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article imageHuman activity is linked to mass dolphin deaths Special

By Elizabeth Batt     Oct 9, 2013 in Environment
It's called morbillivirus, and it's been responsible for hundreds of bottlenose dolphin deaths. Elevated strandings of dolphins have occurred across the Mid-Atlantic region this summer, forcing NOAA to declare an Unusual Mortality Event (UME). Why?
After 91 dead and dying dolphins washed ashore in July, followed by a further 35 in the first week of August, NOAA Fisheries (National Oceanic and Atmospheric Administration) was forced to declare an Unusual Mortality Event (UME) to determine the cause.
Elevated strandings of bottlenose dolphins have and continue to occur across New York, New Jersey, Delaware, Maryland, Virginia and North Carolina. Dolphins of all ages are being impacted, and according to NOAA Fisheries:
Strandings range from a few live animals to mostly dead animals with many very decomposed. Many dolphins have presented with lesions on their skin, mouth, joints, or lungs.
Unexpected deaths prompt investigation
Under the Marine Mammal Protection Act, a UME is defined as, "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response." Declaring the UME, authorized the federal fisheries department to investigate and test the dolphins and attempt to determine what killed them.
At the end of August, NOAA Fisheries tentatively attributed the die-offs to cetacean morbillivirus, a virus in the same family as the virus that causes measles in humans. As of September 23, 2013, the department had tested 93 dolphins, 84 of which were confirmed positive or suspect positive for morbillivirus.
Dolphins were also presenting with secondary infections. Six dolphins stranded in Virginia were confirmed positive or suspect positive for Brucella sp. bacteria. In cetaceans, the Brucella bacteria can cause abortion, brain infection, pneumonia and skin or bone infections.
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NOAA Fisheries
Virus is not new
Morbillivirus is not a new disease. According to NOAA however, it has been "25 years since a 1987-1988 bottlenose dolphin morbillivirus mortality event occurred along the mid-Atlantic coast," resulting in the deaths of at least 900 bottlenose dolphins.
On Oct. 2, Dina Fine Maron, a writer with Scientific American, probed deeper into the reasons behind the mass dolphin die-offs. Maron suggested that some researchers named a "coastal ecosystem, possibly sickened by human activity," as a large factor in the spread of diseases between wild dolphins.
With the last morbillivirus in the mid-Atlantic occurring a quarter of a century ago, dolphins younger than 26 years of age possess little immunity to the virus. Nothing can be done for the sick dolphins and both scientists and conservation groups fear that things will get far worse.
No viable way to help sick dolphins
Courtney Vail, the Campaigns and Programs Manager for Whale and Dolphin Conservation (WDC), told Digital Journal, "unfortunately, there aren’t any direct remedial efforts to stem the deaths that are occurring. This really is a case of us standing by and letting the virus take its course."
Dr. Naomi Rose, the marine mammal scientist for the Animal Welfare Institute agrees with Vail. "There is no vaccine for this," she said, "and even if there was, how would we deliver it? Research on these die-offs tells us what is happening, it doesn’t treat or cure the animals."
As a member of the International Whaling Commission Scientific Committee's Standing Working Group on Environmental Concerns (E) (IWC SC), Rose explained that "the phenomenon of emerging diseases in cetaceans (and other marine mammals) is a growing concern in the marine mammal community."
Rose noted that the issue was a particular focus of CERD — cetacean emerging and resurging diseases, a standing item on the IWC SC's E agenda. She credited a CERD workshop several years ago with identifying morbillivirus as "one of several pathogens of particular concern."
There have been several UMEs across the US and even abroad. Rose said her concern rests with what she described as, the "cumulative and synergistic effects of multiple threats to marine mammals." One major threat for these animals is human-caused environmental pollution.
"The immune systems of many marine mammals, especially coastal species like bottlenose dolphins, can be negatively affected by factors such as agricultural runoff, persistent organic pollutants (e.g., PCBs, DDT) and other contaminants," Rose explained. "Pathogens like morbilliviruses can also mutate," she added, "and any immunity animals build up within a year or two of an outbreak can become obsolete fairly quickly."
The scientist likened the problem to pathogens in hospitals, "where bacteria in particular" she said, "are becoming increasingly resistant to antibiotics."
The UME itself is not unique Rose explained. "There have been morbillivirus outbreaks all over the world," she said, plus "outbreaks of other diseases, in cetaceans and pinnipeds," such as "brucellosis, domoic acid poisoning, phocine distemper." According to the scientist, that means more outbreaks in the future.
"This is an emerging problem," said Rose, "and there is a concern that new diseases will indeed start appearing in the marine environment — diseases that were previously confined to terrestrial species and new strains of existing diseases," she added. The scientist also believes the worst is yet to come.
Vail expects global climate change and the shifts in marine species entering habitats not previously frequented by them, to only contribute to the problem. Furthermore, she added, "as coastal dolphin populations mix and mingle, the virus will be transmitted and take its toll."
While conservation groups feel helpless during these mortality events, Vail believes that the events themselves send a clear message.
"It all comes back to the wider impacts our collective activities and effluent are having on the coastal marine environment," said Vail. "The byproducts of our industrial society are taking a toll on marine life," she added, "including compromised immune systems in dolphins and other marine mammals that bioaccumulate toxins."
As a result Vail said, "this is where the efforts should be focused." Rose agrees. "The only way to stop the die-offs," she added, "is to mitigate our overall impact on the environment."
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