# Fungus deadly to frogs may bode ill for humans



## Sharkdude (Nov 9, 2009)

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Fungus deadly to frogs may bode ill for humans 
Posted at 11:21 PM on Monday, May. 10, 2010
By Mark Grossi / The Fresno Bee
Scientists have been alarmed for years about a mysterious fungus that wipes out frogs around the globe -- even in the wildlife sanctuaries of Yosemite and Sequoia-Kings Canyon national parks.

The fungus blitzes frog populations, allowing little chance for natural defenses to protect the amphibians, new research shows. Now scientists wonder whether some new plague might do the same thing to humans.

"The thought of it makes the hair stand up on the back of my neck," said biologist Vance T. Vredenburg of San Francisco State University. "Emerging diseases for humans are cropping up much faster than before, and they might move like this one. We need to understand this." 

Vredenburg and three other researchers have just finished two studies on the frog disease, called chytrid fungus, based on years of work in Yosemite and Sequoia-Kings Canyon. The studies will appear this week in the Proceedings of the National Academy of Sciences, a research journal established in 1914.

The frog studies are part of the scientific community's push to better understand the broad die-off of amphibians around the world. Some experts believe it is part of a mass extinction of many animals.

More than 40% of the 6,500 known amphibian species have disappeared in the last few years, and chytrid fungus is only one cause. Pollution, pesticides, predatory fish, habitat loss and ultraviolet radiation also are involved. But the fungus may be the least understood.

Vredenburg said there may be ways to protect the frogs from the fungus, perhaps by removing as many as possible when the disease appears.

Scientists couldn't move fast enough in Sequoia-Kings Canyon, where nearly 5,600 male mountain yellow-legged frogs had been reduced in just a few seasons to fewer than 500 by 2008 at Barrett Lakes Basin. There were similar dramatic die-offs at Milestone and Sixty Lake basins in Sequoia-Kings Canyon.

But the news isn't all bad. Vredenburg said some species, such as tree frogs, did not suffer die-offs even though they were exposed to the fungus.

Another glimmer of hope: Though the disease killed most mountain yellow-legged frogs when it entered Yosemite years ago, some small groups have survived.

That could mean the disease moves more slowly after the frog populations have thinned out, said ecologist Cheryl J. Briggs of the University of California at Santa Barbara. Maybe nature will be able to cope with this disease.

"I'm slightly more optimistic for the future," said Briggs, who was the lead author on one of the studies. "But what does rapid removal of so many frogs do to the rest of the aquatic community? That's a good question. We don't have an answer yet."

The 2-inch to 3-inch mountain yellow-legged frog can live more than 15 years in isolated streams and mountain lakes. At high elevation, it doesn't change from tadpole to frog in a single season, instead spending three or four winters under the ice in a lake.

In the Sierra, more than 90% of mountain yellow-legged frogs have disappeared over the last century. Losses have accelerated over the last decade as chytrid fungus has spread. Scientists do not know the origins of the disease.

Vredenburg said up to three-quarters of new human diseases these days are coming from animals, such as swine flu. He said that people could benefit as much as the frogs if researchers can learn ways to slow down diseases that move so quickly.

In Panama, for instance, scientists have removed frogs in areas where the disease is spreading. The frogs will be returned to the wild when the outbreak subsides.

In Sequoia-Kings, researchers next year will capture and treat infected frogs and tadpoles at individual lakes. An antifungal drug, something like the medication for athlete's foot, will be used.

Such treatments have proven successful with frogs, and scientists use gloves and sterile techniques to prevent the unintentional spread of the fungus.

Researchers also might try to grow beneficial bacteria on the skin of the frogs. The bacteria has killed the fungus in laboratory tests.

"We're not trying to get rid of the pathogen in nature," Vredenburg said. "The idea is to give these animals a chance to react with an immune response." 

The reporter can be reached at [email protected] or (559) 441-6316.


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## earthfrog (May 18, 2008)

I don't think fungus is going to make a move on humans since we aren't cold-blooded, notwithstanding immunocompromised folks. 
Viruses and bacteria, maybe, but not fungus without a resting spore. Just a guess--I'm no biophysicist


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## thedude (Nov 28, 2007)

not that i think this particular fungus is a problem, but fungal infections are extremely common in humans. and since there are so many different types its hard to treat for them so they actually pose a serious problem. not picking on you, just pointing it out.


