The distemper virus seems to be the cause of the death of seals

Continued dieback of seals on the New England coast has been associated with an outbreak of the distemper virus.

Nearly 1,000 stranded seals have been reported along the coasts of Maine, New Hampshire and Massachusetts since July. Last week, three-quarters of the seals were dead, according to figures from the National Oceanic and Atmospheric Administration. The remaining seals were reported as live strandings and were probably sick.

The agency reported on Friday that the main pathogen found in most of the dead seals tested was the phocine distemper virus, a particularly virulent disease in harbor seals, one of the most common marine mammals on the east coast is American.

Phocine's disease is similar to distemper and measles. It affects the respiratory, gastrointestinal and nervous systems of mammals, suppressing the immune system and rendering animals vulnerable to other infections or diseases. Square disease can not be transferred to humans, but can affect pets, said NOAA.

Some of the dead seals tested since the beginning of the death have been infected with avian influenza, but further tests have not proven that it was the cause of death, the agency added.

"We are pursuing additional tests to identify any other factors that may be involved in this event and will share these results when they become available," NOAA said in an online statement.

Although a viral infection may be the immediate cause of death, some researchers believe that decades of chemical pollution endangering the immune system of marine mammals are an underlying cause.

Reports of dead seals found on Maine's beaches have come at a steady pace since July and show no signs of slowing down.

"We have always had to deal with dead seals from time to time, this is the first year we see something like this. That's crazy, "said Jackie LaLiberte, the animal control office in Wells. The police service regularly receives more than 10 calls a week from people who have found dead seals while walking on the beach, LaLiberte said. She responded to six sealed seals on Friday.

"We get a lot of calls, it has not changed, whether it's the busy part of summer or the end of September," she said. "I think my job has gone from animal control to the elimination of seals."

DESIGNATED AN UNUSUAL EVENT OF MORTALITY

Phocine's disease was found in seals during an epidemic off the coasts of northern Europe, the United Kingdom and Ireland in 1988. According to a study conducted in the early 1990s, 20 000 seals were killed, nearly 60% of the population. The distemper was linked to another mortality of at least 30,000 seals in the Baltic, North and Wadden seas in 2002.

The virus has also been accused of the most significant death on the east coast for nearly 30 years. In 2006 and 2007, at least 1,500 harbor seals and gray seals were stuck in an epidemic along the coast from Maine to Virginia.

If current trends continue, the number of seal deaths could reach or exceed this year. Respondents reported 999 seals stranded in New England between July and this week. Three-quarters of the animals were found on beaches in southern Maine, particularly in communities south of Portland.

Nearly 500 seals were found stranded in New England in August, nearly nine times the five-year average. So far this month, 336 additional seals have been found, NOAA said.

At the end of August, the federal agency designated the mortality as an unusual event, allowing a special investigation into its cause and a possible reimbursement for relief organizations such as Marine Mammals of Maine that respond to the dead seals and stranded.

LOW IMMUNITY OF HERDES A FACTOR

Scientists do not know why harbor seals seem susceptible to the disease, but they believe that low herd immunity worsens epidemics.

"There are always low levels of animals in the population who have the virus and pass it on, but do not die," said Tracey Goldstein, marine mammal disease specialist at the University of California at Davis. His lab is testing samples of New England seals that have died in the last three months.

"The longer you've spent an epidemic, the fewer animals there are with an antibody," Goldstein said. "The population as a whole does not have immunity or protection against the virus."

Gray seals, on the other hand, seem more resistant to the disease. This means that they can carry the virus without being too sick or dying, but that they can also transmit the virus during the spring breeding season, when many animals of both species gather on the beaches.

If a virus is needed in harbor seals, it can spread quickly, said Goldstein.

"For whatever reason, they are really sensitive to the virus and, when they are exposed, they are really unable to fight the infection," she said.

The effect this outbreak could have on the seal population in the northeast is not certain. There are approximately 76,000 seals in a population of the Bay of Fundy in New York, and the most recent assessment of the federal stock revealed that the population was stable.

Shore seal stranding represents a small proportion of the affected animals. It is therefore unclear how many seals have succumbed to the virus, said Goldstein.

Massive epidemics of phocine disease in Europe in 1988 and 2002 killed half of the population or more, but seals rebounded quickly, she added.

"If the population is strong and remains strong, it should not have a long-term effect," Goldstein said.

A dead seal is found on the coast of Bayview Beach in Saco on August 12th. Staff Photo by Shawn Patrick Ouellette