24 Oct 2011: Report

A Rise in Fungal Diseases is
Taking Growing Toll on Wildlife

In an increasingly interconnected world, fungal diseases are spreading at an alarming rate and have led to deadly outbreaks in amphibian, bat, and bee populations. And in the last decade, researchers note, some of the most virulent strains have infected people.

by michelle nijhuis

On the southeastern outskirts of Washington, D.C., inside the Smithsonian Institution’s cavernous Museum Support Center, one can see some frogs that no longer exist. Alcohol-filled glass jars hold preserved specimens of Incilius periglenes, the Monte Verde golden toad; the Honduran frog Craugastor chrysozetetes, which in life was olive-brown with purple palms and soles; its Costa Rican cousin, Craugastor escoces; and Atelopus ignescens, a black toad not seen in the wild for decades.

All of these extinct species are likely victims of the fungus Batrachochytrium dendrobatidis, which attacks the outer skin layers of amphibians, disrupting their water and electrolyte intake so severely that infected animals can die of cardiac arrest. The fungus, known familiarly as Bd, has been found in more than 500 species of amphibians in 54 countries to date, most recently in Asia. Some areas of Central America have lost more than 40 percent of their amphibian species to Bd infection.

Karen Lips, a University of Maryland herpetologist who has watched Bd march through Central American amphibian populations for almost 20 years, says no amphibian is safe: “We live in a Bd world now,” she says.

Click to enlarge
Panamanian Golden Toad

The BD fungus has been found in more than 500 species of amphibians, including the Panamanian golden toad.
Bd is just one of several modern-day eruptions of fungal disease. White-nose syndrome, first observed in North American bats in New York State in early 2007, is thought to be caused by the fungus Geomyces destructans, and the disease is estimated to have killed well over a million cave-dwelling bats and has now spread to 19 states and four Canadian provinces. Biologists describe the epidemic as the most dramatic decline of North American wildlife in living memory.

Fungal disease also appears to play a key role in colony-collapse disorder, the recent and sudden dieoff of North American bees: Scientists posit that the bees are weakened and killed by multiple factors, including a one-two punch from a virus and a fungal parasite. In the Caribbean, a fungus called Aspergillus sydowii has contributed to the precipitous decline of coral reefs, sweeping through populations of sea fans weakened by rising ocean temperatures.

And in the Pacific Northwest and British Columbia over the past decade, a new and virulent strain of the fungus Cryptococcus gattii, which attacks the lungs and nervous system, has killed more than 30 people, and infected dogs as well.

Many researchers have noticed the number and severity of these emerging fungal diseases. “I think there’s absolutely no question that there’s been a huge increase in fungal infections,” says Joseph Heitman, a microbiologist at Duke University Medical Center who studies Cryptococcus gattii.

The reasons for the trend are multifold, Heitman and other researchers say. Fungal spores, which are more durable and long-lived than bacteria or viruses, can easily hitch rides on humans. As humans move faster and farther around the world, fungi of all kinds are landing in new habitats: Geomyces destructans, which is present but not lethal in European bat
As humans move faster and farther around the world, fungi of all kinds are landing in new habitats.
populations, was likely transported across the Atlantic by humans, even though it seems to spread more often from bat to bat.

Unlike bacteria and viruses, fungi can also reproduce sexually, allowing fungi that encounter each other in new habitats to easily recombine into novel, potentially more virulent strains. Cryptococcus gattii, which began to infect people in British Columbia in 1999 and has since moved south into the U.S. Pacific Northwest, may be a recombination of tropical fungal strains that moved north on imported ornamental plants or soil.

This sort of fungal mischief has long been recognized in food crops and other plant species, and fungal disease outbreaks continue to threaten food supplies. But in recent decades, fungal diseases have also taken a severe and growing toll on wildlife. “Fungi have driven more animal species extinct than any other class of pathogens by quite a long way,” says Matthew Fisher, an epidemiologist at Imperial College in London. Fisher and his colleagues calculate that fungi have caused more than 80 percent of known disease-driven animal extinctions. (Viruses, by comparison, are responsible for only 1 percent.) The vast majority of these fungi-driven extinctions have happened in the past 20 years. The first proven victim, Fisher says, was a captive population of Polynesian tree snails, wiped out by fungal disease in a London zoo in the 1990s.

