- Award ID(s):
- 1717282
- NSF-PAR ID:
- 10355329
- Editor(s):
- Xuan Liu
- Date Published:
- Journal Name:
- Diversity and Distributions
- ISSN:
- 1366-9516
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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.more » « less
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Abstract The emerging fungal pathogen
Batrachochytrium salamandrivorans (Bsal ) is a major threat to amphibian species worldwide with potential to infect many species if it invades salamander biodiversity hotspots in the Americas.Bsal can cause the disease chytridiomycosis, and it is important to assess the risk ofBsal ‐induced chytridiomycosis to species in North America. We evaluated the susceptibility toBsal of the common and widespread spotted salamander,Ambystoma maculatum , across life‐history stages and monitored the effect ofBsal exposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant toBsal because they showed no indication of disease or infection, and experienced minor effects on growth upon exposure. While we focused on a single population for this study, results were consistent across conditions of exposure including high or repeated doses ofBsal , life‐stage at exposure, environmental conditions including two temperatures and two substrates, and promoting pathogen infectivity by conditioningBsal cultures with thyroid hormone. Exposure to high levels ofBsal elicited an acute but not chronic increase in corticosterone in spotted salamanders, and reduced growth. We hypothesize that the early acute increase in corticosterone facilitated mounting an immune response to the pathogen, perhaps through immunoredistribution to the skin, but further study is needed to determine immune responses toBsal . These results will contribute to development of appropriateBsal management plans to conserve species at risk of emerging disease. -
Abstract Detecting pathogens in the live animal trade is critical for tracking and preventing their movement, introduction and spillover into susceptible fauna. However, the scale of the live animal trade makes individually testing animals infeasible for all but the most economically important taxa. For instance, while the fungal pathogen,
Batrachochytrium salamandrivorans (Bsal ), threatens amphibian, particularly caudate diversity, in Europe and the Americas, screening even a fraction of the millions of live amphibians imported into the United States, alone, is impractically laborious and expensive. A promising alternative to individual‐level sampling (e.g. swabbing the skin of salamanders) is to instead collect DNA from the animals' environment (e.g. housing container or water) which allows us to screen a whole group of animals at a time.We used a series of experiments with
Bsal ‐spiked water and substrates and experimentally infected rough‐skinned newts (Taricha granulosa ) to determine which methods yield the mostBsal environmental DNA (eDNA) and evaluate the capacity of these methods to detectBsal ‐infected animals in conditions found in captive settings and trade.We found that filtering water housing infected animals for even an hour can consistently recover detectable levels of
Bsal eDNA, that there is little evidence ofBsal eDNA being clumped in housing containers or swamped or inhibited by dirty housing containers, and that eDNA‐based methods achieves an equivalent or higher chance of detectingBsal infections in a (virtual) population of co‐housed newts with fewer samples than individual swabs.By sampling the genetic materials accumulated from a whole group of animals, eDNA‐based methods are a powerful means of detecting pathogens, such as
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Abstract Resistance and tolerance are unique host defence strategies that can limit the impacts of a pathogen on a host. However, for most wildlife–pathogen systems, there are still fundamental uncertainties regarding (a) how changes in resistance and tolerance can affect disease outcomes and (b) the mechanisms underlying resistance and tolerance in host populations.
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A free
Plain Language Summary can be found within the Supporting Information of this article. -
The emerging fungal pathogen, Batrachochytrium dendrobatidis ( Bd ), which can cause a fatal disease called chytridiomycosis, is implicated in the collapse of hundreds of host amphibian species. We describe chytridiomycosis dynamics in two co-occurring terrestrial salamander species, the Santa Lucia Mountains slender salamander, Batrachoseps luciae , and the arboreal salamander, Aneides lugubris . We (1) conduct a retrospective Bd -infection survey of specimens collected over the last century, (2) estimate present-day Bd infections in wild populations, (3) use generalized linear models (GLM) to identify biotic and abiotic correlates of infection risk, (4) investigate susceptibility of hosts exposed to Bd in laboratory trials, and (5) examine the ability of host skin bacteria to inhibit Bd in culture. Our historical survey of 2,866 specimens revealed that for most of the early 20th century (~1920–1969), Bd was not detected in either species. By the 1990s the proportion of infected specimens was 29 and 17% ( B. luciae and A. lugubris , respectively), and in the 2010s it was 10 and 17%. This was similar to the number of infected samples from contemporary populations (2014–2015) at 10 and 18%. We found that both hosts experience signs of chytridiomycosis and suffered high Bd -caused mortality (88 and 71% for B. luciae and A. lugubris , respectively). Our GLM revealed that Bd -infection probability was positively correlated with intraspecific group size and proximity to heterospecifics but not to abiotic factors such as precipitation, minimum temperature, maximum temperature, mean temperature, and elevation, or to the size of the hosts. Finally, we found that both host species contain symbiotic skin-bacteria that inhibit growth of Bd in laboratory trials. Our results provide new evidence consistent with other studies showing a relatively recent Bd invasion of amphibian host populations in western North America and suggest that the spread of the pathogen may be enabled both through conspecific and heterospecific host interactions. Our results suggest that wildlife disease studies should assess host-pathogen dynamics that consider the interactions and effects of multiple hosts, as well as the historical context of pathogen invasion, establishment, and epizootic to enzootic transitions to better understand and predict disease dynamics.more » « less