PHYSICIAN DIAGNOSIS AND REPORTING OF CIGUATERA FISH POISONING IN AN ENDEMIC AREA. 

Donald B McKee MD1

, Lora E Fleming MD Phd1, Robert Tamer MPH MPA1, Richard Weisman PharmD2, Donna Blythe MD1 

1

NIEHS Marine & Freshwater Biomedical Sciences Center, c/o RSMAS University of Miami, 4600 Rickenbacker Causeway, Miami, 

FL, 33149, USA; 2

Florida Poison Information Center- Miami, Dept of Pediatrics, University of Miami School of Medicine, Miami, 

FL, 33136, USA 

ABSTRACT 

Ciguatera fish poisoning is the most common marine seafood 

toxin disease worldwide. It is associated with the consumption 

of large reef fish contaminated with extremely potent natural 

marine toxins elaborated by micro-algae known as 

dinoflagellates. Although a reportable disease with a proven 

acute therapy, Ciguatera is largely under-diagnosed and underreported in the United States and elsewhere. This study 

presented a classic case of Ciguatera to family medicine 

physicians in the endemic area of Dade County, Florida 

(USA) to evaluate their knowledge of diagnosis, treatment and 

reporting of Ciguatera. 

Of the 78 eligible participants, 36 (46%) participated. The 

majority of the participants were male, born in the US, and 

attended medical school in the US. Although 25(68%) of the 

participants diagnosed Ciguatera, only 6 (17%) correctly 

recommended intravenous mannitol therapy as the acute 

treatment of choice. Almost all the participants (97%) had 

heard of Ciguatera, but only (64%) had ever diagnosed a case 

with an average of 0.14+0.42 cases in the past year. 

Furthermore, only 17 (47%) of the participants knew that 

Ciguatera was a reportable disease. Foreign-born physicians 

were significantly more likely to know that Ciguatera was a 

reportable disease (p=0.02); foreign-trained physicians were 

also more likely to know, although not significantly (p=0.08). 

This study illustrates that even in an endemic area, Ciguatera 

is an under-diagnosed, inadequately treated and underreported disease, especially among US born and US trained 

physicians. 

INTRODUCTION 

Ciguatera fish poisoning is the most common marine seafood 

toxin disease worldwide (1-6). It is associated with the 

consumption of large reef fish contaminated with extremely 

potent natural marine toxins elaborated by the dinoflagellate, 

Gambierdiscus toxicus. This dinoflagellate produces a variety 

of potent neurotoxins, including ciguatoxin and maitotoxin, 

which are heat and acid stable. Very small amounts of these 

toxins (probably picogram doses) cause an acute 

gastrointestinal and neurologic illness with subsequent 

development of a debilitating chronic neurologic disease 

lasting weeks to months (1,3,4-6). 

Ciguatera has been reported since the 1500s, first by European 

explorers as they ventured into the tropical and subtropical 

regions of the world. Until recently, Ciguatera was primarily 

an endemic disease of island peoples in the tropics. However, 

with increasing international tourism, seafood trade and 

consumption, Ciguatera has been reported in non-endemic 

areas, including North America and Europe (7). Of note, at 

this time there are no official monitoring programs for 

Ciguatera in the US seafood industry, although new Food 

Safety Legislation may make it mandatory in the future. 

Although a reportable disease, Ciguatera is highly underreported in the United States and elsewhere (2, 4-6, 8,9). The 

US Centers for Disease Control and Prevention (CDC) 

estimated that Ciguatera is only reported 2-10% of the time 

(2,3). Part of this under-reporting is due to under-diagnosis by 

physicians and other healthcare workers, even in endemic 

areas. Under-diagnosis is an important problem not only 

because it contributes significantly to subsequent underreporting, but also because persons with undiagnosed 

Ciguatera will receive inadequate acute treatment. If Ciguatera 

is not correctly diagnosed within the first days from exposure, 

then the appropriate acute therapy, intravenous mannitol, will 

not be given during its most efficacious period; persons who 

do not receive intravenous mannitol within the first 2-3 days 

from exposure are much more likely to experience subsequent 

chronic Ciguatera, a debilitating neurologic disease, for which 

there is no definitive treatment (4-6, 10-13). 

