Island toad population cleared of killer amphibian fungus

A deadly fungus that has been decimating amphibians worldwide for decades has been eradicated from an island population of wild toads, thanks to a breakthrough study.

Chytridiomycosis—the infection caused by the chytrid fungus—is considered by the IUCN to be the worst disease to affect vertebrates in recorded history, in terms of the number of species impacted and the speed of their demise.

Since it was first identified in the 1990s, the fungal infection has been detected in over 700 amphibian species across five continents, driving many to the brink of extinction and others over it—some before they had even been discovered.

According to the charity Save Our Frogs, the disease spreads when infected amphibians are imported, either for use in research or via the exotic pet trade, and come into contact with native species when they are set free or if their tank water is released into the environment.

But a new study, published in the journal Biology Letters, has shown that it is possible to stem the tide of death by treating both amphibian populations and their habitats. Following a successful project, researchers from the Zoological Society of London (ZSL), the National Museum of Natural History in Spain (MNCN) and Imperial College London have eliminated the chytrid fungus from a population of wild Mallorcan midwife toads (Alytes muletensis).

The seven-year experiment involved applying an antifungal treatment to the tadpoles of the toad species, as well as using a common laboratory disinfectant to sterilise their environment.

‘This study represents a major breakthrough in the fight against this highly-destructive pathogen; for the first time we have managed to rid wild individuals of infection for a continued period,’ said Co-author Dr Trenton Garner, Reader within ZSL’s Institute of Zoology. ‘Amphibian-associated chytrid fungi are a critical conservation issue that requires simple, straightforward and transferable solutions. Our study is a significant step towards providing these.’

Dr Jaime Bosch, Senior Researcher at MNCN, added: ‘This is the first time that chytrid has ever been successfully eliminated from a wild population—a real positive which we can take forward into further research to tackle this deadly disease. Chytrid is a global issue which affects amphibian populations worldwide, and I am proud to be part of a team of leading institutions at the forefront of this pioneering research working towards a solution.’