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Puffer Fish Toxicity in Florida's Indian River Lagoon

Since January 2002, numerous cases of puffer fish poisoning have been associated with the Indian River Lagoon system in Florida. Following a series of temporary bans, harvesting of all puffer fish from five counties was banned indefinitely in June 2004.

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Background

Since January 2002, 28 cases of puffer fish poisoning (PFP) have been reported to Florida officials. All reported cases were associated with eating puffer fish harvested from Florida’s Indian River Lagoon system. PFP is a human illness similar to Paralytic Shellfish Poisoning, which is caused by the consumption of toxic shellfish.

Florida officials were first alerted to the PFP incidents in early 2002. Between January and June, 19 cases of PFP were reported in three states: New Jersey (3 cases), Virginia (2 cases), and Florida (14 cases). In all of these incidents, the affected individuals reported consuming puffer fish (also called puffers or blowfish). All of the illnesses were traced to puffer fish originating from the northern Indian River Lagoon and the Banana River—waterways on Florida’s east coast between Titusville and the Pineda Causeway. In the Florida incidents, fish originated from three areas: Titusville (11 cases), Cocoa (2 cases), and the Pineda Causeway (1 case).

In October 2002, the Florida Department of Health (DOH) announced that two more PFP incidents had occurred in New York. The fish had been caught in the Titusville, Florida, area in March—before the harvesting ban. The fish were then frozen and taken back to New York, where they were eaten several months later. In April 2003, two additional cases of PFP were reported, and five more cases have been reported so far in 2004: two in February, two in April, and one in May 2004. Most of these fish were caught from the Titusville area.

As a result of the PFP incidents, the U.S. Food and Drug Administration (FDA), the Florida Department of Agriculture and Consumer Services (FDACS), and the Florida DOH issued health advisories. The Centers for Disease Control and Prevention (CDC) published two Morbidity and Mortality Weekly Reports of the incidents. In April 2002, the Florida Fish and Wildlife Conservation Commission (FWC) issued the first of two 90-day bans on puffer fish harvesting in Volusia, Brevard, Indian River, and St. Lucie counties. The second 90-day ban was issued in July 2002, and the area affected was extended to include Martin County. Due to continued puffer fish toxicity, the FWC issued two consecutive 1-year bans (effective until October 22, 2004). In June 2004, the ban on harvesting puffer fish from the waters of Volusia, Brevard, Indian River, St. Lucie, and Martin counties was extended indefinitely.

Summary of State and Federal Actions Following PFP Incidents in Florida

Date	State/Federal Authority	Action
April 15, 2002	FDA, FDACS, DOH	Health advisories warn consumers not to eat puffer fish harvested from the Titusville area
April 19, 2002	CDC	Morbidity and Mortality Weekly Report (MMWR), "Neurologic Illness Associated with Eating Florida Puffer Fish, 2002" (Vol. 51, No. 15)
April 25, 2002	FWC	90-day ban (April 25–July 24, 2002) on puffer fish harvested in Volusia, Brevard, Indian River, and St. Lucie counties
May 17, 2002	CDC	MMWR, "Update: Neurologic Illness Associated with Eating Florida Puffer Fish, 2002" (Vol. 51, No. 19)
June 28, 2002	DOH	Health advisory reemphasizes risks associated with eating puffer fish
July 24, 2002	FWC	Ban on puffer fish harvest extended for additional 90 days (July 24–October 23, 2002); area covered expanded to include Martin County
October 21, 2002	FWC	Ban on puffer fish harvest extended for 1 year (until 12:01 a.m., October 22, 2003)
October 21, 2003	FWC	Ban on puffer fish harvest extended for 1 year (until 12:01 a.m., October 22, 2004)
June 9, 2004	FWC	Ban on puffer fish harvest extended indefinitely; ban includes waters of Volusia, Brevard, Indian River, St. Lucie, and Martin counties

Puffer Fish Poisoning

At least 16 species of Puffer Fish or Blowfish (including burrfish, balloonfish, and porcupinefish) are found in Florida. The southern puffer (Sphoeroides nephelus) is the most common, most frequently harvested puffer fish in the Indian River Lagoon, especially in the northern Indian River Lagoon near Titusville. Although unconfirmed, it is likely that southern puffers were consumed in the 28 PFP cases.

