Michelle Verant discusses new research around the early detection and management of white-nose syndrome. The full article, Determinants of Pseudogymnoascus destructans within bat hibernacula: implications for surveillance and management of white-nose syndrome is available in Journal of Applied Ecology.

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Myotis lucifugus affected by white-nose syndrome. Photo credit: A. Hicks

Fungal diseases are on the rise and threatening human health and biodiversity on a global scale. Amphibians, bats and even snakes are being affected with some populations crashing at alarming rates. Combating fungal diseases is not as easy task, as many fungal pathogens can persist within the environment and don’t require a sufficient density of hosts to sustain infections in new individuals. This characteristic of a pathogen increases the chance that a disease will drive a host species to extinction. Therefore, understanding factors that regulate pathogens in the environment and how these environmental reservoirs relate to infections in host species is important for disease surveillance and control.

White-nose syndrome is an emergent fungal disease of hibernating bats that has caused severe population declines of several North American bat species and threatens some with regional extirpation or extinction.  The fungus that causes WNS, Pseudogymnoascus destructans (Pd), is a cold-loving fungus that persists year-round in underground locations and other roosts used by hibernating bats. Although bats are able to clear infections and recover from WNS over the summer, these environmental reservoirs can serve as sources of infection for bats when they return to these sites for hibernation. The presence of the fungus in the environment of a hibernaculum can also be used to identify populations of hibernating bats with WNS. However, environmental sampling strategies and disease control efforts are hindered by an incomplete understanding of the factors that regulate the distribution of Pd within a hibernaculum.

The recent paper, Determinants of Pseudogymnoascus destructans within bat hibernacula: implications for surveillance and management of white-nose syndrome, used model selection to test hypotheses describing the presence-absence and abundance of Pd in environmental substrates and on bats within hibernacula at different stages of WNS. The research team collected data from various environments and bat species within six caves and mines in the eastern US over multiple years. This research demonstrated that the probability of detecting Pd in the environment increased over time and was higher in sediment compared to wall surfaces. When compared to sampling bats, first detection of Pd in the environment at a newly infected hibernaculum lagged up to one year after first detection on bats in that site. Myotis lucifugus and bats with visible signs of WNS had the highest prevalence and abundance of Pd.

Bet on bats! These results indicate that bats are primarily responsible for introduction of Pd into a hibernaculum and should be prioritized for sampling, if available, to facilitate early detection of Pd at a site. Targeting M. lucifugus and bats with visible signs of WNS, including fluorescence of wing membranes under ultraviolet light, can further increase detection probabilities. Alternatively, environmental substrates within hibernacula, particularly sediment, can be sampled year-round for site-level surveillance. However, first detection of Pd in the environment may lag behind first infection in bats at the site.

There’s a fungus among us! Accumulation and persistence of Pd in sediment of hibernacula suggests that control efforts for WNS should consider risks of sustained sources of infection from environmental reservoirs. Modifications of hibernacula to reduce loads of Pd on bats and in the environment have been considered. One strategy involves making a hibernaculum colder based on observations of increased survival and lower infection intensities of Pd on bats hibernating in colder conditions. In the laboratory, temperature has been shown to strongly regulate growth of Pd, but in this study, temperatures at a sampling location only had marginal effects on the distribution of Pd in the environment. Thus, other factors are likely to be more important for regulating Pd in the environment and reducing infection risks for hibernating bats.

Read the full article, Determinants of Pseudogymnoascus destructans within bat hibernacula: implications for surveillance and management of white-nose syndrome in Journal of Applied Ecology.

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