by Berglind Karlsdóttir - May 31, 2018

So far, year 2018 marks a year of significant advances in our understanding of the chytrid fungus, or Batrachochytrium dendrobatidis – a deadly pathogen that has likely caused the declines or extinctions of over 200 amphibians species worldwide.

The pathogen was first discovered in the 1990s after many years of unusually high declines in amphibian populations being simultaneously documented by researchers at different locations. Following research has revealed that there are four strains of the pathogen, which can infect at least 695 species of amphibians around the world. The fungus has been described as the “worst pathogen in the history of the world, in terms of its impact on biodiversity.” (Mat Fisher, Imperial College London).

A dead, bd-infected harlequin toad in Panama

Until this month, the origin of the fungus had remained unclear, with some pointing towards Africa. On the 11th of May, a team of 58 researchers published a study in the Journal Science. The study revealed that the fungus originated in the Korean peninsula, where it coexisted peacefully with the native fauna until sometime in the 1950s. Then, the disease started to spread on an international scale due to human activities, including the pet trade and possibly the Korean War.

The timing of this study coincides with positive news from Panama, published in March. The research showed that some species of amphibians appear to be developing resistance to the chytrid fungus. The researchers began to notice that some species of frogs, which are highly susceptible to fatalities after exposure to the fungus, are persisting and possibly even recovering following outbreaks. Evidence suggests that this resistance might be the result of antimicrobial substances secreted by the skin of wild amphibians.

A male Atelopus limosus, one of the species which have showed resistance.

This study offers optimism for amphibian conservationists working with wild and captive species in affected areas. Yet, continued research and monitoring is needed to understand which species are affected, and how best to ensure their survival.

A third study brings us one step ahead in the race against the fungus. Researchers at Washington State University have successfully detected the chytrid fungus a month before outbreaks occurred in a population of yellow-legged frogs in California. The researchers used environmental DNA (a novel way of analysing genetic material in soil or water) to detect the disease. The method can be used to set up “early warning systems”, which allow for detection of the fungus as it arrives. Management of identified high-risk populations can then be targeted to avoid mass die-outs.

As research continues to emerge, we are better armed in the fight against the chytrid fungus. In combination, these findings offer hope for safeguarding threatened amphibian populations on a global scale.