PFP is usually caused by ingesting tetrodotoxin, which is commonly found in the internal organs of some species of puffer fish. Occasionally, tetrodotoxin is found in puffer meat, or muscle. PFP is fairly common in Japan, where people eat the fish delicacy "fugu." Symptoms of PFP include numbness and tingling around the mouth, face, and in the extremities as well as muscle weakness, nausea, and vomiting. PFP has been responsible for numerous deaths in the Far East.

Although infrequent, PFP has been reported in Florida in the past. Between 1941 and 1974, three people died from eating toxic puffer fish (Benson, 1956; Hemmert, 1974). The toxin involved was not specifically identified, but because PFP is usually associated with tetrodotoxin, investigators likely assumed that tetrodotoxin was the cause. However, the cases of PFP in Florida since 2002 have been different. Dr. Mike Quilliam of the Canadian National Research Council first analyzed puffer fish fillets from one of the New Jersey cases and determined that the toxin was saxitoxin, not tetrodotoxin (Quilliam et al., 2004). Although saxitoxin has been found in puffer fish in the Far East and the Philippines, this is the first report of saxitoxin in puffer fish in the United States. Since 2002, southern puffer fish from the Indian River Lagoon have been surveyed extensively, and FWC and FDA officials have confirmed the presence of saxitoxins (Landsberg et al., 2002).

Saxitoxin, which more commonly accumulates in shellfish, can cause paralytic shellfish poisoning (PSP) when toxic shellfish are consumed. Shellfish usually become toxic from feeding on microalgae that produce saxitoxin, such as Alexandrium spp. PSP from shellfish has been reported previously in the United States, but it has been limited to New England and the Pacific West Coast.

Although saxitoxin and tetrodotoxin are chemically different, they act in a very similar manner and can cause almost identical symptoms. Prior to these incidences, there had been no known occurrences of PFP in Florida since 1974. At this time, there is no evidence that tetrodotoxin played a role in any of the 28 cases mentioned, and all of these cases are being treated as presumptive saxitoxin poisonings.

Toxin Source

There are several possible explanations for puffer fish toxicity:

• Puffers may produce the toxin themselves as a defense mechanism against other predators.
• Bacteria living naturally inside the puffers may produce toxins (either saxitoxin or tetrodotoxin), and these bacteria only produce these toxins in certain species of puffer fish.
• Toxic microalgae that produce saxitoxin may have entered the puffers’ food chain; puffers acquire the toxin by eating filter-feeding bivalves that have consumed toxic microalgae.

Scientists investigating each of these theories have focused on studying species of potentially harmful, possibly toxic microalgae in the Indian River Lagoon. Researchers believe there are several possible explanations for the presence of toxic microalgae:

• Existing microalgae have suddenly become toxic.
• Already toxic microalgae have become more numerous.
• A new toxic species has been introduced into the Indian River Lagoon.

Investigations

FWC Fish and Wildlife Research Institute (FWRI) scientists are currently working with colleagues from the FDA, FDACS, DOH, and other agencies to investigate the source of the saxitoxin and to continue monitoring saxitoxin concentrations in puffer fish. In addition, because there is a potential for saxitoxin to concentrate in other organisms such as shellfish, a number of other species are also being monitored. Based on the samples collected thus far, saxitoxin has been found in shellfish, but concentrations are well below regulatory levels. All species of shellfish and fish—except puffer fish—are usually safe to eat. However, the presence of saxitoxin in the Indian River Lagoon signals a potential threat to public health and to the health of natural resources.

