SEQUIM — Initial tests at sites around Puget Sound have confirmed that Sequim Bay is the only body of saltwater where diarrhetic shellfish poisoning has been found in the state and throughout the U.S., a state Department of Health official said Monday.
“We’ve sampled all parts of the state and have not found other areas affected . . . so that’s good news,” said Frank Cox, marine biotoxin coordinator with the state Department of Health.
State health officials on Aug. 11 reported that three King County residents who ate mussels they harvested at Sequim Bay State Park in late June fell ill with DSP — also called diarrheal shellfish poisoning — in a case that baffles state health officials.
They call it a mystery that can only be solved through testing and analysis of water quality in all parts of Puget Sound.
The state Department of Health closed Sequim Bay to shellfish harvesting upon reporting the marine toxin illnesses, never seen before in unsafe levels in U.S. shellfish.
“I guess you have to call it kind of a hotbed for this one,” Cox said, adding that no other illnesses beyond the three had been reported as of Monday.
As many as 60 have been reported in Canada, believed linked to an island at the north end of the Strait of Georgia in British Columbia (see accompanying box).
Food contaminated with DSP biotoxin may not look or smell spoiled.
Diarrhetic shellfish poisoning can cause diarrhea, nausea, vomiting, abdominal cramps and chills.
The ban on both recreational and commercial harvesting of all types of shellfish in Sequim Bay began Aug. 8, and a recall for all commercially sold shellfish from the area during the past two weeks also went into effect.
DSP comes from a toxin produced by a type of plankton long known to live in high concentrations in Sequim Bay and around Puget Sound, Cox said.
The unsafe threshold of toxicity is 6 micrograms per 100 grams of shellfish tissue, similar to that of paralytic shellfish poisoning, a naturally recurring shellfish toxin that is far more serious than DSP and can cause paralysis and death when ingested.
Most recent tissue samples taken from mussels in Sequim Bay show that the toxin remains.
“We’re pushing ahead with our monitoring,” Cox said. “We are now in the exploratory stage, and how to do that with state budget constraints is yet to be seen.”
Rita Horner, a retired University of Washington marine sciences professor and an expert in the field of harmful phytoplankton in the region’s marine waterways, said DSP has symptoms that last only two to three days.
Its effects are similar to vibrio fibrosis, bacteria that gestate inside oysters when they sit out in the sun too long, and both vibrio fibrosis and DSP are not fatal.
“Sequim Bay is interesting because it doesn’t have a very big opening, so if something gets in there, it’s quite possible it’s going to remain there,” Horner said.
How long the organism will remain in Sequim Bay is unknown, she said.
Study of the organism in phytoplankton that causes DSP has been all but impossible until Korean scientists found a way to grow it in cultures.
“This particular organism up until about five years ago could not be grown and cultured,” she said.
Cox said state Health is not set up to test water for DSP, so samples must be sent to the U.S. Food and Drug Administration lab in Dauphin, Ala.
State Health and Jamestown S’Klallam tribal researchers have been studying the plankton and are working closely with the National Oceanic and Atmospheric Administration, he said.
Unlike bacterial contamination, DSP and toxic paralytic shellfish poisoning, or PSP, are not killed by cooking or freezing.
High levels of PSP prompted the closure in late June of beaches directly on the Strait of Juan de Fuca from Discovery Bay in Jefferson County west to Neah Bay in Clallam County to all recreational harvesting of all species of shellfish.
The closure applied only to sport harvesting, not to commercially harvested shellfish, which are sampled separately, health officials have said.
For more information, phone the Marine Biotoxin Hotline at 800-562-5632 or visit the state website at http://tinyurl.com/4xmftw7.
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Sequim-Dungeness Valley Editor Jeff Chew can be reached at 360-681-2391 or at jeff.chew@peninsuladailynews.com.
