My pet frog Gunther is clamped inside a latex-covered fist. His skinny leg sticks out the side and flails helplessly. Another gloved hand moves in and slips a cotton swab over his leg and between his toes; Gunther does not appear to be enjoying this. He wriggles free and splashes into a tub of water, but the ordeal isn't over yet, and the hands grab him again. Despite several more escape attempts, including a few desperate hops across the lab table, they eventually manage to swab Gunther's belly, backside and both legs.
"The gloves are not to protect him from me or me from him, but to protect the frogs from each other," explains biocultural anthropologist Eben Kirksey of the City University of New York Graduate Center. He has just finished testing my frog for chytrid fungus—a skin disease that is wreaking havoc in frog and salamander populations around the world. "This frog species is sort of like the Typhoid Mary of amphibians," Kirksey says. "It is the likely culprit for bringing the disease around the world initially. What's not known is whether it's still spreading the disease."
That's why Gunther and roughly 50 other African clawed frogs (Xenopus laevis) are taking part in Kirksey's experiment; he wants to find out whether frogs from local pet stores are carrying the fungus. If they are, they may still be introducing the disease into wild populations. On July 14 around a dozen New Yorkers brought their pet frogs in for testing at the Proteus Gowanus gallery in Brooklyn to help out with the study.
"A lot of people are wondering whether the pet trade is exacerbating the spread of [the fungus]," says Lisa Schloegel, a wildlife disease ecologist with EcoHealth Alliance. "It's definitely something that should be investigated."
Chytridiomycosis has devastated at least 200 amphibian species globally. It is caused by a microscopic fungus named Batrachochytrium dendrobatidis (Bd). Infection triggers lethargy, weight loss, sloughing of the skin and, often, death. "Bd may be responsible for the greatest disease-caused loss of biodiversity in recorded history," biologists Kellie Whittaker and Vance Vredenburg wrote on the Web site AmphibiaWeb.
Reid Harris, an ecologist at James Madison University, said that although the precise origins of Bd are uncertain, ample evidence indicates that the disease is native to Africa. The earliest known case (pdf) of chytridiomycosis was documented in an X. laevis individual that had been collected in South Africa in 1938. Beginning in the 1930s large numbers of the species were shipped from Africa to labs in England, the U.S. and Australia, where they became essential in pregnancy tests and laboratory research (pdf). Scientists believe that the fungus traveled with the frogs as they were shipped around the world.
In the wild, 5 to 10 percent of X. laevis harbor Bd on their skin without exhibiting symptoms of disease. (North American bullfrogs are also tolerant of the fungus, suggesting that they may have helped to spread it, too.) Once these carriers bring the fungus to previously unexposed species the disease spreads like wildfire. More than 50 percent of amphibian species become locally extinct within six months of Bd's arrival in an area. Even for species that survive, 80 percent of individuals die. The disease has been detected in nearly every state in the U.S., including in several threatened and endangered species, and on every continent except Antarctica.