Scientists track frog-killing fungus to help curb its spread

Frog skin swabs reveal when and where the deadly disease has popped up in wildlife populations around the world

Date:  September 23, 2019

Source:  University of California - Berkeley

From habitat loss to climate change, amphibians around the world face immense threats to their survival. One emerging and sinister threat is the chytrid fungus, a mysterious pathogen that kills amphibians by disrupting the delicate moisture balance maintained by their skin, and that is decimating frog populations around the world.

"Amphibians are already one of the most imperiled groups on the planet, and this fungal disease is further threatening their biodiversity," said Erica Bree Rosenblum, an associate professor of environmental science, policy and management at the University of California, Berkeley.

With the help of advanced genetic testing and hundreds of frog skin swabs, Rosenblum, along with UC Berkeley graduate student Allison Byrne and an international team of collaborators, has created the most complete map to date of when and where different genetic variants of the fungus -- analogous to different strains of viruses like the flu -- have infected frog populations around the world.

Some of these genetic variants are deadlier than others, so knowing their current geographic distribution is key to preventing future spread of the disease, the researchers said. The investigation also uncovered a whole new genetic lineage of the fungus, one that appears to have originated in Asia and may be the oldest variant yet discovered.

"An invisible aspect of globalization is that when we move plants and animals around, we are moving their diseases around, and that can have really devastating consequences," Rosenblum said. "If we know what lineages are where, we can better predict conservation outcomes, because some of these lineages are really deadly, and others less so."

The study appears online the week of Sept. 23 in the journal Proceedings of the National Academy of Sciences.

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An island haven for frogs in a sea of extinctions. Plan to keep New Guinea's frogs safe from the species-destroying chytrid fungus - via Herp Digest

Date: June 3, 2019

Source: Macquarie University

New Guinea is one of the only places in the world where frogs are safe from the species-destroying chytrid fungus. An international team of scientists has published a new paper that shows how to keep it that way, but they need help to carry out their plan.

The chytrid fungus has wiped out more than 90 frog species around the world, and it's driving hundreds more towards extinction. New Guinea -- the world's largest tropical island, and home to 6% of all known frog species -- is one of the last remaining refuges from the deadly infection.

A team of scientists led by researchers from Macquarie University and the University of New England in Australia think they know how to keep the island's frogs safe, but they need support to establish a long-term program of monitoring and conservation.

Writing in the journal Frontiers in Ecology and the Environment, the group of 30 experts from Australia, the USA, China, Indonesia and Papua New Guinea calls for urgent action.

"You don't often spot a conservation disaster before it happens and get the chance to stop it," says Deborah Bower of the University of New England in Armidale, Australia, who is the first author of the article. "We know what needs to be done.”

The infectious chytrid fungus has been described as the most destructive pathogen known to science. It has destroyed more than 90 species of frog entirely and caused declines in almost 500 more.

The international pet trade helped the chytrid fungus spread rapidly from its origins in East Asia over recent decades, and it now infects frogs on every continent. It is one of the key reasons why 40% of the world's frog species now face the threat of extinction.

New Guinea's tropical climate and hundreds of native frog species make it an ideal environment for chytrid. But field tests have so far found no traces of the killer fungus.

"A lot of New Guinea's frogs are closely related to Australian species that have been devastated by chytrid, so we expect they would be just as vulnerable," says Simon Clulow at Macquarie University in Sydney, Australia, who leads the research team.

"Other New Guinea frog species are unusual because they hatch from eggs as fully formed frogs, rather than going through a tadpole stage, and we don't know how chytrid will affect them.”

The team estimates that around 100 species of frog would be in danger if chytrid reaches New Guinea, and their decline could have huge impacts across the ecosystem as they are predators of insects and other small creatures but also prey for larger animals.

The research team includes international experts in frog conservation -- including Lee Berger, the Australian who first discovered the chytrid fungus and showed it was responsible for frog species declines and extinctions -- alongside local researchers with deep knowledge of the environment of New Guinea.

They have been studying frogs in New Guinea since 2015, and have already started working with zoos, universities and the Papua New Guinea government to build a program to keep captive frogs and store their sperm and eggs to preserve genetic diversity.

The team has developed a 5-step program of preparation, prevention, detection, response and recovery to keep the deadly fungus off New Guinea and to minimise the impact if it does arrive.

As well as preserving New Guinea's frogs, the program would build local capacity in science, and disease surveillance and diagnosis that will have applications for animal and public health.