Since the initial identification of the presence of saxitoxin in the puffer fish, FWRI Fisheries-Independent Monitoring (FIM) has collected numerous fish, shellfish, and water samples. The fish and shellfish samples are analyzed for toxicity levels at FWRI and the FDA, and the water samples are analyzed for the presence of potentially toxic microalgae. FWRI is culturing suspect microalgae, including Pyrodinium bahamense var. bahamense, for toxicity testing. The cultured microalgae were isolated from Indian River Lagoon water and sediment samples. Light and electron microscopy are being used to detect the presence of microalgae in archived water samples collected during various fish kill events in the Indian River Lagoon prior to the 2002 PFP event. Scientists are also using electron microscopy to compare samples of P. bahamense var. bahamense with archived material of P. bahamense var. compressum from a known PSP event in Costa Rica.

In addition to toxicity testing, scientists are collecting common bacteria from puffer fish. All of these bacterial isolates are identified, cataloged, and frozen for further analysis. Bacterial isolates can eventually be cultured to high concentrations and tested for the presence of saxitoxin and tetrodotoxin.

Findings

Microalgae
Scientists at FWRI, in collaboration with the FDA, have determined that the microalga Pyrodinium bahamense produces saxitoxin. This is the first confirmation that this species produces this toxin in the United States.

Pyrodinium bahamense var. bahamense is a planktonic dinoflagellate that produces bioluminescent displays in seawater at night. Unlike its Pacific counterpart, Pyrodinium bahamense var. compressum, which can produce saxitoxin that accumulates in shellfish and causes PSP, the Atlantic Pyrodinium was not previously known to be toxic.

Until the 2002 PFP event, Pyrodinium bahamense var. bahamense bloomed extensively on both coasts of Florida with no apparent adverse effects. Numerous planktonic and benthic microalgal species are found in the Indian River Lagoon. None of these species are known to produce saxitoxin. Although investigations will continue, thus far, no other microalgae in the Indian River Lagoon are known to produce saxitoxin. Saxitoxin can be produced by some bacteria and cyanobacteria as well as by dinoflagellates.

Puffer Fish
Scientists at FWRI, in collaboration with the FDA, have determined that puffer fish in the Indian River Lagoon remain toxic and are not safe to eat. No cleaning or cooking method will remove or neutralize the toxin in the fish; freezing is ineffective as well. As demonstrated by the case reported in October 2002, the fish frozen for at least six months were still toxic. A 2-year comparison of muscle tissue from southern puffer fish collected between Volusia and Martin counties shows that saxitoxin is still found in concentrations above the regulatory level.

 

Toxicity data for 3 years of monitoring show the same trend, with highly toxic puffer fish still being found in the Indian River Lagoon. 

 

Shellfish
FDACS has collected shellfish samples (hard clams, cockles, conch) throughout the Indian River Lagoon. To date, all samples tested by FWRI and the FDA have been below the regulatory limit for saxitoxin, and all the shellfish tested were safe to eat. However, to maintain public health protection, researchers will continue monitoring shellfish samples for saxitoxin analysis.

Summary and Recommendations

Results from field sampling indicate that there is still a public health risk associated with consuming puffer fish caught on Florida’s east coast. The public is advised to avoid eating puffer fish from the Indian River Lagoon. The puffer fish harvesting ban has been extended indefinitely. Species of puffer fish included in the ban are southern puffer, northern puffer, marbled puffer, bandtail puffer, checkered puffer, and least puffer.

Results from current research will help determine the causes of the toxicity and will provide information on whether the toxicity will persist over time. It is critical to continue educating anglers and consumers about the public health risk associated with eating puffer fish from the Indian River Lagoon.

There are additional environmental concerns regarding the Indian River Lagoon. Since 1999, there have been reports of fish kills; horseshoe crab, dolphin, and manatee mortalities; and lowered recruitment and increased prevalence of tumors in natural stocks of hard clams. Possible relationships between these concerns and the current PFP incidents are also being investigated.

References

Benson, J. 1956. Tetradon (blowfish) poisoning. A report of two fatalities. Journal of Forensic Science, 1: 119–126.

Hemert, C.D. 1974. Tetradon (pufferfish) poisoning. Memorandum of the Florida Department of Health, Tallahassee, Florida.

Additional Information

For additional information and links to other FWRI pages about puffer fish, Visit Puffer Fish in Florida.

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