Wednesday, 12 December 2012

Ranavirus, Turtle- USA (02): WestVirginia - via Herp Digest


(Editor must read, Ranavirus can be major threat to wild turtle populations. You can help by reporting any large herp mortality events to local natural resources agency as soon as possible)

A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases this is from their listserv

Date: Sat 24 Nov 2012
Source: Sunday Gazette-Mail [edited]


In July [2012], 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 -- a pathogen that causes 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 (Maryland) biology professor Richard Siegel, leader of a box turtle study at a highway construction site between Baltimore and Washington,DC.

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 6 miles [9.7 km] 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. 31 of the 123 turtles
outfitted with the transmitters and released there were found dead within a 3-year period. Cars or construction equipment killed 3 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 [2012]."Finding over 27 dead turtles in a 2-to-3-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 [0.2 ha] 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 3 frozen box turtle carcasses to Gray for analysis through the University of Tennessee's Center for Wildlife Health.

The best preserved of the 3 carcasses was that of a box turtle that had exhibited signs 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 3 turtle carcasses sent by Archibald, 2 were too decomposed for analysis, Gray said. Because the 3rd 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 1st known incidences involving that species. The National Wildlife Health Center in Madison, Wisconsin, 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."

"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."

[Byline: Rick Steelhammer]

--
Communicated by:
ProMED-mail from HealthMap Alerts

[It becomes increasingly apparent that some infectious diseases are a very important threat to wildlife populations and a growing conservation concern. Amphibians are already being hit by another emerging infectious disease, chytridiomycosis. Also, there is evidence
that these pathogens interact with environmental factors (climate change, pollution, etc.) resulting in greater impact. Ranaviruses are a group of pathogens belonging to the genus Ranavirus (family
Iridoviridae) that have been linked to catastrophic die-offs of larval amphibians in North America and elsewhere. In the United States, ranaviruses are responsible for the majority of disease-related mortality events in amphibians. This virus became an emerging infectious disease possibly due to a novel strain introduction orincreased occurrence of anthropogenic stressors on the landscape.

A few years ago, the World Organization for Animal Health (OIE) listed this pathogen as a notifiable disease.

Although ranaviruses were known to infect reptiles, here and in recent episodes, turtles appear to be the main host species involved. This
host preference jump across taxonomic classes (from amphibians to reptiles) merits concern and a molecular investigation.

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