An outbreak of toxic encephalopathy caused by eating mussels contaminated with domoic acid

In late 1987, an outbreak of illness occurred in Canada in which the patients developed gastrointestinal symptoms, sometimes with neurological complications. The only feature all the patients had in common was that they had eaten mussels from Prince Edward Island. A total of 107 cases were clearly identified, though the number of actual cases is almost certainly larger. Some patients experienced severe neurological complications, which included apparently irreversible damage to the mechanisms of short-term memory; these neurological complications are the subject of a companion article in the June 21, 1990 issue of The New England Journal of Medicine. Three patients died. Many organisms concentrate substances in their bodies which can pose problems for the larger creatures who eat them, and mussels are capable of concentrating a variety of environmental toxins in their bodies. However, in this case, the only poisonous compound which could be identified was domoic acid. Domoic acid is an amino acid which can excite nervous tissue, like the biochemically similar compounds glutamic acid and kainic acid. The source of the domoic acid in the mussels appears to be the microscopic creature Nitzschia pungens, which biologists refer to as a pennate phytoplanktonic diatom. The tiny creatures were eaten by the mussels, which concentrated the poisonous domoic acid in their tissues. Steps have now been taken in Canada to monitor the level of domoic acid in mussels prior to their commercial distribution. (Consumer Summary produced by Reliance Medical Information, Inc.)