Ciguatera fish poisoning

On October 21, 1997, the Southeast Texas Poison Center was contacted by a local physician requesting information about treatment for crew members of a cargo ship docked in Freeport, Texas, who were ill with nausea, vomiting, diarrhea, and muscle weakness. This report summarizes an investigation of this outbreak by the Texas Department of Health (TDH), which indicated that 17 crew members experienced ciguatera fish poisoning resulting from eating a contaminated barracuda.

On October 12 and 13, gastrointestinal illness developed in crew members aboard a Norwegian cargo ship. After the ship had docked, on October 22 interviews were conducted with 23(85%) of 27 crew members. A case was defined as ciguatera fish poisoning if there was a combination of gastrointestinal symptoms (i.e., nausea, vomiting, diarrhea, or abdominal cramps) and neurologic symptoms (i.e., muscle pain, weakness, dizziness, numbness or itching of the mouth, hands, or feet) in a crew member after eating fish on October 12. Of the 23 interviewed, 17(74%) crew members reported the following symptoms: diarrhea (17[100%]), abdominal cramps (14[82%]), nausea (13[76%]), and vomiting (13[76%]). Symptoms occurred within 2-16 hours (median: 4.5 hours) after eating fish at approximately 7 p.m. on October 12. By October 14, all ill crew members had experienced neurologic symptoms characteristic of ciguatera poisoning: 15(88%) reported muscle weakness and pain; 13(76%), numbness or itching of the mouth; 11(65%), pruritus of the feet and/or hands; 11(65%), temperature sensation reversal; 10(59%), dizziness; and eight (47%), aching or loose-feeling teeth.

On October 21, all 17 ill crew members sought medical care at a clinic. None of the crew members were hospitalized; treatment consisted of supportive measures to reduce discomfort from symptoms. All patients were men aged 23-46 years.

Based on food histories from the 23 crew members, TDH suspected consumption of a barracuda caught by crew members while fishing near the Cay Sal Bank of the Bahamas on October 11 as the source of illness. Seventeen crew members ate the barracuda, and all became ill. None of the eight crew members who did not eat barracuda became ill. Although crew members also ate red snapper and grouper at the same meal, neither of these fish were linked epidemiologically with illness.

Results of cultures of stool samples from 16 crew members were negative for Salmonella, Shigella, Campylobacter, Yersinia, and Vibrio. Three samples of leftover raw barracuda and red snapper that were caught simultaneously with the barracuda that was eaten were recovered from cold storage and then tested for ciguatoxin using an experimental membrane immunobead assay at the Department of Pathology, University of Hawaii. The samples from both fish tested positive for ciguatoxin.

Reported by: W Smith, MD, US Health Works, Free port; B Lieber, Southeast Texas Poison Center, Galveston; DM Perrotta, PhD, Bur of Epidemiology, Texas Dept of Health. Y Hokama, Univ of Hawaii, Manoa. Foodborne and Diartheal Diseases Br, Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; Div of Applied Public Health Training, Epidemiology Program Office; and EIS officers, CDC.

Editorial Note: Ciguatera poisoning occurs throughout the Caribbean and tropical Pacific regions, where outbreaks have been reported among both residents and tourists. From 1983 through 1992 in the United States, 129 outbreaks of ciguatera poisoning involving 508 persons were reported to CDC; no ciguatera-related deaths were reported (1,2). Most outbreaks were reported from Hawaii (111) and Florida (10), although outbreaks and sporadic cases in California (two), Vermont (one), New York (one), and Illinois (one) also have been associated with consumption of fish imported from tropical waters (3,4). The outbreak described in this report was recognized in an area not typically associated with ciguatera intoxication and underscores that ciguatera poisoning can occur among travelers returning from areas where ciguatera is endemic or among persons consuming fish imported from those areas.

