A species of frog that was used from the 1930s to the 1950s in human pregnancy tests is a carrier of a deadly amphibian disease that is now threatening hundreds of other species of frogs and salamanders.

The species, the African clawed frog, was shipped across the world for use in human pregnancy tests, until a different method was developed in the mid- 20th century.

The tests involved injecting a woman’s urine into a female frog. If the frog began ovulating within about 10 hours, there was a high likelihood the woman was pregnant.

Released to the wild, the frogs are now
spreading a fungus called Batrachochytrium dendrobatidis, or Bd.

It has led to the recent decline or extinction of 200 frog species worldwide, the researchers report. The frog itself appears to be unaffected by the fungus.

“Evolution has run its course,” said Vance Vredenburg, a conservation biologist at San Francisco State University and one of the researchers involved in the study, which was published Wednesday in the journal PLoS One.

For other species, the pathogen is “the worst disease in vertebrate history,” Vredenburg said.

The disease infects the skin of frogs and salamanders and causes it to thicken 40 times greater than normal, Vredenburg said. Within a couple of weeks, the disease causes an electrolyte imbalance and the amphibians die of heart attacks, he said.