About half of the world's frog and amphibian species are threatened with extinction. In an effort to raise public awareness, 2008 has been named the year of the frog by Amphibian Ark.  Various zoos, aquariums, and conservation organizations have joined the effort, along with several celebrity conservation biologists, including Sir David Attenborough, Jeff Corwin, and Jean-Michel Cousteau.  Their goal is to engage the public, create partnerships, and generate financial support for projects aimed at better understanding and conservation of amphibians.

Frogs, in particular, suffer from multiple problems, including habitat loss, water pollution, climate change, and chytridiomycosis, a skin infection caused by a fungus.  Scientists discovered this organism on frog skin about ten years ago.  The first studies found the infection only in parts of the U.S. and Australia.  Since then, the disease has been diagnosed in frogs worldwide and implicated in the decline or extinction, dating back to the mid-70s, of several frog species.  Initially, the fungus was thought to be a secondary invader, a problem only in frogs whose health was compromised by other variables, such as environmental degradation and global warming. 

Scientists have recently changed their thinking.  The species of frogs declining most rapidly--those living at higher elevations in the tropics of South America--have not experienced rapid changes in their environment, nor have toxins or pollutants been identified that would explain the pattern.  Chytrid infection has been found in nearly every case of frog decline, however.  The fungus has been found in South African frogs (where, however, it does not cause disease).  Humans have apparently caused its spread around the world, primarily via the movement of wildlife, but potentially also on our shoes or in contaminated water, with devastating effects. 

Some frogs are resistant, including three species considered to be invasive: South African clawed frogs, marine toads, and American bullfrogs.  Like the fungus, these species of frog thrive when introduced into new habitats and displace the native species.  Most experts now consider chytrid fungus to be a primary pathogen in native species of frog.  See recent article on Frog Chytridiomycosis in EcoHealth

Little can be done for free-living frogs other than trying to stop the movements of people or wildlife that introduce and spread the disease.  In captivity, the disease can be treated.  Given the rapid rate of extinction among free-living frogs, breeding stocks in zoos and aquariums represent the future for many species.  The challenge will be to keep captive-living frogs breeding and free of chytrid disease.  Perhaps resistance to this organism can even be bred into endangered captive-living frogs destined for eventual reintroduction. 

Many veterinarians have been involved in the development of plans to prevent and treat this infection.   Several years ago I helped with a pilot study to evaluate the effectiveness and safety of several common fungicides, including chlorhexidine and bleach.  The chytrid fungus lives on the frog's skin and is relatively easily destroyed by placing the animal in a shallow bath of dilute disinfectant. 

I noticed on the "2008 Year of the Frog" website that Chlorox chemical company recently signed on as an official sponsor of the campaign.  In captive frog environments, bleach is used to clean everything from containers to keepers’ boots.  The same recommendation has been made for anyone working with wild frogs, particularly those who move from one habitat to another or who work with both captive and free-living frogs.  Itraconazole, a prescription antifungal drug, is currently the treatment of choice for sick frogs. 

Any chemical can be toxic to a frog, however, given that amphibians absorb most things through their skin.  So treatment of chytrid infections must be done very carefully.  The risks associated with chemical use motivated researchers studying endangered yellow-legged frogs from California’s Sierra Nevada mountains to evaluate a more natural approach.  Scientists at James Madison University discovered a bacteria found on the skin of Western red-backed salamanders and found that it delayed the growth of the chytrid fungus in a Petri dish.  Next they used it to treat yellow-legged frogs infected with the fungus. They also found the red-backed salamander bacteria on the skin of unaffected wild yellow-legged frogs.  Their experiments yielded promising results, so much so that the authors of the paper use the term probiotic to describe their new frog medicine. 

The researchers suggest that the bacteria could be used to one day treat wild frogs.  I'm not sure how that will work—sounds like quite a challenge!—but at least their results offer some welcome good news about the amphibian crisis.