The objective of this study was to explore the extent of 

knowledge of Ciguatera, its treatment and reporting 

requirements among family medicine physicians in the 

endemic area of Miami-Dade County, Florida with expected 

incidence rate of 5/10,000/yr (14). 

Methodology 

This study was a cross sectional study of the knowledge and 

behavior of Ciguatera among family physicians in an endemic 

area. Approval for this study was obtained from the 

University of Miami Human Subjects Committee. All family 

medicine physicians listed in the annual Registry of the 

American Academy of Family Physicians (AAFP) in Miami-
Dade County (Florida) were contacted by phone at their 

workplace by the first author, as a 2nd year medical student. 

Once verbal consent to participate in a study was obtained, the 

family physician subject was presented with the following 

classic case of Ciguatera and asked a series of brief questions 

concerning diagnosis, treatment, reporting issues, and 

demographics. 

"We have a 50 year old man who presented with nausea, 

vomiting, and diarrhea, followed within 24 hours by itchy 

skin without a rash and a burning sensation when 

touching cold objects. He and his wife returned from the 

Bahamas 2 days ago where they had caught and eaten a 

large grouper (which was delicious) within hours prior to 

the onset of symptoms. His wife is complaining of similar 

symptoms." 

All physician subjects approached were ultimately offered a 

Ciguatera Information Packet through the mail regardless of 

participation. 

The data were entered into EpiInfo 6 software and analyzed by 

SAS version 7 statistical software. After reviewing 

frequencies and means, the data were evaluated by ttests and 

Fishers exact test for possible associations. 

Results 

From the annual Registry of the American Academy of Family 

Physicians (AAFP) in Miami-Dade County, 78 eligible 

participants were identified. Of those eligible, 36 (46%) 

agreed to participate, 2 refused, and 40 (51%) were lost to 

follow up. Those lost to follow up did not respond after at 

least 3 phone calls/eligible participant. 

Of the 36 (46%) participants, the majority were male (27 

(75%)). Their mean age was 51.3+10.9 years and the mean 

years in practice were 20.6+11.7. The majority were both born 

in the US (19 (53%)) and attended US medical schools (23 

(64%)). 

Although 35 (97%) reportedly had heard of Ciguatera, only 23 

(64%) had ever diagnosed a case, with a mean of 0.14+0.42 

cases/year of practice. The majority, 25 (68%), were able to 

make a correct diagnosis of Ciguatera in response to the 

classic case presentation; there was no significant difference 

by age, gender, years of practice, birthplace, or medical school 

location with respect to making this diagnosis. However, only 

6 (17%) of the physician subjects recommended the correct 

treatment of IV mannitol; again, there was no significant 

difference by age, gender, years of practice, birthplace, or 

medical school location with respect to this prescribing 

treatment. 

Furthermore, only 17 (47%) knew that Ciguatera was a 

reportable disease to the public health authorities. Foreign 

born physicians (p=0.02) and foreign trained physicians 

(p=0.08) were significantly more likely to know that Ciguatera 

was an officially reportable disease; there were no significant 

differences in knowledge by age, gender, or years of practice. 

The majority of the foreign-born and foreign-trained 

physicians were from the Caribbean, a highly endemic 

Ciguatera area. 

Conclusions 

This study is a small cross sectional study of primary care 

physicians in an endemic Ciguatera area. The study is limited 

not only by the small numbers of participants but also by the 

relatively low participation rate. Nevertheless, this is the only 

study of its kind in the marine toxin disease literature. 

In conclusion, family medicine physicians in an endemic area, 

have relatively little experience recognizing and diagnosing 

Ciguatera when presented a classic case to evaluate. 

Furthermore, these physicians do not know the correct 

treatment, intravenous mannitol. Therefore, even if they were 

able to diagnosis a classic acute case, they would not be able 

to prevent the subsequent occurrence of chronic Ciguatera. 

