Treatments for human diseases often come from unexpected places. Several years ago microbiologist Sarah Higginbotham was talking with an ecologist colleague about how she looks for bioactive organisms—those that produce substances that inhibit the growth of other organisms. “When I told him I look for places where lots of organisms live together, he said, ‘Sloths sound perfect,’” she says.

Sloths are microbial jackpots because they move so slowly and infrequently and because their fur contains microscopic grooves that create a perfect breeding ground for algae, fungi, bacteria, cockroaches and caterpillars.

Interest piqued, Higginbotham, during a temporary research stay at the Smithsonian Tropical Research Institute in Panama, obtained hair samples from nine three-toed sloths—the famously sedentary, tree-dwelling mammals from Central and South America. From the samples, she identified 28 different fungal strains, several of which might represent new species. (Chemical testing could help determine whether they are in fact new species.) Higginbotham, now at Queen's University Belfast, and her colleagues published a paper in PLOS ONE confirming bioactivity in some of their fungal strains against the parasites that cause malaria and Chagas' disease, a breast cancer cell line and several types of harmful bacteria. In all, they discovered two dozen drug leads hiding in the fur of sloths.