New research on fungus/wing damage

[PYoungbaer]

The most recent research findings on bat wing damage caused by Geomyces destructans were just put into a different context by a piece written by the USGS' Paul Cryan:
http://promega.wordpress.com/2010/11/29 ... re-on-wns/

Further, if you take what Cryan et al are saying about the regulatory function of bat wings, and read it in the context of a far broader report on the balance between the body temperatures of mammals keeping a host of fungi at bay, then we may be beginning to learn more about the physiological manner in which Geomyces destructans might be throwing this delicate balance out of kilter, thus leading to WNS.

Here's the other report:
http://www.sciencenews.org/view/generic ... arm_enough

[BrianC]

Both of these articles are indeed good, although the first exemplifies what is happening to WNS infected bats, the second doesn't really give any potential for conclusive reason other than a certain temperature is needed for fungal growth. We know this.

[PYoungbaer]

The U. S. Geological Survey just issued this report to Congress today. It refers to the following published research:
http://www.biomedcentral.com/1741-7007/8/135

USGS Congressional Notification December 15, 2010

Tattered wings: bats grounded by white-nose syndrome’s lethal effects on life-support functions of wings

Madison, Wisconsin – Damage to bat wings from the fungus associated with white-nose syndrome (WNS) may cause catastrophic imbalance in life-support processes, according to newly published research.

This imbalance may be to blame for the more than 1 million deaths of bats due to WNS thus far, proposes Carol Meteyer, a pathologist with the U.S. Geological Survey’s National Wildlife Health Center and a lead author of the research published in BMC Biology.

Physiological problems caused by the novel fungus, may, in fact, represent a completely new disease paradigm for mammals, Meteyer and her colleagues wrote. Other skin infections in mammals due to fungi (ringworm, athlete’s foot) remain superficial and do not invade living tissue---typically they only affect the surface of skin, hair and nails.

Not so for the aptly named Geomyces destructans.

“This fungus is amazingly destructive – it digests, erodes, and invades the skin – particularly the wings -- of hibernating bats,” said Meteyer. “The ability of this fungus to invade bats’ wing skin is unlike that of any known skin fungal pathogen in land mammals.”

The authors examined nearly 200 bats that had died from WNS, and also reviewed the critical function and physiology of bat wings during hibernation. As a result, they propose that G. destructans may cause unsustainable dehydration in hibernating bats, triggering thirst-associated arousals. In addition to the direct damage to the wings that would alter flight control, the erosion and invasion of skin may also cause significant changes in circulation, body-temperature regulation and respiratory function.

Since signs of the disease were first observed in New York during the winter of 2006-07, the fungus has spread through 11 states and 2 Canadian provinces, resulting in the first sustained high-mortality disease affecting bats in recorded history. Biologists assume that as the disease spreads to new areas, cave-hibernating bats in those areas will also be at risk, including some that are endangered.

“The high number of bat deaths and range of species being affected far exceeds the rate and magnitude of any previously known natural or human-caused mortality event in bats, and possibly in any other mammals,” said Paul Cryan, a lead author of the paper and a USGS bat ecologist at the Fort Collins Science Center.

Although the powdery white muzzles of affected bats gave the disease its name, the authors believe that the skin of bat wings is the most significant, though often less obvious, target of the fungus.

The order of bats is called Chiroptera, Greek for “hand-wing,” appropriately named since bat wings are essentially modified arms. Imagine, for a moment, your human hand with its fingers spread apart. Then imagine your fingers are 6 feet long, and the whole skeletal affair is covered with two layers of thin, somewhat transparent membranes attached to the sides of your torso and legs. Sandwiched between the membranes are blood and lymphatic vessels, delicate nerves, muscles and special connective tissues that help you fly and help keep you physiologically healthy.

“The disproportionately large areas of exposed skin that make up bat wings play critical roles in maintaining safe internal body conditions during hibernation,” noted Cryan. “Healthy wings are essential for day-to-day survival, even during winter when bats are mostly just hanging around. Wings damaged by the fungus may not always look so bad to the naked eye, but under the microscope things get ugly fast.”

