Unsafe biotoxin levels found at Semiahmoo Spit

Published on Wed, Jul 25, 2012 by Jeremy Schwartz

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Whatcom County health officials have found unsafe levels of a marine biotoxin new to the area in shellfish samples taken from Semiahmoo Spit.

Regular tests have revealed diarrhetic shellfish poison (DSP) for the first time in saltwater in Whatcom County, health department program manager Tom Kunesh said. Shellfish samples from Birch Bay, Bellingham Bay and Semiahmoo Spit all contained DSP, though only shellfish off Semiahmoo showed higher levels of the toxin than the state health department allows.

The organism that produces DSP has been detected in Washington state by National Oceanic and Atmospheric Administration (NOAA) tests in the past, but this is the first time the actual toxin has been detected in shellfish, Kunesh explained. Last July, two people sickened by the toxin after eating shellfish harvested in Sequim Bay in Clallam County were the first reported cases of DSP illness in the state.

“[DSP] hasn’t been a problem in Washington state waters until very recently,” Kunesh said.

Whatcom County beaches have been closed to recreational shellfish harvesting since July after dangerous levels of the deadly paralytic shellfish poison (PSP) were found. While not known to be lethal, DSP can cause diarrhea and vomiting up to three days after ingesting the toxin, Kunesh said.

All species of harvestable shellfish can contain both DSP and PSP, Kunesh explained. Health officials advise against eating the crab butter of crabs caught in Whatcom County and any area under shellfish closure, though crab flesh is safe to eat.
Since crab are not filter feeders, they do not accumulate toxins in their bodies. Shellfish, however, filter gallons of water every day and rely on the algae that can contain the toxin as a food source, Kunesh said.

DSP has been recognized as an emerging health threat, and Kunesh said health officials are not sure what might be causing increased levels of the toxin in shellfish over the past year. Algae blooms associated with DSP don’t seem to be caused by human activity, and the organism that produces the toxin naturally occurs in both pristine waters and off the coasts of urban areas.

“Their presence is not really something we can control,” Kunesh said.

NOAA researchers in Washington started testing for DSP between 2010 and 2011, and the state department of health began conducting its own DSP tests, which differ from tests for PSP, in May of this year, Kunesh explained. Health officials generally agree the organism that produces DSP did not exist in Puget Sound waters five to 10 years ago.

Washington’s capacity for PSP testing is robust, with state health labs able to process weekly samples from areas closed to shellfish harvesting, such as Whatcom County, Kunesh explained. Due to DSP’s relatively recent arrival, however, Kunesh said state health officials can only perform a limited number of DSP test per week.

For up-to-date listings of beaches that are closed to commercial shellfish harvesting, visit the state department of health's website or call 1-800/562-5632.