Story Source:

Materials provided by Macquarie University. Note: Content may be edited for style and length.

Journal Reference:

1. Deborah S Bower, Karen R Lips, Yolarnie Amepou, Stephen Richards, Chris Dahl, Elizah Nagombi, Miriam Supuma, Lisa Dabek, Ross A Alford, Lin Schwarzkopf, Mark Ziembicki, Jeffrey N Noro, Amir Hamidy, Graeme R Gillespie, Lee Berger, Carla Eisemberg, Yiming Li, Xuan Liu, Charlotte K Jennings, Burhan Tjaturadi, Andrew Peters, Andrew K Krockenberger, Dillian Nason, Mirza D Kusrini, Rebecca J Webb, Lee F Skerratt, Chris Banks, Andrew L Mack, Arthur Georges, Simon Clulow. Island of opportunity: can New Guinea protect amphibians from a globally emerging pathogen? Frontiers in Ecology and the Environment, 2019; DOI: 10.1002/fee.2057

An island haven for frogs in a sea of extinctions

Plan to keep New Guinea's frogs safe from the species-destroying chytrid fungus

Date:  June 3, 2019

Source:  Macquarie University

New Guinea is one of the only places in the world where frogs are safe from the species-destroying chytrid fungus. An international team of scientists has published a new paper that shows how to keep it that way, but they need help to carry out their plan.

The chytrid fungus has wiped out more than 90 frog species around the world, and it's driving hundreds more towards extinction. New Guinea -- the world's largest tropical island, and home to 6% of all known frog species -- is one of the last remaining refuges from the deadly infection.

A team of scientists led by researchers from Macquarie University and the University of New England in Australia think they know how to keep the island's frogs safe, but they need support to establish a long-term program of monitoring and conservation.

Writing in the journal Frontiers in Ecology and the Environment, the group of 30 experts from Australia, the USA, China, Indonesia and Papua New Guinea calls for urgent action.

"You don't often spot a conservation disaster before it happens and get the chance to stop it," says Deborah Bower of the University of New England in Armidale, Australia, who is the first author of the article. "We know what needs to be done."

The infectious chytrid fungus has been described as the most destructive pathogen known to science. It has destroyed more than 90 species of frog entirely and caused declines in almost 500 more.

Read more

Tropical frogs found to coexist with deadly fungus

Date: October 3, 2018

Source: University of Maryland

Amphibian biologists from around the world watched in horror in 2004, as the frogs of El Copé, Panama, began dying by the thousands. The culprit: Batrachochytrium dendrobatidis, a deadly fungus more commonly known as chytrid fungus. Within months, roughly half of the frog species native to the area went locally extinct.

A new study led by University of Maryland researchers suggests that, within a decade, the species remaining in El Copé developed the ability to coexist with chytrid fungus. In a field study spanning the years 2010-2014, the researchers found that frogs infected with the fungus survived at a nearly identical rate compared with uninfected frogs.

The results, published October 3, 2018 in the journal Ecological Applications, suggest that frog populations in El Copé underwent ecological and/or evolutionary changes that enabled the community as a whole to persist, despite severe species losses. According to the researchers, the results could mean good news for other hot spots of amphibian biodiversity hit hard by the chytrid fungus, such as South America and Australia.

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Origin of plague causing ongoing 'amphibian extinction crisis' discovered by scientists

Discovery of 'ground zero' for deadly disease has implications for global biosecurity measures

Josh Gabbatiss Science Correspondent 

5 days ago

The origin of a disease that has torn through the world’s amphibian population has been traced to Korea by a team of scientists.

Chytrid fungus is responsible for a decimation of frogs and salamanders that has been going on for decades and is thought to have eradicated over 100 species.

The disease has been found all over the world, but no one has known where and when it first emerged. 

Now an international research team has traced the deadly fungus to East Asia and has concluded that the global trade in amphibians for exotic pet, medical and food purposes is behind its spread.

“Biologists have known since the 1990s that [chytrid fungus] was behind the decline of many amphibian species, but until now we haven’t been able to identify exactly where it came from,” said Dr Simon O’Hanlon, a researcher at Imperial College London and lead author of the study.

Continued 

Skin bacteria may predict vulnerability of amphibians to killer chytrid fungus

February 19, 2018 by Ryan O'hare, Imperial College London

Bacterial communities that live on the skin of frogs and toads could provide vital clues to species' vulnerability to the lethal chytrid fungus.

