Sequim: Oyster parasite found in Dungeness Bay

SEQUIM — Well, Washington is first again.

First, this time, in the United States to discover the presence of Mikrocytos mackini, a parasite that causes mikrocytosis, a deadly disease in oysters.

Scientists found the parasite this spring in a couple of what they call “feral”‘ Pacific oysters during routine surveillance in Dungeness Bay, near Sequim.

Two oysters of a sample of 50 tested positive, but the scientists found no evidence of any shellfish dead or dying as a result of the bug.

The disease produces green pustules in the body of the oyster and brown scars on the adjacent shell.

It may disgust people, but the disease is not known to be harmful to humans.

The disease affects Pacific, Olympia, Kumamoto and European flat oysters, all of which grow commercially in Washington.

It usually kills as many as 40 percent of oysters on a beach, though oysters being grown nearby on longlines (ropes spread over the sand) in Dungeness Bay tested negative for Mikrocytos mackini.

While the disease is most common in oysters more than five years old, it’s seldom found in farmed oysters, which are harvested at two to three years of age.


The rest of this story appears in the Friday/Saturday Peninsula Daily News. Click on SUBSCRIBE to get the PDN delivered to your home or office.

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