Ciguatera fish poisoning

Queensland Health Guidelines for Public Health Units

Revision History

• Causative agent
• Case definition and notification criteria
• Notification procedure
• Objectives of surveillance
• Public health significance and occurrence
• Clinical features
• Reservoir
• Mode of transmission
• Incubation period
• Period of communicability
• Susceptibility
• Management
• Preventive measures
• Outbreak summary
• Other resources
• References

Causative agent

The causative agents of ciguatera fish poisoning (CFP) are ciguatoxins.

Ciguatoxins (CTXs) are naturally occurring marine neurotoxins produced by certain microalgae known as benthic dinoflagellates in the genera Gambierdiscus and Fukuyoa.

CTXs bioaccumulate in particular fish species, undergo biotransformation and become more toxic through the marine food chain.¹ CTXs are generally classified based on region of occurrence as Pacific (P-CTX), Caribbean (C-CTX) and Indian ciguatoxins (I-CTX). These ciguatoxins all share the same cyclic polyether structure but with some variations at the ends of the molecule. The main CTXs in the Pacific are P-CTX-1, P-CTX-2 and P-CTX-3. P-CTX-1 is the principal and most potent toxin, though all three can be present in the same fish in different relative amounts.^2-4

Case definition and notification criteria

Immediately notify confirmed cases.

Confirmed case

Any case meeting the clinical OR epidemiological criteria.

Laboratory definitive evidence

There is currently no laboratory assay available for the detection of CTX in humans.

Clinical evidence

Consumption of suspect reef fish* within 48 hours of onset of the first symptom/s

AND

Reporting any combination of the following symptoms:

• paraesthesia (numbness and/or tingling of extremities and/or perioral region)
• cold allodynia (pain or burning sensation upon skin contact with cold surfaces or cold water)
• pruritus (without urticarial rash), myalgia, arthralgia and dizziness.^3-5

Gastrointestinal and/or cardiovascular symptoms (e.g., nausea, vomiting, diarrhoea, hypotension, bradycardia) may accompany or precede neurosensory symptoms.

CFP diagnosis is supported by detection of CTX in implicated raw or cooked fish remnants. However, confirmation of CTX in an implicated fish is not required to meet the case definition.

Epidemiological evidence

Consumption of the same reef fish of a confirmed case, and reporting at least two of the following symptoms within 48 hours of consumption:

• diarrhoea
• vomiting
• abdominal pain
• myalgia
• arthralgia
• pruritis
• dizziness.

* reef fish:

• Includes herbivorous and carnivorous reef fish caught in tropical and/or subtropical waters, including but not limited to: amberjack, barracuda, cobia, coral trout, green jobfish, kingfish, Spanish & spotted mackerel, mahi mahi, queenfish, emperors, reef cods, samsonfish, snappers, surgeonfish, trevally, and tuskfish.
• Red bass, paddletail, and Chinamanfish present a particularly high risk for transmission of CFP - these fish are no-take species, where if accidentally caught, should be immediately returned to the water. Humphead maori wrasse are also a no-take species (under the Fisheries Act 1994 (Qld), Fisheries Declaration 2019 (Qld)).
• CTX accumulation has also been observed in sharks and several marine invertebrates including sea cucumbers, starfish and giant clams.^{1, 5}
• Does NOT include shellfish, cold water fish like imported hake, hoki and nile perch, or any freshwater fish species like silver and golden perch or Murray cod. Rays, reptiles, mammals or amphibians are also not included.

Information on fish species is available from:

• Fish species guide | Recreation, sport and arts | Queensland Government
• Fishes of Australia

Outbreak criteria:

Two or more cases linked through consumption of the same reef fish.

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Notification procedure

CFP is a clinical diagnosis OR epidemiological notifiable condition and must be notified to the local public health unit immediately.

Objectives of surveillance

1. Promptly detect CFP in Queensland and enable a timely public health response.
2. Better understand the epidemiological characteristics and risk factors associated with CFP in Queensland in order to support public health action.
3. Enable improved data sharing with food safety and seafood regulators.

