disturbance. Because higher richness was correlated with host persistence in the presence of Bd, and richness appeared relatively stable to Bd infection, microbiome richness may contribute to disease resistance, although the latter remains to be directly tested.
Collapse
Affiliation(s)
- Andrea J Jani
- Department of Oceanography, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA
| | - Roland A Knapp
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA 93546, USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, CA 93106, USA
| |
Collapse
|
30
|
Adams AJ, Pessier AP, Briggs CJ. Rapid extirpation of a North American frog coincides with an increase in fungal pathogen prevalence: Historical analysis and implications for reintroduction. Ecol Evol 2017; 7:10216-10232. [PMID: 29238549 PMCID: PMC5723621 DOI: 10.1002/ece3.3468] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2017] [Revised: 08/06/2017] [Accepted: 08/19/2017] [Indexed: 01/14/2023] Open
Abstract
As extinctions continue across the globe, conservation biologists are turning to species reintroduction programs as one optimistic tool for addressing the biodiversity crisis. For repatriation to become a viable strategy, fundamental prerequisites include determining the causes of declines and assessing whether the causes persist in the environment. Invasive species-especially pathogens-are an increasingly significant factor contributing to biodiversity loss. We hypothesized that Batrachochytrium dendrobatidis (Bd), the causative agent of the deadly amphibian disease chytridiomycosis, was important in the rapid (<10 years) localized extirpation of a North American frog (Rana boylii) and that Bd remains widespread among extant amphibians in the region of extirpation. We used an interdisciplinary approach, combining interviews with herpetological experts, analysis of archived field notes and museum specimen collections, and field sampling of the extant amphibian assemblage to examine (1) historical relative abundance of R. boylii; (2) potential causes of R. boylii declines; and (3) historical and contemporary prevalence of Bd. We found that R. boylii were relatively abundant prior to their rapid extirpation, and an increase in Bd prevalence coincided with R. boylii declines during a time of rapid change in the region, wherein backcountry recreation, urban development, and the amphibian pet trade were all on the rise. In addition, extreme flooding during the winter of 1969 coincided with localized extirpations in R. boylii populations observed by interview respondents. We conclude that Bd likely played an important role in the rapid extirpation of R. boylii from southern California and that multiple natural and anthropogenic factors may have worked in concert to make this possible in a relatively short period of time. This study emphasizes the importance of recognizing historical ecological contexts in making future management and reintroduction decisions.
Collapse
Affiliation(s)
- Andrea J Adams
- Department of Ecology, Evolution and Marine Biology University of California, Santa Barbara Santa Barbara CA USA
| | - Allan P Pessier
- Department of Veterinary Microbiology and Pathology College of Veterinary Medicine Washington State University Pullman WA USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology University of California, Santa Barbara Santa Barbara CA USA
| |
Collapse
|
31
|
Hilker FM, Allen LJS, Bokil VA, Briggs CJ, Feng Z, Garrett KA, Gross LJ, Hamelin FM, Jeger MJ, Manore CA, Power AG, Redinbaugh MG, Rúa MA, Cunniffe NJ. Modeling Virus Coinfection to Inform Management of Maize Lethal Necrosis in Kenya. Phytopathology 2017; 107:1095-1108. [PMID: 28535127 DOI: 10.1094/phyto-03-17-0080-fi] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Maize lethal necrosis (MLN) has emerged as a serious threat to food security in sub-Saharan Africa. MLN is caused by coinfection with two viruses, Maize chlorotic mottle virus and a potyvirus, often Sugarcane mosaic virus. To better understand the dynamics of MLN and to provide insight into disease management, we modeled the spread of the viruses causing MLN within and between growing seasons. The model allows for transmission via vectors, soil, and seed, as well as exogenous sources of infection. Following model parameterization, we predict how management affects disease prevalence and crop performance over multiple seasons. Resource-rich farmers with large holdings can achieve good control by combining clean seed and insect control. However, crop rotation is often required to effect full control. Resource-poor farmers with smaller holdings must rely on rotation and roguing, and achieve more limited control. For both types of farmer, unless management is synchronized over large areas, exogenous sources of infection can thwart control. As well as providing practical guidance, our modeling framework is potentially informative for other cropping systems in which coinfection has devastating effects. Our work also emphasizes how mathematical modeling can inform management of an emerging disease even when epidemiological information remains scanty. [Formula: see text] Copyright © 2017 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .
Collapse
Affiliation(s)
- Frank M Hilker
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Linda J S Allen
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Vrushali A Bokil
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Cheryl J Briggs
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Zhilan Feng
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Karen A Garrett
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Louis J Gross
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Frédéric M Hamelin
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Michael J Jeger
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Carrie A Manore
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Alison G Power
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Margaret G Redinbaugh
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Megan A Rúa
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| | - Nik J Cunniffe
- First author: Institute of Environmental Systems Research, School of Mathematics/Computer Science, Osnabrück University, 49069 Osnabrück, Germany; second author: Department of Mathematics and Statistics, Texas Tech University, Lubbock 79409; third author: Department of Mathematics, Oregon State University, Corvallis 97331; fourth author: Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara 93106; fifth author: Department of Mathematics, Purdue University, West Lafayette, IN 47907; sixth author: Plant Pathology Department, Institute for Sustainable Food Systems, and Emerging Pathogens Institute, University of Florida, Gainesville 32611; seventh author: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville 37996; eighth author: IGEPP, Agrocampus Ouest, INRA, Université de Rennes 1, Université Bretagne-Loire, 35000 Rennes, France; ninth author: Centre for Environmental Policy, Imperial College London, Ascot SL5 7PY, United Kingdom; tenth author: Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM 87544; eleventh author: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853; twelfth author: United States Department of Agriculture-Agricultural Research Service Corn, Soybean and Wheat Quality Research Unit and Department of Plant Pathology, Ohio State University, Wooster 44691; thirteenth author: Department of Biological Sciences, Wright State University, Dayton, OH 45435; and fourteenth author: Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom
| |
Collapse
|
32
|
Wilber MQ, Knapp RA, Toothman M, Briggs CJ. Resistance, tolerance and environmental transmission dynamics determine host extinction risk in a load-dependent amphibian disease. Ecol Lett 2017; 20:1169-1181. [PMID: 28745026 DOI: 10.1111/ele.12814] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Revised: 05/12/2017] [Accepted: 06/21/2017] [Indexed: 01/05/2023]
Abstract
While disease-induced extinction is generally considered rare, a number of recently emerging infectious diseases with load-dependent pathology have led to extinction in wildlife populations. Transmission is a critical factor affecting disease-induced extinction, but the relative importance of transmission compared to load-dependent host resistance and tolerance is currently unknown. Using a combination of models and experiments on an amphibian species suffering extirpations from the fungal pathogen Batrachochytrium dendrobatidis (Bd), we show that while transmission from an environmental Bd reservoir increased the ability of Bd to invade an amphibian population and the extinction risk of that population, Bd-induced extinction dynamics were far more sensitive to host resistance and tolerance than to Bd transmission. We demonstrate that this is a general result for load-dependent pathogens, where non-linear resistance and tolerance functions can interact such that small changes in these functions lead to drastic changes in extinction dynamics.
Collapse
Affiliation(s)
- Mark Q Wilber
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106, USA
| | - Roland A Knapp
- Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, CA, 93546, USA
| | - Mary Toothman
- Department of Ecology, Evolution and Marine Biology, 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
| |
Collapse
|
33
|
Adams AJ, Kupferberg SJ, Wilber MQ, Pessier AP, Grefsrud M, Bobzien S, Vredenburg VT, Briggs CJ. Extreme drought, host density, sex, and bullfrogs influence fungal pathogen infection in a declining lotic amphibian. Ecosphere 2017. [DOI: 10.1002/ecs2.1740] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Andrea J. Adams
- Department of Ecology, Evolution, and Marine Biology; University of California; Santa Barbara California 93106 USA
| | - Sarah J. Kupferberg
- Department of Integrative Biology; University of California; Berkeley California 94720 USA
| | - Mark Q. Wilber
- Department of Ecology, Evolution, and Marine Biology; University of California; Santa Barbara California 93106 USA
| | - Allan P. Pessier
- Department of Veterinary Microbiology and Pathology; College of Veterinary Medicine; Washington State University; Pullman Washington 99164 USA
| | - Marcia Grefsrud
- California Department of Fish and Wildlife; Bay Delta Region Napa California 94558 USA
| | - Steve Bobzien
- East Bay Regional Park District; Oakland California 94605 USA
| | | | - Cheryl J. Briggs
- Department of Ecology, Evolution, and Marine Biology; University of California; Santa Barbara California 93106 USA
| |
Collapse
|
34
|
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] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 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.
