Ciguatera is the most common form of algal toxin-induced seafood poisoning in the world and the second most common form of seafood-related food poisoning, resulting in symptoms that can last for years and sometimes even permanently. It results from consuming tropical and subtropical reef fish such as snapper, grouper and barracuda in which ciguatoxins have accumulated.
The foodborne illness affects between 50,000 and 500,000 people worldwide annually. However, ciguatera-tainted fish can’t be detected by appearance, taste or smell, as raw and cooked fish have no signs of spoilage, deterioration or deterioration, which makes the illness extremely difficult to predict and manage.
Now, with the help of a five-year, USD 4 million grant from National Oceanic and Atmospheric Administration, a new research project could lead to better outbreak predictions. Michael Parsons, professor of marine science and director of the Coastal Watershed Institute at Florida Gulf Coast University in Fort Myers, is leading the international research team. He recently talked to SeafoodSource about the project and its goals.
Forristall: Is the risk for ciguatera poisoning increasing?
Parsons: As the U.S. imports more and more fish and with the growing population and switching diets, more and more people are going to be exposed to it.
If you’re catching the fish yourself in places like the Florida Keys and the Caribbean and tropical areas of the Pacific, it’s a concern. We are concerned that it’s spreading as seas are warming. It’s only seen in tropical species, but there have been phenomenon cases in the Gulf of Mexico and the Canary Islands, so the possibility of cigatera’s range expanding is a concern.
Also, with tropical fish being exported, we’ve seen cases of people in Canada, Manhattan and California who have eaten grouper, snapper and barracuda get ciguatera.
It’s also a concern that cases are increasing. More cases have been reported by the Florida Department of Health. Hong Kong has seen a lot more cases because of imported fish from the South Pacific. And, in the EU, it’s a concern because there’s no effective screening method. There’s been talk of halting imports of fish from tropical areas because there’s no good way to test fish to see if they’re toxic.
What does the research project aim to achieve?
We’re not sure if toxin production might be related to changing environmental concerns — if it’s warmer or cooler how does that affect toxin production? There are a lot of unknowns related to that.
The project is designed to study if the abundance of gambierdiscus (the dinoflagellate responsible for the production of toxins that cause ciguatera) is related to changing environmental conditions, [or] seasonal changes one year to the next. We need to get a better grasp on [whether] toxin production is related to environmental conditions, and then we can develop a model to forecast or at least monitor toxin conditions or at least the water conditions.
There aren’t enough resources to monitor every fish, every location, but we can monitor environmental conditions, which is easier and cheaper.
How will the research be conducted?
In the Florida Keys, we’ll do high frequency sampling, taking samples every month. We’ll sample reef, sea grass, beds, etc., getting a sense of different environmental factors. We’ll collect algae to look and see how many gambierdiscus cells are growing on it and isolate it and then see how growth and toxin production is affected by light levels, temperatures, things like that. We’ll also test the water quality every month.
Three times a year we’ll collect fish, both herbivores and carnivores, to see if we can see any pulses of toxin. We’ll see if the pulses are related to high abundances of gambierdiscus and how long it would take the toxins to move from gambierdiscus up into the larger predators. And then with the data we’ll use a computer model and plug in the environmental conditions and get an idea of when gambierdiscus pops up. We’ll do the same thing in St. Thomas.
If a monitoring model is successful, could it result in fishing bans during certain times of year?
That gets a little touchy. You really have to be sure that you have good data. You need to protect human health without affecting the economics. If you have a false alarm, people won’t come back to buy the fish or eat the fish, so that can affect the economy. If you have a false negative and people get sick, you have litigation issues.
Instead of a ban, we could put an advisory out that says the conditions here indicate that ciguatera outbreaks are likely. It’s similar in New England with red tide. They say, “There’s a moderate chance of red tide or a strong change of red tide.” It would be more of a weather forecast.
That being said, one thing with ciguatera is it seems to occur in a very localized area. So if there’s of particular section of a reef or a lagoon where people are getting sick from eating some of the larger fish, we could advise that it’s not safe to eat the fish.
There’s also something we’re trying to do through outreach and partnership activities to reach out to distributors and commercial fishermen to ask them how they would like us to handle some of our findings. For example, if we find out that Species X has a lot of toxin in it, how would you like that handled so it doesn’t drive down prices? We’re asking charter boat captains how we can handle it so it doesn’t ruin their business. We’d like to bring them on board sooner rather than later so maybe we can phrase things a certain way so we’re not always the Boy Who Cried Wolf. They might want us to understate some things. We need to work up a language.
