Researchers identify new shell-eating fungus in turtles

Researchers have pinpointed a fungal disease previously unknown to science as the culprit responsible for eroding the shells of freshwater turtles.

“By causing damage to the shell, it essentially could be a portal by which bacteria could enter and make an animal sick,” said Karen Terio a clinical professor and chief of the Zoological Pathology Program at the University of Illinois and co-author of a study published recently in the Journal of Clinical Microbiology funded by the Morris Animal Foundation, which seeks to bridge science and resources to advance animal health.

Lesions caused by the fungus Emydomyces testavorans on the shell of a western pond turtle. ©Dan Woodburn

Several years back Terio and her co-authors had been finding a number of lesions in the shells of species like red-eared sliders (Trachemys scripta elegans), western pond turtles (Actinemys marmorata) and even mata mata turtles (Chelus fimbriata) from South America. They went back and found similar cases from the early 2000s and before, and wanted to determine the cause of these lesions.

Researchers took samples from 70 turtles, living and dead. While initial polymerase chain reaction-based testing was difficult, they managed to isolate the fungus responsible for these turtle shell lesions. They characterized the fungus physically and genetically, and named it Emydomyces testavorans.

Terio said that this is just the first step of research on this fungus. They know that the fungus lives naturally in soil and occurs in turtles from across the U.S., but they don’t know if the fungus naturally causes the lesions in turtle shells or if the turtle shell is scratched or punctured due to something else before the fungus attacks.

It’s uncertain whether the fungus can eventually kill turtles, but Terio said that the lesions have harmed turtles so badly that individual turtles have been euthanized. The fungus eats away at the shell gradually, moving through the reptile’s bones, and can leave them vulnerable to infection.

The disease is especially prevalent among western pond turtles initially raised in captivity, and is even hampering recovery efforts for that species in Washington state.

While this study is the first to pinpoint the new fungal species responsible for this shell-eating fungus in turtles, the species is in the same family as those affecting other reptiles — notably the Ophidiomyces ophiodiicola fungus which afflicts snakes. Terio said she’s still unsure whether the fungal disease is new, or whether it has been around for a long time and has just eluded detection by researchers.