This lethal pattern is partly explained by the independence and flexibility of fungal species: Unlike viruses, they don’t usually depend on their hosts for survival, and unlike both viruses and bacteria, which tend to be more specialized, they can quickly switch to new hosts. For example, Geomyces destructans can survive in cave sediments before infecting healthy bats. In some caves in the northeastern United States, more than 99 percent of resident bats have died from white-nose; the fungus, however, continues to thrive and spread.

Climate change may also be contributing to the spread of fungal diseases in wildlife populations. There are estimated to be more than 1.5 million
Climate changes may stress species of all kinds, making them less able to resist and recover from infection.
species of fungi worldwide, but only about 150 infect mammals. Arturo Casadevall, a professor at the Albert Einstein College of Medicine, gained notoriety a few years ago for suggesting that warm-bloodedness — an energy-expensive life strategy — protected early mammals from heat-intolerant fungi and led to their global rise. But as average global temperatures ratchet up, Casadevall hypothesizes, fungi may adapt to warmer temperatures and mammals may lose their body-temperature advantage.

Climate changes may also stress species of all kinds, making them less able to resist and recover from infection. “Fungal diseases really haven’t been on our radar screen,” says Casadevall, “but as you raise the temperature, I think they’re going to become completely formidable.”

The Centers for Disease Control are heavily involved in research on the Cryptococcus gattii outbreak, and there are various efforts underway to mitigate disease-driven damage to amphibian, bat, and bee populations. In late August, scientists at Oregon State University reported that a species of freshwater zooplankton will eat the Bd fungus and could serve as a biological control. Another group of biologists, based at the University of Zurich, recently found that some bacteria, when applied directly to amphibian skin in the laboratory, can block the attack of Bd. Bat researchers in the northeastern United States have found that bats in cooler caves are more likely to survive; it’s possible that humans could alter airflow in mines and other artificial habitats to provide some refuge for bats.


A Search for the Vanishing
Bats of the U.S. Northeast

In Aeolus Cave, A Search for the Vanishing Bats of the Northeast
When biologists ventured into a Vermont cave earlier this year, they found evidence that white-nose syndrome was continuing to take its toll on bat populations. But, as Elizabeth Kolbert writes at Yale e360, a critical question remains: What can be done to halt the spread of this still-mysterious ailment?
Recognizing and containing fungal diseases before they gain a foothold is another matter, however. Decades of work by organizations such as the United Nations Food and Agriculture Organization, along with research by agribusiness, have developed some methods of identifying and controlling plant fungal diseases. But Fisher points out that even New Zealand, which has an unusually sophisticated biosecurity system, was not able to protect its amphibians from the Bd fungus.

“We’re importing so much from all kinds of locations, and there’s almost no screening done,” says Heitman. “And some of the methods we do have for screening, such as molecular testing, are just not practical.” He imagines testing truckloads of imported Canadian Christmas trees for evidence of Cryptococcus gattii, and sighs. “We’ve created a global economy, and there are advantages to that. The disadvantage is that it’s a huge mixing pot.”

POSTED ON 24 Oct 2011 IN Biodiversity Business & Innovation Policy & Politics Pollution & Health Pollution & Health Science & Technology Central & South America 


Increasingly interconnected?? Everything has always, and will always be, totally interconnected. We just want to ignore that in order to make a profit or do what we want. Childish of us. We need to grow up.

