Skin fungus causes frog death
The fungal disease is causing catastrophic
declines in frog populations around the world.
Image: iStockphoto

The mystery of how the killer frog disease chytridiomycosis destroys its victims is a step closer to being solved following the work of a group of scientists from James Cook University, the University of Sydney and the University of New Mexico.

Published in the latest edition of Science, the team reports on a series of experiments they conducted designed to test the effects of the fungus on the skin of green tree frogs.

“We measured skin functioning in frogs with severe chytridiomycosis. We also tracked physiological changes in blood and urine, and monitored heart function,” lead author Dr Jamie Voyles from James Cook University said.

“Our team of pathophysiologists, veterinary pathologists and disease ecologists found that the skin’s functions are severely impaired by the fungus. We think this leads to loss of electrolytes and cardiac arrest in frogs infected with the pathogen,” she said.

Dr. Voyles said the focus of this study was to understand how the fungal pathogen kills frogs.

“This question was unresolved for many years because superficial fungal infections are not normally lethal,” she said.

“Resolving the cause of death in infected frogs is an important step in understanding how this disease is causing catastrophic amphibian declines around the world.”

In Australia, chytridiomycosis is thought to be responsible for extinctions of eight species of frogs, and severe reductions in the numbers of other species in all states and territories except NT.

Another of the authors, Dr Lee Berger from James Cook University, said that unfortunately many frog species, including the Southern Corroboree Frog, still faced imminent extinction due to chytridiomycosis.

“Urgent funding is required for work on developing methods for managing the disease in nature,” she said, “because it is resulting in the greatest loss of biodiversity due to disease in recorded history.”

Worldwide, it has caused declines and possibly extinctions in at least 200 species of frogs in Central, South and North America, Europe, Africa, Spain and New Zealand.

Last year, the OIE, the World Organisation for Animal Health, declared chytridiomycosis globally ‘notifiable’ meaning that the 172 countries that are members of the OIE are required to report on the status of this disease in their country every six months and to implement strategies to limit transmission to other countries.

Dr Voyles, who recently passed her PhD examination, is a member of the Amphibian Disease Ecology Group at James Cook University.

JCU scientists have led the research into the disease since 1996, when Professor Rick Speare suggested that the decline in Australian frog species and populations was due to a new, contagious disease moving as an epidemic wave through coastal Queensland.

A year later Dr Berger, then one of Professor Speare’s PhD students, discovered the disease chytridiomycosis, determining it was the spreading disease predicted by Professor Speare.

More recently JCU Research Fellow, Dr Lee Skerratt, confirmed that it is the spread of the disease that has caused its global emergence and the loss of biodiversity and Professor Ross Alford has determined many of the ecological aspects of the disease.

Professor Speare, Dr Berger and Dr Skerratt are fellow authors of the latest paper in Science along with Dr Sam Young and Rebecca Webb from the Amphibian Disease Ecology Group at JCU’s Anton Breinl Centre for Public Health and Tropical Medicine, and Professor Alford from JCU’s School of Marine and Tropical Biology.

The JCU researchers were joined in the paper by Craig Campbell, Dr Anuwatt Dinudom and Dr David Cook from the University of Sydney’s Bosch Institute and Dr Wyatt F. Voyles from the University of New Mexico.

The work has been supported by the Department of the Environment, Water, Heritage and the Arts, and the Australian Research Council.

Editor's Note: Original news release can be found here.