World frog trade spreading killer diseases - environment - 07 May 2009 - New Scientist

Description

Millions of frogs are shifted around the world each year for sale as pets and food. Now research shows, for the first time, that this global trade is spreading two severe diseases – one of which is blamed for driving amphibians towards extinction.

Last year the World Organisation for Animal Health (OIE) took a step towards monitoring both diseases by making them "notifiable", but as yet there are no regulations to prevent the trade of infected frogs.

"This is a major issue," says Peter Daszak , president of the Wildlife Trust , and an expert on amphibian diseases. "Over a million bullfrogs a year come into the USA for food. If only five per cent are infected, that's 50,000 infected animals."

Importing disease

Daszak and colleagues surveyed frogs that were imported through three major US ports: Los Angeles, San Francisco and New York. In each city, they visited market stalls and stores selling live imported bullfrogs or frog parts, purchased samples, and took them back to the lab where they were tested for the fungus Batrachochytrium dendrobatidis (Bd) and for ranaviruses – viruses specific to amphibians.

Bd causes devastating chytrid disease, first identified about a decade ago. In the past few years, a number of studies have shown that it is an important factor in the recent drop-off in amphibian numbers. Worldwide, chytrid disease has caused extinctions and declines in 200 species of frogs. Ranaviruses also cause large die-offs, but scientists do not yet know whether they can contribute to extinctions.

Just over eight per cent of the frogs the researchers sampled had ranaviral diseases, whereas two thirds carried the chytrid fungus.

'Major factor'

"Considering the devastating impact Bd has had on global amphibian populations and the millions of animals being traded on an annual basis, this number is ...

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