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Gray MJ, Carter ED, Piovia-Scott J, Cusaac JPW, Peterson AC, Whetstone RD, Hertz A, Muniz-Torres AY, Bletz MC, Woodhams DC, Romansic JM, Sutton WB, Sheley W, Pessier A, McCusker CD, Wilber MQ, Miller DL. Broad host susceptibility of North American amphibian species to Batrachochytrium salamandrivorans suggests high invasion potential and biodiversity risk. Nat Commun 2023; 14:3270. [PMID: 37277333 DOI: 10.1038/s41467-023-38979-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 05/22/2023] [Indexed: 06/07/2023] Open
Abstract
Batrachochytrium salamandrivorans (Bsal) is a fungal pathogen of amphibians that is emerging in Europe and could be introduced to North America through international trade or other pathways. To evaluate the risk of Bsal invasion to amphibian biodiversity, we performed dose-response experiments on 35 North American species from 10 families, including larvae from five species. We discovered that Bsal caused infection in 74% and mortality in 35% of species tested. Both salamanders and frogs became infected and developed Bsal chytridiomycosis. Based on our host susceptibility results, environmental suitability conditions for Bsal, and geographic ranges of salamanders in the United States, predicted biodiversity loss is expected to be greatest in the Appalachian Region and along the West Coast. Indices of infection and disease susceptibility suggest that North American amphibian species span a spectrum of vulnerability to Bsal chytridiomycosis and most amphibian communities will include an assemblage of resistant, carrier, and amplification species. Predicted salamander losses could exceed 80 species in the United States and 140 species in North America.
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Affiliation(s)
- Matthew J Gray
- Center for Wildlife Health, School of Natural Resources, University of Tennessee, Knoxville, TN, USA.
| | - Edward Davis Carter
- Center for Wildlife Health, School of Natural Resources, University of Tennessee, Knoxville, TN, USA
| | - Jonah Piovia-Scott
- School of Biological Sciences, Washington State University, Vancouver, WA, USA
| | - J Patrick W Cusaac
- Center for Wildlife Health, School of Natural Resources, University of Tennessee, Knoxville, TN, USA
| | - Anna C Peterson
- Center for Wildlife Health, School of Natural Resources, University of Tennessee, Knoxville, TN, USA
| | - Ross D Whetstone
- Biology Department, University of Massachusetts Boston, Boston, MA, USA
| | - Andreas Hertz
- Biology Department, University of Massachusetts Boston, Boston, MA, USA
| | | | - Molly C Bletz
- Biology Department, University of Massachusetts Boston, Boston, MA, USA
| | - Douglas C Woodhams
- Biology Department, University of Massachusetts Boston, Boston, MA, USA
- Smithsonian Tropical Research Institute, Ancón, Panama
| | - John M Romansic
- School of Biological Sciences, Washington State University, Vancouver, WA, USA
| | - William B Sutton
- Department of Agricultural and Environmental Sciences, Tennessee State University, Nashville, TN, USA
| | - Wesley Sheley
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Knoxville, TN, USA
| | - Allan Pessier
- Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, USA
| | | | - Mark Q Wilber
- Center for Wildlife Health, School of Natural Resources, University of Tennessee, Knoxville, TN, USA
| | - Debra L Miller
- Center for Wildlife Health, School of Natural Resources, University of Tennessee, Knoxville, TN, USA
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Knoxville, TN, USA
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Grimaudo AT, Hoyt JR, Yamada SA, Herzog CJ, Bennett AB, Langwig KE. Host traits and environment interact to determine persistence of bat populations impacted by white-nose syndrome. Ecol Lett 2022; 25:483-497. [PMID: 34935272 PMCID: PMC9299823 DOI: 10.1111/ele.13942] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 08/26/2021] [Accepted: 11/17/2021] [Indexed: 11/27/2022]
Abstract
Emerging infectious diseases have resulted in severe population declines across diverse taxa. In some instances, despite attributes associated with high extinction risk, disease emergence and host declines are followed by host stabilisation for unknown reasons. While host, pathogen, and the environment are recognised as important factors that interact to determine host-pathogen coexistence, they are often considered independently. Here, we use a translocation experiment to disentangle the role of host traits and environmental conditions in driving the persistence of remnant bat populations a decade after they declined 70-99% due to white-nose syndrome and subsequently stabilised. While survival was significantly higher than during the initial epidemic within all sites, protection from severe disease only existed within a narrow environmental space, suggesting host traits conducive to surviving disease are highly environmentally dependent. Ultimately, population persistence following pathogen invasion is the product of host-pathogen interactions that vary across a patchwork of environments.
