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1. Broad host susceptibility of North American amphibian species to Batrachochytrium salamandrivorans suggests high invasion potential and biodiversity risk

   https://doi.org/10.1038/s41467-023-38979-4  

   Gray, Matthew J. ; Carter, Edward Davis ; Piovia-Scott, Jonah ; Cusaac, J. Patrick ; Peterson, Anna C. ; Whetstone, Ross D. ; Hertz, Andreas ; Muniz-Torres, Aura Y. ; Bletz, Molly C. ; Woodhams, Douglas C. ; et al ( December 2023 , Nature Communications)

   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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2. Batrachochytrium salamandrivorans elicits acute stress response in spotted salamanders but not infection or mortality

   https://doi.org/10.1111/acv.12565  

   Barnhart, K. ; Bletz, M. C. ; LaBumbard, B. ; Tokash‐Peters, A. ; Gabor, C. R. ; Woodhams, D. C. ( January 2020 , Animal Conservation)

   The emerging fungal pathogenBatrachochytrium 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.Bsalcan cause the disease chytridiomycosis, and it is important to assess the risk ofBsal‐induced chytridiomycosis to species in North America. We evaluated the susceptibility toBsalof the common and widespread spotted salamander,Ambystoma maculatum, across life‐history stages and monitored the effect ofBsalexposure on growth rate and response of the stress hormone, corticosterone. We conclude that spotted salamanders appear resistant toBsalbecause 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 conditioningBsalcultures with thyroid hormone. Exposure to high levels ofBsalelicited 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 appropriateBsalmanagement plans to conserve species at risk of emerging disease.

    

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3. A spatially explicit risk assessment of salamander populations to Batrachochytrium salamandrivorans in the United States

   https://doi.org/10.1111/ddi.13627  

   Moubarak, Michael ; Fischhoff, Ilya R. ; Han, Barbara A. ; Castellanos, Adrian A. ( October 2022 , Diversity and Distributions)

   Xuan Liu (Ed.)

   Aim: Amphibian populations are threatened globally by anthropogenic change and Batrachochytrium dendrobatidis (Bd), a fungal pathogen causing chytridiomycosis disease to varying degrees of severity. A closely related new fungal pathogen, Batrachochytrium salamandrivorans (Bsal), has recently left its supposed native range in Asia and decimated some salamander populations in Europe. Despite being noticed initially for causing chytridiomycosis-related population declines in salamanders, Bsal can also infect anurans and cause non-lethal chytridiomycosis or asymptomatic infections in salamanders. Bsal has not yet been detected in the United States, but given the United States has the highest salamander biodiversity on Earth, predictive assessments of salamander risk to Bsal infection will enable proactive allocation of research and conservation efforts into disease prevention and mitigation. Location: The United States, Europe and Asia. Methods: We first predicted the environmental suitability for the Bsal pathogen in the United States through an ecological niche model based on the pathogen's known native range in Asia, validated on the observed invasive range in Europe using bioclimatic, land cover, elevation, soil characteristics and human modification variables. Second, we predicted the susceptibility of salamander species to Bsal infection using a machine-learning model that correlated life history traits with published data on confirmed species infections. Finally, we mapped the geographic ranges of the subset of species that were predicted to be susceptible to Bsal infection. Results: In the United States, the overlap of environmental suitability and susceptible salamander species was greatest in the Pacific Northwest, near the Gulf of Mexico, and along the Atlantic coast, and in inland states east of the Plains region. Main Conclusions: The overlap of these metrics identify salamander populations that may be at risk of developing Bsal infection and suggests priorities for pre-emptive research and conservation measures to protect at-risk salamander species from an additional pathogenic threat. 

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4. Invasibility of a North American soil ecosystem to amphibian-killing fungal pathogens

   https://doi.org/10.1098/rspb.2023.2658  

   McGrath-Blaser, Sarah E ; McGathey, Natalie ; Pardon, Allison ; Hartmann, Arik M ; Longo, Ana V ( April 2024 , Proceedings of the Royal Society B: Biological Sciences)

   North American salamanders are threatened by intercontinental spread of chytridiomycosis, a deadly disease caused by the fungal pathogenBatrachochytrium salamandrivorans(Bsal). To predict potential dispersal ofBsalspores to salamander habitats, we evaluated the capacity of soil microbial communities to resist invasion. We determined the degree of habitat invasibility using soils from five locations throughout the Great Smoky Mountains National Park, a region with a high abundance of susceptible hosts. Our experimental design consisted of replicate soil microcosms exposed to different propagule pressures of the non-native pathogen,Bsal, and an introduced but endemic pathogen,B. dendrobatidis(Bd). To compare growth and competitive interactions, we used quantitative PCR, live/dead cell viability assays, and full-length 16S rRNA sequencing. We found that soil microcosms with intact bacterial communities inhibited bothBsalandBdgrowth, but inhibitory capacity diminished with increased propagule pressure.Bsalshowed greater persistence thanBd. Linear discriminant analysis (LDA) identified the family Burkolderiaceae as increasing in relative abundance with the decline of both pathogens. Although our findings provide evidence of environmental filtering in soils, such barriers weakened in response to pathogen type and propagule pressure, showing that habitats vary their invasibility based on properties of their local microbial communities.

    

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5. Tracking, Synthesizing, and Sharing Global Batrachochytrium Data at AmphibianDisease.org

   https://doi.org/10.3389/fvets.2021.728232  

   Koo, Michelle S. ; Vredenburg, Vance T. ; Deck, John B. ; Olson, Deanna H. ; Ronnenberg, Kathryn L. ; Wake, David B. ( October 2021 , Frontiers in Veterinary Science)

   Emerging infectious diseases have been especially devastating to amphibians, the most endangered class of vertebrates. For amphibians, the greatest disease threat is chytridiomycosis, caused by one of two chytridiomycete fungal pathogens Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans ( Bsal ). Research over the last two decades has shown that susceptibility to this disease varies greatly with respect to a suite of host and pathogen factors such as phylogeny, geography (including abiotic factors), host community composition, and historical exposure to pathogens; yet, despite a growing body of research, a comprehensive understanding of global chytridiomycosis incidence remains elusive. In a large collaborative effort, Bd -Maps was launched in 2007 to increase multidisciplinary investigations and understanding using compiled global Bd occurrence data ( Bsal was not discovered until 2013). As its database functions aged and became unsustainable, we sought to address critical needs utilizing new technologies to meet the challenges of aggregating data to facilitate research on both Bd and Bsal . Here, we introduce an advanced central online repository to archive, aggregate, and share Bd and Bsal data collected from around the world. The Amphibian Disease Portal ( https://amphibiandisease.org ) addresses several critical community needs while also helping to build basic biological knowledge of chytridiomycosis. This portal could be useful for other amphibian diseases and could also be replicated for uses with other wildlife diseases. We show how the Amphibian Disease Portal provides: (1) a new repository for the legacy Bd- Maps data; (2) a repository for sample-level data to archive datasets and host published data with permanent DOIs; (3) a flexible framework to adapt to advances in field, laboratory, and informatics technologies; and (4) a global aggregation of Bd and Bsal infection data to enable and accelerate research and conservation. The new framework for this project is built using biodiversity informatics best practices and metadata standards to ensure scientific reproducibility and linkages across other biological and biodiversity repositories. 

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