Preventive actions in response to the Bsal threat reduced Bsal risk in the U.S.

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Import regulations and a large surveillance effort have reduced the risk of Batrachochytrium salamandrivorans (Bsal) introduction to the United States. A new study evaluated the impact of these actions and updated a previous Bsal risk assessment to provide information for adaptive decision-making.

Dark colored newt on bright green vegetation.

Eastern newts (Notophthalmus viridescens) are highly susceptible to Bsal and this widespread newt is at high risk from Bsal. (Credit: Dan Grear, USGS National Wildlife Health Center. Public domain.)

The emerging pathogen Bsal is a severe threat to global urodelan (salamanders, newts, and related taxa) biodiversity. Bsal has not been detected, to date, in North America, but the risk is high because North America is one of the global hotspots for urodelan biodiversity. The North American and United States response to the discovery of Bsal in Europe was to take a risk-based approach to preventive management actions, including interim regulations on importation of captive salamanders and a large-scale surveillance effort (Richgels et al., 2016; Yap et al., 2015).

The study found that the regulatory actions put in place in 2016 by the U.S. Fish and Wildlife Service under in the Lacey Act had the intended effect of reducing salamander imports and subsequent risk of introduction. However, further research has confirmed additional species capable of carrying Bsal infection that are common in the captive amphibian global trade network. The overall risk-reduction of the initial regulatory actions was limited by this lack of knowledge.

A widespread surveillance effort conducted by the USGS Amphibian Research and Monitoring Initiative contributed to reducing consequence risk by increasing confidence of Bsal absence in high-risk areas (Waddle et al., 2020). However, the risk-reduction benefit of surveillance is restricted to the time-period when surveillance was conducted. On-going surveillance is important as long as there is continued import and introduction risk.

Ongoing collaboration among the USGS, academic researchers, conservation practitioners, pet industry, and regulatory & management agencies is facilitated by the North American Bsal Task Force to allow exchange of new information and adaptive preventive actions in the face of the Bsal risk.

Two maps of the United States show the change in risk of Bsal.

Relative risk maps of combined Bsal risk, comparing (a) pre-action risk (2010–2015), to (b) risk after implementation of surveillance and of importation restrictions on over 200 salamander species. Relative risk scores were scaled to 2010–2015. (c) Change in relative risk score per county as proportion of pre-action risk. Each point is a county, colored by its risk score in (a). From Grear et al. 2021.

 

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Two maps of the United States show the change in risk of Bsal.
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Maps of Bsal risk in the U.S. comparing pre- and post- action risk

Relative risk maps of combined Bsal risk, comparing (a) pre-action risk (2010–2015), to (b) risk after implementation of surveillance and of importation restrictions on over 200 salamander species. Relative risk scores were scaled to 2010–2015. (c) Change in relative risk score per county as proportion of pre-action risk. Each point is a county, colored by its risk score

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This map shows the sites where Bsal surveillance sampling by the USGS Amphibian Research and Monitoring Initiative has been conducted. Credit: USGS