When Meteyer examined wings of diseased bats microscopically, she discovered wing damage was often so severe that it led her and her colleagues to suggest multiple life-threatening effects on hibernating bats.

“A bat’s wings,” said Meteyer, “are obviously critical for flying, but they also play a vital part in essential functions such as body temperature, blood pressure, water balance and blood and gas circulation and exchange.”

Healthy bats occasionally rouse themselves from hibernation, probably to change roosts, drink, mate and even overcome sleep deprivation, biologists think. But bats afflicted with WNS arouse much more often. In fact, a characteristic of hibernation sites with WNS is daytime flights of affected bats outside caves.

“The prevailing hypothesis is that daytime winter flight is a last-ditch effort for starving bats to find insect prey,” Cryan said. “What we propose is that thirst, and maybe not always hunger, is driving these arousals. Unusual thirst during hibernation may result from water essentially leaking out of wings damaged by the fungus.”

Anecdotally, bats at hibernacula affected by WNS are sometimes seen flying over and drinking from water surfaces or eating snow, highlighting the plausibility of this hypothesis, the authors noted.

Hibernation itself is one reason this emerging disease is so successful. During hibernation, a bat’s immune function and metabolism are dramatically reduced, and body temperature drops significantly. Also, some of the worst-affected bat species roost in humid areas in dense clusters to conserve energy and decrease moisture loss.

“These ideal environmental conditions, combined with the hibernating bat’s suppressed immune system, likely allow the fungus to invade body tissues for nutrients without resistance, making the hibernating bat a most accommodating host for this new disease,” Meteyer said.

The researchers compare the ability of this novel bat fungus to destabilize internal functions with the electrolyte imbalance that occurs in frogs infected by chytrid fungus, which, like G. destructans, is a novel disease of vertebrates. Chytrid infection impairs the ability of frog skin to regulate hydration and internal equilibrium, causing electrolyte imbalance and ultimately cardiac arrest.

“The skin plays a critical role in the physiology of both amphibians and bats,” Meteyer said. “We suggest that a similar, but less subtle, disturbance could be occurring in the wing membranes of bats with WNS.”

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[BrianC]

http://www.biomedcentral.com/1741-7007/8/135

Lots of hypothetical information here, But as it states, it is all opinion. I'm not so sure that their opinion stating that no secondary bacterial infection is considered would be correct. I would( hypothetically of course) have to think that a bacterial concern would be primary. The article states that skin infections don't affect the epidermis as far as eating it. I will strongly disagree, in that when I get athletes foot, It does degrade through my skin. I don't know where they get that information, possibly because they have been lucky enough not to have experienced it. The athletes foot fungus occurs from a constant amount of moisture with obvious nasty contact, with low or no oxygen available to oxidize the fungus.

[PYoungbaer]

Brian, this isn't just opinion, but peer-reviewed research. It has been a consistent finding with G.d. that it does not invade organs, respiratory systems (other than superficially), and that bacteria are not implicated in WNS. The primary point here (their primary hypothesis) is that WNS is disrupting the physiological balance for the bats' health that is provided by properly functioning wings, including the vascular cooling effect.

[John Lovaas]

..when I get athletes foot, It does degrade through my skin...

That's right- it does degrade your skin- your epidermis.

http://en.wikipedia.org/wiki/File:Skin.jpg

Geomyces destructans eats living dermis. The athlete's foot fungus does not. If your 'athlete's foot' is actually eating into your own living dermis- you don't have athlete's foot, and ought to see a doctor ASAP.

[BrianC]

Brian, this isn't just opinion, but peer-reviewed research. It has been a consistent finding with G.d. that it does not invade organs, respiratory systems (other than superficially), and that bacteria are not implicated in WNS. The primary point here (their primary hypothesis) is that WNS is disrupting the physiological balance for the bats' health that is provided by properly functioning wings, including the vascular cooling effect.

