to 10°C or lower and holding them at or below this temperature at all times before cooking and eating. A system based on the Hazard Analysis Critical Control Point would ensure this for commercially handled fish, but the education of subsistence and recreational fishers is also necessary.

Paralytic shellfish poisoning was reported as a minor cause of seafood-borne illness in 1978-1987 with only two deaths. This is a remarkable record in view of the annual occurrence of toxic situations among shellfish on both the East and the West coasts of the United States and indicates that current control measures applied by coastal states are highly effective. However, the increasing occurrence of toxic dinoflagellate blooms and changing eating practices among some sectors of the consuming public require increased surveillance and the development of more rapid and simple tests for toxic shellfish.

Although other natural seafood intoxications have not been reported recently in U.S. consumers (except for an outbreak of neurotoxic shellfish poisoning in North Carolina in 1987), the potential for their occurrence either from domestically produced seafoods or from imports is real. Increased vigilance concerning imported products, based on a requirement for certified nontoxicity, is recommended. Moreover, both state and federal laboratories should be prepared to test for these "other" toxins, and procedures should be in place to deal with outbreaks.

INTRODUCTION

The toxic diseases from fish and shellfish of importance to American consumers include ciguatera, scombroid fish poisoning, paralytic shellfish poisoning, neurotoxic (brevetoxic) shellfish poisoning, puffer fish poisoning, diarrhetic shellfish poisoning, and amnesic shellfish poisoning (Hughes and Merson, 1976; Mills and Passmore, 1988; Ragelis, 1984; Todd, 1989). In all cases, illness is due to ingestion of tissues containing heat-resistant toxins that are not destroyed by normal cooking and whose presence is undetectable by organoleptic means. Except for scombroid poisoning, toxins usually accumulate in fish or shellfish through the food chain, so that the fish or shellfish are toxic at the time of harvest. Scombroid poisoning is caused by bacterial-induced chemical changes resulting from mishandling of fish after capture, which is more readily susceptible to human control (Taylor, 1986).

Fish poisoning, principally ciguatera and scombroid fish poisoning, was responsible for 17.8% of all confirmed food-borne disease outbreaks listed by the Centers for Disease Control (CDC) in 1978-1987. Reports were approximately evenly split between the two principal toxicoses: 179 ciguatera outbreaks involving 791 cases, and 157 outbreaks of scombroid with 757 cases (Table 4-1). However, as noted elsewhere in this report, CDC data are highly skewed, in this case due to the limited area within which ciguatera occurs, which enhances the visibility of this disease, and to the different symptoms associated with scombroid poisoning. Thirteen outbreaks of paralytic shellfish poisoning (PSP), the most dangerous of the intoxications, were reported and involved 134 cases, most of which (94) were from two large California outbreaks in 1980. No cases of puffer fish or diarrhetic shellfish poisoning were reported to CDC in this period. The actual incidences of cases of ciguatera and PSP with milder symptoms are probably higher than indicated due to underreporting, as evident from a comparison of CDC data with those obtained in incidence studies in defined geographical areas (Mills and Passmore, 1988; Morris et al., 1982b; Nishitani and Chew, 1988).



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