While some may not appreciate the sinuous curves of snakes, they should still be concerned about a strange disease that’s killing the reptiles in at least 15 states. Snake fungal disease, or SFD, appears to affect different species differently — it gives some skin lesions, and for others the infection gets into muscles and even organs like the liver.

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Researchers already knew that SFD is caused by Ophidiomyces ophiodiicola (Oo), and knew that its effects are ugly. Now researchers have figured out how the fungus works, reports Jason G. Goldman for Conservation Magazine:

It turns out that Oo survives by eating keratin, the substance out of which human fingernails, rhino horns, and snake scales are made. Researchers have never found an infected snake that survived its infection; “mortality,” writes [University of Illinois comparative biosciences professor Matthew] Allender, “appears to be 100 percent.”

The team reported their findings in the journal Fungal Ecology.

Normally, the fungus lives in soil and is content to digest dead animals. Why it is now infecting snakes is still unclear. Conservationists compare its mysterious, sudden increase in appearance to white-nose syndrome in bats. While SFD cropped up occasionally in the past, it started showing up more frequently in 2006. Diana Yates details more similarities between the bat and snake fungi in a press release from the University of Illinois:

Both the bat and snake fungi can survive on most carbon and nitrogen sources found in soils, said Illinois doctoral student Daniel Raudabaugh, who analyzed both in Miller’s lab. “Like the bat fungus, the snake fungus is tolerant of elevated sulfur compounds,” Raudabaugh said. “It grows on dead fish. It grows on dead mushrooms – most complex carbon sources. It can utilize nitrate, but its growth is not nearly as robust (as the bat fungus) on nitrate.”

The new study represents the first real survey of the fungus. But as the team writes, researchers have a lot yet to learn before they can begin combatting the disease. Even the overall effects the fungus is having on snake population isn’t known. “[S]nakes are extremely difficult to survey and populations could decline precipitously and in most cases we would have no idea,” Auburn University herpetologist David Steen tells Conservation Magazine.