Ciguatera on Kauai: investigation of factors associated with severity of illness.

Epidemiologic characterization of ciguatera fish poisoning has been limited by lack of laboratory confirmation, absence of prospective follow-up, and incomplete analysis of age-related factors. A 1985 outbreak on the island of Kauai in the state of Hawaii that involved 15 persons of various ages was investigated to determine factors associated with disease severity. The presence of ciguatoxin was detected in leftover portions of the implicated fish by enzyme immunoassay. All cases were medically and epidemiologically investigated and followed prospectively. Ten of the 15 cases demonstrated bradycardia; seven were hospitalized, including two requiring placement in intensive care. Bradycardia was associated with increasing age and body weight (P < 0.01 and < 0.05, respectively) as well as the amount of toxic fish consumed (P < 0.01). Duration of illness ranged from two to 132 days. Increasing duration of illness was correlated with both increasing age and weight (rs = 0.64 and rs = 0.72, respectively, both P < 0.01) and was independent of amount and components of toxic fish consumed. The correlation between increasing age and weight with duration and severity of symptoms may be explained by prior subclinical toxin exposure and is consistent with the observation that repeated ciguatoxin exposures are associated with more severe illness. The association between amount of toxic fish consumed and bradycardia is consistent with an increased dose of ciguatoxin. The findings of this outbreak investigation support previously unconfirmed observations.