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Volume 19, Number 3—March 2013

Parallels in Amphibian and Bat Declines from Pathogenic Fungi

Evan A. Eskew1 and Brian D. Todd1Comments to Author 
Author affiliations: Author affiliation: University of California, Davis, California, USA

Main Article


Current knowledge and unresolved research questions regarding the pathogenic fungi Batrachochytrium dendrobatidis and Geomyces destructans, the causative agents of chytridiomycosis and WNS, respectively*

Area of knowledge B. dendrobatidis

G. destructans
Current knowledge Unresolved research questions Current knowledge Unresolved research questions
Disease emergence Multiple regions of endemism and 1 widely introduced hypervirulent lineage (7–9) How and from where did the hypervirulent lineage emerge? Limited genetic differentiation in North America (10) How do strains from North America and Europe compare genetically, and is genetic variation greater in Europe, suggesting historic endemism?

Possibly endemic to Europe and introduced to North America (6,11,12)

Abiotic reservoirs
Can survive in water and soil (13,14)
Can B. dendrobatidis form desiccation-resistant resting spores? Can B. dendrobatidis survive and reproduce as a saprophytic, nonparasitic form?

Apparent persistence in soils and on cave walls (12,15)
How widespread is G. destructans in the environment? Can G. destructans survive and reproduce as a saprophytic, nonparasitic form?
Biotic reservoirs Host generalist pathogen of amphibians (4,5) Can B. dendrobatidis complete its life cycle on other vertebrate hosts? Host generalist pathogen of bats (6) Can G. destructans infect or persist on other vertebrates?

Can also infect reptiles, nematodes, and waterfowl (1618)

Life history and infection risk of the host
Aquatic, biphasic, tropical amphibian species at greatest risk for chytridiomycosis (19)
To what extent can life history characteristics of the host predict global patterns of disease-related population decline among amphibian species?

Bat species that hibernate experience most deaths from WNS (20)
Are only those species that hibernate susceptible to population decline from WNS? What role does life history of the host play in predicting species declines and extinctions from WNS?
Host–pathogen interactions Antimicrobial peptides and antifungal metabolites from skin-associated bacteria contribute to B. dendrobatidis resistance (21) What is the immune response of B. dendrobatidis–tolerant hosts to infection? Host immune down-regulation during hibernation probably important to WNS progression (24) What is the host immune response to G. destructans infection?
Susceptible species appear to show little innate or adaptive immune response to B. dendrobatidis infection (22,23) Does B. dendrobatidis evade the amphibian immune system through activity of secreted proteases? How does host immunity vary seasonally? What role does immune function play in the observed winter season/hibernation mortality from WNS? Do proteases contribute to pathogenicity of G. destructans?

*WNS, white-nose syndrome.

Main Article

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Main Article

1Both authors contributed equally to this article.

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