Collapse
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
| |
Collapse
|
35
|
MacDonald AJ, Hyon DW, Brewington JB, O'Connor KE, Swei A, Briggs CJ. Lyme disease risk in southern California: abiotic and environmental drivers of Ixodes pacificus (Acari: Ixodidae) density and infection prevalence with Borrelia burgdorferi. Parasit Vectors 2017; 10:7. [PMID: 28057067 PMCID: PMC5217405 DOI: 10.1186/s13071-016-1938-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 12/14/2016] [Indexed: 01/25/2023] Open
Abstract
Background Tick-borne diseases, particularly Lyme disease, are emerging across the northern hemisphere. In order to manage emerging diseases and predict where emergence will likely occur, it is necessary to understand the factors influencing the distribution, abundance and infection prevalence of vector species. In North America, Lyme disease is the most common vector-borne disease and is transmitted by blacklegged ticks. This study aimed to explore the abiotic and environmental drivers of density and infection prevalence of western blacklegged ticks (Ixodes pacificus) in southern California, an understudied and densely populated region of North America. Results Over the course of this two-year study, densities of I. pacificus adults were consistently positively associated with host availability for juvenile ticks and dense oak woodland habitat. Densities of nymphal and larval I. pacificus, on the other hand were primarily predicted by host availability for juvenile ticks in the first year of the study, and by habitat characteristics such as dense leaf litter in the second year. Infection with the causative agent of Lyme disease, Borrelia burgdorferi (sensu stricto), and related spirochetes was not predicted by the abiotic conditions promoting I. pacificus populations, but rather by diversity of the tick community, and in particular by the presence of two Ixodes tick species that do not generally feed on humans (Ixodes spinipalpis and Ixodes peromysci). Borrelia spp. infection was not detected in the I. pacificus populations sampled, but was detected in other vector species that may maintain enzootic transmission of the pathogen on the landscape. Conclusions This study identified dense oak woodlands as high-risk habitats for I. pacificus tick encounter in southern California. The shift in relative importance of host availability to habitat characteristics in predicting juvenile tick abundance occurred as California’s historic drought intensified, suggesting that habitat providing suitable microclimates for tick survivorship became centrally important to patterns of abundance in the face of deleterious abiotic conditions. These results underscore the need for further investigation of the effects of climate change on tick-borne disease in California. Finally, despite low risk of human Lyme disease infection posed by I. pacificus in southern California, evidence of infection was found in other tick species, suggesting that enzootic transmission of tick-borne borreliae may be occurring in southern California, and involve parallel enzootic cycles with other tick and host species but not necessarily humans.
Collapse
Affiliation(s)
- Andrew J MacDonald
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106-9620, USA. .,Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA, 94305, USA.
| | - David W Hyon
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106-9620, USA
| | - John B Brewington
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106-9620, USA
| | - Kerry E O'Connor
- Department of Biology, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA, 94132, USA
| | - Andrea Swei
- Department of Biology, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA, 94132, USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, CA, 93106-9620, USA
| |
Collapse
|
36
|
Smith TC, Knapp RA, Briggs CJ. Declines and extinctions of mountain yellow‐legged frogs have small effects on benthic macroinvertebrate communities. Ecosphere 2016. [DOI: 10.1002/ecs2.1327] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Thomas C. Smith
- Department of Ecology, Evolution, and Marine BiologyUniversity of California Santa Barbara California 93106 USA
| | - Roland A. Knapp
- Sierra Nevada Aquatic Research LaboratoryUniversity of California 1016 Mount Morrison Road Mammoth Lakes California 93546 USA
| | - Cheryl J. Briggs
- Department of Ecology, Evolution, and Marine BiologyUniversity of California Santa Barbara California 93106 USA
| |
Collapse
|
37
|
Wilber MQ, Langwig KE, Kilpatrick AM, McCallum HI, Briggs CJ. Integral Projection Models for host-parasite systems with an application to amphibian chytrid fungus. Methods Ecol Evol 2016; 7:1182-1194. [PMID: 28239442 DOI: 10.1111/2041-210x.12561] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Host parasite models are typically constructed under either a microparasite or macroparasite paradigm. However, this has long been recognized as a false dichotomy because many infectious disease agents, including most fungal pathogens, have attributes of both microparasites and macroparasites.We illustrate how Integral Projection Models (IPM)s provide a novel, elegant modeling framework to represent both types of pathogens. We build a simple host-parasite IPM that tracks both the number of susceptible and infected hosts and the distribution of parasite burdens in infected hosts.The vital rate functions necessary to build IPMs for disease dynamics share many commonalities with classic micro and macroparasite models and we discuss how these functions can be parameterized to build a host-parasite IPM. We illustrate the utility of this IPM approach by modeling the temperature-dependent epizootic dynamics of amphibian chytrid fungus in Mountain yellow-legged frogs (Rana muscosa).The host-parasite IPM can be applied to other diseases such as facial tumor disease in Tasmanian devils and white-nose syndrome in bats. Moreover, the host-parasite IPM can be easily extended to capture more complex disease dynamics and provides an exciting new frontier in modeling wildlife disease.
