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Mid-Atlantic's fatal dolphin virus not connected to lagoon deaths

9:49 AM, Aug 28, 2013   |    comments
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(Florida Today) -- Federal scientists hope Indian River Lagoon dolphins are immune to a measles-like virus already suspected to have killed hundreds of bottlenose dolphins from New York to Virginia.

But some biologists worry that morbillivirus, the same pathogen that hammered the bottlenose dolphin population from New Jersey to central Florida in the late 1980s, might follow a similar pattern, spreading to the lagoon region. The virus' re-emergence here could inflict yet another blow to lagoon dolphins already under assault from some other mysterious, fatal ailment.

Studies show some lagoon dolphin have antibodies to morbillivirus, but it's unknown whether that's enough to make them immune.

"It's no different than any other virus. Over time, if you're not exposed to the virus again in lower doses, your immunity wanes," said Greg Bossart, a marine mammal pathologist at the Georgia Aquarium, who led a major federal study of lagoon dolphins' health. "While they have antibodies against the disease, it doesn't mean they're protected."

On Tuesday, NOAA officials said they suspect morbillivirus has killed or stranded more than 300 bottlenose dolphins from New York to Virginia in the past few months.

In July and August, more than nine times the historical average of bottlenose dolphins died or stranded in the mid-Atlantic region, including New York, New Jersey, Delaware, Maryland and Virginia.

The mid-Atlantic deaths prompted NOAA Fisheries this month to declare an "Unusual Mortality Event," triggering a formal federal investigation by the agency.

The agency made a similar designation in July for the Indian River Lagoon region.

At least 66 bottlenose dolphins have died or stranded in the lagoon this year, about three times the average.

"It may be totally unrelated, or indeed it could be related," Bossart said of the two unusual dieoffs.

Scientists are concerned that the 600-plus dolphins that live almost exclusively in the lagoon could get exposed to morbillivirus carried here by dolphins migrating from the mid-Atlantic.

"That population is a migratory population, so we are expecting to see those dolphins in another month or two to come to Florida," said Megan Stolen, a research scientist with Hubbs-SeaWorld Research Institute. "But there's no evidence that those dolphins mix with the lagoon populations."

But during the 1987-88 morbillivirus outbreak, some dead dolphins washed up in lagoon inlets and along local beaches, according to a 2009 research paper Bossart co-authored. Testing of archived samples showed the virus had infected lagoon dolphins at least five years earlier, according to the paper.

The lagoon dolphins may serve as an early-warning system for morbillivirus, the paper concluded, emphasizing the need for ongoing surveillance of live and stranded dolphins.

The telltale symptoms for morbillivirus - skin and oral lesions - have not been seen in the dead dolphins from the lagoon, Stolen said.

She's more worried about bottlenose dolphins offshore Brevard getting infected. "Then, we have a die-off on both sides of the barrier island, which is kind of frightening," Stolen said.

In April, NOAA formally declared the manatees dying in the lagoon an unusual die-off. More than 111 manatees have perished from an unknown cause.

Biologists also are investigating the death of 250 to 300 brown pelicans this year.

As with the dolphin deaths in the Brevard County region, all age groups of dolphins have been involved in the mid-Atlantic deaths, and all but a few of the dolphins found have died.

Virginia has the largest increase over the long-term average dolphin deaths.

In 1987 and 1988, biologists confirmed more than 740 bottlenose dolphins died of morbillivirus infections along the mid-Atlantic coast, from New Jersey to Florida.

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