Grandma’s Pregnancy Test and the Extinction of Species
Posted by Richard Conniff on May 15, 2013
Ever since The Hot Zone became a non-fiction bestseller 20 years ago, people have been fretting about the likelihood that an emerging pathogen could cause a global pandemic, killing tens of millions of humans. But they seldom pause to consider that it is already happening in the animal world—or that the pandemic that’s now decimating frogs and other amphibians provides a perfect model for how it could also happen to us.
The pathogen this time is the chytrid fungus, which has raced around the world over the past two decades, and now afflicts more than 500 amphibian species in 52 countries. When spores of this fungus penetrate a victim’s skin, a slough of dead cells builds up on the surface, blocking respiration. The electrolytes go out of balance. The brain swells. The frog sits with its legs skewed out oddly to the sides. Death soon follows, often for an entire community of amphibians around a pond or wetland. The chorus of peepers goes silent.
“I can’t think of another disease on the planet more significant than this amphibian disease,” says Peter Daszak, president of EcoHealth Alliance, a New York-based group focused on the role of the wildlife trade in the introduction of dangerous pathogens. “No disease of humans has ever wiped us out.” But he estimates that the chytrid fungus pandemic has already caused the extinction of more than 100 species, including the golden toad in the cloud forests of Costa Rica, the gastric brooding frog in Queensland, Australia, and 20 or 30 species of brilliantly colored Harlequin frogs in Central and South America. “And it’s still causing extinctions.”
A paper being published today in the science journal PLOS ONE adds new evidence to the story of how innocent and even seemingly humane missteps unleashed this killer on the amphibian world. Maybe it’s best to start with our own families: For anyone born from the 1920s up until the late 1970s, the way our mothers generally got the happy news of our impending arrival was by way of the African clawed frog, an East African species in the genus Xenopus. … click here to read the rest of the story.