The fungus that is exterminating bats

Bats, the second most diverse group of mammals, play an important role in mitigating agricultural pests. However, millions of hibernating bats across North America are dying from white-nose syndrome (WNS), a fatal emerging disease caused by the cold-loving fungus Pseudogymnoascus destructans.

SNB is believed to be responsible for a decline of more than 95% in some species and the eradication of entire populations in some regions.

Although WNS was discovered decades ago, there is no practical way to stop the spread of the disease among susceptible bat species, highlighting an urgent need for treatment and prevention strategies.

Lack of understanding of how P. destructans invades host tissue, particularly when bats hibernate, has hampered the development of interventions against WNS.

To help resolve these questions, Marcos Isidoro-Ayaza and Bruce Klein, both at the University of Wisconsin-Madison in the United States, developed a novel immortalized keratinocyte cell line from the brown bat (Myotis lucifugus) and studied the in vivo invasion of P. destructans at different temperatures to mimic hibernation and awakening.

Isidoro-Ayaza and Klein discovered that the fungus uses different strategies to invade the bat’s epidermal cells depending on whether the host is in a state of hibernation (cold and inactive) or in an awake state (warm and active).

During hibernation, when endocytic uptake is inactive in the host, fungal hyphae emerging from germinating spores actively pierce keratinocytes.

Surprisingly, borer hyphae do not activate immune defenses in host cells.

A hibernating bat affected by white-nose syndrome. (Photo: Jonathan Mays)

In contrast, when temperatures are warmer and bats are active, the fungus is internalized by keratinocytes through endocytosis.

Based on these findings, both routes of infection require the epidermal growth factor receptor (EGFR) and the authors of the study have found that blocking EGFR using the drug gefitinib (approved by the US Food and Drug Administration) and anti-EGFR antibodies is able to prevent the entry of P. destructans into host keratinocytes.

The study is titled “Pathogenic strategies of Pseudogymnoascus destructans during torpor and arousal of hibernating bats.” It has been published in the academic journal Science. (Source: AAAS)