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Scombroid Fish Poisoning --- Pennsylvania, 1998

In December 1998, the Chester County Health Department (CCHD) in Pennsylvania received reports of four cases of scombroid fish poisoning among patrons at a local restaurant. This report summarizes the investigation of these cases by CCHD, the Pennsylvania Department of Agriculture (PDAg), and the Pennsylvania Department of Health (PDOH). Findings from this investigation suggest that initial processes that are not regulated by the Food and Drug Administration (FDA) (i.e., from hooking the fish to unloading the fish on the dock) may permit scombrotoxin formation.

On December 3, 1998, four adults became ill after eating tuna-spinach salad at the restaurant. Symptoms of illness included a burning sensation in the mouth, a metallic taste, facial flushing, nausea, diarrhea, sweating, and headache; symptoms occurred approximately 5 minutes to 2 hours after eating the salad. One patient was taken to the local emergency department and treated with diphenhydramine, cimetidine, and epinephrine. The other three patients were not examined by physicians and their symptoms resolved within a few hours. A presumptive diagnosis of scombroid fish poisoning was made based on clinical and epidemiologic features of the illness.

A sample of the remaining fish obtained from the restaurant was sent to PDOH for testing. The fish was positive for coliform and Escherichia coli, and tests were positive for histamine levels >50 ppm (fresh fish normally contain histamine levels of <10 ppm [1]) using an enzyme-linked immunoabsorbent assay.

CCHD and PDAg conducted a traceback investigation of the source of the tuna. The wholesale-to-retail chain of events involved transporting the fish across national, state, and municipal borders and involved five transporters and four processors. The tuna was from a 40--60 lb yellow-fin tuna caught by a commercial fishing boat in the Gulf of Mexico during late November 1998. The fish was caught using the long-line method, which uses a mainline up to 60 miles long with a series of suspended hook lines. The water temperature where the fish was caught was 78.5 F (25.8 C). The catch of tuna was shipped from the fishing boat in iced vats by truck to a processor on November 24. The average temperature of the fish was 32 F--33 F (0 C--1 C). Of this catch, 785 lbs of tuna were shipped the same day to the wholesaler in Pennsylvania. The wholesaler received the shipment on November 27, and the average temperature of the fish was recorded as 36 F (2 C). Three of these fish were delivered to the retail supplier; two large fillets, weighing 11.1 lbs each and noted to be in good physical appearance, were delivered to the restaurant on November 27. The fish was divided into 30 portions, kept in the freezer, and removed for thawing as needed for use. During November 28--December 4, 17 portions of the fish were served. The only four persons reporting illness ate the tuna-spinach salad on December 3.

CCHD and PDAg reviewed the records of each distributor involved in the wholesale-to-retail process of the tuna. All of the fish plants involved were inspected regularly by the FDA and/or PDAg and have Hazard Analysis and Critical Control Point (HACCP) procedures. No deviations in HACCP procedures in the wholesale-to-retail distribution of the tuna could be identified. However, the long-line method of fishing is not covered as part of the FDA Seafood HACCP regulations.

Reported by: JP Maher, MD, JA Worth, J Arvay, K Raum, Chester County Health Dept, West Chester; L Iampetro, Pennsylvania Dept of Health Bur of Laboratories; JR Welte, Food Safety and Laboratory Svcs, Region 7, Pennsylvania Dept of Agriculture. Food and Drug Administration. Div of Bacterial and Mycotic Diseases, National Center for Infectious Diseases; and an EIS Officer, CDC.

Editorial Note:

Scombroid fish poisoning has been associated primarily with the consumption of tuna, mahi-mahi, and bluefish. It is caused by histamine and other products produced by certain bacteria on some types of fish; these bacteria grow in warm temperatures and produce the enzyme histidine decarboxylase that converts free histidine in fish flesh to histamine and other products (2--6).

National surveillance data on scombroid fish poisoning is based on outbreaks of acute foodborne disease reported by state health departments to CDC (7,8). During 1988--1997, scombroid fish poisoning was reported in 145 outbreaks involving 811 persons from at least 20 states (7,8); however, many cases probably are not reported.

Since December 18, 1997, all processors of fish are required by FDA to conduct a hazard analysis of their operation and to implement a HACCP plan to control each identified hazard (9). The HACCP plan must be specific for each location where fish and fish products are processed and for each species processed (10). The fish implicated in these scombroid fish poisonings was caught by the long-line method of fishing, which consists of suspending a monofilament line, up to 60 miles long, with up to 3000 baited hooks in the water. The retrieval process may take up to 12--14 hours, and the fish may be retained on the lines up to 20 hours. Although no deviations in HACCP procedures were documented in this outbreak, the time from hooking the fish to unloading the fish on the dock is not covered by HACCP. Conditions permitting histamine production could have occurred while the fish were in warm water suspended on the long line.

Scombrotoxin formation also could have resulted from fish handling practices anywhere along the distribution chain after the fish was caught to serving at the restaurant. The reportedly good color and appearance of the fish at the retailer and the lack of other reported illnesses may indicate that scombrotoxin formation occurred at the restaurant during processing and handling of the fish.

This outbreak suggests interventions that could reduce the risk for scombroid poisoning. First, consideration should be given to limiting the amount of time that fish can remain on the line during the long-line method of fishing. Second, efforts should focus on maintaining adequate refrigeration of fish during distribution and in restaurants to prevent conditions favorable for scombrotoxin production. The key to prevention of scombroid fish poisoning is continuous icing or refrigeration at <32 F (<0 C) of all potential scombrotoxin-producing fish from the time they are caught until they are cooked.


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  9. Food and Drug Administration. Procedures for the safe and sanitary processing and importing of fish and fishery products. Federal Register 1995;60:65096--202.
  10. Food and Drug Administration. Fish and fisheries products hazards and controls guide. 2nd ed. Washington, DC: US Department of Health and Human Services, Food and Drug Administration, 1998.

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