Public health significance and occurrence

CFP is the most commonly reported seafood-toxin illness in the world and accounts for the majority of seafood-related outbreaks in Australia.^{6, 7} CFP affects 50,000–500,000 persons per year worldwide.³ The large majority of CFP events in Australia are reported from Queensland. CFP became notifiable in Queensland in 1990. The Northern Territory is the only other jurisdiction in Australia where this condition is notifiable. However, other states and territories may investigate suspected outbreaks of CFP that involve two or more cases.

Ciguatoxic fish are usually reported from tropical and sub-tropical areas between latitudes 35° north and 35° south, particularly the Caribbean Sea, Pacific and Indian Oceans. However, the global incidence and distribution of CFP are expected to increase in coming years due to changing ecological and environmental factors and increased international seafood trade.^{3, 8} The public health impact of CFP is underestimated due to misdiagnosis and under-reporting. In addition, it is estimated that only 2–20 per cent of cases present to health authorities.^{1, 6}

Transfer of CTXs can occur when fish consume toxic algae growing on coral reefs. CTXs accumulate in the flesh, head and internal organs (viscera) of larger predatory fish and become more potent as they are biotransformed up through the food chain. CTX is present in greater concentrations in the head and viscera of fish compared to the flesh. It is not possible to determine whether a fish is contaminated with CTX through its appearance, texture, smell or taste, and it is not possible to remove the toxin from the fish through cooking or freezing.^{3, 8}

More than 400 species of fish have been implicated worldwide as a cause of CFP.⁹ In Australia, most reports of CFP have resulted from reef fish caught in Queensland, with Coral Trout and Spanish Mackerel commonly implicated. During the 10-year period, 2015 to 2024, there were 35 outbreaks comprising 122 cases, and a further 38 sporadic cases of CFP investigated in Queensland (Source: OzFoodNet Queensland).

Clinical features

CTXs bind to and activate voltage-gated sodium channels in the cell membranes of nerves and muscles, leading to prolonged sodium influx and neuronal hyperexcitability. This interaction underlies the neurological, cardiovascular, and gastrointestinal symptoms associated with ciguatera poisoning.^{3, 10}

CFP, although defined by its neurological symptoms, is characterised by an extensive and complex array of gastrointestinal, neurological and cardiovascular symptoms. These may be severe and acute, and in some cases, may take weeks, months, or occasionally years to recover from.^{1, 4, 6} Symptoms vary from person to person and can depend on individual host factors, the amount of toxin ingested, any previous exposure to CTX and geographic source of the implicated fish (Caribbean Sea, Pacific, or Indian Ocean).^{4, 11} Ciguatera-related fatalities are rare (<0.1%).¹

Onset of gastrointestinal and/or neurological symptoms may appear within several hours after fish consumption. Gastrointestinal symptoms (vomiting, abdominal pain and diarrhoea) are usually self-limiting and resolve within 1–2 days. Neurological symptoms vary among patients and include paresthesia in the hands, feet and oral region, metallic taste, dental pain, dizziness and aberrant temperature perceptions.^{6, 11} A commonly reported neurological symptom of CFP is cold allodynia, a painful, burning or ‘electric shock’ sensation following contact with cold fluids or cold surfaces.^{3, 5} Non-specific acute-phase symptoms include generalized pruritus, myalgia, arthralgia and fatigue. Cardiovascular symptoms may also occur in the early stage of the illness in combination with gastrointestinal and/or neurologic symptoms and include hypotension and bradycardia.^{1, 3} Whilst gastrointestinal and cardiovascular symptoms usually resolve within a few days, neurological symptoms can persist for weeks or months.

CFP does not confer any immunity to affected persons.⁶ Some patients may experience a recurrence of neurological symptoms weeks or months after the initial exposure, triggered by consumption of drinks such as alco­hol, coffee or tea, or foods such as any fish (including freshwater species), meats and nuts. In most cases, the frequency and intensity of recurrent or chronic manifestations diminish and resolve over time.^{4, 11}

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Differential diagnosis

Marine intoxications with clinical presentations similar to CFP include scombroid poisoning, tetrodotoxin poisoning, paralytic shellfish poisoning and neurotoxic shellfish poisoning (Table 1). The type of seafood, latency period and symptoms aid in the differential diagnosis.

Table 1. Marine intoxications with clinical presentations similar to CFP.

