TONNING – Since early October, at least 180 dead seals have been found along the North Sea coast of the German state of Schleswig-Holstein.

Dead fish and sea creatures often wash up onto beaches along the North and Baltic seas, but experts now say that these seals may have died of a virus that risks spreading further.

The situation is particularly worrisome because 200 of the 1500 seals living on the Danish Baltic Sea island of Anholt have died since August. "A flu virus was found in the cadavers," says Hendrik Brunckhorst, spokesman for the state government-owned Company for Coastal Protection, National Parks and Ocean Protection in Schleswig-Holstein.

To stem further deaths, seal hunters have been called to kill sick seals on the beaches of Helgoland, Amrum, Föhr and Sylt islands. "Ninety-five percent of the seals found on the beaches are already dead," says Sylt-based hunter Thomas Diedrichsen.

Except for a cough, the animals do not show outward signs of being sick, says seal expert Britta Diederichs of the National park service in Tönning. Experts at the Hannover Graduate School for Veterinary Pathobiology, Neuroinfectiology and Translational Medicinein Büsum are currently investigating the cause of death.

Phocine distemper virus or flu viruses could be the cause with devasting results as seals lie close to one another on sand banks thus facilitating spread of the disease by direct contact or droplet-borne infection.

During the last two outbreaks of phocine distemper in 2002 some 22,000 animals died, while 18,000 died in 1988. Expert Diederichs says the present outbreak is not expected to reach those proportions. "But nevertheless, we could be looking at 1,000 dead seals," she says.

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Common Seals near Terschelling, Netherlands — Photo: Mhaesen

Twelve-thousand seals currently live along the Schleswig-Holstein North Sea coast. "The number of seals has grown considerably in the past few years," says Diederichs. "The coughing we’re seeing could be down to a number of things, phocine distemper being just one of them."

Phocine distemper can lead to death within two weeks. It is caused by a virus similar to that which causes canine distemper. It weakens the animals’ immune system and makes them susceptible to infections like pneumonia. Coughing, shortness of breath and fever are typical symptoms.

Pollutants such as lead, mercury and cadmium that flow into the North Sea from rivers increase susceptibility to infection. A vaccine does exist, but the logistics of administering it to thousands of seals makes it impracticable. The virus is not dangerous to humans but experts recommend keeping a distance from sick or dead animals on beaches.