Bd Invades Everywhere (Via HerpDigest)

Bd Invades Everywhere
Smithsonoanian Tropical Research Inst. 1/31/10

Bd is a waterborne pathogen, and until recently, was thought to be limited by temperature, but the extent to which it persists and causes disease in amphibians at lower elevations in the neotropics is not known


A group of scientists led by Vanessa L. Kilburn of McGill University and including Roberto Ibáñez, director of STRI´s Amphibian Rescue and Conservation Center in Panama, Oris Sanjur and Eldredge Bermingham, also from STRI, Justin P. Suraci of Simon Frazer University and David M. Green of McGill, has just published an article in EcoHealth on the "Ubiquity of the pathogenic chytrid fungus, Batrachochytrium dendrobatidis, in anuran communities in Panama."

Batrachochytrium dendrobatidis (Bd) has been implicated as the main driver of many enigmatic amphibian declines in neotropical sites at high elevations.

Bd is a waterborne pathogen, and until recently, was thought to be limited by temperature, but the extent to which it persists and causes disease in amphibians at lower elevations in the neotropics is not known. It also is unclear by what mechanisms Bd emerged as a pathogenic organism; there is debate as to whether it is endemic to the region and for some reason its pathogenicity increased, or if it is a new pathogen to the region.

In this research, conducted in western Panama in 2006, several study sites were established along the epidemic gradient caused by Bd, including sites where the epidemic had not yet arrived, places right in the middle of the epidemic and others two and 10 years after the epidemic. Other sites were also established along an altitude gradient between 45 and 1,215 meters above sea level. 

After analyzing samples obtained from the skin of the frogs using quantitative PCR analyses to detect the fungus, the scientists found that there were infected frogs everywhere, including sites where the fungus arrived years ago, as well as lowland sites.

When comparing lowland frog abundance with previous years, the scientists also noticed a decline in frog diversity and abundance.

It is very difficult to know if Bd is an endemic organism or a new, recent arrival. However, based on the results of this study and current knowledge, the scientists maintain the idea that chytridiomycosis is new and invasive and that it is spreading all over the world.