Diseased Frogs Discovered in San Diego

African clawed frogs living locally tested positive for a "deadly amphibian pathogen"

African clawed frog
Courtesy of Brian Gatwicke

Two African clawed frogs found in San Diego tested positive for a deadly disease, according to researchers at Stanford University.

Each frog harbored a “deadly amphibian pathogen,” according to Stanford University School of Medicine scientists. The pathogen, called batrachochytrium dendrobatis, is transmitted by water and turns into a fungus which can infect other amphibians, which can kill them.

The African clawed frog is a non-native species that live in San Diego now, according to Dr. Sherril Green at Stanford, who researched the issue. The San Diego frogs that were tested for the disease were collected for scientific research in 2001, but Green said it is highly likely the African clawed frogs still live here.

“The San Diego community has a very healthy and well established population of the African frogs,” she said. “San Diego has those large drainage ditches, which is an ideal habitat for them.”

But what does that mean for San Diegans? The disease does not affect humans or other animals, though birds are known to carry the pathogen, said Green.

But the disease could prove deadly for amphibian populations. The disease could possibly eradicate native frog species, which could have an effect on the local ecosystem.

“We’ve lost about 200 different species of frogs with habitat loss, pollution and the spread of this fungus,” Green said. “It has decimated many populations.”

These frogs were introduced to the U.S. because of their use to biomedical research, according to Stanford researchers. Their first contribution to modern medicine? Pregnancy testing.

In the 1920s the frogs were used to help determine if a woman was having a baby. It turns out that injecting the frogs with urine from pregnant women would encourage egg production in the frog.

But now the frogs are known to be an invasive species and their use and transport are highly regulated in California and 11 other states.

Green warned that African clawed frogs can out-compete other species as they are reproductive year-round, so people should not interfere with their activity.

“This species of frog is restricted in California, you need to have a permit for research scientist and they cannot be owned as pets,” she said. “What we’ve learned from this is that releasing these animals into the wild it can have a negative impact on the environment.”

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