Fish Poisoning Syndromes: Paralytic Shellfish, Ciguatera, and Domoic Acid

Most of the natural toxins in fish are produced by naturally occurring algae (phytoplankton). They build up in guts of shellfish and fish when they feed on large blooms of algae that produce toxins or other fish that have eaten algae. There is no visible, taste, or odor difference between fish or shellfish with toxins and those without. Cooking does not destroy the toxins, so the best way to avoid the toxins is to follow specially issued advisories or warnings.

Paralytic shellfish poisoning (PSP)
PSP associated with consumption of mussels, oysters, clams, and scallops, and guts or viscera of crabs and lobsters. PSP affects the central nervous system, causing tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms are typically followed by loss of balance and coordination, slurred speech, and difficulty swallowing. In severe poisonings, muscular paralysis and death from asphyxiation can occur. It is absolutely critical to seek medical care immediately if PSP exposure is suspected. The California PSP hotline number is: 800-553-4133.

Ciguatera toxin
This toxin is more commonly found in fish like barracuda, mackerel, and snapper from warm and tropical water areas. The symptoms of ciguatera begin within 6 hours after contaminated food is eaten. They include nausea, cramping, vomiting, headache, flushing, and tingling or numbing sensation on the lips, tongue, or mouth. In more severe cases, cold objects feel hot and hot objects feel cold.

Domoic acid
Domoic acid is another naturally occurring toxin that can be found in clams, mussels, scallops, oysters, and organs or guts of anchovies and sardines, and crab. Symptoms of domoic acid poisoning can occur within 30 minutes to 24 hours after eating toxic seafood. In mild cases, symptoms may include vomiting, diarrhea, abdominal cramps, headache, and dizziness. These symptoms commonly disappear within several days. In severe cases, the individual may experience lung secretions, breathing difficulty, confusion, disorientation, unstable blood pressure and irregular heartbeat, seizures, permanent loss of short-term memory, coma, and even death.

Recommendations

• Obtain your shellfish from a reputable market. All commercial shellfish harvesters in California are certified by the California Department of Health Services and must follow strict requirements to ensure that all oysters, clams, and mussels sold in stores are free of toxins. Commercial harvesting is stopped immediately if potentially dangerous levels of toxins are found.
• People who harvest or collect their own shellfish or catch their own fish should check with the local health department to see if any advisories or warnings about naturally occurring toxins have been issued.
• The California Department of Health Services warns people to not eat mussels they harvest themselves from May 1 through October 31 in all areas of the California coast, including bays and estuaries. In some areas, local health departments post warnings, but the absence of posted warnings does not mean the mussels are safe. Other warnings or advisories may be issued depending on levels of the natural toxins detected, such as for domoic acid.

Vibrio vulnificus

Vibrio vulnificus is a naturally occurring bacteria that can be found in warm coastal waters. Symptoms associated with an infection caused by Vibrio vulnificus include sudden chills, fever, nausea, vomiting, stomach pain, swelling and pain in the legs. It can also cause blood poisoning which can lead to death within two days.

Recommendations

• Thoroughly cook food to destroy this bacteria. Eating raw shellfish, like oysters, mussels or clams, with hot sauce or lemon, or while drinking alcohol does not kill the bacteria.
• People with any of the following health conditions should avoid eating raw shellfish: liver disease, chronic alcohol use, cancer, AIDS, Hodgkin’s disease, diabetes, chronic kidney disease,reduced stomach acidity.

Scromboid Poisoning

Scromboid poisoning results when certain bacteria build up in fish and form too much of a protein called histamine. Cooking does not affect histamine. Symptoms, which can include flushed skin, headaches, dizziness, nausea, and rashes, can occur within minutes to two hours after fish has been eaten.

 Recommendations

• Make sure the fish you eat is very fresh.
• Take special care in handling, washing, icing, and refrigerating the fish to prevent bacterial growth.

Parasites

Parasites like nematodes or roundworms and tapeworms or flukes can also be of concern in seafood.

Recommendations

• Thorough cooking usually kills parasites.
• People with immune disorders should be especially careful to avoid eating raw seafood.
• For more information, contact the US Food and Drug Administration Food Safety Information Hotline at 800-332-4010, or check their website at http://www.cfsan.fda.gov/
• You should contact a physician immediately if any of the symptoms of poisoning appear from toxins.