Ciguatera toxins are produced by dinoflagellates, which herbivorous fish consume. These fish are then eaten by large, predatory reef fish (e.g., barracuda, grouper, and amberjacks), which appear to be unharmed by the toxin; because the toxins are lipid-soluble, they accumulate through the food chain. The toxin may be most concentrated in the head, viscera, and roe. Ciguatoxin-containing fish may be highly localized; islands may have some reefs where the fish are inedible because of the toxin and other reefs where the fish are unaffected. No deep-sea fish (e.g., tuna, dolphin, or wahoo) have been found to carry ciguatoxin.

As in this outbreak, ciguatera fish poisoning is diagnosed by the characteristic combination of acute gastrointestinal symptoms (developing within 3-6 hours after ingestion of contaminated fish; watery diarrhea, nausea, and abdominal pain occur and typically lasting approximately 12 hours) and neurologic symptoms (circumoral and extremity paresthesia, severe pruritus, and hot-cold temperature reversal) in persons who eat large, predatory reef fish. Neurologic symptoms may be worsened by alcohol consumption, exercise, sexual intercourse, or changes in dietary behavior, such as dieting or high-protein meals (5; R.W. Dickey, Ph.D., Center for Food Safety and Applied Nutrition, Food and Drug Administration, personal communication, 1998). Occasionally, hypotension, respiratory depression, and coma develop in patients. Mean duration of acute illness is typically 8.5 days, although neurologic symptoms may last for months (6). Because there is no approved human assay for ciguatoxin, the diagnosis is based on clinica l findings and by the detection of toxin in samples of fish. No known antidote for ciguatoxin poisoning has been proven, and treatment is primarily for relief of symptoms. Intravenous mannitol may be effective early in the course of illness, but the results of a randomized, placebo-controlled trial of mannitol therapy have not been reported (7-9).

Ciguatoxins are odorless, colorless, tasteless, and unaffected by either cooking or freezing; therefore, persons living in or traveling to areas where ciguatera toxin is endemic should follow these general precautions: 1) avoid consuming large, predatory reef fish, especially barracuda; 2) avoid eating the head, viscera, or roe of any reef fish; and 3) avoid eating fish caught at sites with known ciguatera toxins. Persons traveling to areas where ciguatera is endemic should contact local health officials for more specific recommendations pertaining to that area. Fishermen should avoid known ciguatera-contaminated areas, and vendors should not sell fish caught in those areas.

III persons with suspected ciguatera poisoning should promptly seek medical care and save any uneaten portions of fish in a freezer. Suspected cases should be reported to state or local public health officials to assist with the investigation and control of a possible outbreak. Additional information is available about ciguatoxin testing of implicated fish from the Gulf Coast Seafood Laboratory of the Food and Drug Administration (FDA) in Dauphin Island, Alabama, telephone (334) 694-4480, or the University of Hawaii, Honolulu, telephone (808) 956-8682. For general information about seafood safety, call FDA's Seafood Hotline, telephone (800) 332-4010.

References

1. CDC. Foodborne disease outbreaks, 5-year summary, 1983-i 987. MMWR 1990;39(no. SS- 1): 15-57.

2. CDC. Surveillance for foodborne disease outbreaks, United States, 1988-1992. MMWR 1996;45(no. SS-5).

3. CDC. Ciguatera fish poisoning-Vermont. MMWR 1986;35:263-4.

4. Swift AEB, Swift TR. Ciguatera. Clin Toxicol 1993;31 :1-29.

5. Lange WR. Ciguatera fish poisoning. Am Fam Physician 1994;50:579-84.

6. Hughes JM, Merson MH. Fish and shellfish poisoning. N Engl J Med 1976;295:1117-20.

7. Palafox NA, Jam LG, Pinano AZ, et al. Successful treatment of ciguatera fish poisoning with intravenous mannitol. JAMA 1 988;259:2740-2.

8. Blythe DG, De Sylva DP, Fleming LE, et al. Clinical experience with IV mannitol in the treatment of ciguatera. Bull Soc Path Ex 1992;85:425-6.

9. Bagnis R, Spiegel A, Boutin JP, et al. Evaluation of the mannitol's efficiency in the treatment of ciguatera in French Polynesia. Med Tropicale 1992;52:67-73.

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