Marine researchers aim to crack shellfish poisoning mystery
January 20, 1992
RICHLAND, Wash. –
The crabbing season has been reopened along the coasts of Washington, Oregon and California, but questions remain about a potentially lethal poison that shut down commercial Dungeness crab fishing and processing during December. The same toxin also prompted state officials to cut short the recreational razor clam season in November after 11 people became ill from eating clams.
Researchers at Battelle's Marine Sciences Laboratory, in Sequim, Washington, along with several agencies, are looking for answers to help protect shellfish consumers and preserve the livelihoods of crab fishermen and commercial shellfish distributors.
Varying amounts of domoic acid, a naturally occurring toxin, have been found in Dungeness crabs and razor clams along the Pacific coast. Health officials believe that domoic acid can cause intestinal problems, mental confusion and in rare cases, death. The condition, named amnesic shellfish poisoning, was first identified in 1987 near Prince Edward Island in Canada when more than 100 people became ill, and three people died after eating mussels. No other cases have been reported in Canada since that time.
The shellfish accumulate the domoic acid by feeding on microscopic algae that suddenly appear in large quantities in the water, similar to the condition that creates more common red tides.
"First of all, we'd like to know if this problem has always been here and has just been identified or whether we're looking at a new phenomenon," said Ralph Elston, a researcher at the MSL. Elston believes that the marine algae, which are sources of domoic acid, likely have been in Pacific waters for some time, but the key is to discover how, why and when it becomes a public health threat.
To ensure consumer safety, a multi-agency research committee has been
formed and is chaired by Ann Drum, a technical specialist at the MSL. The committee is seeking answers to these key questions:
- What other marine species are susceptible to the toxin?
- Is there a "safe" level of toxin?
- How often should shellfish be tested for the toxin?
- How fast do crabs and clams assimilate and expel the toxin?
- Do certain crabs or clams absorb more of the toxin than others?
- Is there a way to destroy the toxin during food preparation or storage?
- Can the algae or its domoic acid production be controlled?
- Why do the algae produce domoic acid only at certain times?
Unique holding tanks or wet labs at the MSL are being used to conduct research to answer some of these questions and to analyze the effects of domoic acid on the shellfish.
The domoic acid doesn't appear to be harming the crabs and clams themselves, but that is one area that also needs further study, according to Elston.
Washington state officials have sampled Washington oysters and mussels for domoic acid, but so far it only has been detected in Dungeness crabs and razor clams. "Since domoic acid was found in the mussels in Canada, we know they can be affected. Why the mussels in our area apparently are free from the toxin is unknown, but could be an important clue to learning more about the problem," said Elston.
The MSL is working in conjunction with the U.S. Food and Drug Administration in Seattle and Washington, D.C., the National Marine Fisheries Service, the Washington State Department of Health, the Washington Department of Fisheries, the Oregon Department of Health, the University of Washington, Seattle, and representatives from Northwest shellfish industries.
The group also is collaborating with Canadian experts and seeking information from East Coast researchers who also have experienced problems with domoic acid.
Battelle's Pacific Northwest Division, with laboratories in Richland, Seattle and Sequim, Washington, performs research and development for industrial sponsors and government agencies. The Division is a component of Battelle Memorial Institute, an international technology organization that serves industry and government by developing, commercializing and managing technology.
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