Collapse
Affiliation(s)
- Mark Q Wilber
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, 93117
| | - Kate E Langwig
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, 95064
| | - A Marm Kilpatrick
- Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, CA, 95064
| | - Hamish I McCallum
- Griffith School of Environment, Griffith University, Nathan QLD 4111, Australia
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, 93117
| |
Collapse
|
38
|
Wilber MQ, Weinstein SB, Briggs CJ. Detecting and quantifying parasite-induced host mortality from intensity data: method comparisons and limitations. Int J Parasitol 2015; 46:59-66. [PMID: 26475963 DOI: 10.1016/j.ijpara.2015.08.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 08/15/2015] [Accepted: 08/24/2015] [Indexed: 10/22/2022]
Abstract
Parasites can significantly impact animal populations by changing host behaviour, reproduction and survival. Detecting and quantifying these impacts is critical for understanding disease dynamics and managing wild animal populations. However, for wild hosts infected with macroparasites, it is notoriously difficult to quantify the fatal parasite load and number of animals that have died due to disease. When ethical or logistical constraints prohibit experimental determination of these values, examination of parasite intensity and distribution data may offer an alternative solution. In this study we introduce a novel method for using intensity data to detect and quantify parasite-induced mortality in wildlife populations. We use simulations to show that this method is more reliable than previously proposed methods while providing quantitative estimates of parasite-induced mortality from empirical data that are consistent with previously published qualitative estimates. However this method, and all techniques that estimate parasite-induced mortality from intensity data alone, have several important assumptions that must be scrutinised before applying those to real-world data. Given that these assumptions are met, our method is a new exploratory tool that can help inform more rigorous studies of parasite-induced host mortality.
Collapse
Affiliation(s)
- Mark Q Wilber
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States.
| | - Sara B Weinstein
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, CA, United States
| |
Collapse
|
39
|
Abstract
Food-web dynamics arise from predator-prey, parasite-host, and herbivore-plant interactions. Models for such interactions include up to three consumer activity states (questing, attacking, consuming) and up to four resource response states (susceptible, exposed, ingested, resistant). Articulating these states into a general model allows for dissecting, comparing, and deriving consumer-resource models. We specify this general model for 11 generic consumer strategies that group mathematically into predators, parasites, and micropredators and then derive conditions for consumer success, including a universal saturating functional response. We further show how to use this framework to create simple models with a common mathematical lineage and transparent assumptions. Underlying assumptions, missing elements, and composite parameters are revealed when classic consumer-resource models are derived from the general model.
Collapse
Affiliation(s)
- Kevin D Lafferty
- Western Ecological Research Center, U.S. Geological Survey, Marine Science Institute, University of California-Santa Barbara, Santa Barbara, CA, USA.
| | - Giulio DeLeo
- Hopkins Marine Station Woods Institute for the Environment, Stanford University, Stanford, CA, USA
| | - Cheryl J Briggs
- Ecology, Evolution and Marine Biology, University of California-Santa Barbara, Santa Barbara, CA, USA
| | - Andrew P Dobson
- Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA. Santa Fe Institute, Hyde Park Road, Santa Fe, NM, USA
| | - Thilo Gross
- Department of Engineering Mathematics, University of Bristol, Bristol, UK
| | - Armand M Kuris
- Ecology, Evolution and Marine Biology, University of California-Santa Barbara, Santa Barbara, CA, USA
| |
Collapse
|
40
|
Voyles J, Kilpatrick AM, Collins JP, Fisher MC, Frick WF, McCallum H, Willis CKR, Blehert DS, Murray KA, Puschendorf R, Rosenblum EB, Bolker BM, Cheng TL, Langwig KE, Lindner DL, Toothman M, Wilber MQ, Briggs CJ. Moving Beyond Too Little, Too Late: Managing Emerging Infectious Diseases in Wild Populations Requires International Policy and Partnerships. Ecohealth 2015; 12:404-7. [PMID: 25287279 PMCID: PMC7088098 DOI: 10.1007/s10393-014-0980-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 08/28/2014] [Accepted: 09/02/2014] [Indexed: 05/26/2023]
Affiliation(s)
- Jamie Voyles
- Department of Biology, New Mexico Tech, Socorro, New Mexico, USA.
