Deadly Frog Fungus Spreads in Virus-Like Waves

April 1, 2008

A frog-killing fungus in Central and South America spreads in waves like other infectious diseases, challenging a theory that climate change is to blame, a new study says.

The study runs counter to the results of a 2006 study published in the journal Nature, which found that global warming promoted the spread of the chytrid fungus.

The disease affects the skin of frogs and salamanders.

Chytrid spreads from central points of initial infection into surrounding areas in a wavelike pattern over time—similar to how the Ebola or West Nile virus moves, the new findings show.

The results appeared in the March 25 issue of the journal PLoS Biology.

Environmental Trigger

If global warming was triggering chytrid outbreaks, amphibian declines would occur in multiple spots simultaneously, according to lead author Karen Lips, a zoologist at Southern Illinois University.

"The idea is that the fungus is a native thing that naturally occurs in these areas, and that some environmental trigger causes it to break out, going from some form that doesn't infect or kill frogs to something that does," said Lips, who has received funding from the National Geographic Society. (The National Geographic Society owns National Geographic News.)

But the team found no evidence of concurrent declines.

Lips cited an example of two geographically similar sites in Central America separated by about 30 miles (50 kilometers). Frogs were dying in one site but were safe in the other.

"If temperature change was causing this outbreak, then the temperature change 50 kilometers away at the same elevation should be about the same and cause the outbreak of disease there," Lips said.

(Related news: "'Frog Hotel' to Shelter Panama Species From Lethal Fungus" [November 2, 2006].)

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