(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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