The fungus (Batrachochytrium dendrobatidis or (Bd)) is currently decimating amphibian populations worldwide, and has been linked with the decline and extinction of tropical species.

According to a pioneering new genetic study, led by Zoological Society of London and involving Imperial researchers, the animals' own microbes could play a key role in the course of disease.

Previous studies indicate that the outcome of infection is linked to the virulence of the particular Bd strain the animals come into contact with, but more recent evidence suggests that bacteria living naturally on amphibian skin can actually provide protection from the fungus.

In the latest study, published in the journal Nature Communications, researchers used more than a decade of data collected from midwife toads (Alytes obstetricans) in the French and Spanish Pyrenees to investigate why certain populations of the toads demonstrated a degree of resistance to Bd, while elsewhere the disease has contributed to catastrophic declines in similar animals.

Read more at: 

Climate change driving toad disease from fungus in Pyrenees

Date: October 23, 2016

Source: Imperial College London

At high altitudes, frogs and toads are being infected by a deadly chytrid fungus at increasingly high rates in the Pyrenees Aspe Valley, France. The spike in mortality of these toads is blamed on warming in these mountains, which drives fungal infection in frogs and toads, and is expected to get worse.

Following years of speculation that climate change was driving deaths by chytrid, this eight-year study by researchers at Imperial College London and ZSL (Zoological Society of London), published in the Philosophical Transactions of the Royal Society B, is the first to compare temperature with amounts of disease in order to infer future patterns at high altitudes. The fungus Batrachochytrium dendrobatidis (Bd) has severely affected over 700 amphibian species worldwide causing more extinction events than any other infectious disease known to science.

From analysing lake melt and amphibian infection rates over eight years, the researchers found that the earlier that the valley's lakes melted in the springtime, the higher were the rates of infection for both frogs and toads.

They then created predictive climate models that focused on regional temperatures across this part of the Pyrenees mountains. This research predicted that the region will continue to warm significantly and that frozen lakes will become increasingly rare, meaning that the midwife toad tadpoles in these lakes will spend increasingly less time under ice, with the effect that they multiply the effects of Bd infection in other species of frogs and toad.

Although the link between lake melt and rates of Bd infection is clear, it isn't known why temperature has this effect. Theories range from whether warmer lakes provide the ideal temperatures for chytrid growth, to whether predators of chytrid fungal zoospores are less active in warmer lakes.

Continued

Deadly fungus threatens African frogs

Date: May 6, 2016

Source: University of Florida

Misty mountains, glistening forests and blue-green lakes make Cameroon, the wettest part of Africa, a tropical wonderland for amphibians.

The country holds more than half the species living on the continent, including dozens of endemic frogs -- an animal that has been under attack across the world by the pervasive chytrid fungus (Batrachochytrium dendrobatidis). Africa has been mostly spared from the deadly and rampant pathogen that wiped out entire species in Australia, Madagascar and Panama, until now.

University of Florida herpetologist David Blackburn and colleagues at the Museum für Naturkunde in Berlin have documented declines in frog species on Cameroon's Mount Oku and Mount Manengouba over a span of more than 12 years. The scientists link the decline of at least five species of frogs found only in these mountains to chytrid, which may have been exacerbated by habitat destruction, pollution and climate change resulting in weaker and more susceptible frogs, said Blackburn, an associate curator of herpetology at the Florida Museum of Natural History on the UF campus.

"There's been this perception that frogs in Africa are not affected by chytrid at all, but we have evidence of the disease in some animals," said Blackburn, co-author of a new study appearing online this week in PLOS ONE. "This is the first real case of a decline across multiple amphibian species in Africa."

Study scientists collected and documented abundance and diversity of frog species living on the two mountains before and after the immergence of chytrid in the area between 2008-2010. The persistent pestilence latches onto the frog's skin and can spread internally to the animal's organs, quickly leading to death.

Read on …

Deadly amphibian fungus may decline, study finds

Date:January 14, 2016

Source:Wildlife Conservation Society

A new study by WCS and other groups offers a glimmer of hope for some amphibian populations decimated by the deadly chytrid fungus: climate change may make environmental conditions for the fungus unsuitable in some regions and potentially stave off the spread of disease in African amphibian populations struggling to adapt to changes brought about by global warming.