| | - A Marm Kilpatrick
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, California, USA
| | - James P Collins
- School of Life Sciences, Arizona State University, Tempe, Arizona, USA
| | - Matthew C Fisher
- Department of Infectious Disease Epidemiology, Imperial College of London, London, UK
| | - Winifred F Frick
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, California, USA
| | - Hamish McCallum
- School of Environment, Griffith University, Nathan, Queensland, Australia
| | - Craig K R Willis
- Department of Biology, University of Winnipeg, Winnipeg, Manitoba, Canada
| | - David S Blehert
- United States Geological Survey, National Wildlife Health Center, Madison, Wisconsin, USA
| | | | | | - Erica Bree Rosenblum
- Department of Environmental Science, Policy and Management, University of California, Berkeley, Berkeley, California, USA
| | - Benjamin M Bolker
- Departments of Mathematics & Statistics and Biology, McMaster University, Hamilton, Ontario, Canada
| | - Tina L Cheng
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, California, USA
| | - Kate E Langwig
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Santa Cruz, California, USA
| | - Daniel L Lindner
- United States Forest Service, Center for Mycology Research, Madison, Wisconsin, USA
| | - Mary Toothman
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Mark Q Wilber
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology, University of California, Santa Barbara, Santa Barbara, California, USA
| |
Collapse
|
41
|
Adams AJ, LaBonte JP, Ball ML, Richards-Hrdlicka KL, Toothman MH, Briggs CJ. DNA Extraction Method Affects the Detection of a Fungal Pathogen in Formalin-Fixed Specimens Using qPCR. PLoS One 2015; 10:e0135389. [PMID: 26291624 PMCID: PMC4546330 DOI: 10.1371/journal.pone.0135389] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 07/21/2015] [Indexed: 12/02/2022] Open
Abstract
Museum collections provide indispensable repositories for obtaining information about the historical presence of disease in wildlife populations. The pathogenic amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) has played a significant role in global amphibian declines, and examining preserved specimens for Bd can improve our understanding of its emergence and spread. Quantitative PCR (qPCR) enables Bd detection with minimal disturbance to amphibian skin and is significantly more sensitive to detecting Bd than histology; therefore, developing effective qPCR methodologies for detecting Bd DNA in formalin-fixed specimens can provide an efficient and effective approach to examining historical Bd emergence and prevalence. Techniques for detecting Bd in museum specimens have not been evaluated for their effectiveness in control specimens that mimic the conditions of animals most likely to be encountered in museums, including those with low pathogen loads. We used American bullfrogs (Lithobates catesbeianus) of known infection status to evaluate the success of qPCR to detect Bd in formalin-fixed specimens after three years of ethanol storage. Our objectives were to compare the most commonly used DNA extraction method for Bd (PrepMan, PM) to Macherey-Nagel DNA FFPE (MN), test optimizations for Bd detection with PM, and provide recommendations for maximizing Bd detection. We found that successful detection is relatively high (80-90%) when Bd loads before formalin fixation are high, regardless of the extraction method used; however, at lower infection levels, detection probabilities were significantly reduced. The MN DNA extraction method increased Bd detection by as much as 50% at moderate infection levels. Our results indicate that, for animals characterized by lower pathogen loads (i.e., those most commonly encountered in museum collections), current methods may underestimate the proportion of Bd-infected amphibians. Those extracting DNA from archived museum specimens should ensure that the techniques they are using are known to provide high-quality throughput DNA for later analysis.
Collapse
Affiliation(s)
- Andrea J. Adams
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, United States of America
| | - John P. LaBonte
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, United States of America
| | - Morgan L. Ball
- Wildlands Conservation Science, Lompoc, California, United States of America
| | | | - Mary H. Toothman
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, United States of America
| | - Cheryl J. Briggs
- Department of Ecology, Evolution, and Marine Biology, University of California, Santa Barbara, California, United States of America
| |
Collapse
|
42
|
Voyles J, Johnson LR, Briggs CJ, Cashins SD, Alford RA, Berger L, Skerratt LF, Speare R, Rosenblum EB. Experimental evolution alters the rate and temporal pattern of population growth in Batrachochytrium dendrobatidis, a lethal fungal pathogen of amphibians. Ecol Evol 2014; 4:3633-41. [PMID: 25478154 PMCID: PMC4224537 DOI: 10.1002/ece3.1199] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Revised: 07/21/2014] [Accepted: 07/25/2014] [Indexed: 11/13/2022] Open
Abstract
Virulence of infectious pathogens can be unstable and evolve rapidly depending on the evolutionary dynamics of the organism. Experimental evolution can be used to characterize pathogen evolution, often with the underlying objective of understanding evolution of virulence. We used experimental evolution techniques (serial transfer experiments) to investigate differential growth and virulence of Batrachochytrium dendrobatidis (Bd), a fungal pathogen that causes amphibian chytridiomycosis. We tested two lineages of Bd that were derived from a single cryo-archived isolate; one lineage (P10) was passaged 10 times, whereas the second lineage (P50) was passaged 50 times. We quantified time to zoospore release, maximum zoospore densities, and timing of zoospore activity and then modeled population growth rates. We also conducted exposure experiments with a susceptible amphibian species, the common green tree frog (Litoria caerulea) to test the differential pathogenicity. We found that the P50 lineage had shorter time to zoospore production (Tmin), faster rate of sporangia death (ds), and an overall greater intrinsic population growth rate (λ). These patterns of population growth in vitro corresponded with higher prevalence and intensities of infection in exposed Litoria caerulea, although the differences were not significant. Our results corroborate studies that suggest that Bd may be able to evolve relatively rapidly. Our findings also challenge the general assumption that pathogens will always attenuate in culture because shifts in Bd virulence may depend on laboratory culturing practices. These findings have practical implications for the laboratory maintenance of Bd isolates and underscore the importance of understanding the evolution of virulence in amphibian chytridiomycosis.