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Reservoir

Gambierdiscus and Fukuyoa species are usually found in tropical and sub-tropical waters between 35°N and 35°S, encompassing most of the world’s warm coastal regions, including the coastal waters of northern Australia and along much of the Queensland coast. However, recent studies have indicated that these species can also be found in some temperate areas. These organisms are bottom-dwelling microalgae that live on seagrass, living and dead corals, and other surfaces in shallow coastal habitats (e.g. reefs, atolls).^{1, 3} Small herbivorous fish graze on macroalgae on which toxic dinoflagellates are present, thus becoming primary vectors for CTXs. As the small herbivorous fish are consumed by larger tropical and sub-tropical carnivorous reef fish, CTXs are transferred, metabolised and concentrated, increasing the CTX toxicity in fish higher in the food chain.⁴

Mode of transmission

• CFP is acquired through foodborne transmission.
• Person to person transmission of CTX is extremely rare, though case reports of transmission from mother to child during breastfeeding or across the placenta, and sexual transmission have been described.⁵

Incubation period

Usually 1 to 12 hours, but occasionally up to 24 to 48 hours after ingesting toxic fish. The case definition is based on a maximum period of 48 hours from consumption of fish to the initial symptom/s.

Period of communicability

Person to person transmission is extremely rare (see Mode of Transmission).

Susceptibility

All persons who consume reef fish are susceptible, though symptom severity can vary. CFP does not confer immunity to the affected person but often results in increased sensitivity which can lead to more severe symptoms following subsequent exposure to ciguatoxic reef fish.

Management

Cases

Investigation 

Investigate all suspected CFP cases using the questionnaire available at: Ciguatera poisoning | Communicable disease control guidance

A public health physician should confirm that each case meets the case definition for CFP before the notification is entered into the Notifiable Conditions System (NoCS).

Send the completed case questionnaire and an outbreak summary (if ≥2 cases) to OzFoodNetQLD at OzFoodNetQLD@health.qld.gov.au for data entry (ciguatera surveillance database and outbreak register).

Restriction

Nil enteric precautions required.

Treatment

No therapy has demonstrated efficacy for treating acute or chronic neurological symptoms of CFP. Treatment is primarily supportive, corresponding to case symptoms, clinical observations, and pathophysiology in the context of neurotoxin poisoning.

Intravenous mannitol infusion, given within 48–72 hours of ingestion of the toxic fish, has been proposed as a potential therapy for CFP.³ There have been several descriptive case reports/series and a randomised clinical trial suggesting that IV mannitol was associated with rapid improvement and even resolution of acute CFP signs and symptoms.¹² Conversely, one double-blind randomised controlled trial did not find mannitol to be superior to normal saline for treatment of CFP. However, the design and sample size of this study were among several limitations affecting the interpretation of results.⁶ Based on the limited evidence to date, it remains unclear whether mannitol is an effective treatment for acute CFP.

Counselling

The case should be advised of the nature of the condition and its mode of transmission.

Advise the case that ingestion of some substances (mainly alcohol and any type of fish including freshwater species) during the 3–6 month period following the initial intoxication may cause recurrent CFP symptoms, and should be consumed with caution.³

Since CFP may be transmitted through breastfeeding and unprotected sexual intercourse, refraining from these activities while the patient is symptomatic should be recommended.

Provide the case a fact sheet.

Contacts

Investigate persons who have eaten or may have eaten the same fish as the case.

Persons similarly exposed should be:

• assessed for similar symptoms as the case, or diarrhoea, nausea, vomiting, abdominal pain, muscle pain, joint pain or pruritus (epidemiologically linked evidence)
• advised that symptoms may develop up to 48 hours after consumption of the suspect fish.

Community outbreaks

Two or more cases of CFP linked to the same fish constitutes an outbreak.

Environmental health

Remove any remaining portions of the suspect fish for sampling. Where feasible, discuss with the individual, seller, or wholesaler, to establish the source of the fish (species, catch location and date). Recommend that fish from the same location and time be discarded (if for personal consumption) or voluntarily withdrawn from sale and discarded (if in the supply chain).

