Batrachochytrium salamandrivorans (Bsal) Surveillance
Scientists of the USGS National Wildlife Health Center (NWHC) in collaboration with partners have developed risk assessments for Batrachochytrium salamandrivorans (Bsal) in the United States and are sampling high-risk locations for the fungus.
Bsal has caused mass mortality events and severe population declines in European salamanders via introduction into wild populations from the pet trade. North America has the highest diversity of salamanders in the world, particularly in the U.S. Southeast and Northwest, and an introduction of this pathogen could lead to population declines or localized extinctions of species.
USGS scientists developed a series of county-specific Bsal risk assessments for the US by analyzing characteristics of Bsal ecology such as optimal temperatures for fungal growth, data on amphibian imports, pet trade locations, the regional diversity of salamander species, risk-mitigation actions implemented to prevent entry of Bsal, and where surveillance has occurred. They found that if Bsal enters the country:
- The total risk of Bsal to salamanders is highest throughout the eastern US, particularly in the mid-Atlantic states of New York, Massachusetts, Rhode Island, Connecticut, New Jersey, Pennsylvania, Delaware and Maryland.
- The Pacific coast and Appalachian Mountains are likely to have significant population declines due to high concentrations of diverse salamander species and mild climates that are well suited to Bsal growth.
- The risk assessments have been used to support World Organization for Animal Health Guidelines for Addressing Disease Risk in Wildlife Trade
The NWHC is working collaboratively with the USGS Amphibian Research and Monitoring Initiative (ARMI), to determine the presence of Bsal in North American salamander populations in targeted locations with high biodiversity and increased risk of exposure to the Bsal pathogen. The NWHC, ARMI, and other partners have collected and tested over 15,000 samples from 39 states and over 55 species since 2016 and have not detected Bsal (Waddle et al., 2020).
NWHC continues to support Bsal surveillance by supporting state, federal, and Tribal partners in investigating amphibian mortality and morbidity, as well as providing surveillance services for species of local, regional, and national interest.
NWHC is also the coordinating laboratory for the Student Network for Amphibian Pathogen Surveillance (SNAPS). SNAPS is an experiential learning network of students, educators, and scientists committed to surveillance for the threat of deadly emerging pathogens, with a focus on Bsal. SNAPS has mobilized over 1,200 students across the U. S. to lead the search for emerging amphibian pathogens in North America. As of 2025, SNAPS has a network of 60 universities, schools, and education programs participating in Bsal surveillance efforts.
Scientists of the USGS National Wildlife Health Center (NWHC) in collaboration with partners have developed risk assessments for Batrachochytrium salamandrivorans (Bsal) in the United States and are sampling high-risk locations for the fungus.
Bsal has caused mass mortality events and severe population declines in European salamanders via introduction into wild populations from the pet trade. North America has the highest diversity of salamanders in the world, particularly in the U.S. Southeast and Northwest, and an introduction of this pathogen could lead to population declines or localized extinctions of species.
USGS scientists developed a series of county-specific Bsal risk assessments for the US by analyzing characteristics of Bsal ecology such as optimal temperatures for fungal growth, data on amphibian imports, pet trade locations, the regional diversity of salamander species, risk-mitigation actions implemented to prevent entry of Bsal, and where surveillance has occurred. They found that if Bsal enters the country:
- The total risk of Bsal to salamanders is highest throughout the eastern US, particularly in the mid-Atlantic states of New York, Massachusetts, Rhode Island, Connecticut, New Jersey, Pennsylvania, Delaware and Maryland.
- The Pacific coast and Appalachian Mountains are likely to have significant population declines due to high concentrations of diverse salamander species and mild climates that are well suited to Bsal growth.
- The risk assessments have been used to support World Organization for Animal Health Guidelines for Addressing Disease Risk in Wildlife Trade
The NWHC is working collaboratively with the USGS Amphibian Research and Monitoring Initiative (ARMI), to determine the presence of Bsal in North American salamander populations in targeted locations with high biodiversity and increased risk of exposure to the Bsal pathogen. The NWHC, ARMI, and other partners have collected and tested over 15,000 samples from 39 states and over 55 species since 2016 and have not detected Bsal (Waddle et al., 2020).
NWHC continues to support Bsal surveillance by supporting state, federal, and Tribal partners in investigating amphibian mortality and morbidity, as well as providing surveillance services for species of local, regional, and national interest.
NWHC is also the coordinating laboratory for the Student Network for Amphibian Pathogen Surveillance (SNAPS). SNAPS is an experiential learning network of students, educators, and scientists committed to surveillance for the threat of deadly emerging pathogens, with a focus on Bsal. SNAPS has mobilized over 1,200 students across the U. S. to lead the search for emerging amphibian pathogens in North America. As of 2025, SNAPS has a network of 60 universities, schools, and education programs participating in Bsal surveillance efforts.