Collapse
Affiliation(s)
- Jamie Voyles
- Department of Biology, New Mexico Tech Socorro, New Mexico, 87801
| | - Leah R Johnson
- Department of Integrative Biology, University of South Florida Tampa, Florida, 33620 ; Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, California, 93106
| | - Cheryl J Briggs
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, California, 93106
| | - Scott D Cashins
- School of Public Health, Tropical Medicine and Rehabilitation Sciences, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia
| | - Ross A Alford
- School of Marine and Tropical Biology, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia
| | - Lee Berger
- School of Public Health, Tropical Medicine and Rehabilitation Sciences, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia
| | - Lee F Skerratt
- School of Public Health, Tropical Medicine and Rehabilitation Sciences, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia
| | - Rick Speare
- School of Public Health, Tropical Medicine and Rehabilitation Sciences, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy and Management, University of California- Berkeley Berkeley, California, 94720-3144
| |
Collapse
|
43
|
Voyles J, Johnson LR, Briggs CJ, Cashins SD, Alford RA, Berger L, Skerratt LF, Speare R, Rosenblum EB. Temperature alters reproductive life history patterns in Batrachochytrium dendrobatidis, a lethal pathogen associated with the global loss of amphibians. Ecol Evol 2012; 2:2241-9. [PMID: 23139882 PMCID: PMC3488674 DOI: 10.1002/ece3.334] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2012] [Revised: 06/20/2012] [Accepted: 06/22/2012] [Indexed: 11/11/2022] Open
Abstract
Understanding how pathogens respond to changing environmental conditions is a central challenge in disease ecology. The environmentally sensitive fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the amphibian disease chytridiomycosis, has spread globally causing amphibian extirpations in a wide variety of climatic regions. To gain an in-depth understanding of Bd's responses to temperature, we used an integrative approach, combining empirical laboratory experiments with mathematical modeling. First, we selected a single Bd isolate and serially propagated two lineages of the isolate for multiple generations in two stable thermal conditions: 4°C (cold-adapted lineage) and 23°C (warm-adapted lineage). We quantified the production of infectious zoospores (fecundity), the timing of zoospore release, and zoospore activity in reciprocal temperature transplant experiments in which both Bd lineages were grown in either high or low temperature conditions. We then developed population growth models for the Bd lineages under each set of temperature conditions. We found that Bd had lower population growth rates, but longer periods of zoospore activity in the low temperature treatment (4°C) compared to the high temperature treatment (23°C). This effect was more pronounced in Bd lineages that were propagated in the low temperature treatment (4°C), suggesting a shift in Bd's response to low temperature conditions. Our results provide novel insights into the mechanisms by which Bd can thrive in a wide variety of temperature conditions, potentially altering the dynamics of chytridiomycosis and thus, the propensity for Bd to cause amphibian population collapse. We also suggest that the adaptive responses of Bd to thermal conditions warrant further investigation, especially in the face of global climate change.
Collapse
Affiliation(s)
- Jamie Voyles
- Department of Environmental Science, Policy and Management, University of California- Berkeley Berkeley, California, 94720-3144, USA ; School of Public Health, Tropical Medicine and Rehabilitation Sciences, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Swei A, Briggs CJ, Lane RS, Ostfeld RS. Impacts of an introduced forest pathogen on the risk of Lyme disease in California. Vector Borne Zoonotic Dis 2012; 12:623-32. [PMID: 22607076 DOI: 10.1089/vbz.2011.0783] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Global changes such as deforestation, climate change, and invasive species have the potential to greatly alter zoonotic disease systems through impacts on biodiversity. This study examined the impact of the invasive pathogen that causes sudden oak death (SOD) on the ecology of Lyme disease in California. The Lyme disease bacterium, Borrelia burgdorferi, is maintained in the far western United States by a suite of animal reservoirs including the dusky-footed woodrat (Neotoma fuscipes) and deer mouse (Peromyscus maniculatus), and is transmitted by the western black-legged tick (Ixodes pacificus). Other vertebrates, such as the western fence lizard (Sceloporus occidentalis), are important tick hosts but are not reservoirs of the pathogen. Previous work found that higher levels of SOD are correlated with greater abundance of P. maniculatus and S. occidentalis and lower N. fuscipes abundance. Here we model the contribution of these tick hosts to Lyme disease risk and also evaluate the potential impact of SOD on infection prevalence of the tick vector. By empirically parameterizing a static model with field and laboratory data on tick hosts, we predict that SOD reduces an important index of disease risk, nymphal infection prevalence, leading to a reduction in Lyme disease risk in certain coastal woodlands. Direct observational analysis of the impact of SOD on nymphal infection prevalence supports these model results. This study underscores the important direct and indirect impacts of invasive plant pathogens on biodiversity, the transmission cycles of zoonotic diseases, and ultimately human health.
