SAN FRANCISCO, May 16 (UPI) -- African frogs imported into the United States for early 20th century pregnancy tests carried a deadly disease that has decimated amphibians, researchers say.
African clawed frogs have long been suspected of introducing Batrachochytrium dendrobatidis, a fungus that has led to the recent decline or extinction of 200 frog species worldwide, researchers at San Francisco State University said.
From the 1930s to 1950s, thousands of African clawed frogs were exported across the world for scientific research, the pet trade, and for pregnancy tests since these frogs will ovulate when injected with a pregnant woman's urine.
"We found that African clawed frogs that have been introduced in California are carrying this harmful fungus," San Francisco State biologist Vance Vredenburg said. "This is the first evidence of the disease among introduced feral populations in the U.S., and it suggests these frogs may be responsible for introducing a devastating, non-native disease to amphibians in the United States."
African clawed frogs are potentially potent carriers of the fungus because they can be infected for long periods of time without dying, allowing them to pass it on to more vulnerable species, he said in a university release Wednesday.
"It's amazing that more than half a century after being brought to California, these frogs are still here, and they still carry this highly infectious disease," Vredenburg said.
While the frogs' use, sale and transport are now highly regulated in California, the damage has been done, he said.
"Now we need to be cautious about other introduced species," Vredenburg said. "There could be other animals out there that are carrying diseases that we don't even know about yet."