Any samples of the suspect fish or leftover meal should be sent to the Queensland Health Public and Environmental Health Reference Laboratory (Organic Chemistry) for ciguatoxin testing and fish speciation; contact the laboratory for sampling and transport advice. Ciguatoxin levels and fish species identification should be recorded in NoCS, where available, and a copy of laboratory results forwarded to OzFoodNet QLD at OzFoodNetQLD@health.qld.gov.au

If two or more sporadic cases are linked to a common source (e.g. wholesaler, retailer or restaurant), this is suggestive of an outbreak and the environmental health team from the relevant public health unit, together with other agencies as required, should undertake an investigation.

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Preventive measures

• Avoid eating large, warm water (tropical/sub-tropical) reef fish. Ciguatoxin will accumulate in older fish as they increase in size and weight.¹³
• Avoid eating the head, roe, liver or other viscera of warm water reef fish, as ciguatoxin concentrates in these parts.
• When eating a warm water ocean fish, only eat a small portion (no more than 300 grams). If tingling sensations and/or numbness develop, do not eat further portions of the fish and seek medical advice.
• Listen to local advice about which fish to avoid and where not to fish. Local fishers, bait and tackle shops, and charter operators are good sources of up-to-date information, particularly for those unfamiliar with an area along the Queensland coast or in a known ciguatera risk zone.
• Respect fishing rules and restrictions made under the Fisheries Act 1994 (Qld) and the Fisheries Declaration 2019 (Qld). These laws set out no-take species, size and possession limits, and no-fishing zones to support conservation, protect breeding areas, manage fish stocks, and in some cases, protect public health where ciguatera risk is known.

Outbreak summary

Complete the Gastrointestinal/Foodborne Outbreak Summary Form for OzFoodNetQLD

• Ensure that all reported cases that meet the case definition are entered into NoCS, including ciguatoxin results if available.
• Send completed questionnaires to NoCS data entry team at CDIS-NOCS-Support@health.qld.gov.au and to OzFoodNetQLD at OzFoodNetQLD@health.qld.gov.au

Other resources

Queensland Health Guideline for the investigation and management of suspected foodborne illness outbreaks, December 2018

References

1.  Chinain, M., et al., Ciguatera poisonings: A global review of occurrences and trends. Harmful Algae, 2021. 102: p. 101873.

2.  Chan, T.Y., Epidemiology and clinical features of ciguatera fish poisoning in Hong Kong. Toxins (Basel), 2014. 6(10): p. 2989–97.

3.  Friedman, M.A., et al., An Updated Review of Ciguatera Fish Poisoning: Clinical, Epidemiological, Environmental, and Public Health Management. Mar Drugs, 2017. 15(3).

4.  Stewart, I., et al., Emerging tropical diseases in Australia. Part 2. Ciguatera fish poisoning. Ann Trop Med Parasitol, 2010. 104(7): p. 557–71.

5.  (WHO), F.a.A.O.o.t.N.F.a.W.H.O., Report of the Expert Meeting on Ciguatera Poisoning. https://doi.org/10.4060/ca8817en, 2020.

6.  Friedman, M.A., et al., Ciguatera fish poisoning: treatment, prevention and management. Mar Drugs, 2008. 6(3): p. 456–79.

7.  Stafford, R. The epidemiology of ciguatera fish poisoning in Australia. In SafeFish Ciguatera Workshop, 2019, Brisbane.

8.  Chan, T.Y., Characteristic Features and Contributory Factors in Fatal Ciguatera Fish Poisoning—Implications for Prevention and Public Education. Am J Trop Med Hyg, 2016. 94(4): p. 704–9.

9.  de Haro, L., et al., Ciguatera fish poisoning in France: experience of the French Poison Control Centre Network from 2012 to 2019. Clin Toxicol (Phila), 2021. 59(3): p. 252–255.

10. Alexander, J., Scientific opinion on marine biotoxins in shellfish – Emerging toxins: Ciguatera group. EFSA, 2010. 8: p. 1627.

11. Chinain, M., et al., Ciguatera poisoning in French Polynesia: insights into the novel trends of an ancient disease. New Microbes New Infect, 2019. 31: p. 100565.

12. Mullins, M.E. and R.S. Hoffman, Is mannitol the treatment of choice for patients with ciguatera fish poisoning? Clin Toxicol (Phila), 2017. 55(9): p. 947–955.

13. Sydney Fish Market, Seafood Handling Guidelines 2025, 2024, pp. 43–44.

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