Clinical and epidemiological features of neurotoxic shellfish poisoning in North Carolina

In October 1987, a red tide due to P. brevis affected the North Carolina coast for the first time. The purpose of our study was to describe the clinical and epidemiological features of neurotoxic shellfish poisoning (NSP), an illness caused by eating shellfish contaminated with the neurotoxins of P. brevis.

Active surveillance was established for cases of NSP. A descriptive study of the NSP cases was then completed.

Forty-eight persons, who had eaten oysters at 20 meals, met the case definition. A variety of gastrointestinal tract and neurological symptoms were reported. The illnesses were generally mild and of short duration, and there were no deaths. Forty-one (85 percent) affected persons lived in five communities located within a 70-kilometer area along the coast. Cases occurred from October 27 to December 9; 27 (56 percent) of the cases occurred before the first closure of affected shellfish waters on November 2. There was a significant increase in the illness attack rate with an increase in the number of oysters eaten.

Routine monitoring of coastal waters for P. brevis is needed to facilitate earlier recognition of red tides, closure of affected areas, and education of the public before substantial exposure to contaminated shellfish occurs.