Posted by Linda on 25 Oct 2011

EXCELLENT work! Now, if only our physicians knew the extent to which humans are exposed to and succumb to pathogenic fungal spores. About 40 species have proven to be pathogenic to man, yet only Candida species are studied as causing symptoms. Fungi produce poisonous byproducts called "mycotoxins" and most are immunosuppresive, accounting for the fact that so many of us believe the answer lies in flu shots over common sense mold avoidance. Several species are also carcinogenic, yet oncologists haven't any idea! Ironically, one grows on corn and peanuts, commonly consumed in every country. There is no money or funding for understanding the etiology, rather only for treating symptoms and/or disease. Truly amazing in the 21st Century!


Posted by Doug on 25 Oct 2011

Agree completely with Doug; however, the fact that there is minimal funding for fungal pathology research in humans may have more to do with pharmaceuticals understanding that if you nip fungal pathologies in the bud, you eliminate your future customer base. As an RN, we were trained (circa 1974), to 'chase' all antibiotic prescriptions given in hospital, with Nystatin, an anti-fungal, because it was understood that using antibiotics created a microbial imbalance that favored the proliferation of fungi. To prevent that, it was standard procedure in most hospitals, that you automatically follow that antibiotic course with an anti-fungal.

In the early 80's, all of a sudden, that practice ceased, and patients were simply told to "eat yogurt" post- antibiotic therapy.(That's like peeing in the ocean...) What happened? Microbial life hadn't changed; R+D in big pharma discovered the fungal connection to many, many common maladies, including cancer, (untreated fungus over decades), and through the power of their endowments to medical schools, had most Fungal Pathology courses removed, creating a doctor population that today does not recognize the fungal blow-back in human beings after nearly 40 years of overusing antibiotics. Add to that our national Sugar Addiction, and, voila`, welcome to our undiagnosed Candida Epidemic. Some will say this is intentional. Do we put it past them?

Posted by Pamela, RN on 25 Oct 2011

About a month ago, at ICAAC, an infectious disease conference sponsored by ASM, I learned, among other things, that bacteria are responsible for generating about 4 degrees of our body temperature. Antibiotics can lower temperature by killing off bacteria, which opens the door to heat intolerant fungi.

Could the uptick in the use of antibiotics and antimicrobials over the last few decades have spilled into the environment in such a way as to contribute to collapse disorders? For example, there are some recent looking at Triclosan, which doesn't necessarily break down in sewage treatment facilities. Triclosan laced water, even quite dilute, gets into waterways where critters such as frogs are splashing about. It's enough to affect diatom populations. Could it be enough to increase frogs' vulnerability to fungal infections?

I know this is an "out there" idea, and clearly trade and travel are the prime movers in global spread. But collapse disorders are about perfect storms and aggregate threat.

There is a certain irony that the spread of fungul infections is aided by global warming, but organism vulnerability may be a factor of a kind of localized cooling.

I would be very curious to know whether anyone thinks there might be a "there there" to this idea.

Posted by J. A. Ginsburg on 26 Oct 2011

The ocean and all global waterways have a virus-like pathogen in them. the pathogen called an Oomycete or Prion has no relation to pollution. Humans can take antibiotics and superdrugs, unfortunately the fish and other marine animals cannot and will soon be ALL dead worldwide. We have no scallops oysters or prawns in Australia either plus lots of dead dolphins turtles whales, seabirds etc, same in Asia, same in Africa, same in New zealand, same in Chile, Better we get used to eating EHD deer (another new prion virus). Sad really that we wasted it all. Hippynige in Australia.

Posted by hippynige on 27 Oct 2011

I have to agree with the hidden agenda as highlighted by Pamela. Yes there is a link to the use of anti-biotics and the sudden emergence of fungal infections. But as they say in the Pharmaceutical world 'There is no profit in a healthy nation' so its infect and profit, through creating ignorance in the population and advertising the 'Pill for every Ill' mantra at every opportunity.

