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1. 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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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. 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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4. Preparing for invasion: Assessing risk of infection by chytrid fungi in southeastern plethodontid salamanders

   https://doi.org/10.1002/jez.2427  

   Friday, Brenna ; Holzheuser, Chace ; Lips, Karen R. ; Longo, Ana V. ( November 2020 , Journal of Experimental Zoology Part A: Ecological and Integrative Physiology)

   Understanding the responses of naïve communities to the invasion of multihost pathogens requires accurate estimates of susceptibility across taxa. In the Americas, the likely emergence of a second amphibian pathogenic fungus (Batrachochytrium salamandrivorans, Bsal) calls for new ways of prioritizing disease mitigation among species due to the high diversity of naïve hosts with priorB. dendrobatidis(Bd) infections. Here, we applied the concept of pathogenic potential to quantify the virulence of chytrid fungi on naïve amphibians and evaluate species for conservation efforts in the event of an outbreak. The benefit of this measure is that it combines and summarizes the variation in disease effects into a single numerical index, allowing for comparisons across species, populations or groups of individuals that may inherently exhibit differences in susceptibility. As a proof of concept, we obtained standardized responses of disease severity by performing experimental infections withBsalon five plethodontid salamanders from southeastern United States. Four out of five species carried natural infections ofBdat the start of the experiments. We showed thatBsalexhibited its highest value of pathogenic potential in a species that is already declining (Desmognathus auriculatus). We find that this index provides additional information beyond the standard measures of disease prevalence, intensity, and mortality, because it leveraged these disease parameters within each categorical group. Scientists and practitioners could use this measure to justify research, funding, trade, or conservation measures.

    

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5. Investigating the influence of thermal environment on infection dynamics of Bsal in Plethodontid salamanders

   Claunch, Natalie M ; Guralnick, Robert P ; Longo, Ana V. ( August 2022 , Global Amphibian and Reptile Disease Conference)

   The potential emergence of Batrachochytrium salamandrivorans (Bsal) in North America threatens salamander diversity and ecosystem functioning, thus an understanding of mechanisms influencing host survival during infection is key to predict future impacts. Previous studies indicate that temperature plays a role in regulating infection dynamics, in that access to a thermal gradient provides the means to prevent infections. Phenotypic flexibility is a likely mechanism, as temperature can enhance (or suppress) host functional capacity in both lunged and lungless salamanders. However, we know very little about how hosts are using thermal environments to achieve effective immune gene expression during Bsal infection. Through a series of experiments, we aim to 1) reveal if interspecific differences in disease susceptibility and functional responses are exacerbated by thermal environments, 2) determine if hosts can minimize the metabolic costs of infections by selecting optimal environments, and 3) project susceptibility risk across the landscape using information about species’ thermal preferences. We discuss our plans to evaluate immune gene expression, metabolic rates and thermoregulation relating to infection with Bsal and access to different thermal environments in plethodontid salamanders from Florida. Additionally, to develop models to predict infection susceptibility, we are seeking collaborations in compiling data on thermal preferences and thermal limits across plethodontid salamander species. 

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