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## LorenK (Apr 3, 2008)

I suspect this is really quoted out of context. He is likely saying that understanding more about fast spreading diseases will help us in treating those that may effect humans.

I don't read anywhere where this guy is saying we need to be worried about chytrid harming humans.


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## earthfrog (May 18, 2008)

The ones I've heard of usually happen in chemo patients or those otherwise compromised. Are there fungal infections that attack healthy people in a way they can't overcome?


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## earthfrog (May 18, 2008)

LorenK said:


> I suspect this is really quoted out of context. He is likely saying that understanding more about fast spreading diseases will help us in treating those that may effect humans.
> 
> I don't read anywhere where this guy is saying we need to be worried about chytrid harming humans.


There's some kind of ranabacteria(sp?) that's being tested and improving the health of frogs tested---the guy doing it said he'd get back in touch with me about test specimens if they branch off to DF testing in the future. 
It's a good prospect, for sure.


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## JimO (May 14, 2010)

I'm a moderator on FluTrackers.com - a non-profit website that tracks all kinds of human diseases. This has been a busy year for us with the H1N1 Pandemic Flu (aka Swine Flu). Most people think the threat has passed, but it is gaining momentum again in the Southern Hemisphere as they enter their winter. Brazil is particularly hard hit. Interestingly, this same article appeared on our site and, as I understand it, the concern expressed isn't for fungal infections in humans per se. It's the concern over a deadly pathogen evolving that we have no previous exposure to, thus no immunity. It could kill hundreds of millions very quickly.

There was an H1N1 flu pandemic in 1917-18 that killed an estimated 50 to 100 million people. With today's population and the density of population, an equally deadly flu virus would kill as much as 5x that number today. The concern has been that the Swine Flu would mutate into a more virulent form that transmits easily from human to human (H2H). So far that hasn't happened; however, scientists are finding that a particular mutation that allows the virus to replicate in the deep lung tissue more easily than in the bronchial passages or upper respiratory track is associated with more serious/fatal cases. Many of the fatal cases had been tested from a throat swab and it showed only the more common and less deadly variant; however, after death, the results of autopsies showed the deadly variant in lung samples.

Sorry to ramble, but the point is that the frog fungus should remind us that we are just as vulnerable to devastating epidemics. We have lived during a time when antibiotics and vaccines have been discovered and broadly used. The bacteria and viruses have begun adapting and we are starting to lose the arms race. MRSA was just the beginning. Now there are resistant TB and E. Coli variants. 

The biggest threat right now is the spread of H5N1 avian influenza. That kind of got lost in the news after everyone realized that the threat wasn't imminent. But, it has been spreading and changing. It is far more widespread globally in bird populations from migrating infected birds (I guess they're getting us humans back for spreading diseases among animal populations these past few hundred years). Eqypt and Vietnam are seeing increased human cases and a lower death rate. When it started, the death rate was nearly 100%, but there was no H2H transmission and it was rarely passed to humans from birds. Current cases have a lower fatality rate (between 30 and 40%). This might seem like good news, but virologists fear that it is becoming more acclimated to humans. After all, a virus can't survive if it quickly kills its host. But, even a 10% death rate would be catastrophic. The 1917-18 pandemic had about a 2% death rate. If you the numbers quoted above by 5, then there are scenarios where nearly half the world's population would die in a period of a couple of years. Although many people think we are over-populated, that kind of loss would end civilization as we know it and would be devastating to the environment. Imagine how little concern there would be for animals, plants, ecosystems, etc. if every living person was dealing with the unexpected death of half the people they know. Imagine if we lost half the workers, half the police and military, half the farmers, half the people who provide energy (fuel and electricity).

I'll end on that happy note.


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## earthfrog (May 18, 2008)

That's a good point. 
While I don't believe the world will be wiped out through germ warfare or mutation (for personal reasons), it is important to count the cost of irresponsibility and WASH YOUR HANDS and CHANGE YOUR CLOTHES when you get home from an outing. 
I have not gotten anything more serious than a stomach virus (from my kids) in the past 3 yrs. living this way. Take vitamins, wash hands, get plenty of rest and exercise. You will be one of the 'lucky ones'. 

Anyhow, I agree that the decline in animal well being parallels our own, the human animal. We must soberly consider that as we guard the animals we were entrusted to care for.


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