So without further ado, here's one of the nastiest little germs that has flared up recently: the scourge of cave dwelling Chiropterans, White-nose Syndrome (WNS).
Figure1: Little brown bat; close-up of nose with fungus, New York, Oct. 2008.
Photo courtesy Ryan von Linden/NY Department of Environmental Conservation.
Photo courtesy Ryan von Linden/NY Department of Environmental Conservation.
In short, while bats hibernate the fungal pathogen somehow manages to subvert their immune defenses (somehow the fungal hyphae that penetrate the skin don't elicit an inflammatory response), and infect their skin - especially on the muzzle. Infection often causes them to come out of hibernation early (I would imagine this is a consequence of their taxed energy reserves and/or the infection triggering some sort of "wake up and turn on your immune system!" response, though that's purely speculation on my part) and seems to almost always result in death.
It is still unclear whether the sole cause of the disease is Geomyces destructans or if there might be a third factor facilitating the progression and spread of WNS. Initially researchers were cautious -- the G. destructans infections could have been a symptom of some other less visible disease (e.g. some sort of bat immunodeficiency virus or a build-up of some new environmental toxin) or the primary cause. Recent work suggests the fungus is likely the culprit, but folks are still working to rule out other factors. From this page on the fungal pathogen ...
Another set of experiments is underway to try to prove that G. destructans is the actual cause of death. Koch's postulates have not yet been fulfilled, so it has not been strictly proven that Geomyces destructans causes death in bats. The histopathology has been well documented, and it is very clear that this fungus is the causal agent of white-nose syndrome cutaneous infection. So far, the correlation between the presence of the fungus and bat death is quite substantial, but *cause* has not yet been proven.Even without knowing the causal details one thing is clear: WNS is decimating bat populations in the northeast. Once a hibernaculum is infected, winter mortality rates seem to be very high: from near 80% up to 97% in some locations. Even worse, it's possible fungal spores can persist in these caves across multiple winters, and the list of infected hibernacula seems to be increasing in number and extending into previously uninfected areas (click here for a map from this page).
To get a better feel for the real severity of this disease, here's a video by Gerrit Vyn based on his experiences following field researchers during the winter of 2008-2009.
White-nose Syndrome is a mysterious disease that is currently decimating bat populations in the northeastern United States. First observed near Albany, New York in 2006, it had spread as far as Virginia by 2009. Scientists fear this disease could rapidly push an entire group of species to extinction and will trigger unknown ecological consequences. Why the bats are dying remains a mystery.
I accompanied researchers to several caves and mines in New York and Vermont during the winter of 2009 in an effort to document the situation. This piece is a result of that effort and aims to communicate the urgency of the situation to the public and policy-makers and to elicit an emotional response to a group of species that are often disregarded or disliked.
Related Links
- More on the pathogen Geomyces destructans at http://botit.botany.wisc.edu/toms_fungi/may2009.html
- Meteyer et. al. 2009. Histopathological criteria to confirm white-nose syndrome in bats. J Vet Diagn Invest 21:411-414.
- National Speleological Society's WNS web site: http://www.caves.org/WNS
- White-nose Syndrome in Bats: FAQ from the U.S. Fish and Wildlife Service.
- White-nose Syndrome pages at the USFWS, USGS National Wildlife Health Center, USGS Ft. Collins Science Center, and from Bat Conservation and Management, Inc.
- Public Domain photos provided by the U.S. Fish and Wildlife Service at http://www.fws.gov/northeast/wnspics.html
- December 2009 Interview with U.S. Fish and Wildlife's Jeremy Coleman, North Country Public Radio
- A July 2009 article "Coping with White-nose Syndrome" by David J. Thomas is the Arkansas Underground.
- A November 2009 article from the Boston Globe.
- And lots of other information compiled by the caving community at http://www.caves.org/grotto/dcg/white-nose.html
