What is ciguatera fish poisoning. How does ciguatera toxin accumulate in fish. What are the common symptoms of ciguatera poisoning. Which fish species are most likely to cause ciguatera. How can ciguatera poisoning be prevented. What treatment options are available for ciguatera poisoning. Where are ciguatera-contaminated fish commonly found.

Understanding Ciguatera Fish Poisoning: A Comprehensive Overview

Ciguatera fish poisoning is a form of food poisoning caused by consuming warm water ocean finfish that contain ciguatera toxins. These toxins are produced by microscopic organisms called dinoflagellates, specifically Gambierdiscus toxicus, which attach themselves to algae in warm ocean reef areas. The toxins then accumulate up the food chain, from small plant-eating fish to larger predatory fish, and ultimately to humans who consume these contaminated fish.

In Australia, approximately 150 cases of ciguatera poisoning are reported annually. However, the global impact is likely much larger, with ciguatera being one of the most common forms of marine food poisoning worldwide.

The Bioaccumulation Process: How Ciguatera Toxins Build Up in Fish

The process of ciguatera toxin accumulation in fish is a prime example of bioaccumulation in marine ecosystems. Here’s how it works:

1. Dinoflagellates produce ciguatoxins and attach to algae in warm reef waters.
2. Small herbivorous fish consume the toxic algae.
3. Larger predatory fish eat these smaller fish, accumulating higher concentrations of the toxin.
4. Even larger fish prey on these contaminated fish, further concentrating the toxins.
5. Humans consume large predatory fish, ingesting potentially harmful levels of ciguatoxins.

This process explains why larger fish, particularly those weighing over 2.5kg, are more likely to cause ciguatera poisoning in humans. It’s important to note that the toxins cannot be removed by cleaning or cooking the fish, making prevention crucial.

Geographical Distribution: Where Ciguatera-Contaminated Fish Are Found

Ciguatera-contaminated fish are primarily found in tropical and subtropical waters, particularly in coral reef ecosystems. In Australia’s Northern Territory, several areas are known to harbor fish with ciguatera toxins:

• The south end of Bremer Island
• East Bremer islets
• Bonner Rocks
• Miles Island
• Cape Arnhem area
• Nhulunbuy (Gove)
• Connexion Island off Groote Eylandt

However, it’s important to note that ciguatera-contaminated fish may be present in other waters as well. The geographical range of ciguatera is expanding due to factors such as climate change and increased sea surface temperatures, potentially putting more populations at risk.

High-Risk Fish Species: Identifying Potential Ciguatera Carriers

While over 300 fish species have been suspected of causing ciguatera poisoning, some are more commonly associated with the condition. These include:

• Chinamanfish
• Tripletail maori wrasse
• Humphead maori wrasse
• Red bass
• Paddletail
• Giant moray
• Pickhandle barracuda
• Coral rockcod
• Coral trout
• Kingfish
• Various mackerel species (including Spanish mackerel)
• Giant queenfish
• Red emperor
• Reef cods
• Lined bristletooth (surgeon fish)
• Spangled emperor
• Trevally
• Tuskfish

It’s crucial to be aware of these high-risk species, especially when fishing or consuming seafood in known ciguatera-prone areas.

Recognizing the Symptoms: Clinical Presentation of Ciguatera Poisoning

Ciguatera poisoning can manifest with a wide range of symptoms, typically appearing 3 to 6 hours after consuming contaminated fish. However, symptom onset can be delayed for up to 30 hours in some cases. The clinical presentation often includes both gastrointestinal and neurological symptoms.

Gastrointestinal Symptoms

Initial symptoms often mimic typical food poisoning and may include:

• Nausea and vomiting
• Diarrhea
• Abdominal cramps
• Tiredness and lethargy

Neurological Symptoms

Characteristic neurological symptoms, which can help distinguish ciguatera from other forms of food poisoning, include:

• Joint and muscle pain and weakness
• Tingling or numbness around the lips, hands, or feet
• Severe itching, often exacerbated by alcohol consumption
• Headache
• Sensation of loose or aching teeth
• Temperature sensation reversal (cold objects feeling hot and vice versa)

Cardiovascular Symptoms

In some cases, cardiovascular symptoms may occur:

• Heart palpitations
• Low blood pressure
• Slow pulse

In severe cases, difficulty breathing may occur. It’s important to note that some symptoms can persist for several months, and in rare instances, for several years. Stress and alcohol consumption can exacerbate these long-lasting symptoms.

Diagnosis and Treatment: Managing Ciguatera Poisoning

Diagnosing ciguatera poisoning can be challenging due to the lack of a specific diagnostic test. Typically, diagnosis is based on the patient’s symptoms and recent seafood consumption history. In some cases, leftover fish may be sent to laboratories for research purposes, but these results are not used for immediate diagnosis due to the time required for analysis.

Diagnostic Challenges

What makes diagnosing ciguatera poisoning difficult? The absence of a specific test means that healthcare providers must rely on clinical presentation and patient history. This can lead to potential misdiagnosis, especially in areas where ciguatera is less common. Additionally, the symptoms can mimic other forms of food poisoning or neurological conditions, further complicating the diagnostic process.

Treatment Approaches

While there is no cure that can eliminate the ciguatera toxin from the body, treatment focuses on managing symptoms and providing supportive care. Key aspects of treatment include:

• Symptom management: Medications may be prescribed to alleviate specific symptoms such as nausea, diarrhea, or neurological discomfort.
• Fluid replacement: Patients who have experienced severe vomiting and diarrhea may require intravenous fluids to prevent dehydration.
• Supportive care: In severe cases, patients may need monitoring for potential respiratory or cardiovascular complications.