Peter,at the beginning of the article it states it is an opinion. I just reiterated this. All through the review it claims all is hypothetical. I want to show exactly why cavers are so considered bad guys for spreading WNS. The review was well organized and written for the purpose of securing funds for further research. No actual facts have been expressed other than observations. The entire reason cavers have been excluded from caves is hypothetical rhetoric. rhetoric...rhetoric...

[BrianC]

..when I get athletes foot, It does degrade through my skin...

That's right- it does degrade your skin- your epidermis.

http://en.wikipedia.org/wiki/File:Skin.jpg

Geomyces destructans eats living dermis. The athlete's foot fungus does not. If your 'athlete's foot' is actually eating into your own living dermis- you don't have athlete's foot, and ought to see a doctor ASAP.

Tinactin works just fine, but when I get athletes foot, it does get through my epidermis, could be from scraping it?, it doesn't appear to grow from the nutrition available through digesting my skin though, or I think it would cause excretions, and those excretions would grow into a visible fungus. In this case I believe it would be considered bacterial, as many bacteria could thrive on tissue and CO2 for nutrition? This is all opinion of course, once you review this, it will be pier reviewed.

[BrianC]

In order for the fungus to eat the bats skin to be factual, the fungus would have to be using the skin as food energy?

[John Lovaas]

In order for the fungus to eat the bats skin to be factual, the fungus would have to be using the skin as food energy?

Yes.

[wyandottecaver]

hmm,

interesting. it sounds like a viable theory but just because its peer reviewed dont mean its not crap. (not saying this is) Just remember its publish or perish out there in acadamia and WHAT you publish is often secondary to how many "hits" or references your article generates.

The questions that come to my mind are:

I have seen several bats with wing damage that *seemed* ok. Since we havent really followed bats with wing damage through time though, both I and the authors are just guessin, albiet their guesses are probably better

Many hibernacula I have seen have free water available and we know about regular arousal of bats. Thus "leakage" might influence how much they drink, but unless its really severe, does leakage based dehydration alone have that big an impact?

We have often seen better survival in very DRY low humidity cases. One would think hydration based mortality would be higher in those sites....

Finally they are outright incorrect in their "paradigm shift" about fungi. blastomycosis and several other fungal infections DO affect mammals (including humans) past superficial dermis infections...to the point of sometimes killing them.

Overall, it seems like good science..just not ready to buy it lock stock and barrel yet.

[Batgirl]

I find this to be very interesting research. It seems the scientists are getting much closer to finding the cause of death. This is wonderful. Once we know the cause of death, then we can find a way to treat it. I also find it interesting that the research says that this fungus is similar to Chytrid. How close? What are the differences in the fungi? If dehydration due to loss of water/gas balance in the wing membranes may be the primary reason for dehydration which leads to a reduction in their immune response, then is it possible to provide a means for bats to obtain the water they need while hibernating? It also says that the higher the humidity, the more the conida is amplified. What happens if humidity levels in caves were changed? How does this affect other cave biota? What are the lowest humidity levels a bat can sustain and still hibernate?

[wyandottecaver]

well remember there are other "good" papers about cause of death out there.
1) GD inhibits digestion of chitin thus bats both cant get overwinter energy from chitin remains in their gut and they cant empty their gut to feed in spring.
2) GD invades and establishes in a "passive" immune system and causes the bats to initiate a "active" immune response (costing energy, (like a fever?)) thus starving them.
3) GD causes metabolic collapse through the effects of tissue damage..like dehydration.

The only similarity to chytrid they noted was that the presumed effect was one of interfering with metabolic processes.

The immune supression was not a function of dehydration. Its presumed that the passive state of bat immune systems (normal) allows GD to get its foothold. Most hibernacula contain at least some free water either in-cave or nearby.

GD has occured in caves with widely varying humidity levels. Lower humidty seems to slow the progression but not stop it. (counter to a dehydration theory I would think) Bats dont sustain humidity, its a function of the cave. Humidity levels in midwest hibernacula tend to vary between about 60-90 percent with 70-80 being common.

