Food-borne Illness from Marine Toxins

Consumption of fish and shellfish in the United States has increased since the 1980s. Imported fish and shellfish account for more than 80% of all domestically consumed seafood. Food processors are regulated by the FDA’s Imported Seafood Safety Program, while vessels that harvest or transport but do not process seafood are exempt. Nutrient runoff and climate change have expanded the geographic range of algal species that produce some marine toxins. Algal blooms have also become more frequent, longer, and more intense due to climate change.

Marine toxins are consistently the most commonly reported cause of noninfectious food-borne disease outbreaks in the United States. A study published in Morbidity and Mortality Weekly Report analyzed 402 disease outbreaks in the United States caused by marine toxins in fish and shellfish from 2011 through 2023. The analysis revealed 1,280 illnesses, 96 hospitalizations, and 1 death. 

Scombroid toxin and ciguatoxin cause the most outbreaks. More than half of scombroid toxin outbreaks are caused by consumption of imported fish and fish prepared in sit-down dining restaurants. Scombroid toxin poisoning occurs after the consumption of high levels of histamine produced in fish that were not properly refrigerated after being caught. Improper holding and storage of fish at temperatures of 40°F or higher allows bacteria in the fish to proliferate and break down tissue. Bacteria with  histidine carboxylase activity produce high levels of histamine. Scombroid fish poisoning is an allergic-like reaction that occurs within hours of consuming fish with high levels of histamine.  

Ciguatoxin is endemic in fish, such as barracuda and grouper, that live in tropical and subtropical waters. It is produced by dinoflagellates (algae) that accumulate in the flesh of fish and shellfish. Most ciguatoxin outbreaks are caused by consumption of locally caught reef fish that are prepared in private homes. 

Outbreaks attributed to shellfish-associated toxins were most commonly caused by consumption of mussels, sea snails, and clams that were not imported and were prepared in private homes. Nearly all outbreaks had been reported by Florida, Hawaii, and Puerto Rico. 

Marine toxins that cause food-borne illness are tasteless, odorless, and resistant to cooking or freezing, making it difficult to prevent illness once marine animals have been contaminated. Illnesses from marine toxins can cause a wide range of nonspecific gastrointestinal and neurologic symptoms, including nausea, vomiting, diarrhea, flushing, numbness, tingling, and painful responses to cold stimuli. In some cases, symptoms might persist for months or years. Shellfish-associated toxins produce more severe paralytic and neurotoxic disease than outbreaks by scomboid and ciguatoxin. 

References

Hartley CM, et al. Foodborne Disease Outbreaks Associated with Marine Toxins — Foodborne Disease Outbreak Surveillance System, United States, 2011–2023. MMWR Surveill Summ 2026;75(No. SS-3):1–13.

Friedman MA, et al. An updated review of ciguatera fish poisoning: clinical, epidemiological, environmental, and public health management. Mar Drugs 2017;15:72.

Anderson DM, et al. Marine harmful algal blooms (HABs) in the United States: history, current status and future trends. Harmful Algae 2021;102:101975.