Assessing the capacity for migratory bats to serve as long-distance vectors of white-nose syndrome pathogen Pseudogymnoascus destructans

Background/Question/Methods

The emerging fungal epizootic disease white-nose syndrome (WNS) has caused dramatic declines in bat populations across North America. The causative fungus, Pseudogymnoascus destructans (Pd), affects and kills hibernating bats during the winter and is transmitted via substrate or other infected individuals. The disease was first detected in New York state in 2006-7 and was advancing westward across North America at a rate of ~500 km/yr, until it “jumped” several thousand kilometers to Washington state, USA, in March 2016, arriving more than two decades earlier than anticipated. Although disease-affected bats had been assumed to be the primary vectors of Pd between caves, their relatively small capacity for dispersal cannot account for this acceleration in spread. Here, we present a conceptual framework to assess the capacity of migratory species unafflicted by WNS to spread the causative fungus, comprising three components: 1) repeated exposure by focal species to Pd+ substrates; 2) persistence of Pd on focal species tissues; and 3) long-distance movements by focal species. We quantified each of these components by aggregating records of migratory tree-roosting species entering and interacting with substrates in bat hibernacula; conducting a meta-analysis of the prevalence of Pd on species; and providing a synthesis of dispersal behavior and capacity.

Results/Conclusions

We aggregated a database of records dating back to 1892 of migratory Lasiurus and Lasionycteris spp. found in likely hibernacula. These genera were selected due to their propensity for long-distance dispersal and documented records of Pd DNA detections. Lasiurus spp. were most associated with hibernacula during autumn, which occurs during peak swarming and migratory activity. Lasionycteris spp. were most associated with underground hibernacula while overwintering, although records overlap probable spring migratory periods. Our meta-analysis of Pd detections on these genera indicate that Pd persists on migratory bat tissue and is detected on individuals well into the summer and active autumn migration season. Finally, numerous instances of long-distance migration by these species, during overlapping intervals with records of Pd detections, indicate natural Pd dispersal by these species is possible. This study represents the first effort to quantify the likelihood of migratory WNS-resistant bats to serve as vectors of Pd, which we conclude is possible but likely rare.