Batrachochytrium salamandrivorans (Bsal)

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Batrachochytrium salamandrivorans (Bsal) is an emerging pathogen capable of causing significant morbidity and mortality in salamanders.

Rough-Skinned Newt

The rough-skinned newt (Taricha granulosa) is a western U.S. species of salamander that is highly susceptible to Bsal, based on laboratory studies. Photograph credit: Teal Waterstrat, U.S. Fish and Wildlife Service (Public domain.)

The U.S. has the largest diversity of salamanders in the world and introduction of Bsal to North America could have severe impacts on biodiversity and amphibian conservation. The USGS National Wildlife Health Center (NWHC) is collaborating with multiple federal and state partners, including the multi-agency Bsal Task Force, to conduct diagnostic investigations and monitor for Bsal to better understand the fungus and to raise awareness about this threat to our native salamanders.

In 2013, unexpected mortalities of captive and wild fire salamanders (Salamandra salamandra), ultimately attributed to Bsal, were first observed in Belgium and the Netherlands, leading to significant salamander population declines. Since then, Bsal has also been detected in captive salamanders in the United Kingdom and Germany. Studies suggest that Bsal is likely endemic to Asia and may have been introduced into Europe through the global pet trade. Subsequent spillover from captive to wild populations is strongly suspected. From 2010 to 2014, over 750,000 salamanders were imported into the U.S., creating a high probability that Bsal could be introduced into the U.S. The USGS developed a risk assessment to predict the potential distribution of Bsal invasion within the U.S. and analyzed the potential consequences of an introduction (Richgels et al., 2016). The assessment identified that the total risk of Bsal introduction into the U.S. is greatest for the Pacific coast, southern Appalachian Mountains, and mid-Atlantic regions. Overall, the total risk is highest throughout the eastern U.S.

Scientist swabbing newt.

USGS scientist swabbing a Central Newt in Wisconsin to look for an invasive fungus, Batrachochytrium salamandrivorans (Bsal). (Public domain.)

Currently, the NWHC is providing technical and diagnostic support for an intense surveillance effort in collaboration with the USGS Amphibian Research and Monitoring Initiative (ARMI). Sampling will focus on sites where the probability of introduction is highest and on salamander species that are most susceptible to the disease. In addition to the surveillance project, unusual morbidity and mortality events involving salamanders should be reported to the appropriate state or federal agency or to the NWHC.

Batrachochytrium salamandrivorans is closely related to the amphibian pathogen Batrachochytrium dendrobatidis (Bd) which is known to affect more than 200 amphibian species, is linked to spread through the global pet trade, has caused extinctions, and continues to be a leading cause of amphibian mortality events worldwide. Thus, the potential impact of Bsal on salamander biodiversity is a serious concern. Early detection of Bsal would allow for the rapid institution of management actions to prevent and control the spread of the fungus should it be detected in North America.