Killer ranavirus threatens frogs, turtles in Delaware-The disease blamed for a worldwide decline in amphibians has been spreading to reptiles.- via Herp Digest

Molly Murray, The (Wilmington, Del.) News Journal 7:55 p.m. EDT June 2, 2014

A virus partially blamed for a worldwide amphibian decline has made its way to Delaware, killing tadpoles and raising fears it will spread to reptile species.

The ranavirus, a type of virus that affects cold-blooded species, has been found in wood frog tadpoles in all of Delaware's counties and eight in Maryland. And there is concern it could impact iconic reptile species like the Eastern box turtle or endangered species like the bog turtle.

"Of 23 Delaware ponds tested in 2013, ranavirus was detected in 14 – 61 percent – and amphibian die-offs were recorded for two of those during the sampling period," said Holly Niederriter, wildlife biologist with the state's Species Conservation and Research Program.

In addition, a dead bog turtle found three years ago in Delaware likely died from a predator attack but it was infected with ranavirus, herpes and mycoplasma, she said.

Tracking the potential impact on relatively secretive turtle species is difficult, why is why Niederriter has been out again this year re-sampling ponds. She is finding similar signs of the virus.

She said that infectious diseases such as ranavirus – which is likely spread by contact with water or sick or dead tadpoles – are a large cause of the worldwide amphibian decline.

The disease is found throughout the United States in both frogs and turtles but it has not been found in birds or mammals. With some tadpole frog species, the mortality rate is as high as 99 percent.

"The virus can also be spread via water, in soil and on the boots, nets and gear of humans," Niederriter said.

The ranavirus was identified in Maryland in 2001 in Prince George's County, said Scott Smith, a wildlife ecologist with the Maryland Department of Natural Resources.

Delaware officials began looking for the disease in wooded ponds last year as part of a regional effort, prompted by a turtle die-off discovered as part of a study on the impact of a proposed new highway in the Maryland suburbs of Washington.

A researcher at Towson University put radio transmitters on Eastern box turtles to see how they would fair if they were moved to new locations as part of a road construction mitigation project.

But the transmitters turned up something unexpected.

"They'd be sick one day and dead the next," Niederriter said.

Smith said the researcher lost both his control site and his two test plots to ranavirus in the study that took place from 2008 to 2011.

One reason for the concern, Smith said, is that box turtles are long-lived and have reproductive strategy that differs from frogs. Frogs typically lay eggs in woodland ponds by the hundreds.

But box turtles, while laying several clutches of eggs, may only lay three to eight at a time.

Smith said with frogs, especially wood frogs, the disease seems to have highest impact on the tadpoles but doesn't kill adults. That means the adults, which typically live five to eight years, can return to breed again the following year.

There are species, like bullfrogs, that appear more resistant to the disease, he said.

So far, researchers believe the disease in our area has the greatest impact on wood frogs and spotted salamanders. No one is certain how it spreads from pond to pond, though there is some thought that other wildlife may spread it, including bullfrogs, which can travel three miles to breeding pools.

Researchers have found that one day a pond can seem fine and then the entire wood frog tadpole population can be wiped out in as little as five days.

Over several days in late May, Niederriter and research assistant Christine Tilton set out to sample wood frog tadpoles.

The two scientists waded into slightly less than knee deep water at Blackbird State Forest. In March, they marked the areas where wood frogs laid their egg masses with orange survey tape.

Last week, they took long-handled nets and swept through the leaves and water in the survey area, searching for inch-and-a-half long tadpoles.

They needed 30 animals, which they collected in a bucket and took back to a test site in a cleared area in the woods.

"They have to be a certain age," Niederriter explained. The telltale sign is that the tadpoles are starting to develop legs. At this stage of development, the tadpoles may even show signs of the disease – red splotches.

For this study, the tadpoles are killed with a numbing agent before being examined because they must be sent out to a lab for positive confirmation of the disease.

"This year we're finding die-offs in more of the ponds," Niederriter said.