Yes, G. destructans has been known for
some time to cause the fungal outbreaks seen on
infected bats, but the real question was whether
the fungus caused this in otherwise healthy bats,
or whether it was an adventitious infection that
took hold because the bats' immune systems were
otherwise compromised (due to insecticide
residues, environmental stresses, other disease,
etc.). This study used normal, healthy bats and
found that they contracted WNS from the fungus,
which is why they say it has been proven to be
the primary cause. This is an important
distinction to make, because it narrows down the
search for methods of prevention and/or cure.
Mark Minton
At 09:17 AM 10/27/2011, [email protected] wrote:
From what I read below, I don't see that the
study confirmed G. destructans as entirely
responsible for WNS. First two caveats: I am
not a bat biologist and I did not read the article in Nature2.
That being said, WNS has at least two symptoms,
the white fungal growth on and the death of
bats. Syndromes typically are thought to have
multiple causes. It was my understanding that
the white fungal growth had already been
identified as G. destructans. This study does
confirm bat to bat transmission of the
fungus. There have been a number of bats found
by mist netting with lesions from the fungus
that did not die. However, it is my
understanding that in North America, there is a
difference between the dead bats and the bats
that survive infection from the fungus and that
is that the dead bats have no chitinase
producing bacteria in their guts and that bats
that survive the fungus do. If that is the
case, then there may well be multiple causes of
WNS, the fungus as an irritant that wakes the
bats from torpor, and whatever is killing off
the chitinase producing bacteria. If there were
not the low body weight from insufficient
protein digestion, is that enough to cause
death? According to this study, in 102 days it
resulted in no mortality. That seems like a
long time without any mortality. I think it is
unfortunate that the study was not run as long
as the northeastern hibernation season. It
seems to me that saying that the culprit has
been found without being able to attribute all
of the symptoms is overconfident, premature, and
smacks of assuming one's conclusions. This
study only accounted for one of the symptoms of
WNS and not the one I think most of us think is the most important.
Philip Moss
http://www.nature.com/news/2011/111026/full/news.2011.613.html
Culprit behind bat scourge confirmed
A cold-loving fungus is behind an epidemic decimating bat populations
in North America.
By: Susan Young
Researchers have confirmed that a recently identified fungus is
responsible for white-nose syndrome, a deadly disease that is sweeping
through bat colonies in eastern North America.
The fungus, Geomyces destructans, infects the skin of hibernating
bats, causing lesions on the animals' wings and a fluffy white
outgrowth on the muzzle. When white-nose syndrome takes hold of a
hibernating colony, more than 90% of the bats can die (see Disease
epidemic killing only US bats). The disease was first documented in
February 2006 in a cave in New York, and has spread to at least 16
other US states and four Canadian provinces.
The culpability of G. destructans for this sudden outbreak was thrown
into question when the fungus was found on healthy bats in Europe,
where it is not associated with the grim mortality levels seen in
North America1. Some proposed that the fungus was not the primary
cause of the catastrophic die offs, and that another factor such as
an undetected virus must bt be to blame. But a study published today in
Nature2 reveals that G. destructans is indeed guilty.
"The fungus alone is sufficient to recreate all the pathology
diagnostic for the disease," says David Blehert, a microbiologist at
the National Wildlife Health Center in Madison, Wisconsin, and senior
author on the report.
Bat-to-bat spread
Blehert and his colleagues collected healthy little brown bats (Myotis
lucifugus) from Wisconsin, which is well beyond the known range of
white-nose syndrome. They infected the bats by direct administration
of G. destructans spores to the skin or by contact with infected bats
from New York. By the end of the 102-day experiment, the tell-tale
white fungus was growing on the muzzles and wings of all of the
directly infected Wisconsin bats and 16 of the 18 exposed to sick
bats.
This is the first experimental evidence that white-nose syndrome can
be passed from bat to bat, and is very worrying from a conservation
point of view because bats huddle together in large numbers in caves
and mate in large swarms, says Emma Teeling, a bat biologist at
University College Dublin in Ireland. "If a bat has this fungus on
them, it's going to spread quickly throughout the population," says
Teeling, who was not involved with the study. "It's like a perfect
storm."
The infected Wisconsin bats did not die during the experiment, which
may be due to the limited timeline of infection, the authors suggest.
Although the study does not directly show that a healthy bat will die
from infection with G. destructans, the results did show that the
fungus alone was sufficient to cause lesions diagnostic of white-nose
syndrome to form on previously healthy bats, indicating that the
fungus is the cause of the deaths so often associated with white-nose
syndrome in the wild.
To stop a scourge
Since it first appeared, white-nose syndrome has behaved like a novel
pathogen spreading from a single origin through a naive population,
says Jonathan Sleeman, director of the National Wildlife Health
Center, who was not involved in the study. Proof that G. destructans
is the primary cause of white-nose syndrome will "help us focus our
actions or management efforts into the future", he says.
Although little can be done to control the spread of the disease
through bat-to-bat transmission, the US Fish and Wildlife Service
(FWS) has asked people to stay out of caves in and near affected
areas, and has closed some caves on agency-managed land.
On 21 October, the FWS announced that up to $1 million in funding will
be made available for research on white-nose syndrome. Projects
covering topics such as how the fungus proliferates within caves and
mines, and the potential for biological means or environmental
manipulations to improve bat survival, are among the service's top
priorities.
*
References
1. Puechmaille, S. J. et al. Trends Ecol. Evol. 26, 570-576 (2011).
2. Lorch, J. M. et al. Nature doi:10.1038/nature10590 (2011).
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