'Pregnancy Test' Frogs: Bearers of Killer Fungus African clawed frogs wreak havoc on ecosystems By Kevin Spak, Newser Staff Posted May 16, 2013 1:52 PM CDT 14 comments Comments This photo provided by the Nevada Department of Wildlife shows an African clawed frog Friday Aug. 1, 2008 in Reno Nevada. (AP Photo/Nevada Department of Wildlife) (Newser) – A species of frog that was once spread around the world as an early pregnancy test turns out to carry a horrifically deadly pathogen that can decimate local ecosystems. Mid-20th-century doctors used African clawed frogs as a weird-but-reliable pregnancy test—the frogs tend to ovulate when injected with a pregnant woman's urine, the New York Times reports. They were shipped everywhere from California to London to China, and often ultimately released into the wild, researchers said. That may not have been the greatest idea. A new study has found that the frogs carry Batrachochytrium dendrobatidis, a fungus that one researcher calls "the worst disease in vertebrate history." The fungus hardens amphibians' skin, which is generally fatal—except to the African clawed frog, which evolved in arid South Africa, the LA Times explains. The fungus is blamed for the decline or extinction of roughly 200 species globally. The discovery "tightens the noose around the idea that humans really are responsible for moving this pathogen around," the researcher said.