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Affiliation(s)
| | - Joseph R. Hoyt
- Department of Biological SciencesVirginia TechBlacksburgVirginiaUSA
| | | | - Carl J. Herzog
- New York State Department of Environmental ConservationAlbanyNew YorkUSA
| | | | - Kate E. Langwig
- Department of Biological SciencesVirginia TechBlacksburgVirginiaUSA
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Sheley WC, Gray MJ, Wilber MQ, Cray C, Carter ED, Miller DL. Electrolyte imbalances and dehydration play a key role in Batrachochytrium salamandrivorans chytridiomycosis. Front Vet Sci 2022; 9:1055153. [PMID: 36713878 PMCID: PMC9880075 DOI: 10.3389/fvets.2022.1055153] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 12/28/2022] [Indexed: 01/15/2023] Open
Abstract
Introduction One of the most important emerging infectious diseases of amphibians is caused by the fungal pathogen Batrachochytrium salamandrivorans (Bsal). Bsal was recently discovered and is of global concern due to its potential to cause high mortality in amphibians, especially salamander species. To date, little has been reported on the pathophysiological effects of Bsal; however, studies of a similar fungus, B. dendrobatidis (Bd), have shown that electrolyte losses and immunosuppression likely play a key role in morbidity and mortality associated with this disease. The goal of this study was to investigate pathophysiological effects and immune responses associated with Bsal chytridiomycosis using 49 rough-skinned newts (Taricha granulosa) as the model species. Methods Taricha granulosa were exposed to a 1 × 107 per 10 mL dose of Bsal zoospores and allowed to reach various stages of disease progression before being humanely euthanized. At the time of euthanasia, blood was collected for biochemical and hematological analyses as well as protein electrophoresis. Ten standardized body sections were histologically examined, and Bsal-induced skin lesions were counted and graded on a scale of 1-5 based on severity. Results Results indicated that electrolyte imbalances and dehydration induced by damage to the epidermis likely play a major role in the pathogenesis of Bsal chytridiomycosis in this species. Additionally, Bsal-infected, clinically diseased T. granulosa exhibited a systemic inflammatory response identified through alterations in complete blood counts and protein electrophoretograms. Discussion Overall, these results provide foundational information on the pathogenesis of this disease and highlight the differences and similarities between Bsal and Bd chytridiomycosis.
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Affiliation(s)
- Wesley C. Sheley
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Knoxville, TN, United States
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, United States
- *Correspondence: Wesley C. Sheley
| | - Matthew J. Gray
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, United States
| | - Mark Q. Wilber
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, United States
| | - Carolyn Cray
- Division of Comparative Pathology, University of Miami Miller School of Medicine, Miami, FL, United States
| | - E. Davis Carter
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, United States
| | - Debra L. Miller
- Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, Knoxville, TN, United States
- Center for Wildlife Health, University of Tennessee Institute of Agriculture, Knoxville, TN, United States
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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] [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.
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Seal S, Dharmarajan G, Khan I. Evolution of pathogen tolerance and emerging infections: A missing experimental paradigm. eLife 2021; 10:e68874. [PMID: 34544548 PMCID: PMC8455132 DOI: 10.7554/elife.68874] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 08/23/2021] [Indexed: 12/11/2022] Open
Abstract
Researchers worldwide are repeatedly warning us against future zoonotic diseases resulting from humankind's insurgence into natural ecosystems. The same zoonotic pathogens that cause severe infections in a human host frequently fail to produce any disease outcome in their natural hosts. What precise features of the immune system enable natural reservoirs to carry these pathogens so efficiently? To understand these effects, we highlight the importance of tracing the evolutionary basis of pathogen tolerance in reservoir hosts, while drawing implications from their diverse physiological and life-history traits, and ecological contexts of host-pathogen interactions. Long-term co-evolution might allow reservoir hosts to modulate immunity and evolve tolerance to zoonotic pathogens, increasing their circulation and infectious period. Such processes can also create a genetically diverse pathogen pool by allowing more mutations and genetic exchanges between circulating strains, thereby harboring rare alive-on-arrival variants with extended infectivity to new hosts (i.e., spillover). Finally, we end by underscoring the indispensability of a large multidisciplinary empirical framework to explore the proposed link between evolved tolerance, pathogen prevalence, and spillover in the wild.
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Affiliation(s)
| | - Guha Dharmarajan
- Savannah River Ecology Laboratory, University of GeorgiaAikenUnited States
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