Discussions focus on ciguatera poisoning
Published: December 11, 2010
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ST. THOMAS - Scientists researching ciguatera fish poisoning in the territory discussed some of their preliminary findings Friday at the University of the Virgin Islands.
While the three-year study of ciguatera was just launched last December, some surprising findings have already come to light from the study that brings together a wide range of scientists and experts.
The project's purpose is to study how ciguatera works its way up the food chain, how it affects human health and if climate change or environmental factors contribute to higher or lower instances of the poisoned fish.
Ciguatera poisoning is caused by naturally occurring toxins, called ciguatoxins, which are produced by microscopic plants - gambierdiscus toxicus - that live on seaweed and other surfaces within coral reef communities. When fish eat seaweed or algae they consume the organisms, too, and the ciguatoxins build up in the fish's flesh.
The toxin is fat soluble - it is stored in the fishes' body and not excreted - so it builds up as it goes up the food chain. The bigger fish eat the little fish and the toxin gets passed on until it is consumed by humans.
Predators at the top of the food chain - like barracuda - can end up with large amounts of the toxin in their flesh. No test can be done to determine if the fish is poisoned and cooking and preparation methods have no affect on the toxin.
At a UVI seminar Friday, the researchers involved in different aspects of the project gave presentations on what they had found to this point - emphasizing that the results are preliminary and most of the data has not been properly analyzed yet.
UVI coral reef researcher Tyler Smith and students at UVI's Center for Marine and Environmental Studies have spent the last year collecting samples of plants, algae and fish at four sites on a monthly basis and sending them to the project's investigators for analysis. The four sites identified as Black Point, Flat Cay, Benner Bay and Seahorse.
Smith found a link between the abundance of microscopic plants which produce ciguatoxins and the seasonal fluctuations in water temperature, although he said more study must be done.
"This is why this type of research is really exciting, because you never know what you're going to find," Smith said.
The microscopic plant cells secrete mucus, which they use to attach to algae and other surfaces, but Smith said they cannot attach to live coral. Woods Hole Oceanographic Institution research associate Mindy Richlen, the co-principal investigator for the project, said she has hypothesized that events which cause massive coral death - like coral bleaching due to warmer water temperatures or dredging projects - may lead to more cases of ciguatera. She said when there is less live coral, there are more surfaces available for the ciguatoxin producing plants to attach to, which could mean an increase in the amount of toxins consumed by reef fish and ultimately the amount of toxic fish consumed by humans.
Alison Robertson, a bio-analytical chemist with the Food and Drug Administration, has been studying the fish samples Smith and his students have been collecting.
She has found that the three spot damsel fish has the highest toxicity levels of all the small reef fish sampled. She said more research needs to be done, but it may be a result of the way the species feeds.
Samples of schoolmaster snapper - which many local fishermen believe to be toxic - were provided by the St. Thomas Fishermen's Association for study. Surprisingly, only 20 percent of the samples contained ciguatoxins, she said.
Because the territory is experiencing an influx of Pacific lionfish, Robertson decided to see if the newly introduced invasive species carried ciguatoxins.
Robertson looked at seven lionfish caught in the V.I. and found four of them were toxic.
Aside from looking at the reef for evidence of ciguatoxins in the Virgin Islands, the study's researchers are also looking at the fish poisoning as it presents itself in people by working with Schneider Hospital.
When cases of ciguatera poisoning come into the emergency room, doctors ask patients to participate in the study to provide information for the scientists. In the last year there have been 45 ciguatera cases at the hospital, which is only about half the number of the previous year. Smith said he does not know why the number of cases dropped so dramatically this year, but he hopes more data may lead to an explanation.
Parterns in the Ciguatera Fish Poisoning Monitoring project include the Emerging Pathogens Institute at the University of Florida, UVI, the University of Maryland School of Medicine, Woods Hole Oceanographic Institution, Schneider Hospital, the Food and Drug Administration Dauphin Island Lab and Florida State University.
The project is funded through a $1 million grant from the Centers for Disease Control and Prevention.
For more information on the ciguatera research project visit www.CaribCATCH.org.
- Contact reporter Aldeth Lewin at 774-7882 ext. 311 or e-mail email@example.com.
Symptoms of ciguatera fish poisoning can appear within hours to a few days after eating infected fish. Treatments are available and the symptoms may pass within a few days to six months.
Symptoms can include:
- nausea or vomiting
- electric-shock-like or painful sensations
- reversal of hot and cold sensations
- intense itching or tingling fingers and toes
- slowed heart rate and a drop in blood pressure
- weakness or fatigue
- muscle or joint pain