After putting on surgical gloves, Matthew Allender gingerly picked up a Blanding’s turtle to inspect it for signs of a rare fungal pathogen. The fungus was recently discovered in the state-endangered Blanding’s and red-eared slider turtles, underscoring the importance of conservation efforts across Illinois.
The first documented cases of Emydomyces testavorans in the state were part of a study published in October in the Journal of Wildlife Disease, which was led by researchers from the University of Illinois Wildlife Epidemiology Lab and the Brookfield Zoo, where Allender is director of conservation, medicine and science.
Tucked into her shell, the turtle he held refused to be examined. So he reached for her front flipper.
“Oftentimes, when they come to the doctor, they get nervous. So, it’s weird, but they do better when you hold their hand,” Allender said, doing so with his thumb and index finger.
The turtle tentatively peeked out and blinked. To the untrained eye, she might’ve looked healthy, but her shell was dull instead of glossy — a sign that she was infected with the fungus. While she wasn’t part of the original study, her condition allows researchers at the zoo to continue their work.
“She gives us an opportunity to not only study the disease but study the impact that it has on individuals,” Allender said, pointing out divots and flaking on the scutes, the external bony plates or shield-like scales that make the shell look like a soccer ball.
E. testavorans primarily attacks the carapace, or outer covering, which, like human fingernails, is made of keratin. Once the fungus gains a foothold in that keratin, it digs into and eats at the bone. It can also create internal nodules. Often the disease is fatal.
Turtles are among the most endangered vertebrates on the planet; almost half of all 357 species are considered threatened. Besides disease, threats include wildlife poaching and trafficking, road mortality and loss of habitat like wetlands — of which Illinois has lost as much as 90% to urban development and agriculture. Smaller populations are also more vulnerable to disasters like floods and fires.
The early discoveries of the fungus in Illinois put the state in an unusual position to be a world leader in the containment and treatment of it, Allender said: “We’re going to be identifying the threats before they become threats.”
Four turtles with the fungus were discovered in a statewide health surveillance effort from 2019 to 2021 that was used in the study examining hundreds of wild turtles across six species. Like a human doctor would do in a medical checkup, researchers checked the eyes, ears, nose, throat, feet and shell of Blanding’s turtles, painted turtles, common snapping turtles, red-eared sliders, eastern box turtles and ornate box turtles. They also took blood samples and mouth swabs.
Three infected wild Blanding’s turtles were found on private property in Lake County, so the spread was contained. Those were transported to the College of Veterinary Medicine at the University of Illinois Urbana-Champaign for treatment. One free-ranging red-eared slider also tested positive for the fungus in Cook County.
“We would have never found it naturally until about 10 to 15 years (later), probably after it already got into the wild,” Allender said. That was the unfortunate case in the Pacific Northwest, where the fungus was identified in its wild western pond turtles — more than a decade too late, according to Allender. Between 65% and 85% of the population in Washington is infected.
During the most recent statewide health assessment here, scientists found no new cases in the wild.
“This year, we sampled 1,200 turtles in the state of Illinois, and we had zero positives,” Allender said. “So we are really feeling good that the mechanisms that we’re using are helping to protect wild populations.”
The main conservation concern is the rapid spread of the fungal infection across wild populations, but the fungus is more common in zoos and aquariums. Other semi-aquatic turtles that share the Blanding’s indoor habitat in the Brookfield Zoo’s swamp exhibit, including red-eared sliders and a common musk turtle, have also tested positive for the fungus while in captivity.
No turtle with this fungal infection has been successfully treated anywhere in the world, Allender said. Now more than two years into treatment trials for the affected turtles in the state, researchers at the zoo and U. of I. finally have promising results for a treatment and are waiting to apply them to their clinical cases.
Being out in the field all summer, moving between different locations to find and test turtles, the researchers came up against a particular veterinary issue that required parallel work: developing disinfection protocols that effectively targeted the newly discovered pathogen. As responsible conservationists, Allender said, they wanted to avoid taking E. testavorans from one place to the next and possibly infecting healthy turtles elsewhere.
So they published another study analyzing effective and safe options that can help other clinical veterinarians similarly working with turtles limit the reptiles’ exposure to E. testavorans.
“This (fungus) is a significant threat to the conservation of certain species, and especially our at-risk endangered species,” Allender said. “And we have other fungal diseases that affect wildlife. … We know so much less about (E. testavorans), but that’s changing every month and every year. We’re learning more and more.”
The main study, Allender said, underscores the need to effectively manage the state’s population of invasive red-eared sliders, which easily spread disease and outcompete and displace native species.
Proactive health assessments and extra care in handling also will be critical to protecting wild turtles in the state, including Blanding’s turtles, of which fewer than 500 are left in Illinois. An update to the state’s wildlife action plan in 2025 is expected to include protections for the endangered species and emphasize the importance of monitoring wildlife health.
Allender said population numbers likely won’t bounce back to what they were hundreds of years ago, but it’s important to develop conservation and mitigation strategies that work within today’s urbanization and human encroachment.
“When you’re doing wildlife conservation, you want to put the animals in the best position to be successful,” Allender said. “Protecting biodiversity is important for planetary ecosystem health. Threats to biodiversity — which could be loss of population in an area or loss of a species on the planet — can have immeasurable effects (and) downstream impacts on human and other animal health.”
