White Nose Syndrome: Winter is Coming

Aliases: white-nose syndrome, WNS

Unless they directly endanger humans (i.e. avian flu), wildlife diseases don’t often get much press. This is shortsighted; even if we are immune to the illness, our welfare is intimately linked to that other animals. White-nose syndrome (WNS), a fungal disease that is decimating bat populations in the northeastern US and Canada, is an excellent example of the wide-ranging effects of wildlife diseases.

Since its discovery in eastern New York State in 20072, confirmed cases of WNS have been found in 25 US states and 5 Canadian provinces3, reaching as far south as Mississippi2. The fungus that causes WNS, aptly named Pseudogymnoascus destructans, thrives cold and humid environments, such as caves and mines, where bats commonly hibernate2 (these areas are called hibernacula). Consequently, hibernating bat species are the most affected by WNS. To date, WNS has killed more than 5.7 million bats in northeastern North America1, and has caused bat population declines of approximately 80% in the northeastern US3.

But hibernacula aren’t the only things that WNS will leave barren. WNS typically affects long-lived bat species, which only produce a single offspring (aka pup) per year. This means that the hard-hit bat populations will be slow to recover and build back up to their former size. The severe drop in bat numbers will not only affect natural ecosystems, but also profoundly impact agriculture. Bats are fantastic insect predators, and they are the biggest consumers of many agricultural pests. In fact, bats provide an estimated $4-50 billion worth of insect pest suppression a year3, so their absence could affect everything from crop yield to food prices.

white nose syndrome
Killer cuddling.

Cause: WNS is caused by P. destructans infection in the muzzle, ears, tail and wings of bats2,3. Although the transmission of WNS is not well understood, it is thought to be transmitted directly from bat to bat during hibernation, and possibly by humans who carry the fungus out of infected hibernacula on clothing and equipment. There’s good, bad, and really bad news about WNS’s range. The good news is that of the more than 20 hibernating bat species inhabiting the US and Canada, only 7 species have had confirmed cases of WNS2. The bad news is that two of the affected species are endangered and three more have been detected carrying the fungus, though they had not contracted WNS2. The really bad news is that P. destructans may be a generalist fungus, so all bat species within its range may be at risk5.

Consequence: P. destructans infection causes skin erosion and may result in white fungal growth, though it doesn’t always. It may also result in abnormal behavior during hibernation, such as daytime winter flights, when temperatures are at or below freezing, movement toward and clustering near hibernacula entrances, and death2,3. These behaviors may deplete the affected bat’s fat stores and cause emaciation3. Although mortality rates vary by site and species, it can be as high as 100%2.

Cure: While research exploring possible treatments is underway4, there is currently no cure for WNS. In the meantime, the US Fish and Wildlife Service is trying to combat its spread; it has put a voluntary moratorium on caving in infected states2.

References

1. About white-nose syndrome. White-Nose Syndrome.org Web. 7 July 2014. https://www.whitenosesyndrome.org/about-white-nose-syndrome

2. Frequently Asked Questions. White-Nose Syndrome.org Web. 6 July 2014. https://www.whitenosesyndrome.org/faqs

3. White-nose syndrome. National Wildlife Health Center. 29 May 2014. Web. 6 July 2014. http://www.nwhc.usgs.gov/disease_information/white-nose_syndrome/

4. White-nose syndrome. US Fish & Wildlife Service. June 2014. Web. 7 July 2014. https://www.whitenosesyndrome.org/sites/default/files/resource/white-nose_fact_sheet_6-2014_1.pdf

5. Zukal, J, H Bandouchova, T Bartonicka, H Berkova, V Brack, J Brichta, M Dolinay, KS Jaron, V Kovacova, M Kovarik, N Martínková, K Ondracek, Z Rehak, GG Turner, & J Pikula. White-nose syndrome fungus: a generalist pathogen of hibernating bats. PLOS One, 9(5), e97224.

Image source: Wikimedia Commons, http://commons.wikimedia.org/wiki/File:Hibernating_bats_(5600306079).jpg

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Suzi Claflin

I am a postdoctoral fellow studying chronic disease epidemiology.

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