Successful disease elimination offers hope for amphibians

Midwife toad

Midwife toad

23 August 2016

Scientists have reported one of the first big wins in the fight against an invasive fungal disease that's cutting a swathe through the world's frogs, toads, newts and salamanders.

New diseases are one of the biggest threats to natural ecosystems worldwide, and we urgently need new ways to control them. Researchers have had some success in clearing the deadly Batrachochytrium dendrobatidis (Bd) fungus from captive populations, but this is the first time anyone's managed to do so in the wild.

A study in Biology Letters describes how researchers from Imperial College London, the National Museum of Natural History in Spain and the Zoological Society of London tried over five years to eliminate Bd fungus from ponds on the Mediterranean island of Mallorca, where it was introduced by human activities.

Initially the scientists tried taking tadpoles of the Mallorcan midwife toad into the lab and treating them with antifungal chemicals. This worked, but the animals tended to be re-infected once they were reintroduced to the ponds they'd hatched in.

So the researchers decided to try also disinfecting the ponds themselves, using a common laboratory decontaminant chemical, suitably diluted. The results were very encouraging; at four of the five pools treated, the Bd infection has been eliminated and hasn't returned in two years.

Bd has ravaged and even destroyed amphibian populations across five continents; so far it's infected more than 700 species. The new method won't be enough on its own to deal with the threat, as the evidence suggests the fungus is being frequently carried around the globe and so will probably return unless other steps are also taken. And introducing laboratory decontaminant chemicals into the environment isn't something to be done lightly. But as part of wider efforts to control the spread of Bd and other emerging fungal diseases, this method could offer hope for populations that are under severe pressure.

DOI: 10.1098/rsbl.2015.0874.