Live Bullfrog Trade Helping to Spread Deadly Fungus

A Frogs Are Green reader alerted us to a recent Dot Earth (New York Times) blog post by Andrew C. Revkin, “Genetic Study Finds Bullfrog Trade is Prime Pathway For Devastating Amphibian Fungus.”

University of Michigan mycologist Tim James and colleagues conducted a genetic analysis and have found that the global trade of live bullfrogs is helping to spread the deadly chytrid fungus, which has devastated worldwide amphibian populations. The results were published in the journal Molecular Ecology.

As Revkin notes, it isn’t clear why the fungus is devastating to amphibians in some areas, but seems to be harmless to those in other areas. For example, although there are deadly strains in the Northeast, there are no chytrid-related declines reported. Environmental conditions or other issues might account for this.

The researchers examined the role of bullfrog farming in spreading the chytrid fungus between the forests and frog farms of Brazil and then to the United States and Japan. They collected and analyzed bullfrogs sold at Asian food shops in seven U.S. cities and found that 41 percent of the frogs were infected with chytrid fungus, which is harmless to humans. Frogs in these shops are imported live primarily from farms in Taiwan, Brazil and Ecuador and sold as food for their legs.


“A lot of the movement of this fungus is related to the live food trade, which is something we should probably stop doing,” James said. “We don’t need to have millions of live frogs being shipped from foreign countries into the United States.”

For more information: Press release from the University of Michigan


Frogs Legs: Worldwide Consumption Contributing to their Extinction

Eating frogs legs is a bit of a joke to Americans. Most of us would never consider eating them. Yet we need to take this very real threat to frogs seriously.

A recent article in Scientific American, “How Eating Frogs Legs Is Causing Frog Extinctions,”* listed some pretty amazing statistics:

  • Over two thousand metric tons of frog legs are imported into the U.S. each year. Another two thousand metric tons of live frogs are imported every year for sale in Asian-American markets.
  • The European Union imports an annual average of 4,600 metric tons of frog legs, mostly to Belgium (53 percent), France (23 percent) and the Netherlands (17 percent), the equivalent of about one billion frogs.

The numbers in the Scientific American article come from a recent report, “Canapés to Extinction: The International Trade in Frogs’ Legs and Its Ecological Impact” (pdf), released on July 26 by the wildlife conservation groups Pro Wildlife, Defenders of Wildlife and the Animal Welfare Institute.

According to Alejandra Goyenechea, acting director of international conservation programs for Defenders of Wildlife:

Humans have been eating frogs for ages. But today the practice is not sustainable on a global scale. Billions of frogs are traded internationally each year for human consumption, and that industry is responsible for depleting wild populations, spreading deadly disease, and allowing invasive species to destroy the health of native ecosystems.

This huge demand for frogs legs is contributing to frog extinctions for two reasons:

  • Too many frogs, collected from the wild, are depleting natural populations
  • The international trade in frogs legs and live frogs is the major reason for the spread of the deadly chytrid fungus (Batrachochytrium dendrobatidis), which has already been blamed for amphibian extinctions around the globe.

According to the report, most frog and frog leg imports to the U.S. come from China, Taiwan, Ecuador, Brazil, the Dominican Republic, Vietnam, Mexico and Indonesia. One of the species farmed is the Bullfrog, an American native species that has spread around the world. But Bullfrogs are one of the most notorious carriers of the chytrid fungus. According to Save the Frogs, as quoted in the SciAm article:

A recent study estimated that 62 percent of the bullfrogs entering California from Asian frog farms are infected with the chytrid fungus. Bullfrogs serve as perfect vectors for fungus, as the frogs can survive infection loads of millions of chytrid zoospores. Because the infected frogs don’t die from the fungus, they are able to spread the pathogen to native amphibian populations.

Bullfrogs are usually resistant to the chytrid fungus and rarely, if ever, die from exposure to it. Most other amphibian species have an 80 percent mortality rate when exposed to the fungus.

Exact statistics on which species are being imported and eaten are incomplete, because most imports are already skinned, processed and frozen, making them hard to identify.

The three organizations behind this report are now calling for increased regulation of the frog trade under the Convention on Trade in Endangered Species of Wild Fauna and Flora (CITES). That agency has the authority to restrict some hunting and harvesting, create humane standards for frog handling and killing, set monitoring criteria for wild populations, and require that all imported meat be frozen, which would slow the spread of disease.

Last year, the U.S. Fish and Wildlife Service asked for public comments on a proposal to ban the import of live frogs under the Lacey Act, which regulates the import or transport of wildlife species that are either dangerous to humans or the environment. The public comment period ended in December, but so far there is no word yet on if the proposal will become law.

For more information:

*Information from this post comes from:

Scientific American, “How Eating Frogs Legs Is Causing Frog Extinctions

Defenders of Wildlife: Amphibians in Crisis

Save the Frogs: The Problem with Frogs Legs