Killer leapfrogs globe

July 26, 2002

The French love of frogs' legs is helping to spread a killer disease that threatens to wipe out amphibians around the world, according to new research.

The international trade in frogs has been identified as a key factor in the spread of a devastating amphibian fungal infection.

Scientists knew that the main cause of the global decline of frog, toad and newt populations was a combination of environmental factors and a number of diseases. But for years they had been puzzled by the relentless spread of the fungal infection.

Now, British-born Peter Dasak, chief executive of the Consortium for Conservation Medicine at Columbia University, New York, has discovered that the DNA of the fungal infection, which is harmless to humans, is identical all over the world.

At last week's Conservation Biology annual meeting in Canterbury, Dr Dasak said a disease would have to travel rapidly to avoid evolving genetic differences along the way. He believes the trade in frogs explains the fungal infection's rapid transit and lack of DNA mutations.

He said: "When you eat frogs' legs in Paris, they don't come from Europe. They have usually been bred in South America or Asia and transported live to the continent." The trade is vast. Each year, he said, China exported 2,500 tonnes to Europe. North America was a big importer, too.

The bull frog, a favourite in the food industry, can survive with infected skin. The fungus can enter the wild and infect other amphibian species when diseased bull frogs escape in transit and when restaurants discard the skin.

Europe's indigenous amphibian populations have had no time to build defences against the disease, so infection is usually fatal.

Dr Dasak's team, which is developing kits to test frogs for infection, wants better regulation of the food and pet trade.

Jim Collins of Arizona State University announced a newly mapped virus DNA sequence at the conference. It should help scientists discover how rapidly introduced amphibian diseases spread.

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