Chytidiomycosis and the Frogs that Lived

By now anybody who is remotely involved in biology has heard about the massive loss of amphibians around the world. And that one of the causes is fungal infection. The notorious amphibian Chytrid fungus (Batrachochytrium dendrobatidis, Bd) is a major culprit, leading to sporadic death in some species populations and up to 100% death in others.

 Batrachochytrium dendrobatidis

Chytridiomycosis, the infection name, hits the amphibian in stages. Upon first contact to amphibious skin, zoospores give rapid production to sporangia which then produces more zoospores. Those zoospores reinfect the host, causing a cascade of infection. This leads to a reddening and eventual sloughing of skin over the body, convulsions, lethargic changes in behavior and eventual death.

Luckily there have been some cases of treatment options for Chytrdiomycosis. Reid Harris of James Madison University found in 2009 that coating certain species with the bacterium Janthinobacterium lividum seems to offer protection from infection. Applying the chemical chloramhenicol to infected specimens of Archey’s frog (Leiopelma archeyi) cured them of the disease. And even use of Rooibos tea in water has been found to ward off chytridiomycosis in certain posion dart frogs.

In the June 07 online issue of PloS One journal, a study by Laura A. Brannelly, Matthew W. H. Chatfield, and Corinne L. Richards-Zawacki at the Tulane Univesity demonstrates that there are some species of Amphibians that are even resistant naturally to infection.

Field and Laboratory Studies of the Susceptibility of the Green Treefrog (Hyla cinerea) to Batrachochytrium dendrobatidis Infection

Their study was based on the observation that while amphibians around the world were succumbing to Bd there has not been a noticeable impact on the populations of southeastern United States.

With this in mind they chose a common amphibian from the region, the green treefrog (Hyla cinerea) and ran tests to determine the susceptibility of the species. They gathered frogs from a local wildlife area and found an absence of Bd. The team then went about inoculating them in the lab with strains of the fungus both from the region and more virulent strain from the Philippines.

While they were able to establish infection, the team found that some specimens cured themselves over the study, and those that maintained infection showed no clinical change in body condition over the 26 week experiment.

Their clinical evidence, along with the absence of Bd found on collected specimens of green tree frogs from other collections has lead the team to conclude that H. cinerea is not susceptible to the fungus that has been wreaking havoc on the amphibians of the world.

So, even facing a fungal based Amphibian Apocalypse in the rest of the world, you will always be able to retreat to the deep south to enjoy the chirping of frogs on a balmy summer night.

Phot Cred. Johnson ML, Speare R via. Wikimedia