Development of a multi-year white-nose syndrome mitigation strategy using antifungal volatile organic compounds

Abstract

Pseudogymnoascus destructans is a fungal pathogen responsible for a deadly disease among North American bats known as white-nose syndrome (WNS). Since detection of WNS in the United States in 2006, its rapid spread and high mortality has challenged development of treatment and prevention methods, a significant objective for wildlife management agencies. In an effort to mitigate precipitous declines in bat populations due to WNS, we have developed and implemented a multi-year mitigation strategy at Black Diamond Tunnel (BDT), Georgia, singly known as one of the most substantial winter colony sites for tricolored bats (Perimyotis subflavus), with pre-WNS abundance exceeding 5000 individuals. Our mitigation approach involved in situ treatment of bats at the colony level through aerosol distribution of antifungal volatile organic compounds (VOCs) that demonstrated an in vitro ability to inhibit P. destructans conidia germination and mycelial growth through contact-independent exposure. The VOCs evaluated have been identified from microbes inhabiting naturally-occurring fungistatic soils and endophytic fungi. These VOCs are of low toxicity to mammals and have been observed to elicit antagonism of P. destructans at low gaseous concentrations. Cumulatively, our observations resolved no detrimental impact on bat behavior or health, yet indicated a potential for attenuation of WNS related declines at BDT and demonstrated the feasibility of this novel disease management approach.

Fig 1. Bat populations at Black Diamond Tunnel and Stumphouse Tunnel from 2010 to 2016.

Yearly tricolored census at Black Diamond Tunnel in Clayton, Georgia, and Stumphouse Tunnel in Oconee County, South Carolina. The red line indicates when WNS was first detected. Percentages indicate the percent decline at each tunnel since WNS was detected.

Fig 2. Diagram of the infrastructure at Black Diamond Tunnel.

Fig 3. Aerosolizer acoustic output.

Acoustic output of a jet nebulizer (a), blower aerosolizer (b), and L-30 rotary atomizer (c). The x-axis is time and the y-axis is frequency in kHz. Amplitude is represented on a spectrum with louder measurements being darker. The green bars identify the common range P. subflavus uses for echolocation (45–90 kHz).

Fig 4. Comparison of bat population censuses at Black Diamond Tunnel and Stumphouse Tunnel.