Scientists find frog legs trade may facilitate spread of pathogens

Nov 19, 2009
These are frog legs for sale at a market in Indonesia. Credit: A. Roselli

Most countries throughout the world participate in the $40-million-per-year culinary trade of frog legs in some way, with 75 percent of frog legs consumed in France, Belgium and the United States. Scientists at the Smithsonian Institution and colleagues have found that this trade is a potential carrier of pathogens deadly to amphibians. The team's findings are published in the scientific journal Frontiers in Ecology, Thursday, Nov. 19.

Amphibians are rapidly declining worldwide. More than one-third of the nearly 6,000 amphibian species are threatened with —disease is one of the main causes. Among the known amphibian pathogens, the parasitic fungus Batrachochytrium dendrobatidis, also known as amphibian chytrid (KI-trid), is a top concern. The fungus, which attacks keratin proteins in the skin of amphibians, including frogs, causes respiratory and and eventually death.

"Amphibian chytrid is an unusual example of a disease that is a primary cause of extinction in amphibian species," said Brian Gratwicke, biologist at the Smithsonian's National Zoo and lead author of the team's paper. "In fact, amphibian chytrid has been listed as a likely threat in 94 cases out of the 159 extinct and potentially extinct . There are several hypotheses about how amphibian chytrid has spread around the world, but the trade in amphibians for food, bait, pets and laboratory animals has been identified as the most likely mode of spread."

This chart illustrates global exporters and importers of frog legs (1996-2006). Credit: Data from the UN Commodity Trade Statistics Database

Although consuming amphibian legs is familiar to many people as a culinary curiosity, the global extent of the international trade is unknown. The team of scientists' research focused on 1996 through 2006, during which more than 100,000 metric tons of frog legs were imported from both wild and farmed sources, at a net value approaching half a billion dollars. One kilogram of frog legs averaged about $4 over this period—a kilogram of frog legs requires 10 to 40 individual animals translating to approximately 100 to 400 million animals per year.

The scientists found no recorded cases of the extinction of a frog species caused by collection for food. However, given the growing importance of aquaculture to supply frog legs to global markets, the team stresses that the risk of disease spread through poorly regulated amphibian trade is probably an even greater risk to amphibian biodiversity than the direct population effects of overharvesting.

In countries such as Indonesia, which exports about 45 percent of all frog legs, the majority of animals are thought to be wild-caught and there is little to no effort to monitor this food source for disease pathogens. "Any trade in live frogs or fresh, un-skinned frog legs presents a substantial risk of the spread of amphibian chytrid," said Gratwicke. "The implementation and enforcement of some key amphibian trade policies could be a cost-effective conservation tool to mitigate disease risks associated with the trade."

The American bullfrog is one of the many species used in the frog leg trade. Credit: Mehgan Murphy / Smithsonian's National Zoo

The exact origin of amphibian chytrid is unknown, but one theory is that it originated in Southern Africa and was distributed worldwide in the 1950s through the trade of the African clawed frog for pregnancy-testing and other amphibian trade. Amphibian chytrid has been detected in many parts of the United States, but some species are apparently resistant to the fungus, and it is not always associated with amphibian declines. The most dramatic declines have been observed in mountainous parts of Central and South America and Australia where it is responsible for the disappearance and probable extinction of many species.

Source: Smithsonian (news : web)

Explore further: 'K-to-M' histone mutations: How repressing the repressors may drive tissue-specific cancers

add to favorites email to friend print save as pdf

Related Stories

Bullfrogs may be deadly fungus carriers

May 24, 2006

A British-led study suggests the introduction of the North American bullfrog into many nations might be causing the spread of a deadly fungus.

Colombian frog believed extinct found alive

May 18, 2006

Researchers exploring a Colombian mountain range found surviving members of a species of Harlequin frog believed extinct due to a killer fungus wiping out amphibian populations in Central and South America.

Recommended for you

Hydrogen powers important nitrogen-transforming bacteria

22 hours ago

Nitrite-oxidizing bacteria are key players in the natural nitrogen cycle on Earth and in biological wastewater treatment plants. For decades, these specialist bacteria were thought to depend on nitrite as ...

New tool aids stem cell engineering for medical research

Aug 28, 2014

A Mayo Clinic researcher and his collaborators have developed an online analytic tool that will speed up and enhance the process of re-engineering cells for biomedical investigation. CellNet is a free-use Internet platform ...

User comments : 0