The race to stop a global killer

A deadly fungus sweeping the world is behind the mass death of hundreds of amphibian species. Researchers in Europe have teamed up to work out how to stop it – can they succeed? Scientific endeavour isn’t always as glamorous as crashing atoms into each other deep underground in Switzerland, or sending rovers to roam the…”
Editors Online
November 24, 2012 2:28 am

A deadly fungus sweeping the world is behind the mass death of hundreds of amphibian species. Researchers in Europe have teamed up to work out how to stop it – can they succeed?

Scientific endeavour isn’t always as glamorous as crashing atoms into each other deep underground in Switzerland, or sending rovers to roam the surface of Mars looking for clues to life. For Dirk Schmeller, a researcher at the CNRS research centre in Moulis, southern France, there are more fundamental problems to deal with – like how to get a stubborn ass to shift.

Donkeys and mules may not be the most hi-tech option for lugging large volumes of water down a Pyrenees mountain, but it’s the most effective… until you get an uncooperative animal, of course. “We can thank Gaston and Justin, but we aren’t thanking Emile,” says biologist Adeline Loyau, Schmeller’s co-worker and wife, while discussing who to include in the acknowledgements section when writing up their research. Gaston, Justin and Emile were the donkeys Loyau and Schmeller hired to carry lake-water samples down from the mountain last summer. Her displeasure with Emile stems from a stressful day she spent unsuccessfully trying to get the beast to budge, in turn condemning Loyau to a backbreaking hike to and from a lake with up to 30 kilos (66 pounds) of water.

The donkeys have a key role in trying and save some of the world’s most vulnerable amphibians from their plight. Schmeller, Loyau and their colleagues are part of a Europe-wide project, RACE (Risk Assessment of Chytridiomycosis to European Amphibian Biodiversity), investigating – and trying to halt the spread of – a fungal disease that threatens to devastate amphibian populations across the globe.

The disease is already responsible for the mass death of over 350 amphibian species, pushing many to the brink of extinction. “If a single pathogen were causing the death, decline and extinction of 30% of mammal species (including humans), the entire world would be paying attention,” wrote the evolutionary biologists Valerie McKenzie and Anna Peterson from the University of Colorado last month. “This is what has been happening to the world’s amphibians.”

Jaime Bosch first encountered the amphibian threat in Europe just over a decade ago. He was studying communication between midwife toads (Alytes obstreticans) in a lake in the Peñalara national park outside Madrid, when his worst nightmare began to appear before his eyes. The toads were beginning to die off in huge numbers, a once thriving lake became a graveyard for countless floating bodies. By 1999, Bosch and his colleagues at the Museo Nacional de Ciencias Naturales in Madrid reported that no living animals were found in 86% of the toad’s usual mating ponds in Central Spain.

But this wasn’t just happening in Spain. Thousands of dead amphibians were found floating in waters in North and Central America, and Australia. What was causing this mass slaughter seemed to have little regard for borders or which species it infected. In 1999, scientists finally tracked down the culprit and gave the disease a name: Batrachochytrium dendrobatidis, or Bd.

Lakes of death

Since then, a handful of scientists have got together to track its spread throughout Europe. Fungal epidemiologist Matthew Fisher, now at Imperial College, London, recalls how he first got involved in Europe’s Bd fight in 2002. He had just returned to the UK from studying the evolution of killer fungi at the University of Berkeley, California, when he read Bosch’s work on this mysterious new disease. Fisher got in touch, little suspecting the gruesome nature of what he was about to encounter.

“Jaime started FedEx-ing me these boxes of rotting frogs,” Fisher explains. As well as stinking out a lab, rotten bodies aren’t very useful for studying the genetic roots of the disease. Fisher needed a live sample of the fungus, but even Bd has its limits, and is easily killed by the bacteria in rotting flesh. “You have to get it from a frog that is either close to death, or recently dead,” he says.

Once he started to receive very fresh animals, Fisher managed to successfully grow the fungus in culture. “From that point on we could look at it’s virulence, and genetics, and to start to do proper epidemiology,” he says. Fisher was finally in a position to study the genome of the disease, to try and understand how it evolved.

In 2003, Fisher and Bosch began driving around Spain looking for amphibians to sample for the disease. At the end of a long days’ hiking in the Spanish Pyrenees they arrived at a mountain lake called Ibon Acherito. They were confronted by an amphibian horror scene, a “lake of death” Fisher says. “We saw dead animals everywhere,” says Fisher. They found more gruesome scenes in other lakes in the Aspe and Lescun valleys of the French Western Pyrenees. Ever since that grisly hiking trip Fisher and his team have been regularly revisiting the lakes to monitor the health of the animals and the spread of the disease.

Meanwhile, Schmeller arrived at the tiny French Pyrenean village of Moulis, tucked away in the lush, remote Ariege area of Southern France. Moulis hosts a French national research centre, and Schmeller started work there in 2007 to monitor the area’s biodiversity. Around the time Fisher and Bosch were getting to grips with rotten toads and frogs, Schmeller was investigating the population genetics of waterfrogs at the University of Mainz, Germany, and met PhD student Trent Garner through his work. Garner moved to Fisher’s lab, and realised that Schmeller, newly landed in Moulis, was perfectly poised to investigate this mysterious disease in the Pyrenees. “I was working with amphibians and genetics before, but diseases was a whole new thing to me,” says Schmeller.

They gathered together other researchers, and initiated the Europe-wide RACE project, with €1.5 million funding from the EU’s Biodiversa network, as a concerted, organised effort to understand Bd in Europe. Schmeller’s team work with Fisher in the Aspe and Lescun valleys, and also monitor eastern Pyrenean lakes every year, to see whether Bd has reached them. There they hike up to the Bassies mountain refuge in the Auzat-Vicdessos valley, and spend hours waist-deep in cool mountain lakes, collecting frogs, toads and newts. They swab them, weigh and measure them and sometimes mark them with tiny electronic tags.

Cold comfort

So far, even though Bd has reached the western Pyrenees, the lakes Schmeller and his colleagues are monitoring in the east are disease-free, although Schmeller doesn’t expect them to remain so for much longer. “You can run but you can’t hide from Bd. It will get there in the end,” Fisher told a meeting of all RACE participants in May this year.

The end is pretty horrific for frogs, toads and other amphibians. Once Bd infection sets in, the skin thickens. This is deadly for amphibians because they absorb water and nutrients through their skin, not through the mouth like we do. The disruption in fluid balance leads to heart failure, and eventually death.

Culled From: Punch

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