US authorities are investigating an ongoing outbreak of scombrotoxin fish poisoning traced to yellowfin tuna. They have blocked all incoming shipments of the fish from a Vietnamese company that has refused to initiate a recall.
Public health officials have confirmed at least 47 people from unspecified states as outbreak patients. The most recent illness began Oct. 15, according to an outbreak investigation notice posted today by the U.S. Food and Drug Administration. The first patient, known of at this time, became ill on Aug. 8.
Scombrotoxin fish poisoning occurs when fish begins to spoil and histamine levels in it increase. Histamine cannot be destroyed by freezing or cooking.
The FDA reported that all yellowfin tuna from Truong Phu Xanh Co. Ltd. of Vietnam with 2019 production dates is implicated and should be thrown away.
Stores, restaurants and other foodservice operators are expected to pull the tuna, but the FDA wants consumers to shoulder some responsibility, too. The agency’s notice tells consumers to ask whether yellowfin tuna — also called ahi tuna — being sold is from the specific company named by the FDA.
FDA officials have not used the agency’s power to force the Vietnamese company to recall the tuna, even though the firm has been determined to have supplied the fish.
“FDA asked for the supplier of yellowfin tuna associated with most of the illnesses, Truong Phu Xanh Co. Ltd. of Vietnam, to initiate a voluntary recall of all of its imported yellowfin tuna with production dates from January 2019 to the present. At this time, the firm has not recalled any product,” the FDA reported today.
“Because scombrotoxin fish poisoning causes temporary or medically reversible adverse health consequences this incident did not meet the threshold for the use of FDA’s mandatory recall authority.”
Although the Vietnamese supplier has not issued a recall, some companies in the United States have posted recalls for the implicated tuna, the FDA reported. The agency, working with officials in unnamed states, gathered information from victims and entities in the supply chain that led to those third-party recalls.
The FDA notice says some of the tuna could still be on the market.
“Tuna from this supplier could have been sold thawed or frozen; and could have been sold as ground tuna meat, poke cubes, steaks, or loins; this product could still be within its shelf life,” the notice states.
Because of the outbreak investigation and findings to date, the FDA placed Truong Phu Xanh Co. Ltd. of Vietnam on “Import Alert,” which means the firm’s yellowfin tuna can be detained at U.S. borders and ports of entry without physical examination.
A concurrent investigation of cases of scombroid fish poisoning by the Seattle-King County Public Health Department is not related to the FDA’s investigation of Truong Phu Xanh Co. Ltd., according to federal officials.
Testing for the toxin
Standard tests used during enforcement activities and other kinds foodborne illness investigations are not effective for situations of suspected scombroidtoxin fish poisoning, according to the FDA’s outbreak notice.
The samples collected thus far by federal and state investigators cannot be linked to samples from patients by Whole Genome Sequencing (WGS) or Pulsed-Field Gel Electrophoresis (PFGE) analysis. Pathogens such as specific strains of Salmonella or E. coli are generally pinpointed with WGS or PFGE processes, but the spoilage factor in the scombroid scenario makes that impossible.
“Scombrotoxin fish poisoning occurs when fish begin to spoil, resulting in increased histamine levels,” FDA’s notice says. “Multiple samples have been collected and analyzed, with positive results for decomposition or high histamine levels in products imported from Truong Phu Xanh Co. LTD.”
About scombroid poisoning
Symptoms of scombroid poisoning can become evident within minutes to two hours following consumption of contaminated fish, according to the FDA.
Initial signs can mimic an allergic response and include facial flushing, sweating, burning-peppery taste sensations about the mouth and throat, dizziness, nausea and headache. Symptoms can intensify to facial rash, hives, swelling, diarrhea and abdominal cramps. Severe reactions to the poison can include blurred vision, respiratory stress, and swelling of the tongue.
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