First Detection of Bat White-Nose Syndrome in Western North America

Abstract

White-nose syndrome (WNS) is an emerging fungal disease of bats caused by Pseudogymnoascus destructans. Since it was first detected near Albany, NY, in 2006, the fungus has spread across eastern North America, killing unprecedented numbers of hibernating bats. The devastating impacts of WNS on Nearctic bat species are attributed to the likely introduction of P. destructans from Eurasia to naive host populations in eastern North America. Since 2006, the disease has spread in a gradual wavelike pattern consistent with introduction of the pathogen at a single location. Here, we describe the first detection of P. destructans in western North America in a little brown bat (Myotis lucifugus) from near Seattle, WA, far from the previously recognized geographic distribution of the fungus. Whole-genome sequencing and phylogenetic analyses indicated that the isolate of P. destructans from Washington grouped with other isolates of a presumed clonal lineage from the eastern United States. Thus, the occurrence of P. destructans in Washington does not likely represent a novel introduction of the fungus from Eurasia, and the lack of intensive surveillance in the western United States makes it difficult to interpret whether the occurrence of P. destructans in the Pacific Northwest is disjunct from that in eastern North America. Although there is uncertainty surrounding the impacts of WNS in the Pacific Northwest, the presence of the pathogen in western North America could have major consequences for bat conservation. IMPORTANCE White-nose syndrome (WNS) represents one of the most consequential wildlife diseases of modern times. Since it was first documented in New York in 2006, the disease has killed millions of bats and threatens several formerly abundant species with extirpation or extinction. The spread of WNS in eastern North America has been relatively gradual, inducing optimism that disease mitigation strategies could be established in time to conserve bats susceptible to WNS in western North America. The recent detection of the fungus that causes WNS in the Pacific Northwest, far from its previous known distribution, increases the urgency for understanding the long-term impacts of this disease and for developing strategies to conserve imperiled bat species.

Keywords: Pseudogymnoascus destructans; Washington; bat; white-nose syndrome.

FIG 1

Generalized spatiotemporal spread of Pseudogymnoascus destructans across North America since the initial detection of white-nose syndrome (WNS) in New York in 2006. The map was generated using the natural-neighbor raster interpolation tool in ArcMap 10.2.1 (ESRI, Redlands, CA), based on first detection of P. destructans within a county or first classification of a county as suspect for WNS. The map was generated using data from the U.S. Geological Survey, National Wildlife Health Center, and https://www.whitenosesyndrome.org/resources/map. Each color represents the spread of the pathogen during a given winter (hibernation) season spanning from November to May.

FIG 2

Phylogenetic relationships based on whole-genome sequence analysis of nine isolates of Pseudogymnoascus destructans from North America and Europe. A core alignment of 13,379 SNPs was generated for each isolate, using Snippy (11), and phylogeny was inferred by drawing an unrooted neighbor-joining tree supported with 1,000 bootstrap replicates (branch lengths represent the number of substitutions per site). A second analysis using maximum likelihood produced a tree with identical topology. Thus far, isolates of P. destructans from North America appear to be clonal, whereas there is considerable variation in populations of P. destructans in Europe (even in this small sample size of isolates from a limited geographical range). Isolates from both mating types (MAT1-1 and MAT1-2) are found in Europe, suggesting that sexually recombining populations contribute to the increase in genomic variability. A single mating type (MAT1-1) is known from North America. Bootstrap values (neighbor-joining analysis/maximum-likelihood analysis) for well-supported nodes (>90) are presented.