Winter/Spring 2012 Aesculapian Magazine - University of Georgia ...

The fungus’s “perfect environment”
First observed in the United States just five years ago, the
fungus associated with White-Nose Syndrome (WNS) appears as
white fuzz on the faces and wings of hibernating bats and rouses
them prematurely from their winter torpor. Confused, sick—and
possibly irritated by the fungus — they take wing, using up scant
energy reserves when they should be holed up until warmer
temperatures and ample food sources emerge in the spring. Their
emaciated corpses, first found by recreational cavers and more
recently by state wildlife biologists who are monitoring caves,
often end up here at SCWDS, a federal-state cooperative housed
in the University of Georgia’s College of Veterinary Medicine.
While it’s difficult to confirm the fungus’ source in the
United States, Keel says the best theory at present is that it was
brought from Europe by cavers or tourists who visited Howe
Caverns near Albany, NY. It was there in 2006 that a caver first
saw and photographed some white-nosed bats, and discovered
several others dead on the cave floor.
“Unlike most fungal pathogens, this one is cold-loving; it
grows at temperatures between 40 and 50 degrees,” said Keel.
“Unfortunately, its introduction into a cave means that it had the
perfect environment to thrive and infect bats. Bats actually cool
down to ambient temperatures during hibernation, and the fact
that they have minimal body heat could be important to the
fungus’s ability to infect them. It’s so sensitive to heat that it might
not be able to grow on a warmer animal.”
The syndrome has so far been confirmed in nine bat species,
including two (the Indiana and the gray bat) that are already
endangered. The mortality rate in some colonies has been
greater than 90 percent — Keel calls WNS “the most devastating
infectious wildlife disease we’ve ever seen.” And because many
bats produce only one “pup” a year, scientists now fear that
several once-common species may suffer a major population
collapse that could wipe them out entirely in some regions.
That’s a serious concern given the critical role that bats
play as insect predators, consuming half their weight or more
in mosquitoes and other bugs each night, many of which would
otherwise eat or
damage crops. A new
analysis, published
in the April 1, 2011,
issue of Science,
estimated the value
of bats’ pest-control
services in the United
States alone at more
than $3.7 billion
a year. The report
also warned that the
United States will see
“noticeable economic
losses in the next four
to five years as a result
of WNS and other
emerging threats to
bat populations.”
In addition to
eating millions of
Kevin Keel,
a veterinary
pathologist at
SCWDS.
insects, bats also disperse seeds and pollinate some important
agricultural crops, including bananas, vanilla beans, peaches,
and avocados. Their waste, called guano, provides vital nutrients
in cave habitats. And composted guano is a powerful organic
fertilizer.
Because little is understood about how WNS actually infects
bats, officials in some states have closed caves to recreational
cavers, who are almost certainly helping to spread the fungus. But
its spread to new states suggests that the bats themselves transmit it
— and not just among their own colonies but to other bat species and
hibernacula. Still, there are anomalies. “Bats often hibernate in huge
colonies ear-to-ear with other species,” said Keel. And yet, some
species — such as the federally listed Virginia and Ozark big-eared
bats, which have been exposed — haven’t shown symptoms.
Photo By PAUL EFLAND/UGA
The samples included
this tri-colored bat from
Kentucky.
Justin Brown, a
SCWDS research
scientist, unpacks
dead bats sent for
testing.
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The University of Georgia College of Veterinary Medicine