Chytrid or Bd -- short for Batrachochytrium dendrobatidis -- can cause a disease called chytridiomycosis, which is found worldwide and is a major contributor to amphibian declines and extinctions.

Continued ...

Cure for chytrid: Scientists discover method to eliminate killer fungus

Breakthrough discovery leads to eradication of fatal amphibian disease

Date:November 18, 2015

Source:Zoological Society of London

Research published details the first-ever successful elimination of a fatal chytrid fungus in a wild amphibian, marking a major breakthrough in the fight against the disease responsible for devastating amphibian populations worldwide. The highly-infectious chytrid pathogen has severely affected over 700 amphibian species worldwide; driving population declines, extirpations and species extinctions across five continents.

Results from the seven-year study show the first evidence of eradicating the chytrid pathogen Batrachochytrium dendrobatidis (Bd) affecting amphibians in situ. Published inBiology Letters, the paper details the outcome of a project led by scientists from the Zoological Society of London (ZSL), the National Museum of Natural History in Spain (MNCN-CSIC), and Imperial College London.

The study combined antifungal treatment of Mallorcan midwife toad (Alytes muletensis) tadpoles with environmental disinfection. By using an antifungal to treat tadpoles and a common laboratory decontaminant to sterilise the environment, researchers were able to clear infection from populations of the toad over the research period.

Co-author Dr Trenton Garner, Reader within ZSL's Institute of Zoology, said: "This study represents a major breakthrough in the fight against this highly-destructive pathogen; for the first time we have managed to rid wild individuals of infection for a continued period.

"Amphibian-associated chytrid fungi are a critical conservation issue that requires simple, straightforward and transferrable solutions. Our study is a significant step towards providing these."

Continued ...

Research could lead to protective probiotics for frogs

Date: July 30, 2015

Source: American Society for Microbiology

Summary: In research that could lead to protective probiotics to fight the 'chytrid' fungus that has been decimating amphibian populations worldwide, researchers have grown bacterial species from the skin microbiome of four species of amphibians.

Continued ...

Amphibian chytrid fungus reaches Madagascar

Date:

February 26, 2015

Source:

Helmholtz Centre for Environmental Research - UFZ

Summary:

The chytrid fungus, which is fatal to amphibians, has been detected in Madagascar for the first time. This means that the chytridiomycosis pandemic has now reached a biodiversity hotspot. Researchers are therefore proposing an emergency plan. This includes monitoring the spread of the pathogenic fungus, building amphibian breeding stations and developing probiotic treatments, say the scientists.

Continued ...

Potential cure for captive amphibians with chytrid fungus

Date:

May 12, 2014

Source:

American Society for Microbiology

Summary:

Researchers have identified an alternative to a sometimes toxic therapy that protects frogs in zoos from a deadly fungal infection that has been destroying the amphibian populations worldwide.

Continued

Deadly Fungus Detected in Southeast Asia's Amphibian Trade

Mar. 6, 2013 — A team of scientists led by the Wildlife Conservation Society (WCS) and the National University of Singapore (NUS), revealed in a new study, for the first time, the presence of the pathogenic chytrid fungus (Batrachochytrium dendrobatidis) in amphibians sampled in Singapore. And the American bullfrog may be a central player in the spread of the disease.

The study appears in the current issue of the journal EcoHealth, and is the first to consider the role that Southeast Asia's commercial trade plays in the spread of amphibian pathogens.

Demand for amphibians through local and international trade is high and fueled by use of frogs as pets, food, bait, and as a source of traditional 'medicine.' More than 40 percent of amphibian species are in decline globally due, not only to chytrid fungus, but also overharvesting, competition from invasive species, habitat loss, pollution, and climate change.

In the study, scientists collected samples from 2,389 individual animals in Lao PDR, Cambodia, Vietnam, and Singapore at 51 different sites including farms, locally supplied markets, pet stores, and from the wild.

Continued:  http://www.sciencedaily.com/releases/2013/03/130306133815.htm

Genetic Matchmaking Saves Endangered Frogs – via Herp Digest

Jan. 8, 2013 — What if Noah got it wrong? What if he paired a male and a female animal thinking they were the same species, and then discovered they were not the same and could not produce offspring? As researchers from the Smithsonian's Panama Amphibian Rescue and Conservation Project race to save frogs from a devastating disease by breeding them in captivity, a genetic test averts mating mix-ups.

