Resistance, tolerance and environmental transmission dynamics determine host extinction risk in a load‐dependent amphibian disease

Wilber, M.; Knapp, Roland A.; Toothman, Mary; Briggs, Cheryl J.

doi:10.1111/ele.12814

Cited by 49 publications

(75 citation statements)

References 80 publications

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“…While theoretical models of Bd dynamics have explained the occurrence of low‐level Bd infections in host populations by assuming low rates of zoospore production (Briggs et al., ) and high levels of host resistance (Wilber et al., ), the effects demonstrated in our first experiment suggest that escape (Altizer et al., ) and recovery (Shaw & Binning, ) from infection during periods of terrestrial activity could also generate these patterns in semi‐terrestrial hosts. Accounting for periods that newts spend outside of aquatic habitat, our experiments generated infection patterns that were consistent with patterns in two populations of wild newts, emphasizing the ecological relevance of our experimental infections.…”

Section: Discussionmentioning

confidence: 78%

“…In the case of newts, fully aquatic habitats are required for mating and offspring development. Since Bd ‐induced mortality appears to be a function of infection loads rather than infection status in various amphibian species (Stockwell, Clulow, & Mahony, ; Wilber et al., ), and since newts can reduce or even remove infections by switching to adjacent terrestrial habitat (as demonstrated in Experiment 1), the reproductive and energetic consequences of avoiding Bd exposure may be more costly than becoming infected. Given the conflicts that can arise from avoiding parasite exposure, and since most parasite infections do not deterministically lead to death, load‐dependent rather than risk‐dependent adjustments in routine habitat use may be an expected strategy for many wildlife species.…”

Section: Discussionmentioning

confidence: 99%

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Routine habitat switching alters the likelihood and persistence of infection with a pathogenic parasite

et al. 2018

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191. Animals switch habitats on a regular basis, and when habitats vary in suitability 20 for parasitism, routine habitat switching alters the frequency of parasite exposure 21 and may affect post-infection parasite proliferation. However, the effects of 22 routine habitat switching on infection dynamics are not well understood. 23 2.We performed infection experiments, behavioural observations, and field 24 surveillance to evaluate how routine habitat switching by adult alpine newts 25 (Ichthyosaura alpestris) influences infection dynamics of the pathogenic parasite, 26Batrachochytrium dendrobatidis (Bd). 27 3. We show that when newts are exposed to equal total doses of Bd in aquatic 28 habitats, differences in exposure frequency and post-exposure habitat alter 29 infection trajectories: newts developed more infections that persisted longer when 30 doses were broken into multiple, reduced-intensity exposures. Intensity and 31 persistence of infections was reduced among newts that were switched to 32 terrestrial habitats following exposure. 33 4. When presented with a choice of habitats, newts did not avoid exposure to Bd, 34 but heavily infected newts were more prone to reduce time spent in water. 35 5. Accounting for routine switching between aquatic and terrestrial habitat in the 36 experiments generated distributions of infection loads that were consistent with 37 those in two populations of wild newts. 38 6. Together, these findings emphasize that differential habitat use and behaviours 39 associated with daily movement can be important ecological determinants of 40 infection risk and severity. 41 42 3

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Section: Discussionmentioning

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Routine habitat switching alters the likelihood and persistence of infection with a pathogenic parasite

et al. 2018

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“…Total mortality and mortality rate were greater and the LD‐50 estimate lower in the North Carolina population compared to the Virginia population. Interestingly, the ID‐50 estimate for the Virginia population was lower than North Carolina, suggesting greater tolerance of the Virginia population to Bsal infection (Wilber, Knapp, Toothman, & Briggs, ). Variation in infection tolerance to amphibian pathogens among populations has been reported and could be related to differences in genetic diversity or local conditions that affected innate and adaptive immune defenses (Pearman & Garner, ; Savage & Zamudio, ).…”

Section: Discussionmentioning

confidence: 99%

Conservation risk of Batrachochytrium salamandrivorans to endemic lungless salamanders

Carter

Miller

Peterson

et al. 2019

CONSERVATION LETTERS

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The emerging fungal pathogen, Batrachochytrium salamandrivorans (Bsal), is a significant conservation threat to salamander biodiversity in Europe, although its potential to affect North American species is poorly understood. We tested the susceptibility of two genera (Eurycea and Pseudotriton) and three populations of lungless salamanders (Plethodontidae) to Bsal. All species became infected with Bsal and two (Pseudotriton ruber and Eurycea wilderae) developed chytridiomycosis. We also documented that susceptibility of E. wilderae differed among populations. Regardless of susceptibility, all species reduced feeding when exposed to Bsal at the highest zoospore dose, and P. ruber and one population of E. wilderae used cover objects less. Our results indicate that Bsal invasion in eastern North America could have significant negative impacts on endemic lungless salamander populations. Future conservation efforts should include surveillance for Bsal in the wild and in captivity, and championing legislation that requires and subsidizes pathogen‐free trade of amphibians.

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“…), make identifying the factors that lead to extinction a conservation priority (Wilber et al. ). Geographic isolation of populations, host species community richness, variation in climate, and habitat differences across sites have all been suggested to influence amphibian– Bd dynamics (Searle et al.…”

Section: Introductionmentioning

confidence: 99%

Host–pathogen metapopulation dynamics suggest high elevation refugia for boreal toads

Mosher

Bailey

Muths

et al. 2018

Ecological Applications

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Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads (Anaxyrus boreas boreas) in the southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic data set, we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be suboptimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian-Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.

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Resistance, tolerance and environmental transmission dynamics determine host extinction risk in a load‐dependent amphibian disease

Cited by 49 publications

References 80 publications

Routine habitat switching alters the likelihood and persistence of infection with a pathogenic parasite

Routine habitat switching alters the likelihood and persistence of infection with a pathogenic parasite

Conservation risk of Batrachochytrium salamandrivorans to endemic lungless salamanders

Host–pathogen metapopulation dynamics suggest high elevation refugia for boreal toads

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