The majority (53%) of these family medicine physicians did 

not know that Ciguatera is a reportable disease to health 

authorities. Therefore, there is no possibility of primary 

prevention by removing contaminated fish from the home, 

eating establishments and fish stores before it is shared with 

others, leading to the possibility of additional cases of 

Ciguatera. Furthermore, this finding helps to explain the 

significant public health under-reporting of this marine toxin 

associated disease, even in an endemic area. 

In order to ensure timely diagnosis, treatment and reporting of 

Ciguatera, physician education is essential (2, 4-6). Given its 

acute presentation, education should be targeted not only at 

primary care providers, but also at emergency rooms. Official 

reporting to health authorities must be made as simple and 

efficient as possible given the time constraints on busy 

healthcare providers. 

In Florida, for example, the Florida Poison Information 

Centers in collaboration with the Florida Department of 

Health and the National Institute of Environmental Health 

Sciences (NIEHS) Marine Center at the University of Miami 

have established a toll free, 24 hour/day, 365 days/year Marine 

Hotline (888-232-8635) in English, Spanish and Haitian 

Creole (with access to other languages if necessary). Not only 

does this Marine Hotline provide diagnosis and treatment 

information concerning all the marine toxin related diseases 

for all callers including healthcare providers, official reporting 

of Ciguatera and other marine toxin disease cases are made to 

the Florida Dept of Health by the Florida Poison Information 

Center- Miami on behalf of the healthcare provider. 

Acknowledgements 

The Authors would like to thank the physician subjects who 
participated in this study. This study was funded in part by the 

National Institute of Environmental Health Sciences (NIEHS) 

Marine and Freshwater Biomedical Sciences Center at the 

University of Miami and a NIEHS Shannon Award to Dr 

Fleming, and by the American Academy of Family Physician 

Student Research Award to Dr. McKee. 

References

1. L.E. Fleming, D. Blythe, D. Baden. 1,1-4 (1997). 

2. L.E. Fleming, J.A. Bean, D. Katz, R. Hammond. Hui, Kits, 

Stanfield, eds. Seafood and Environmental Toxins. (Marcel 

Dekker, New York) (2000). 

3. D. Baden, L. Fleming, J. Bean, in: Handbook of Clinical 

Neurology: Intoxications of the Nervous System. FA deWolff 

(Ed). (Elsevier Press, Amsterdam), pp. 141-175 (1995). 

4. J. Pearn. Mem Queensland Museum 34(3), 601-604 (1994). 

5. T.A.Ruff, R.J. Lewis. Mem Queensland Museum 34(3), 

609-619 (1994). 

6. P. Glaziou, A.-M. Legrand. Mem Queensland Museum 

34(3), 609-619 (1994). 

7. W.R. Lange, F.R. Snyder, P.J. Fudala. Archives of Internal 

Medicine 152, 2049-53 (1992). 

8. Centers for Disease Control (CDC). 45:SS-5 (1996). 

9. L.E. Fleming, J.A. Bean, D. Baden In: UNESCO-IOC 

Manual on Harmful Marine Phytoplankton #33. Hallegraeff 

GM, Anderson DAN, Cembella AD. (UNESCO, Paris), pgs. 

475-488 (1995). 

10. D. Blythe, L.E. Fleming, D.R. Ayyar, D. Baden, D. De 

Sylva, K. Shrank. Memoirs Queensland Museum. 34, 465-470 

(1994). 

11. D.G. Blythe, D.P. De Sylva, L.E. Fleming, R.A. Ayyar, D. 

Baden, K. Schrank. Bull Soc Path Ex. 85, 425-426 (1992). 

12. N.A. Palafox, L.G Jaina, A.Z. Pisano, et al. J.A.M.A. 259, 

274-2742 (1988). 

13. R. Bagnis, A. Spiegel, J.P. Boutin et al. Med Trop 52, 67-

73 (1992). 

14. D.N. Lawrence, M.B. Enriquez, R.M. Lumish, A. Maceo. 

J.A.M.A. 244, 254-258 (1980).