At the El Valle Amphibian Conservation Center, project scientists breed 11 different species of highland frogs threatened by the chytrid fungus Batrachochytrium dendrobatidis, which has already decimated amphibian populations worldwide. They hope that someday they will be able to re-release frogs into Panama's highland streams.

Different frog species may look very similar. "If we accidentally choose frogs to breed that are not the same species, we may be unsuccessful or unknowingly create hybrid animals that are maladapted to their parents' native environment," said Andrew J. Crawford, research associate at the Smithsonian Tropical Research Institute in Panama and professor at Colombia's Universidad de los Andes. Crawford and his colleagues make use of a genetic technique called DNA barcoding to tell amphibian species apart. By comparing gene sequences in a frog's skin cells sampled with a cotton swab, they discover how closely the frogs are related.

New knowledge about frog genetics contributes to saving amphibians from extinction, the mission of the Panama Amphibian Rescue and Conservation Project. Participating institutions include Africam Safari, Panama's Autoridad Nacional del Ambiente, Cheyenne Mountain Zoo, Defenders of Wildlife, El Valle Amphibian Conservation Center, Houston Zoo, Smithsonian's National Zoological Park, the Smithsonian Tropical Research Institute and Zoo New England.

Journal Reference:

Andrew J. Crawford, Catalina Cruz, Edgardo Griffith, Heidi Ross, Roberto Ibáñez, Karen R. Lips, Amy C. Driskell, Eldredge Bermingham, Paul Crump. DNA barcoding applied toex situtropical amphibian conservation programme reveals cryptic diversity in captive populations. Molecular Ecology Resources, 2012; DOI: 10.1111/1755-0998.12054

Crayfish Harbor Fungus That's Wiping Out Amphibians – via Herp Digest

Freshwater crustaceans could be the key to understanding how the chytrid fungus persists in the ecosystem long after the last amphibian is gone.

Helen Fields

for National Geographic News

Published December 17, 2012

Scientists have found a new culprit in spreading the disease that's been driving the world's frogs to the brink of extinction: crayfish.

In the last few decades, the disease caused by the chytrid fungus has been a disaster for frogs and other amphibians. More than 300 species are nearly extinct because of it. Many probably have gone extinct, but it can be difficult to know for sure when a tiny, rare species disappears from the face of the Earth. (Related photos: "Ten Most Wanted 'Extinct' Amphibians.")

"This pathogen is bad news. It's worse news than any other pathogen in the history of life on Earth as far as we know it," says Vance Vredenburg, a conservation biologist at San Francisco State University who studies frogs but did not work on the new study.

The chytrid fungus was only discovered in the late 1990s. Since then, scientists have been scrambling to figure out how it spreads and how it works.

One of the biggest mysteries is how chytrid can persist in a frogless pond. Researchers saw it happen many times and were perplexed: If all of a pond's amphibians were wiped out, and a few frogs or salamanders came back and recolonized the pond, they would also die—even though there were no amphibians in the pond to harbor the disease. (Learn about vanishing amphibians.)

One possible reason is that chytrid infects other animals. For a study published today in Proceedings of the National Academy of Sciences, Taegan McMahon, a graduate student in ecology at the University of South Florida in Tampa, looked at some possible suspects and focused on crayfish, those lobsterlike crustaceans living in freshwater. They seemed like a good possibility because they're widespread and because their bodies have a lot of keratin, a protein the fungus attacks.

In the lab, McMahon exposed crayfish to the disease and they got sick. More than a third died within seven weeks, and most of the survivors were carrying the fungus. She also put infected crayfish in the water with tadpoles—separated by mesh, so the crustaceans wouldn't eat the baby frogs—and the tadpoles got infected. When McMahon and her colleagues checked out wetlands in Louisiana and Colorado, they also found infected crayfish.

That means crayfish can probably act as a reservoir for the disease. The fungus seems to be able to dine on crayfish then leap back to amphibians when it gets a chance. No one knows for sure where the fungus originally came from or why it's been such a problem in recent decades, but this research suggests one way that it could have been spread. Crayfish are sometimes moved from pond to pond as fish bait and are sold around the world as food and aquarium pets. (Related photos: "New Giant 'Bearded' Crayfish Species.")

The study doesn't answer every last question about the disease. For one thing, crayfish are common, but they aren't everywhere; there are no crayfish in some of the places where frogs have been hardest hit, Vredenburg says. But, he says, the new research shows that "we need to start looking a little more broadly at other potential hosts."