The importance of regulating trade really hit home recently after Fisher and his team published a detailed look at Bd’s genome. When Fisher and his team deciphered the DNA from 20 fungus samples, they found three distinct strains of Bd. One is isolated in South Africa, another in Switzerland, both of which aren’t as deadly as the third.
The bad news for the European team is that the third strain, the one found in the Pyrenees, is hypervirulent – extra deadly. This strain, BdGPL, is also responsible for infections in Central and North America, and Australia. It seems likely the only way the fungus travelled such distances is through human movements – mainly through trade. That trade could also be responsible for BdGPL’s deadly characteristics – its genome reveals that it was formed from the recombination of different, possibly harmless, strains of Bd to become the lethal frog-killing fungus. “We’re dealing with a much more complex evolutionary history than previously expected,” says Fisher.
So far the story seems gloomy at best. Amid all the monitoring experiments, mitigation efforts and genomic analyses, it’s hard to see a rosy prognosis for amphibians, particularly those destined to live at high altitudes. “The reintroduction doesn’t work, disinfection is very difficult, cleaning of ponds in Mallorca didn’t work,” says Schmeller. “It’s very difficult.”
Time will tell. Optimism is essential for researchers in this field, and Fisher thinks there are reasons to be cheerful. “I’d be very sceptical of a shock horror story in Europe,” he says, despite having witnessed “lakes of death” for himself. Bd will continue to cause population declines in high altitude places, including the Pyrenees, he predicts, but things could change.
One glimmer of light is that Fisher’s genome work revealed something else about Bd – “the fungus has an extraordinarily dynamic genome,” he says, “This means there could be very rapid selection for less virulent lineages,” Fisher explains. It makes sense: the disease can’t propagate if it kills off all its hosts. What would be a much better scenario for the fungus’s survival is a milder version that can live together with the amphibians it infects.
Bosch, who first witnessed the devastating effects of Bd, agrees. “In the end, most amphibian species here will co-exist with Bd,” he says. That’s not to say that amphibians are safe. “Just for a few of them, in high elevation areas, most populations will disappear,” Bosch adds. “In my opinion, the key is just to try to keep these populations alive for a few generations to allow natural selection to act.” This is why he believes his breeding centre is so important.
Schmeller is about to take up a new post at the Helmholtz institute in Leipzig, but he’s determined to keep a close eye on amphibians in the Pyrenees, even if natural selection might end up being the only answer. “We need to stay vigilant,” he says. So until Bd is better understood, or trade rules tightened to control its spread, Schmeller and his team will continue wading through chilly mountain lakes swabbing toads and newts. With or without the help of those stubborn donkeys.