Host traits and environment interact to determine persistence of bat populations impacted by white-nose syndrome.

Emerging infectious diseases have resulted in severe population declines across diverse taxa. In some instances, despite attributes associated with high extinction risk, disease emergence and host declines are followed by host stabilisation for unknown reasons. While host, pathogen, and the environment are recognised as important factors that interact to determine host-pathogen coexistence, they are often considered independently. Here, we use a translocation experiment to disentangle the role of host traits and environmental conditions in driving the persistence of remnant bat populations a decade after they declined 70-99% due to white-nose syndrome and subsequently stabilised. While survival was significantly higher than during the initial epidemic within all sites, protection from severe disease only existed within a narrow environmental space, suggesting host traits conducive to surviving disease are highly environmentally dependent. Ultimately, population persistence following pathogen invasion is the product of host-pathogen interactions that vary across a patchwork of environments.

Genomic signatures of selection in bats surviving white-nose syndrome.

Rapid evolution of advantageous traits following abrupt environmental change can help populations recover from demographic decline. However, for many introduced diseases affecting longer-lived, slower reproducing hosts, mortality is likely to outpace the acquisition of adaptive de novo mutations. Adaptive alleles must therefore be selected from standing genetic variation, a process that leaves few detectable genomic signatures. Here, we present whole genome evidence for selection in bat populations that are recovering from white-nose syndrome (WNS). We collected samples both during and after a WNS-induced mass mortality event in two little brown bat populations that are beginning to show signs of recovery and found signatures of soft sweeps from standing genetic variation at multiple loci throughout the genome. We identified one locus putatively under selection in a gene associated with the immune system. Multiple loci putatively under selection were located within genes previously linked to host response to WNS as well as to changes in metabolism during hibernation. Results from two additional populations suggested that loci under selection may differ somewhat among populations. Through these findings, we suggest that WNS-induced selection may contribute to genetic resistance in this slowly reproducing species threatened with extinction.

The scope and severity of white-nose syndrome on hibernating bats in North America.

Assessing the scope and severity of threats is necessary for evaluating impacts on populations to inform conservation planning. Quantitative threat assessment often requires monitoring programs that provide reliable data over relevant spatial and temporal scales, yet such programs can be difficult to justify until there is an apparent stressor. Leveraging efforts of wildlife management agencies to record winter counts of hibernating bats, we collated data for 5 species from over 200 sites across 27 U.S. states and 2 Canadian provinces from 1995 to 2018 to determine the impact of white-nose syndrome (WNS), a deadly disease of hibernating bats. We estimated declines of winter counts of bat colonies at sites where the invasive fungus that causes WNS (Pseudogymnoascus destructans) had been detected to assess the threat impact of WNS. Three species undergoing species status assessment by the U.S. Fish and Wildlife Service (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus) declined by more than 90%, which warrants classifying the severity of the WNS threat as extreme based on criteria used by NatureServe. The scope of the WNS threat as defined by NatureServe criteria was large (36% of Myotis lucifugus range) to pervasive (79% of Myotis septentrionalis range) for these species. Declines for 2 other species (Myotis sodalis and Eptesicus fuscus) were less severe but still qualified as moderate to serious based on NatureServe criteria. Data-sharing across jurisdictions provided a comprehensive evaluation of scope and severity of the threat of WNS and indicated regional differences that can inform response efforts at international, national, and state or provincial jurisdictions. We assessed the threat impact of an emerging infectious disease by uniting monitoring efforts across jurisdictional boundaries and demonstrated the importance of coordinated monitoring programs, such as the North American Bat Monitoring Program (NABat), for data-driven conservation assessments and planning.

