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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. Preparing for a Bsal invasion into North America has improved multi-sector readiness

   https://doi.org/10.3389/famrs.2024.1347541  

   Olson, Deanna H; Grant, Evan_H Campbell; Bletz, Molly; Piovia-Scott, Jonah; Lesbarrères, David; Kerby, Jacob L; Adams, Michael J; Breitman, Maria Florencia; Christman, Michelle R; Forzán, María J; et al (March 2024, Frontiers in Amphibian and Reptile Science)

   Western palearctic salamander susceptibility to the skin disease caused by the amphibian chytrid fungusBatrachochytrium salamandrivorans(Bsal) was recognized in 2014, eliciting concerns for a potential novel wave of amphibian declines following theB. dendrobatidis(Bd) chytridiomycosis global pandemic. Although Bsal had not been detected in North America, initial experimental trials supported the heightened susceptibility of caudate amphibians to Bsal chytridiomycosis, recognizing the critical threat this pathogen poses to the North American salamander biodiversity hotspot. Here, we take stock of 10 years of research, collaboration, engagement, and outreach by the North American Bsal Task Force. We summarize main knowledge and conservation actions to both forestall and respond to Bsal invasion into North America. We address the questions: what have we learned; what are current challenges; and are we ready for a more effective reaction to Bsal’s eventual detection? We expect that the many contributions to preemptive planning accrued over the past decade will pay dividends in amphibian conservation effectiveness and can inform future responses to other novel wildlife diseases and extreme threats. 

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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. 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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5. Skin Defenses and Host-Environment Microbiome Interactions in Spotted Salamanders

   https://doi.org/10.1093/icb/icaf098  

   Urrutia-Carter, Julian; Madison, Joseph_D; Frederick, John_Adam; Muletz Wolz, Carly_R (June 2025, Integrative And Comparative Biology)

   Synopsis Emerging infectious diseases have been of particular interest as a major threat to global biodiversity. In amphibians, two fungal sister taxa, Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal), along with the viral pathogen ranavirus, have affected global populations. Factors such as host traits, abiotic and biotic environmental conditions, and pathogen prevalence contribute to species-specific disease susceptibility. The eastern United States is home to the Appalachian Mountain system, known as a “hotspot” for salamander biodiversity. Bd and ranavirus are present throughout the Appalachians, and a Bsal emergence could be imminent. Throughout the Appalachians are the spotted salamanders, Ambystoma maculatum, a mostly terrestrial salamander that participates in mass breeding migration to ponds and vernal pools in the late spring. Previous experimental studies have shown that spotted salamanders appear to be resistant to Bd and Bsal infection, but the mechanisms behind Bd defense remain unknown. Spotted salamanders emerging from their overwintering habitats were hypothesized to have potent anti-Bd function expressed in their mucus and in their skin microbiomes, as a countermeasure to annual Bd re-emergence. We used non-invasive sampling at two pools during the spotted salamander annual breeding event to (I) determine pathogen prevalence, (II) quantify the antifungal potential of salamander skin mucus, and (III) characterize the diversity and composition of the salamander skin microbiome and contrast it to that of the corresponding environmental microbiome. We did not detect any Bd, Bsal, or ranavirus in the salamanders. The salamander mucus did not inhibit Bd growth in vitro, and anti-Bd bacteria were at low relative abundance in the microbiome. The salamander microbiome sourced a proportion of bacteria from the environment and appeared to select rare taxa from their respective pools; however, their functional relevance in pathogen defense is unclear. Our results suggest that the spotted salamander mucosal secretions and skin microbiome are not the mechanisms of defense against Bd. Rather, elements not captured by the mucosome (e.g., immune cell gene expression) may confer resistance. This study contributes to the understanding of salamander intraspecies variation in disease susceptibility. 

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