UI scientists worried about cause of turtle deaths
DANVILLE — Wildlife veterinarian Matt Allender has been spending some extra time in Vermilion County parks this month after discovering several dead turtles that have tested positive for ranavirus.
"I'm still holding out hope that it's a random occurrence," said Allender, who is also a clinical assistant professor of comparative biosciences at the University of Illinois.
Vermilion County Conservation District staff contacted Allender in early August to let him know they had found a couple dead turtles. He traveled to Vermilion County to take a look and found what were, most likely, two different dead turtles than the ones first spotted by park staff. Allender said the two turtles he found tested positive for ranavirus. He has been back to search Kennekuk County Park since then and altogether has found 19 dead turtles, including one that was found at nearby Kickapoo State Park.
According to Allender, box turtles typically get three diseases that are contagious, but one, ranavirus, is the most concerning, because of its high mortality rate, and the fact that it's a serious threat to salamanders and frogs. Nationwide, Allender said, ranavirus has been classified as the biggest threat to amphibian biodiversity.
"It's significant. It affects so many things. It will kill almost every amphibian," said Allender, who added that it can also infect fish.
Ken Konsis, director of the Vermilion County Conservation District, said the outbreak is concerning, especially in light of a turtle kill-off that was discovered in early spring 2011 at another conservation district park, Forest Glen Preserve. About 50 dead turtles were initially found in one area of the preserve, and upon further investigation a total of 65 were found dead.
Allender and Chris Phillips, a herpetologist with the Illinois Natural History Survey, a division of the Prairie Research Institute at the UI, investigated the 2011 incident and found about a dozen other turtles that were sick, some missing all or parts of limbs and eventually determined that a bacterial infection was the culprit. The bacterium responsible occurs in many environments, can infect a wide range of hosts, like birds and mammals, but is commonly present without causing infection. Allender concluded that the health of the afflicted turtles had already been compromised in some other way.
But knowing the serious threat ranavirus poses to amphibians, Allender has made multiple trips to Vermilion County this month after the initial visit prompted by the call from park staff. On his second visit after the call, he walked two hours up a stream at Kennekuk and found six dead turtles and others that were sick that later died. And he has also found half a dozen dead amphibians, including frogs, which were positive for ranavirus.
"It's definitely an outbreak," said Allender, who does not know the cause of the virus. There are multiple possibilities, he said, including a naturally occurring event. Allender said none of the dead turtles were ones used in the 49th Turtle Reunion and Races earlier this summer. Each year, local mushroom hunters gather box turtles to be used in the charity event, but after receiving a complaint from a private citizen, state conservation officials contacted event organizers to notify them that collecting and holding almost 100 turtles violates state conservation laws.
In cooperation with event organizers, Allender examined the turtles, and only one showed signs of illness, and then he marked all of them for field research purposes before they were released back into the wild. Allender said none of the dead turtles found this month had markings from the turtle races.
Allender said causes of the ranavirus could include a carrier animal that, because of temperature and humidity changes, started to shed the virus and susceptible animals started to die. Also, a new animal may have been released into that area, either on purpose or by accident, like a pet frog or turtle that was a carrier, according to Allender. It's also possible, he said, that the virus was naturally occurring in the soil or water and rain turned over those areas and activated the virus.
Allender said it's difficult to know how widespread it could be, because he's searched only a small area.
"It's possible it's much more severe, and we just haven't found" all the turtles, he said.
Allender's students at the UI are also helping him search and analyze what they find. Although it's a sad situation, he said, it's also a good learning opportunity for the students to be actively involved in an outbreak like this, and a good opportunity to talk about many things. For instance, he said, this is why people try to protect natural habitats. Allender said although ranavirus does not spread to humans, this is still a virus that's occurring in the same environment upon which humans draw resources. He said turtles are good sentinels for the health of an environment.
"If turtles are healthy, it means the environment is healthy," he said.