Fish poisoning rates in Florida underestimated, study suggests

1 Jul

Researchers have discovered that the number of people poisoned in Florida every year by a dangerous food-borne toxin carried by reef fish may be significantly underreported in public health records.

A school of barracuda.
Barracuda are recognized as having a high risk of carrying ciguatera toxins.

Prevalence of the poisoning in the state was previously estimated to be 0.2 cases per 100,000 people. According to the new study, published in the American Journal of Tropical Medicine and Hygiene, the true number is estimated to be closer to 5.6 cases per 100,000 people.

The toxin in question is called ciguatera and is known to be carried by fish such as barracuda, grouper, amberjack, snapper, tuna and sea bass. Warnings already exist concerning the consumption of barracuda, but these do not extend to other popular sports fish.

“I think there is a broader awareness the farther south you go that barracuda are carriers but perhaps not as much awareness that a fish like grouper or amberjack can carry ciguatera,” says lead author Elizabeth Radke.

Ciguatera is a toxin found in algae that typically grows on coral reefs and is initially transmitted to small fish that feed on reef vegetation. In humans, ciguatera poisoning can lead to diarrhea and vomiting within 1-3 hours of consumption, along with aches and pains, painful urination and other neurological symptoms.

It is the most common form of fish-related food poisoning in the world and one of the most resilient. There are no tests to detect the presence of ciguatera, and the heat-stable toxin cannot be destroyed by cooking or freezing contaminated fish.

Due to the effects of climate change, experts have expressed concern that increasing seawater temperatures could lead to ciguatera migrating from the tropical and subtropical areas worldwide where it is most common.

“There have been cases reported as far north as Georgia and South Carolina, but those likely involved fish that picked up the poison in South Florida or the Caribbean and migrated north,” reports Radke. “But there needs to be continued surveillance at the toxin’s geographic borders.”

For the study, researchers from the University of Florida surveyed recreational fisherman across the state of Florida and analyzed reports of ciguatera made to the Florida Department of Health (FDOH). By identifying high-risk demographic groups, high-risk fish types and fishing locations, the researchers aimed to be able to adjust their findings for underreporting.

Unreported cases could be due to lack of treatment or misclassification

The survey of fishermen revealed to the researchers a large number of unreported cases.
For example, FDOH records hold that ciguatera affects around 1 per 100,000 people in Miami-Dade and 3 per 100,000 in Monroe County every year respectively.

According to Radke and her colleagues, however, the actual incidence of ciguatera poisoning was around 28 per 100,000 people in Miami-Dade and 84 per 100,000 in Monroe County.

The researchers believe that the disparity in case incidence between state records and their own findings could be attributable to people who became poisoned not seeing physicians or physicians treating patients and either not reporting cases or not identifying them as distinct ciguatera cases.

“Moving forward, FDOH may be able to improve reporting by educating physicians on the possibility of acquiring ciguatera from fish caught outside typical areas, and emphasizing the unique clinical presentation of ciguatera illness,” the authors conclude.

“We need to be vigilant for any increase in disease, as the spread of ciguatera could be particularly harmful to people who are more reliant on fish like barracuda and grouper for food and income,” states Christopher Plowe, president of the American Society of Tropical Medicine and Hygiene.

Although the study suggests that ciguatera poisoning in Florida is more common than previously imagined, Radke states that the team found no evidence that rates of infection had increased in recent times.

She also believes that people should not be too worried about the potential dangers of eating fish such as grouper and amberjack that are less closely associated with ciguatera than barracuda.

“I don’t think that people necessarily need to stop eating these other fish,” she says, “but they need to be aware there is a risk, and if they start feeling sick after eating, they should see a physician.”

Last year, Medical News Today reported on a study finding that young children have an increased risk of salmonella from pet reptiles and amphibians.

Written by James McIntosh