Blood samples show deadly frog fungus at work in the wild

Apr 25, 2012

The fungal infection that has killed a record number of amphibians worldwide leads to deadly dehydration in frogs in the wild, according to a new study by University of California, Berkeley and San Francisco State University researchers.

High levels of an aquatic fungus called Batrachochytrium dendrobatidis (Bd) disrupt fluid and electrolyte balance in wild , the scientists say, severely depleting the frogs' sodium and and causing cardiac arrest and death.

Their findings confirm what researchers have seen in carefully controlled lab experiments with the fungus, but SF State biologist Vance Vredenburg said the data from wild frogs provide a much better idea of how the disease progresses.

"The mode of death discovered in the lab seems to be what's actually happening in the field," he said, "and it's that understanding that is key to doing something about it in the future."

The study is published online by peer-reviewed journal and funded through the joint National Science Foundation and National Institutes of Health program, of Infectious Diseases.

At the heart of the new study are blood samples drawn from mountain yellow-legged frogs by Vredenburg, who is an assistant professor of biology at SF State, and colleagues in 2004, as the chytrid epidemic swept through the basins of the Sierra Nevada range.

"It's really rare to be able to study physiology in the wild like this, at the exact moment of a disease outbreak," said UC Berkeley ecologist Jamie Voyles, the lead author of the study.

Unfortunately, it is a study that can't be duplicated, at least not in the Sierra Nevada. there have been devastated by chytrid, declining by 95 percent after the fungus was first detected in 2004.

"It's been really sad to walk around the basins and think, 'wow, they're really all gone,'" Vredenburg said.

The attacks an amphibian's skin, causing it to become up to 40 times thicker in some instances. Since frogs depend on their skin to absorb water and essential electrolytes like sodium from their environment, Voyles and her colleagues knew that chytrid would disrupt fluid balance in the infected amphibians, but were surprised to find that electrolyte levels were much lower than anticipated for the sample.

"It's clear that this fungus has a profound effect in the wild," Voyles said.

"Wildlife diseases can be just as devastating to our health and economy as agricultural and human diseases," says Sam Scheiner, NSF program officer for EEID. "Bd has been decimating frog and salamander species worldwide, which may fundamentally disrupt natural systems. This study is an important advance in our understanding of the disease, a first step in finding a way to reduce its effects."

Scientists want to learn as much as they can about how chytrid affects wild amphibians, with the hope that these findings will lead to better treatments for the infection.

For instance, Voyles said, the new study suggests that individual frogs being treated for the infection might benefit from having electrolyte supplementation in the advanced stages of the disease.

Researchers like Vredenburg already are experimenting with different ways of treating individual frogs, such as applying antifungal therapies or inoculating the frogs with "probiotic" bacteria that produce a compound that kills the fungus.

"The disease is not very hard to treat in the lab with antifungals. We know we can treat animals there," Vredenburg said. "But in nature, the disease is still a moving target."

It is still unclear exactly how chytrid spreads across a region, and which frogs might be susceptible to re-infection after treatment. Earlier this year, Vredenburg and colleagues published a paper showing that a common North American frog might be an important carrier of the infection.

Chytrid has killed off more than 200 amphibian species across the globe, but Voyles said the new studies offer "sort of a glimmer of hope that it might be possible to do something to mitigate the loss of frogs in the field."

Explore further: Male monkey filmed caring for dying mate (w/ Video)

More information: dx.plos.org/10.1371/journal.pone.0035374

Related Stories

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

Apr 18, 2014

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.