Scientists solve mystery of dolphin deaths off N.J. Virus akin to the onethat causes human measles is blamed


PHILADELPHIA - Bob Schoelkopf knew the ocean was awash with an unknown horror when he looked at the tortured skin of the dolphins dying on the beach.

The animals were pocked with eruptions that "looked like craters on the moon, but bloody, with the skin literally peeling off the body in some instances," he recalls.

Ten years ago, Bob Schoelkopf was the undertaker. Into his Marine Mammal Stranding Center at Brigantine, he dragged the carcasses of dozens of dolphins killed in an unprecedented plague along the Jersey coast.

Before it was over, 742 bottlenose dolphins had washed up along the Atlantic shoreline from New Jersey to Florida. And experts predicted it would take decades before the decimated species would thrive again.

In the past three years, much has been learned about the disease that struck the dolphins.

And in summer, the playful dolphins leap again from the water off the New Jersey beaches, despite their new federal designation as a "depleted" species.

"People have been very excited about watching them frolic around like they're supposed to," says Cindy Zipf, director of the New Jersey-based Clean Ocean Action.

What went wrong

What went wrong with the dolphins, and could it happen again? New laboratory testing methods have allowed researchers to solve a major part of this medical mystery. They have pinned much of the blame on viruses akin to canine distemper or human measles.

"I think today we would say that in the East Coast outbreak, the primary cause was morbillivirus," said Dean Wilkinson, national stranding coordinator for the National Marine Fisheries Service.

Before the Atlantic dolphins began dying in 1987, this type of virus had never been known to cause epidemics among creatures of the sea. (Other morbilliviruses were known to cause measles, canine distemper, and diseases in cows, sheep and goats.)

But in the past two years, little-publicized research has identified the dolphin deaths as the first of five major die-offs linked to viruses of this type among aquatic animals in North America, Europe and Asia.

Among the dead: 17,000 harbor seals in northwestern Europe; thousands of Baikal seals in Lake Baikal, Russia; thousands of striped dolphins in the Mediterranean Sea, and hundreds of bottlenose dolphins in the Gulf of Mexico, researchers said.

Sometimes the morbillivirus itself kills. Sometimes it opens the door to other killers.

'Weakens immune system'

"It weakens the immune system and allows other infection like bacteria and fungi to be the actual cause of death. In some cases the virus itself is fatal," said Lt. Col. Thomas Lipscomb, chief of veterinary pathology for the Armed Forces Institute of Pathology in Washington.

Like a measles vaccination or a canine distemper shot, exposure to morbilliviruses affecting dolphins appears to create a period of immunity.

No one knows how long that immunity may last.

Wilkinson said it's too early to tell if the dolphins are rebuilding their population. Their slow reproductive cycle means lost animals are not rapidly replaced.

But dolphin counts and aerial surveys "do not show an obvious decrease in the number of dolphins in that area," says Joseph R. Geraci, chief scientist at the National Aquarium in Baltimore. "They're showing that the population is a healthy population."

Researchers are uncertain whether pollution - which plagued the Jersey shore with waves of trash and medical waste in 1987 - played a role in the Atlantic Coast epidemic.

High levels of PCBs, known to damage the immune system, are found in many stranded dolphins. Another theory suggests a threat from ship paint.

For thousands of beachgoers, the dying dolphins quickly became a symbol of what many feared was a deep lasting degradation of the ocean. The deaths boosted pressure to end ocean dumping and to study and protect the bottlenose dolphin as a species.

Since the days of the dolphin deaths, the federal government has closed two major sewage dumps and an acid waste dump off the Middle Atlantic coast.

Municipal sewage systems pump less pollution into rivers and the sea. And this September, officials will close the last dump off the Jersey shore - the so-called "mud dump" for sometimes-toxic waste from harbor dredging.

"I think we've come an extraordinary long way," Zipf said.

Deadly spring of 1987

The procession of death began soon after the bottlenose dolphins' annual migration north from eastern Florida during the spring of 1987.

"They started, one or two animals," Schoelkopf said. By summer, seven or eight animals were stranding each day.

He and his wife, Sheila Dean, often worked unaided, 20 hours a day, wrestling the dead or dying dolphins onto a truck and back to the stranding center.

When people saw the hideous lesions on the animals, they were afraid to help.

In all his experience in saving or burying seals and dolphins, Schoelkopf had seen nothing like it. "Their lungs looked like they were burned, almost as they had inhaled some toxic gas."

He went to state and national fishing officials, and he went to the Army with questions about mustard gas and other chemicals dumped in the ocean long ago.

And by late summer, a team of U.S. and Canadian marine mammal experts headed by Geraci was probing the cause of the disaster, which then moved south with the animals' return to Florida.

Geraci's conclusion, announced in 1989, was that the dolphins were poisoned when they ate fish contaminated with a natural toxin produced by red tide off Florida. The weakened animals, he said, then fell prey to bacteria and viruses in the environment.

He and others feared the epicdemic had destroyed half the entire coastal poulation of dolphins.

"At the time, we found dolphins had been exposed to morbillivirus," Geraci said recently. "We did not know what importance to attach to that finding."

That discovery came five years later.

Antigens found

At the Armed Forces Institute of Pathology, Lipscomb and others found antigens - signs of exposure to morbillivirus - in the lungs and lymph nodes of more than half the Atlantic bottlenose dolphins they tested from the 1987-1988 epidemic.

And as they examined the animals' preserved lung tissue, the researchers found lesions, pneumonia and other evidence that allowed them to diagnose actual morbillivirus-induced disease.

They immediately linked these findings to major die-offs of seals and striped dolphins that occurred in Europe in the years after the East Coast disaster.

In additional studies, they diagnosed morbillivirus in dolphins stranded in the Gulf of Mexico in 1993 and 1994.

Geraci today readily acknowledges that morbillivirus killed at least some of the dolphins. But he's not ready to dismiss the red tide toxin as another possible cause, noting it wiped out 150 manatees off Florida a year ago

"In some cases the mystery always continues," Geraci said.

Most urgent question

The most urgent mystery, from a dolphin's viewpoint, is how the potentially deadly morbilliviruses spread.

Geraci and another scientist have suggested pilot whales may act as long-distance carriers between North America and Europe. And Lipscomb's group believes the Atlantic bottlenose dolphins transmitted the disease to those in the Gulf of Mexico.

The Atlantic dolphins were hit hard in 1987, said Schoelkopf, because they "had never contracted the virus before."

But infection causes longstanding immunity, much as measles does, said Lipscomb. The dolphins may now be basking in a window of immunity.

After this good news comes bad.

"Over time," said Lipscomb," "the immunity in the population wanes. So after a period of years--we don't know how long it will be--but if the dolphins aren't re-exposed, then they'll become fully susceptible again."

Pub Date: 4/17/97

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