Batrachochytrium salamandrivorans (Bsal) is an emerging chytrid fungal pathogen capable of causing significant morbidity and mortality in salamanders. North America has the highest diversity of salamanders in the world and introduction of Bsal to North America would have severe impacts on biodiversity and amphibian conservation. There is currently no evidence to suggest Bsal has been introduced to North America, but early surveillance efforts have been limited to few local areas and opportunistic sampling. The USGS National Wildlife Health Center (NWHC) and Amphibian Research and Monitoring Initiative (ARMI) collaborated to sample salamander populations across the U.S. in an attempt to detect Bsal infection on wild salamanders, if the pathogen is present. Our surveillance effort was focused on areas where recent Bsal risk assessments identified the highest relative risk of Bsal introduction, biodiversity consequences, and presence of species that are susceptible to Bsal infection in lab trials.
Between January 2016 and June 2017, we collected skin swab samples from nearly 10,000 individuals in 34 U.S. states and used a dual Bsal - B. dendrobatis real-time PCR assay to test for the presence of chytrid DNA. We did not detect any Bsal. The majority of samples from the eastern and western U.S. were eastern newts (Notophthalmus viridescens) and Pacific newts (Taricha spp.), respectively. We also tested species from other salamander and anuran genera including Ambystoma, Amphiuma, Anaxyrus, Batrachoseps, Desmognathus, Dicamptodon, Ensatina, Eurycea, Gyrinophilus, Necturus, Plethodon, Pseudacris, Pseudotriton, Rana, and Siren from sites where they were opportunistically available. Our diagnostics did detect B. dendrobatis with an overall apparent prevalence of approximately 35% in salamander species and 20% in anuran species. Our surveillance effort increases the confidence that Bsal is not present in the U.S., but does not reduce future introduction risk. Continuous efforts to (1) develop mitigation plans in the event of a Bsal introduction, (2) increase knowledge of susceptible North American species, and (3) iteratively use surveillance information to direct ongoing monitoring will be necessary to decrease the probability that we incur the most severe biodiversity consequences if Bsal exists undetected or is introduced into North America.