Collapse
Affiliation(s)
- Andrea Swei
- Department of Laboratory Medicine, University of California-San Francisco, San Francisco, California, USA.
| | | | | | | |
Collapse
|
45
|
Voyles J, Vredenburg VT, Tunstall TS, Parker JM, Briggs CJ, Rosenblum EB. Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak. PLoS One 2012; 7:e35374. [PMID: 22558145 PMCID: PMC3338830 DOI: 10.1371/journal.pone.0035374] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 03/15/2012] [Indexed: 11/18/2022] Open
Abstract
The disease chytridiomycosis is responsible for declines and extirpations of amphibians worldwide. Chytridiomycosis is caused by a fungal pathogen (Batrachochytrium dendrobatidis) that infects amphibian skin. Although we have a basic understanding of the pathophysiology from laboratory experiments, many mechanistic details remain unresolved and it is unknown if disease development is similar in wild amphibian populations. To gain a better understanding of chytridiomycosis pathophysiology in wild amphibian populations, we collected blood biochemistry measurements during an outbreak in mountain yellow-legged frogs (Rana muscosa) in the Sierra Nevada Mountains of California. We found that pathogen load is associated with disruptions in fluid and electrolyte balance, yet is not associated with fluctuations acid-base balance. These findings enhance our knowledge of the pathophysiology of this disease and indicate that disease development is consistent across multiple species and in both laboratory and natural conditions. We recommend integrating an understanding of chytridiomycosis pathophysiology with mitigation practices to improve amphibian conservation.
Collapse
Affiliation(s)
- Jamie Voyles
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California United States of America
| | - Vance T. Vredenburg
- Department of Biology, San Francisco State University, San Francisco, California United States of America
| | - Tate S. Tunstall
- Department of Integrative Biology, University of California, Berkeley, California United States of America
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California United States of America
| | - John M. Parker
- Animal Care Facility, University of California San Francisco, San Francisco, California, California United States of America
| | - Cheryl J. Briggs
- Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California United States of America
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy and Management, University of California, Berkeley, California United States of America
| |
Collapse
|
46
|
Fisher MC, Henk DA, Briggs CJ, Brownstein JS, Madoff LC, McCraw SL, Gurr SJ. Emerging fungal threats to animal, plant and ecosystem health. Nature 2012; 484:186-94. [PMID: 22498624 PMCID: PMC3821985 DOI: 10.1038/nature10947] [Citation(s) in RCA: 1719] [Impact Index Per Article: 143.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 01/25/2012] [Indexed: 01/15/2023]
Abstract
The past two decades have seen an increasing number of virulent infectious diseases in natural populations and managed landscapes. In both animals and plants, an unprecedented number of fungal and fungal-like diseases have recently caused some of the most severe die-offs and extinctions ever witnessed in wild species, and are jeopardizing food security. Human activity is intensifying fungal disease dispersal by modifying natural environments and thus creating new opportunities for evolution. We argue that nascent fungal infections will cause increasing attrition of biodiversity, with wider implications for human and ecosystem health, unless steps are taken to tighten biosecurity worldwide.
Collapse
Affiliation(s)
- Matthew C Fisher
- Department of Infectious Disease Epidemiology, Imperial College, London W2 1PG, UK.
| | | | | | | | | | | | | |
Collapse
|
47
|
Woodhams DC, Geiger CC, Reinert LK, Rollins-Smith LA, Lam B, Harris RN, Briggs CJ, Vredenburg VT, Voyles J. Treatment of amphibians infected with chytrid fungus: learning from failed trials with itraconazole, antimicrobial peptides, bacteria, and heat therapy. Dis Aquat Organ 2012; 98:11-25. [PMID: 22422126 DOI: 10.3354/dao02429] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Amphibian conservation goals depend on effective disease-treatment protocols. Desirable protocols are species, life stage, and context specific, but currently few treatment options exist for amphibians infected with the chytrid fungus Batrachochytrium dendrobatidis (Bd). Treatment options, at present, include antifungal drugs and heat therapy, but risks of toxicity and side-effects make these options untenable in some cases. Here, we report on the comparison of several novel treatments with a more generally accepted antifungal treatment in experimental scientific trials to treat Bd-infected frogs including Alytes obstetricans tadpoles and metamorphs, Bufo bufo and Limnodynastes peronii metamorphs, and Lithobates pipiens and Rana muscosa adults. The experimental treatments included commercial antifungal products (itraconazole, mandipropamid, steriplantN, and PIP Pond Plus), antimicrobial skin peptides from the Bd-resistant Pelophylax esculentus, microbial treatments (Pedobacter cryoconitis), and heat therapy (35°C for 24 h). None of the new experimental treatments were considered successful in terms of improving survival; however, these results may advance future research by indicating the limits and potential of the various protocols. Caution in the use of itraconazole is warranted because of observed toxicity in metamorphic and adult frogs, even at low concentrations. Results suggest that rather than focusing on a single cure-all, diverse lines of research may provide multiple options for treating Bd infection in amphibians. Learning from 'failed treatments' is essential for the timely achievement of conservation goals and one of the primary aims for a publicly accessible treatment database under development.