Now as for the fungal infections increasing globally within mammal populations, amphibians and even tree and plant species we have to remember that we have been using all manner of toxic cocktails for decades. These things destabilise natural ecosystems just as anti-biotics destabilise the human immune system. The entire world is made up of finely balanced systems with each having its constant little upheavals of one species type or another trying and vying for supremacy within the system. But like every system when one species of life fails to make any inroads it ups sticks and moves to another playground. Its called evolution and adaptation. Bit like the kids playing ball until one gets upset at being beaten all the time so takes the ball and goes elsewhere. I know its a bit of a silly analogy but it is still relevant.
So what is the solution?

We could start with the quality of the food we eat. Growing food using permaculture methods would certainly do a lot of good for the stressed environment. It would also enable us humans to intake the necessary nutrients minus the toxic cocktail of chemicals we have been subjected to for the profit of the chemical industry.

We could also mitigate climate changing pollution emissions at the same time. This in turn creates a healthier environment which would enable species to live healthier and more stabel lives. As stresses affect humans they affect animals and plants equally so. I believe these increases in infections are also human generated not just because we move around a lot (although that is one mechanism) but because of what we do when we actually land in one area or another.

Back to basics i think before we lose everything.

Posted by Kev C on 27 Oct 2011

No one ever talks or writes about the chemical pollution that humans generate and flood across the globe. Weak immune systems due to chemical pollution is causing fungi to attack and kill everything. Fungi proliferate just before a mass extinction, so is this the final warning before the end? Its too late to stop the chemical overload, so brace for the worst.

Posted by Patrick on 30 Oct 2011

“Decades of work by organizations such as the United Nations Food and Agriculture Organization, along with research by agribusiness, have developed some methods of identifying and controlling plant fungal diseases.” As we all seem to be on the same page here does anyone else have a problem with this? Most if not all Genetically Modified Food Organisms have an antibiotic marker attached to the foreign gene inserted. So as we severely over prescribe these antibiotics in our chronic symptom treatment system we call healthcare, we have had plants growing their own for almost 20 years putting so much more into the food web. Not including all the herbicides, pesticides, & long term health affects that go hand in hand with these crops.

I’m sorry but agribusiness/chemical companies, “one in the same”, have done nothing but to exacerbate the problem of disrupting the ecosystems of this planet in the sight of profits. I completely agree with Ken C. on the back to the basics idealism, the more we try to control our environment, the more we upset it. Unless we the people take back the power, like cut the ties from capitalist extremists to governments, it will be a race to see who or what kill us first. I don’t want to say it but, we’re doomed.

Posted by Mishka V. on 03 Nov 2011

Frogs and bats are cured of fungal infections using probiotics. How do we treat whole environments to put them back in the equation? What if we look at what tips the scales in the first place. Hmmm. Pesticides kill probiotics and affect the bioavailability of nutrients in the soil for decades. I'm just saying...

Posted by Beth Martell on 04 Nov 2011

You know there's a professor here at Southern Illinois University who was the first to pinpoint the fungal disease that's decimating the world's frog population? She's the one who told me amphibians respond well to probiotics when I mentioned how well they work with my parrots. How do you treat whole forests of well camouflaged creatures and entire caves?

This information used to be readily available on the EPA's Pesticide Industry Sales and Usage 1996-97 Market Estimates:

The Environmental Protection Agency concedes, "Economic benefits from pesticide use are not achieved without potential risks to human health and the environment due to the toxicity of pesticide chemicals.

In the U.S. in a typical year, about 4.6 billion pounds of chemicals are used as pesticides (measured on basis of active ingredient).

Conventional pesticides account for 27% of the total amount used.

About 75% of conventional pesticides are utilized by farmers.

Records show 2.2 billion pounds (active ingredient) have been spread on farms in the past 27 years. That averages out to 683 million pounds being spread on farms each year in the 70's, about 763 million pounds each year in the 80's, and 752 million pounds annually between 1990-97.

Agricultural pesticide usage is something that affects us all. Data from the U.S. Geological Survey in 1998 indicates that "pesticides are widespread in streams and groundwater, occuring in geographic and seasonal patterns that follow land use and related pesticide use.

