W.Va. turtle die-off linked to ranavirus disease
CLENDENIN, W.Va. -- In July, while walking near a small pond he had built on his farm near Clendenin, Bill Archibald spotted a pair of dead eastern box turtles in the brush.
"I didn't think a whole lot about it at first," Archibald recalled, "but then I noticed other turtles in the same area acting kind of lethargic, with swelling around their eyes, lying in the same spot for days, and I started to wonder what was going on."
When Archibald returned to his farm following a weeklong trip to Alaska, "every day that I walked up to the pond I'd find dead turtles."
The mysterious deaths, which numbered 26 by the end of the summer, didn't sit well with Archibald, a graduate of the state Division of Natural Resources' Master Naturalist program, who had built the pond to enhance habitat for the frogs, salamanders and turtles living on his land. He emailed Doug Wood, a retired Department of Environmental Protection biologist who teaches several Master Naturalist classes.
"Bill sent me one of those unusual queries I get from time to time -- 'Hey, Doug, do you know what this is?' " Wood recalled. After consulting the Internet and some professional colleagues, Wood supplied Archibald with the contact information he believed could solve the mystery about what was killing the box turtles on his land.
As it turned out, the turtle was infected with ranavirus -- an animal disease known to have caused large localized die-offs, mainly in populations of frogs, salamanders and other amphibians, in 25 states since 1997. In more recent years, the virus is known to have infected scattered populations of box turtles, which are reptiles, in several states.
At Wood's suggestion, Archibald got in touch with Towson University (Md.) biology professor Richard Siegel, leader of a box turtle study at a highway construction site between Baltimore and Washington, D.C.
There, local turtles were outfitted with radio transmitters and released in areas safe from blasting and heavy machinery. The study was designed to determine whether relocated turtles did better by being moved to a site six miles from the construction zone, or to an area just across a fence from the new highway site.
But Siegel and his Towson colleagues found that an alarming number of turtles -- which can live to be 50 or older and normally have a 98 percent survival rate from year to year -- were dying at the relocation area near the construction site. Thirty-one of the 123 turtles outfitted with the transmitters and released there were found dead within a three-year period. Cars or construction equipment killed three of the turtles, but the rest were felled by disease, which turned out to be ranavirus in 27 cases.
"Finding even one dead turtle is unusual," Siegel said in a Washington Post story about the die-off that appeared earlier this year. "Finding over 27 dead turtles in a two-to-three-year period was bizarre."
In addition to killing the Maryland box turtles, ranavirus is believed to have been the cause of death of nearly every tadpole and young salamander in the study area since spring of 2010.
Siegel referred Archibald, who had lost a similar number of turtles on a half-acre tract of land within a single season, to Dr. Matthew Gray, professor of wetland ecology at the University of Tennessee in Knoxville, and a ranavirus researcher. The Clendenin area man sent three frozen box turtle carcasses to Gray for analysis through the University of Tennessee's Center for Wildlife Health.
The best preserved of the three carcasses was that of a box turtle that had exhibited symptoms similar to those shown by the ranavirus-infected turtles in the Maryland study -- foot lesions, lethargy, difficulty breathing, swollen eyes, and bubble production at the nose and mouth.
"We verified that ranavirus was the likely disease agent that killed the turtles on Bill Archibald's property," said Gray.
Of the three turtle carcasses sent by Archibald, two were too decomposed for analysis, Gray said. Because the third carcass -- which tested positive for ranavirus, had been frozen, damaging tissue cell structure -- a test could not be made to confirm that ranavirus directly killed the turtle.
"We can say that the turtle from Bill Archibald's property was infected with ranavirus, but without histology -- inspecting tissues microscopically for damage by the pathogen -- we cannot make an assessment if the infection caused the disease leading to death," Gray said. "We plan to stay in contact with Bill, and will process additional specimens if he observes mortality. Future plans are to sequence a portion of the virus genome to determine if it is a common or unique type of ranavirus."
Unlike the ranavirus incident in Maryland, frog and tadpole life in and around Archibald's pond appears unaffected by the box turtle die-off.
Researchers believe people, pets, farm animals and warm-blooded wildlife species are immune to ranavirus, because their bodies are too warm to support the disease.
Wildlife biologists worry about how far ranavirus has spread, how fast it is spreading, how often it recurs, and how quickly amphibians and turtles can develop a resistance to it. Ranavirus-associated die-offs involving more than 20 species of amphibians and turtles have been recorded in at least 25 states since 1997.
The ranavirus outbreak that killed the Maryland box turtles was one of the first known incidences involving that species. The National Wildlife Health Center in Madison, Wis., lists it as the nation's only confirmed case of a ranaviral infection involving wild box turtles. But the center acknowledges that similar ranaviral outbreaks in box turtles have been reported in New York, Pennsylvania, Georgia and Florida, North Carolina and Virginia prior to the case reported at Archibald's farm.
"Ranavirus tends to hit amphibians in their young life stages, so when it shows up, it can wipe out a whole age class," said Dr. Anne Ballman, wildlife disease specialist at the National Wildlife Health Center. "If a local population runs out of young recruits, a species can be wiped out for a season. If ranavirus occurs repeatedly, there is the potential of that population declining dramatically in localized areas."
Because there is no required monitoring of wildlife deaths due to disease, it's difficult for wildlife biologists to know how far-reaching and fast-moving the virus is.
"That's why it's important for people who come across large mortality events involving amphibians or turtles to report them to their local natural resource agency," Ballman said.
Researchers believe ranavirus is spread through direct contact with infected animals, by exposure to contaminated water or sediment, or by preying upon or cannibalizing animals carrying the virus.
"Observant folks who enjoy the woods, like Bill, are often the front line of defense in documenting the spread of biological infestations or infections," said Wood. Archibald's interest and action "led to what appears to be the first known, or at least, first publicized finding of ranavirus in a wild box turtle population in West Virginia. This speaks highly of citizen involvement in conservation concerns."
On a hike near his pond last week, Archibald came across the bodies of two additional box turtles.
"I wonder how the virus got here, whether it will come back again, and why the frogs and tadpoles in the pond weren't affected by it," he said. "I hope that by studying what happened here, researchers can find some answers."
Reach Rick Steelhammer at firstname.lastname@example.org or 304-348-5169.