The fungus coats the animals' undersides and legs, which suffocates them because they breathe through their skins. Though unknown before 1988, the fungus has now been discovered affecting 24 different species of frogs and toads in a range of countries, in both wild and captive sites. It is a new genus of a fungus group, the chytrids, which had previously only been known to attack invertebrates.
However it has taken almost 10 years to reach the diagnosis, after frogs and toads in zoos in the United States began falling ill. At first scientists thought it was caused by a water-dwelling bacterium, and only changed tack in 1996. By then the disease had become established.
Now that scientists have the answer, they are facing up to the possibility that they are themselves spreading the illness. Researchers investigating the declining numbers of the animals have realised that their visits to sites could infect healthy animals.
The effect of a rapid fall in frog and toad numbers could be to upset food chains, because larger animals which rely on them for food could go hungry. Frogs from high-altitude rain forests appear to be particularly susceptible.
The fungus's role in the deaths was discovered simultaneously in the US and Australia, and scientists are now puzzling over how to treat it. An anti-fungal agent would work in zoos, but applying it in the wild presents a huge problem. To cut the risk of spreading the fungus, members of the Task Force have drawn up a code of practice for field workers who handle amphibians.
They have to remove mud and debris from clothing, traps and vehicles, scrub equipment with ethanol and wear disposable gloves.