Long-Term Persistence of Pseudogymnoascus destructans, the Causative Agent of White-Nose Syndrome, in the Absence of Bats

Abstract

Wildlife diseases have been implicated in the declines and extinctions of several species. The ability of a pathogen to persist outside its host, existing as an "environmental reservoir", can exacerbate the impact of a disease and increase the likelihood of host extinction. Pseudogymnoascus destructans, the fungal pathogen that causes white-nose syndrome in bats, has been found in cave soil during the summer when hibernating bats had likely been absent for several months. However, whether the pathogen can persist over multiple years in the absence of bats is unknown, and long-term persistence of the pathogen can influence whether hibernacula where bats have been locally extirpated due to disease can be subsequently recolonized. Here, we show that P. destructans is capable of long-term persistence in the laboratory in the absence of bats. We cultured P. destructans from dried agar plates that had been kept at 5°C and low humidity conditions (30-40% RH) for more than 5 years. This suggests that P. destructans can persist in the absence of bats for long periods which may prevent the recolonization of hibernation, sites where bat populations were extirpated. This increases the extinction risk of bats affected by this disease.

Invasion Dynamics of White-Nose Syndrome Fungus, Midwestern United States, 2012–2014

“…The widespread occurrence of P. destructans in the environment at this time may have contributed to higher prevalence among bats because most bats clear infections during the summer, when their body temperature is too high for P. destructans growth ( 7 , 11 ). Long-term persistence of P. destructans in the absence of bats ( 8 , 12 ) suggests that an environmental reservoir of P. destructans may contribute to WNS persistence, as occurs for other diseases, such as cholera ( 13 ). …”

Host persistence or extinction from emerging infectious disease: insights from white-nose syndrome in endemic and invading regions

“…The pathogen that causes WNS, Pseudogymnoascus destructans, is a cold growing fungus that infects bats' skin during their hibernation period [19][20][21], and can persist in the environment for long periods of time in the absence of bats [22,23]. The resulting infections lead to the disruption of homeostatic processes and ultimately mortality [24,25].…”

Resistance in persisting bat populations after white-nose syndrome invasion

“…Mortality from WNS occurred 70-100 days after infection in laboratory studies, and in the field mortality peaks between January and April in the northeast USA, when pathogen loads on bats are highest [28,29,32]. After bats emerge from hibernation in the summer, they clear P. destructans from their skin surfaces, but the fungus can persist in hibernacula environments for long periods of time in the absence of bats, owing to its likely origins as a soil saprotroph [33][34][35][36][37]. Therefore, when bats return to hibernacula in the fall, P. destructans can continually re-infect bats [31,32,34].…”

“…After bats emerge from hibernation in the summer, they clear P. destructans from their skin surfaces, but the fungus can persist in hibernacula environments for long periods of time in the absence of bats, owing to its likely origins as a soil saprotroph [33][34][35][36][37]. Therefore, when bats return to hibernacula in the fall, P. destructans can continually re-infect bats [31,32,34]. WNS appears to be endemic to Eurasia [38,39], and bats in Asia bats have lower levels of P. destructans infection, which may indicate increased resistance [15].…”