A study to determine if Cayman’s lionfish carry the toxin that causes ciguatera poisoning is under way, but so far there have been no reports of humans contracting the illness from eating the invasive species. 

Researcher Bill Davin, an associate biology professor at Berry College in Mount Berry, Georgia, has been examining lionfish samples supplied by the Cayman Islands to see if they contain the naturally occurring toxin. 

He has carried out examinations on 20 lionfish from all three islands – 12 from Cayman Brac, two from Little Cayman and six from Grand Cayman. 

“Only one of the fish extracts thus far has shown signs of bio-activity, but those levels were relatively low compared to previous research I have done on ciguatoxic fish,” he said. 

He is rerunning the screening test on all the samples at a higher concentration and carrying out further tests on any samples that show bio-activity, which usually indicates the presence of the toxin that causes ciguatera. 

St. Maarten’s Nature Foundation last year recommended lionfish not be eaten based on a study that found ciguatoxins in flesh samples of larger lionfish caught in the island’s waters. 

A US Food and Drug Administration study in the Caribbean has also revealed presence of the toxin in the flesh of lionfish.  

“To date we have received no official reports of illness associated with the consumption of lionfish, but in endemic areas of ciguatera, toxins have been detected at levels exceeding FDA guidance and therefore could cause illness if consumed,” said Pat El-Hinnawy, an FDA public affairs officer. “The Virgin Islands is one of those areas. We have collected more than 186 fish from the waters around the US Virgin Islands, including St Croix, St. Thomas and St. John, and Puerto Rico. Of these, we have tested 74 fish to date with 26 per cent confirmed to contain ciguatoxins at levels exceeding FDA guidance.  

“Our testing continues in this and other regions,” Ms El-Hinnawy said. “These results are consistent with other species of fish that are well known to be ciguatera hazards in endemic areas.” 

Mr. Davin said people eating lionfish should use the same precautions they use when eating other Caribbean reef fish that can carry the ciguatera toxin.  

“Avoid fish taken from established or known ciguatera hotspots and if a person has already had ciguatera, they should certainly be more careful, since they are certainly at a higher risk of re-intoxification than someone that has never had the disease,” he said. 

He added: “While the number of toxic lionfish being reported from St. Thomas and St. Maarten seem high, I have not been able to find a single report of anyone contracting ciguatera from the consumption of lionfish.” 

Compared with some other areas in the Caribbean, the presence of ciguatoxin on Cayman’s reef is small. According to statistics from the Caribbean Epidemiology centre, in the 25 years from 1980 to 2005, of the 9,301 cases of ciguatera reported in the region, Cayman accounted for just 4 per cent. The majority of cases, 49 per cent, were reported by Antigua and Barbuda, with the Bahamas reporting 22 per cent of the cases. 

Bradley Johnson, research officer at the Department of Environment, said several species of fish are likely to have ciguatera, such as big groupers, snappers, Cavalli jack and barracuda.  

He said there was anecdotal evidence of ciguatera in these fish, but not many statistics available locally. 

“There has been a lot of controversy over the results in St Maarten as it had a small sample size. A lot of fish in the eastern Caribbean have high levels of ciguatera. It is not high in lionfish. It’s normal for this region.  

“I am not aware of any lionfish cases of ciguatera poisoning here,” Mr. Johnson said.  

“I’m not saying there’s no risk. There are risks with all species of fish. We have not had any evidence of it happening with lionfish so far.  

“What we feel comfortable saying is [lionfish] statistically are just as likely to give you ciguatera as any other larger species of fish around, but that being said, we have not had any reports of it,” he said. 

Mr. Johnson said he had spoken to doctors at the hospital’s emergency room, but none could recall a case of ciguatera involving lionfish.  

“It’s very tough to track down and pinpoint what it is,” he said. 

Eating lionfish has become an increasingly viable way of dealing with the invasion of lionfish in Cayman’s, and the Caribbean’s, coral reefs. In the past two years, several lionfish catching tournaments have been held in Cayman, with hundreds of lionfish captured and subsequently cooked and eaten, with no adverse effects. Lionfish have been featured at local culinary events Cayman Cookout and Taste of Cayman and is available in restaurants and stores. 

Tests for ciguatera 

There are a number of tests that, according to folklore, can show if a fish contains the ciguatera toxin, including the colouration of a fish; flies will not land on exposed flesh of ciguatoxic fish and ants and cats won’t eat toxic fish. 

According to a report from the National Oceanic and Atmospheric Administration, none of these can be considered reliable, although one test that appears to work is feeding some fish flesh to a cat or mongoose and seeing if the animal gets sick. 

Mr. Davin agreed  

and said: “All the wives tales about the cat I have looked at indicate the cat needs to consume the fish and then gets sick. The main problem is they typically use stray cats and it is hard to keep up with them to see if they really get sick.” 

Some ants may also be able to tell if a fish is toxic, but not the ants in the Caribbean, he said.  

“There are some species of meat eating ants that seem to reject toxic flesh, but most of the ants around the Caribbean are sugar consuming ants and it does not work. There was also an article published a while back on a species of fly larvae (a maggot) that died if it was place on ciguatoxic flesh, however that species of fly is only found in Egypt,” he said. 

The tests being carried out by Mr. Davin and his students are not being done to determine to determine if lionfish are safe for human consumption, but to detect measurable levels of ciguatoxin from lionfish harvested from the waters around the three islands. 

In December last year, the National Oceanic and Atmospheric Administration awarded the first year of an anticipated five-year, US$4 million grant to scientists researching the causes of ciguatera fish poisoning. 

Toxin 

The ciguatera toxin is produced by dinoflagellates that stick to coral, algae and seaweed in tropical waters where they are eaten by herbivorous fish that in turn are eaten by larger carnivorous fish. The toxins accumulate as they move up the food chain within bigger fish. Ciguatoxin is heat-resistent so cooking does not get rid of the toxin. 

People with ciguatera poisoning usually experience a numbness and tingling of the lips and tongue, which may spread to the extremities, as well as nausea, vomiting, diarrhoea, joint and muscle pain, headache, reversal of sensation of hot and cold, acute sensitivity to temperature extremes, vertigo, irregular heartbeat and reduced blood pressure. Gastrointestinal symptoms may develop within two hours following consumption of toxic fish while neurological and cardiovascular symptoms will usually emerge within six hours of eating the fish. 

The ciguatera toxin is not related to the venomous toxins in a lionfish’s spines.