Collapse
Affiliation(s)
- Douglas C Woodhams
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland.
| | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Swei A, Rowley JJL, Rödder D, Diesmos MLL, Diesmos AC, Briggs CJ, Brown R, Cao TT, Cheng TL, Chong RA, Han B, Hero JM, Hoang HD, Kusrini MD, Le DTT, McGuire JA, Meegaskumbura M, Min MS, Mulcahy DG, Neang T, Phimmachak S, Rao DQ, Reeder NM, Schoville SD, Sivongxay N, Srei N, Stöck M, Stuart BL, Torres LS, Tran DTA, Tunstall TS, Vieites D, Vredenburg VT. Is chytridiomycosis an emerging infectious disease in Asia? PLoS One 2011; 6:e23179. [PMID: 21887238 PMCID: PMC3156717 DOI: 10.1371/journal.pone.0023179] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 07/07/2011] [Indexed: 12/02/2022] Open
Abstract
The disease chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis (Bd), has caused dramatic amphibian population declines and extinctions in Australia, Central and North America, and Europe. Bd is associated with >200 species extinctions of amphibians, but not all species that become infected are susceptible to the disease. Specifically, Bd has rapidly emerged in some areas of the world, such as in Australia, USA, and throughout Central and South America, causing population and species collapse. The mechanism behind the rapid global emergence of the disease is poorly understood, in part due to an incomplete picture of the global distribution of Bd. At present, there is a considerable amount of geographic bias in survey effort for Bd, with Asia being the most neglected continent. To date, Bd surveys have been published for few Asian countries, and infected amphibians have been reported only from Indonesia, South Korea, China and Japan. Thus far, there have been no substantiated reports of enigmatic or suspected disease-caused population declines of the kind that has been attributed to Bd in other areas. In order to gain a more detailed picture of the distribution of Bd in Asia, we undertook a widespread, opportunistic survey of over 3,000 amphibians for Bd throughout Asia and adjoining Papua New Guinea. Survey sites spanned 15 countries, approximately 36° latitude, 111° longitude, and over 2000 m in elevation. Bd prevalence was very low throughout our survey area (2.35% overall) and infected animals were not clumped as would be expected in epizootic events. This suggests that Bd is either newly emerging in Asia, endemic at low prevalence, or that some other ecological factor is preventing Bd from fully invading Asian amphibians. The current observed pattern in Asia differs from that in many other parts of the world.
Collapse
Affiliation(s)
- Andrea Swei
- Cary Institute of Ecosystem Studies, Millbrook, New York, United States of America.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Knapp RA, Briggs CJ, Smith TC, Maurer JR. Nowhere to hide: impact of a temperature-sensitive amphibian pathogen along an elevation gradient in the temperate zone. Ecosphere 2011. [DOI: 10.1890/es11-00028.1] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
50
|
Woodhams DC, Bosch J, Briggs CJ, Cashins S, Davis LR, Lauer A, Muths E, Puschendorf R, Schmidt BR, Sheafor B, Voyles J. Mitigating amphibian disease: strategies to maintain wild populations and control chytridiomycosis. Front Zool 2011; 8:8. [PMID: 21496358 PMCID: PMC3098159 DOI: 10.1186/1742-9994-8-8] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 04/18/2011] [Indexed: 12/29/2022] Open
Abstract
Background Rescuing amphibian diversity is an achievable conservation challenge. Disease mitigation is one essential component of population management. Here we assess existing disease mitigation strategies, some in early experimental stages, which focus on the globally emerging chytrid fungus Batrachochytrium dendrobatidis. We discuss the precedent for each strategy in systems ranging from agriculture to human medicine, and the outlook for each strategy in terms of research needs and long-term potential. Results We find that the effects of exposure to Batrachochytrium dendrobatidis occur on a spectrum from transient commensal to lethal pathogen. Management priorities are divided between (1) halting pathogen spread and developing survival assurance colonies, and (2) prophylactic or remedial disease treatment. Epidemiological models of chytridiomycosis suggest that mitigation strategies can control disease without eliminating the pathogen. Ecological ethics guide wildlife disease research, but several ethical questions remain for managing disease in the field. Conclusions Because sustainable conservation of amphibians in nature is dependent on long-term population persistence and co-evolution with potentially lethal pathogens, we suggest that disease mitigation not focus exclusively on the elimination or containment of the pathogen, or on the captive breeding of amphibian hosts. Rather, successful disease mitigation must be context specific with epidemiologically informed strategies to manage already infected populations by decreasing pathogenicity and host susceptibility. We propose population level treatments based on three steps: first, identify mechanisms of disease suppression; second, parameterize epizootiological models of disease and population dynamics for testing under semi-natural conditions; and third, begin a process of adaptive management in field trials with natural populations.
Collapse
Affiliation(s)
- Douglas C Woodhams
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|