Within Five Years, a Strange Disease Destroys Bat Populations

First identified in a New York cave in February 2006, White nose syndrome (WNS) has since devastated over one million bats in ten different northeastern U.S. states (including our very own Massachusetts), and continues to contribute to a decline in bat populations of unprecedented proportions. Likened to such mysterious phenomena as colony collapse disorder in bee colonies and chytridiomycosis in amphibians, WNS has struck rapidly and elusively, and currently poses the greatest threat to bat populations ever encountered. WNS derives from a fungus of the genus Geomyces, and affected bats can be identified by a characteristic white fungal ring that forms around their nose, mouth, and ears.

A little brown bat (Myotis lucifugus) with white fungal growth on its muzzle, symptomatic of White nose syndrome.

The fungus thrives in cold, damp conditions, and thus typically infects the bats during their most vulnerable period: hibernation. However, it is unclear if the fungus is the actual cause of the disease, or if instead it is an opportunistic infection (one that takes advantage of a compromised immune system). The bats expend additional energy when combating an infection, and if this occurs during hibernation, an ailing bat will deplete its fat stores quickly. In turn, the bat is susceptible to pneumonia, starvation and/or exposure, and will consequently die. And because bats colonize in enormous numbers (some hibernaculums house several thousand bats), the disease is spread easily and rapidly. Some losses are reported to exceed 90% of an affected colony’s population.

Since WNS’s discovery, little progress has been made on its understanding or treatment, and it continues to spread and reduce colonies across the U.S. Moreover, bat populations are not expected to recover readily, since impacted species have long life spans and low birthrates. One particular species, the Indiana bat (Myotis sodalis), is already endangered, and further complications from WNS threatens their very existence.

An Indiana bat (Myotis sodalis), whose populations are threatened by White nose syndrome, pesticides, and human deforestation.

This alarming trend has tremendous implications for humans as well– bats are one of our most valuable agricultural assets, and serve an important role in controlling insect populations. A single bat can consume nearly its own body weight in insects each night. If bat populations decline, farmers will have to resort to using more insecticides and other tactics to protect their crops, which would be costly and environmentally destructive. Additionally, some of the bat species dine on mosquitoes and other pathogen-bearing insects, thereby decreasing disease transmission. Despite efforts by various conservation agencies, WNS remains a huge concern for a number of species and will undoubtedly disturb our delicate ecological balance. Greater awareness and investigation of this problem is absolutely necessary for its resolution.

Notable research at BU and additional information on WNS in bats can be found here.

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