Magazine article Science News

Dog Virus Seals Fate of European Seals

Magazine article Science News

Dog Virus Seals Fate of European Seals

Article excerpt

Dog virus seals fate of European seals

Over the last five months, harbor seals in the North and Baltic Seas have died in vast numbers from unknown causes. The deaths have occurred in Scandinavian, German and Dutch waters, and the British population of seals, the largest in Europe, now appears threatened. Although scientists have isolated two viruses from dead seals, they have been unable to establish a causal link to the fatal disease. Others have blamed persistent pollutants, such as PCBs or dioxins -- which are known to affect immune response -- in the deaths of an estimated 8,000 to 9,000 seals.

Now a Dutch research group says it has discovered the apparent cause: another virus, canine distemper virus (CDV) or a close relative. CDV belongs to the morbillivirus family, which includes the human measles virus. The work was led by Alfred D.M.E. Osterhaus of the Dutch National Institute of Public Health and Environmental Protection in Bilthoven and ElizabethJ. Vedder of the Seal Orphanage in Pieterburen.

Osterhaus and others initially isolated a herpesvirus from the lungs and other organs of 8 of 35 dead seals from the afflicted areas, and a picornavirus from the lungs of 20 of 22 seals investigated. In a letter in the July 28 NATURE, he proposed that one or both of these viruses "probably caused" the outbreak.

But when the scientists attempted to confirm the hypothesis with blood studies, they found "no correlation" between disease symptoms and a rise in antibody levels against either virus -- although virus-neutralizing antibodies were present in the blood of the seals coming from afflicted waters. On this basis, and after failed efforts to immunize young seals in the orphanage, the scientists searched for other viruses.

Meanwhile, Swedish workers at the National Veterinary Institute in Uppsala observed that tissue damage in diseased seals resembled that in dogs with distemper, leading the Dutch to test for CDV. …

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