More than 99% of the samples collected from streams and 50% of the samples collected from wells contained at least one pesticide.

The geographic distribution of pesticide concentrations generally follows regional patterns in agriculture use and the influence of urban areas, although this relationship is stronger for streams than groundwater.

Long-term exposure to low-level mixtures of pesticides compounds, punctuated with seasonal pulses of high concentrations, is an exposure pattern that may not be adequately accounted for.

This information leads me to suspect pesticides as the primary suspect considering the sheer volume of poison involved. Add to that the antibiotics, hormones, viagra, and heart medicine flushed into the water supply from 7 billion people worldwide? Really?

Forests and caves are the wettest environments we have. I suspect the fungus is just the symptom and unless we treat the underlying malady, we won't solve the problem. With everyone drinking bottled water we've created the illusion that there is some kind of escape if you have enough money to buy it.

Posted by Beth Martell on 05 Nov 2011

Here's the statement made by the North American Commission for Environmental Cooperation, "State of the Environment" report a decade ago:

"In North America, as in much of the world, humans are reshaping the environment and using up many parts of it faster than nature can renew itself ... Sustainable development means meeting the needs of the present without compromising the ability of future generations to meet their own needs. The transition will not be easy. It will require adapting policies, institutions, technologies, and lifestyles. It will mean altering deep and enduring attitude, values, and behaviors that underlie our economic and social systems."

Posted by Beth Martell on 05 Nov 2011

National Geographic published an article called, "Deadly Frog Fungus Spreads in Virus-Like Waves" in April of 2008 that's very interesting.

Posted by Beth Martell on 05 Nov 2011

What fascinates me is that the general public has no knowledge of bacteria affecting body temperature, of antibiotics leading to opportunities for fungi, of possible immunosuppression, etc. If they did, they might be more worried about other species and the environment, rather than only themselves. How do we bring this type of awareness of interconnection into the mainstream? We're trying to do this at Izilwane.org, an all volunteer, participatory, conservation, media organization. The site is www.izilwane.org. This article is the type of article that makes people sit up and take notice and think, "Wow, dying bats could affect me and I, as a human, could be the reason the bats are dying." Kudos to Michelle for writing this article.

Posted by Tara Lumpkin on 11 Nov 2011

Makes one feel ill thinking about all the life thats dying because of all the chemical poisons being put in our air soil and water. They WON"T stop because of $$$. I believe in the bible. God says He has a set day to Bring to ruin those ruining the earth. Rev 11:18

All prophecy is coming true before our eyes. Bible says the meek will inherit the earth and the wicked will be torn from it. Psalms 37: 10, 11 It will take power from the creator to bring an end to the destruction of our planet and life on it. In the meantime those who want to live on a cleansed earth free of crime war hatred poverty must not go along with the majority but fight to do whats right and good before the one who made the heavens and earth. Jehovah aka Yahweh Daniel 12: 10 Many will cleanse themselves and whiten themselves and will be refined. And the wicked ones will certainly act wickedly, and no wicked ones at all will understand; but the ones having insight will understand.

Posted by luvtruth on 12 Nov 2011

Interesting article. Lot of information. Also interesting considerations by the commentators. It surprises how the author repeatedly and without any rationale cites global warming as the only possible cause of increasing fungus infection. But it's the kind of brain-washing that the new religion impose.

Posted by Carlo Castellani on 17 Apr 2012

What a relief ...finally you are addressing the fungal issue. Thank you for your wisdom and courage.

Posted by carollee beltz on 19 Oct 2012

Comments have been closed on this feature.
michelle nijhuisABOUT THE AUTHOR
Michelle Nijhuis is a contributing editor of the environmental magazine High Country News. Her writing about science and conservation has also appeared in Smithsonian, National Geographic, The Atlantic, and the anthologies Best American Science Writing and Best American Science and Nature Writing. In 2011, as an Alicia Patterson Foundation fellow, she is researching the science and ethics of rescuing critically endangered species.



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