Virus threatens Europe's seals

A deadly seal virus is sweeping across the seas of Northern Europe and is threatening to match the devastating epidemic of 14 years ago that wiped out half the seal population in those waters, said an international study released tonight.

Scientific tests on the carcasses confirm that phocine distemper virus, which does not affect humans, has infected seal communities in Denmark, Sweden and the Netherlands, said the study published in the journal Science.

Populations had barely recovered from the 1988 disaster when the first seal victims were discovered in May. The disease spreads rapidly because seals travel hundreds of miles within a few days, and researchers said they found the identical virus from widely separated regions.

It has not yet peaked and “the death will continue,” said Albert Osterhaus of the Erasmus Medical Centre in Rotterdam. He heads a team of seven researching the disease.

Nearly 1,500 seals have perished this summer and washed onto beaches, said Bettina Reineking, a spokeswoman for Common Wadden Sea Secretariat, which monitors seal deaths from Germany.

The latest outbreak was discovered on the eastern Danish island of Anholt, but it is still unclear where it originated, the study said.

“The current sequence of events parallels the early pattern” of the last epidemic, when 18,000 seals, or half the population in Northern Europe, died from distemper, the report said. From April to August 1988, the disease swept from the Danish islands to the Dutch Wadden Sea, then to the Baltic and on to British waters.

The virus usually causes severely matted eyes, runny noses and pneumonia, spreading from animal to animal through direct contact with body fluids or by scratching, clawing or biting.

Most seals actually die from other diseases caught because of a weakened immune systems, experts said. Mortality rates can vary from 5 percent to 60 percent, said John Harwood, a population biologist at St Andrews University in Scotland.

Although there are many similarities with the 1988 outbreak, Harwood said the current epidemic seems to be spreading less rapidly, possibly because it started six weeks later in the breeding season.

Breeding seals may be less inclined to travel long distances while nursing their young, he said.

“We all agree that this is a highly infectious disease that spreads very rapidly,” Harwood said. “There is a real risk that it could spread throughout the whole of Europe.”

Even though Britain anticipated the infection of its seal population, it is virtually impossible to stop, Harwood said, because “wildlife diseases are difficult to control and tend to run their course.”

Scientists are puzzled by the source of the latest outbreak, which has spread from Denmark to the Netherlands without infecting seals in Germany.

Infection rates are highest in Sweden at 10-20 percent, and if they continue to climb, could kill thousands in the waters off that country, said Osterhaus, the Dutch researcher.

Scientists from the three European countries examined tissue samples of the lungs, kidneys, bladders and brains from dead seals before diagnosing symptoms of showing “a reintroduction of the same disease,” Osterhaus said.

“The effect of the current epidemic will depend on the overall resistance and specific immunity of the Northern European population,” according to the report.

But Osterhaus said results from immunity tests on seals over the past 10 years are discouraging, with only 5% showing resistance.

“What that means is that the vast majority of the population, the other 95 percent, is susceptible to the virus,” he said.

Dutch authorities have posted warnings in coastal areas for dog owners to keep their pets away from dead seals. Dogs can become infected, but most domesticated animals are inoculated against distemper.

A variant of distemper that killed thousands of seals in the Caspian Sea in 2000 is believed to have been introduced by wild dogs.

Research in the North Sea the year after the 1988 outbreak indicated that seals in polluted waters were more susceptible to the disease, prompting bitter accusations from environmental groups.

Public outrage over the epidemic in Sweden fuelled support for the Green Party, which entered parliament for the first time that year.