Alcance y Severidad del Síndrome de Nariz Blanca en los Murciélagos Hibernando en América del Norte Resumen La evaluación del alcance y la severidad de las amenazas es necesaria para los análisis de impacto sobre las poblaciones que se usan para orientar a la planeación de la conservación. La evaluación cuantitativa de amenazas con frecuencia requiere de programas de monitoreo que proporcionen datos confiables en escalas espaciales y temporales, aunque dichos programas pueden ser difíciles de justificar hasta que exista un estresante aparente. Gracias a una movilización de esfuerzos de las agencias de manejo de fauna para registrar los conteos invernales de murciélagos hibernadores, recopilamos datos para cinco especies en más de 200 sitios a lo largos de 27 estados de EUA y dos provincias canadienses entre 1995 y 2018 para determinar el impacto del síndrome de nariz blanca (SNB), una enfermedad mortal de los murciélagos hibernadores. Estimamos declinaciones en los conteos invernales de las colonias de murciélagos en sitios en donde el hongo invasivo que ocasiona el SNB (Pseudogymnoascus destructans) había sido detectado para evaluar el impacto de amenaza del SNB. Tres especies que se encuentran bajo valoración por parte del Servicio de Pesca y Vida Silvestre de los EUA (Myotis septentrionalis, Myotis lucifugus y Perimyotis subflavus) tuvieron una declinación de más del 90%, lo que justifica la clasificación de la severidad de la amenaza del SNB como extrema con base en el criterio usado por NatureServe. El alcance de la amenaza del SNB definido por el criterio de NatureServe fue desde amplio (36% de la distribución de Myotis lucifugus) hasta dominante (79% de la distribución de Myotis septentrionalis) para estas especies. Las declinaciones de otras dos especies (Myotis sodalis y Eptesicus fuscus) fueron menos severas, pero de igual manera quedaron clasificadas desde moderada hasta seria con base en los criterios de NatureServe. El intercambio de datos entre las jurisdicciones proporcionó una evaluación completa del alcance y la severidad de la amenaza del SNB e indicó las diferencias regionales que pueden guiar a los esfuerzos de respuesta realizados en las jurisdicciones internacionales, nacionales, estatales o provinciales. Evaluamos el impacto de amenaza de una enfermedad infecciosa emergente mediante la combinación de los esfuerzos de monitoreo que sobrepasan fronteras jurisdiccionales y demostramos la importancia que tienen para la planeación y la evaluación basadas en datos de la conservación los programas de monitoreo coordinados, como el Programa de Monitoreo de los Murciélagos Norteamericanos (NABat).

Interannual Survival of Myotis lucifugus (Chiroptera: Vespertilionidae) near the Epicenter of White-Nose Syndrome.

Reduced populations of Myotis lucifugus (Little Brown Myotis) devastated by white-nose syndrome (WNS) persist in eastern North America. Between 2009 and 2013, we recaptured 113 marked individuals that survived between 1 and 6 winters in New England since the arrival of WNS. We also observed signs of reproductive success in 57 recaptured bats.

Persist or Perish: Can Bats Threatened with Extinction Persist and Recover from White-nose Syndrome?

Emerging mycoses are an increasing concern in wildlife and human health. Given the historical rarity of fungal pathogens in warm-bodied vertebrates, there is a need to better understand how to manage mycoses and facilitate recovery in affected host populations. We explore challenges to host survival and mechanisms of host recovery in three bat species (Myotis lucifugus, Perimyotis subflavus, and M. septentrionalis) threatened with extinction by the mycosis, white-nose syndrome (WNS) as it continues to spread across North America. We present evidence from the literature that bats surviving WNS are exhibiting mechanisms of avoidance (by selecting microclimates within roosts) and tolerance (by increasing winter fat reserves), which may help avoid costs of immunopathology incurred by a maladaptive host resistance response. We discuss management actions for facilitating species recovery that take into consideration disease pressures (e.g., environmental reservoirs) and mechanisms underlying persistence, and suggest strategies that alleviate costs of immunopathology and target mechanisms of avoidance (protect or create refugia) and tolerance (increase body condition). We also propose strategies that target population and species-level recovery, including increasing reproductive success and reducing other stressors (e.g., wind turbine mortality). The rarity of fungal pathogens paired with the increasing frequency of emerging mycoses in warm-bodied vertebrate systems, including humans, requires a need to challenge common conventions about how diseases operate, how hosts respond, and how these systems could be managed to increase probability of recovery in host populations.

First Report of the Bat Tick Carios kelleyi (Acari: Ixodida: Argasidae) From Vermont, United States.

The soft tick Carios kelleyi (Cooley and Kohls, 1941) is an ectoparasite of bats that can harbor bacteria known to cause disease in humans, such as Rickettsia spp., Bartonella spp., and relapsing fever Borrelia spp. Human-tick encounters may occur when bats occupy attics or similar dwellings with access points to human-inhabited areas. During May 2021, a partially engorged adult female C. kelleyi was collected from a Vermont home with an attic that was being used as a roost by big brown bats, Eptesicus fuscus (Chiroptera: Vespertilionidae). The source of the blood in the tick was the domestic dog, Canis lupus familiaris. Subsequently, eight C. kelleyi larvae were collected from a rescued E. fuscus adult. This is the first report of a soft tick species from Vermont and it is unknown how long C. kelleyi has been present in this state. Reports of C. kelleyi are on the rise across the northeastern United States but the implications for the health of humans, domestic animals, and bats in northern New England remain unclear. Bat management plans should consider the importance of bat exclusion in preventing tick encounters with members of the household and should include a tick monitoring component if bats are evicted.