Pathophysiology of white-nose syndrome in bats: a mechanistic model linking wing damage to mortality

White-nose syndrome is devastating North American bat populations but we lack basic information on disease mechanisms. Altered blood physiology owing to epidermal invasion by the fungal pathogen Geomyces destructans ( Gd ) has been hypothesized as a cause of disrupted torpor patterns of affected hibernating bats, leading to mortality. Here, we present data on blood electrolyte concentration, haematology and acid–base balance of hibernating little brown bats, Myotis lucifugus , following experimental inoculation with Gd . Compared with controls, infected bats showed electrolyte depletion (i.e. lower plasma sodium), changes in haematology (i.e. increased haematocrit and decreased glucose) and disrupted acid–base balance (i.e. lower CO 2 partial pressure and bicarbonate). These findings indicate hypotonic dehydration, hypovolaemia and metabolic acidosis. We propose a mechanistic model linking tissue damage to altered homeostasis and morbidity/mortality.

Psychrophilic and Psychrotolerant Fungi on Bats and the Presence of Geomyces spp. on Bat Wings Prior to the Arrival of White Nose Syndrome

ABSTRACTSince 2006,Geomyces destructans, the causative agent of white nose syndrome (WNS), has killed over 5.7 million bats in North America. The current hypothesis suggests that this novel fungus is an invasive species from Europe, but little is known about the diversity within the genusGeomycesand its distribution on bats in the United States. We documented the psychrophilic and psychrotolerant fungal flora of hibernating bats prior to the arrival of WNS using culture-based techniques. A total of 149 cultures, which were obtained from 30 bats in five bat hibernacula located in four caves and one mine, were sequenced for the entire internal transcribed spacer (ITS) nuclear ribosomal DNA (nrDNA) region. Approximately 53 operational taxonomic units (OTUs) at 97% similarity were recovered from bat wings, with the community dominated by fungi within the generaCladosporium,Fusarium,Geomyces,Mortierella,Penicillium, andTrichosporon. ElevenGeomycesisolates were obtained and placed in at least seven distinctGeomycesclades based on maximum-likelihood phylogenetic analyses. Temperature experiments revealed that allGeomycesstrains isolated are psychrotolerant, unlikeG. destructans, which is a true psychrophile. Our results confirm that a large diversity of fungi, including severalGeomycesisolates, occurs on bats prior to the arrival of WNS. Most of these isolates were obtained from damaged wings. Additional studies need to be conducted to determine potential ecological roles of these abundantGeomycesstrains isolated from bats.

A review of factors affecting cave climates for hibernating bats in temperate North America

The fungal pathogen Geomyces destructans, which causes white-nose syndrome in bats, thrives in the cold and moist conditions found in caves where bats hibernate. To aid managers and researchers address this disease, an updated and accessible review of cave hibernacula and cave microclimates is presented. To maximize energy savings and reduce evaporative water loss during winter, most temperate vespertilionid bats in North America select caves with temperatures between 2 and 10 °C, with 60%–100% relative humidity. Generally, the temperature in caves is similar to the mean annual surface temperature (MAST) of a region, which varies by latitude, altitude, and topography. However, MAST for most areas where caves are found in eastern North America is well above 10 °C. Thus, various factors cause cold-air infiltration that reduces temperatures of these caves during winter. These factors include depth of cave, topographic setting, airflow patterns, cave configuration, and water infiltration. Factors affecting humidity, condensation, and evaporation are also addressed. In areas where MAST is above or below the thermal requirements of Geomyces destructans, many caves used by bats as hibernacula may still provide favorable sites for optimal growth of this fungus.