[PYoungbaer]

Wyandottecaver,

This is primarily a USGS piece, not an academia one, and, knowing the individuals involved, I doubt that this is their motivation.

That said, I also wondered about the availability of water issue. I'd love to hear some discussion of that point from the researchers (and I will ask them). Perhaps the availability of water becomes moot once a certain level of wing damage is reached.

Also, UV light shows damage from Geomyces destructans on wings well before it's visible to the naked eye, and much more damage then what is seen even when the naked eye sees it.

Batgirl,

There is clearly a correlation between WNS and both temperature and humidity, as well as species preference. I've seen several instances in the field where different bat species choose particular cave passages, or locations within the same cave, based on microclimate. Look at the stark differences we saw in Hellhole, where the Virginia Big Eareds roosted at 32 degrees F. and 70% humidity, and were unaffected, but the Little Browns, Indianas, and Tricolors were in areas of 100% humidity and 45 degrees F.

[Batgirl]

I remember the early research about the lack of Chitin in bats stomachs, but that apparently is not the root of the problem, but another physiological symptom. I pulled up the full text of the paper and re-read it again. It seems to me that the scientists may be saying the real problem is the vascular circulatory interruption of their wing membrane which then results in dehydration and starvation. I think that is pretty significant. I would be interested to know what physiological similarities exist between the bats that are infected in Europe and here? I am sure there is some science being conducted on this. Peter, what do you know? Why are the bats in Europe surviving, but not here?

As far as its similarity to Chytrid goes, the full text goes into great detail about the similarities between the two fungi.

Recent studies demonstrated that infection by B. dendrobatidis impairs the ability of frog skin to regulate hydration and homeostasis, causing electrolyte imbalance and ultimately cardiac arrest [49]. Like WNS in hibernating bats, chytridiomycosis has caused precipitous declines among multiple species of wild amphibians. Additional similarities between skin infections of hibernating bats by G. destructans and of amphibians by B. dendrobatidis include the critical role the skin plays in the physiology of both hosts, as well as a lack of host inflammatory response to both cutaneous pathogens. The lack of inflammation in frogs is due to the superficial nature of infection. The lack of inflammation in bats is likely to be the result of natural downregulation of the mammalian immune system during hibernation [11-14]. A dramatic difference between these host-pathogen relationships is the limited nature of epidermal invasion by B. dendrobatidis in amphibians (Figure 3) compared with the severe erosion, invasion and destruction of living tissues by G. destructans (Figures 1c and 2a).

Despite the relatively minor visible changes associated with B. dendrobatidis infections, it is still a lethal physiological pathogen because of the role that the amphibian skin plays in the regulation of hydration and blood chemistry. We suggest that a similar, but less subtle, perturbation could be occurring in the wing membranes of bats with WNS. Damage to bat wings caused by G. destructans is often more extensive than can be appreciated with the naked eye. It took researchers decades to establish the causal link between skin infection by B. dendrobatidis and mortality in amphibians. A contributing factor to this delay was the challenge of demonstrating the potential significance of what appeared to be a superficial infection, and then documenting the magnitude of its physiological consequences. In addition, this novel fungal pathogen of amphibians belonged to a genus that was previously known only as a saprophyte that did not infect vertebrates - it was a new disease paradigm. Infection of bat wings by G. destructans, also a member of a genus typically defined as saprophytes, may similarly represent a completely new disease paradigm for mammals.

They are both similar in their mission - both cause skin infection and hydration imbalance. I am not a biologist, so forgive me if this is a stupid question. But I am wondering whether spores can adapt/change/morph? Perhaps like a bacterial flu strain? or are they fixed? Since both fungi are members of the same genus, could G. destructans have adapted by or because of the Chytrid fungus? That's what I meant when I asked what the similarities were and how close.

These new fungi didn't just appear out of nowhere. Chytrid was first discovered by modern man in Australia and Panama, but has been around for thousands of years. Perhaps G. destructans is the same and we just never new anything about it? Why now? What has changed climatically to cause they paleo-fungi to re-emerge?