It’s crucial for individuals experiencing symptoms of ciguatera poisoning to seek medical attention promptly. While fatalities from ciguatera poisoning are rare, they can occur in severe cases due to respiratory paralysis or cardiovascular shock.

Long-Term Management

For patients with persistent symptoms, long-term management strategies may include:

• Avoiding foods and activities that may trigger symptom recurrence, such as consuming alcohol or certain types of fish
• Regular follow-ups with healthcare providers to monitor symptom progression
• Potential referral to specialists for managing specific long-lasting symptoms

It’s important to note that having ciguatera poisoning once does not confer immunity. In fact, individuals who have experienced ciguatera poisoning may be more sensitive to the toxin in subsequent exposures, emphasizing the importance of prevention.

Prevention Strategies: Reducing the Risk of Ciguatera Poisoning

Preventing ciguatera poisoning is crucial, given the potential severity and duration of symptoms. While it’s impossible to completely eliminate the risk, several strategies can significantly reduce the likelihood of exposure:

Avoid High-Risk Areas

One of the most effective prevention strategies is to avoid fishing in known ciguatera-prone areas. If you’re unfamiliar with local waters, consult with local authorities or experienced fishermen about areas to avoid.

Size Matters

Larger fish are more likely to contain higher concentrations of ciguatoxins due to bioaccumulation. To reduce risk:

• Avoid eating fish species suspected of ciguatera that weigh more than 2.5kg
• Limit portion sizes of warm water ocean fish to no more than 200g

Selective Consumption

Certain parts of the fish tend to concentrate ciguatoxins more than others. To minimize exposure:

• Avoid eating the head, roe, liver, and other viscera (guts) of warm water ocean fish
• If unsure about a fish’s safety, it’s better to err on the side of caution and avoid consuming it

Stay Informed

Keep yourself updated on local advisories and warnings about ciguatera. Many coastal regions with a history of ciguatera poisoning have systems in place to alert the public about high-risk areas or fish species.

Proper Fish Handling

While proper handling won’t eliminate ciguatoxins, it’s important to remember that any fish spoilage can lead to food poisoning. Always ensure that fish are cleaned properly and stored at safe temperatures to prevent additional health risks.

Education and Awareness

Educate yourself and others about the risks of ciguatera poisoning, especially if you live in or frequently visit tropical or subtropical coastal areas. Understanding the signs and symptoms can lead to faster diagnosis and treatment if exposure does occur.

By implementing these prevention strategies, individuals can significantly reduce their risk of ciguatera poisoning while still enjoying the benefits of consuming fish as part of a healthy diet.

Public Health Implications: The Broader Impact of Ciguatera Poisoning

Ciguatera fish poisoning is not just an individual health concern; it has broader implications for public health, the fishing industry, and coastal communities. Understanding these wider impacts is crucial for developing comprehensive strategies to address the issue.

Economic Impact

Ciguatera poisoning can have significant economic consequences:

• Reduced fish consumption: Fear of ciguatera can lead to decreased demand for certain fish species, impacting local fishing industries.
• Tourism effects: Regions known for ciguatera outbreaks may experience reduced tourism, particularly for activities like recreational fishing.
• Healthcare costs: Treating ciguatera poisoning, especially long-lasting cases, can result in substantial healthcare expenditures.

Surveillance and Reporting

Effective management of ciguatera poisoning at a public health level requires robust surveillance and reporting systems. In many regions, ciguatera poisoning is a notifiable condition, meaning healthcare providers are required to report cases to public health authorities. This helps in:

• Identifying outbreaks and high-risk areas
• Monitoring trends in ciguatera poisoning over time
• Informing public health interventions and policies

Climate Change Considerations

The geographical distribution of ciguatera-causing dinoflagellates is influenced by environmental factors, including water temperature. As global temperatures rise due to climate change, there’s potential for:

• Expansion of ciguatera-prone areas into previously unaffected regions
• Increased frequency of ciguatera poisoning in traditional hotspots
• Changes in the distribution of fish species, potentially introducing new risks

Research and Development

Ongoing research is crucial for improving our understanding and management of ciguatera poisoning. Key areas of focus include:

• Developing rapid and accurate diagnostic tests for ciguatera toxins in fish and humans
• Exploring potential treatments to neutralize or eliminate ciguatoxins from the body
• Improving methods for detecting and monitoring ciguatera-causing organisms in marine environments

Policy and Regulation

Effective management of ciguatera risk requires coordinated policy efforts, which may include:

• Implementing fishing restrictions in high-risk areas
• Developing guidelines for safe fish consumption in affected regions
• Establishing protocols for monitoring and testing fish in commercial markets
• Enhancing public education and awareness programs about ciguatera risks and prevention

By addressing ciguatera poisoning from these multiple angles, public health authorities can work towards reducing its impact on both individual health and broader societal concerns. This comprehensive approach is essential for managing the complex challenges posed by ciguatera in an ever-changing global environment.

Ciguatera poisoning | NT.GOV.AU

Ciguatera poisoning is caused by eating certain types of reef fish found in warm tropical waters.

These fish eat a type of algae called Gambierdiscus toxicus, which makes ciguatoxins.

Small fish that eat this algae are eaten by bigger fish, and then they’re eaten by even bigger fish.

Each time this happens, the toxin in the fish increases, and it’s the large fish that are most likely to make you sick.

The toxin can’t be removed by cleaning or cooking the fish.

In Australia, about 150 cases of ciguatera poisoning occur each year.

Where is it found

Fish with ciguatera are found in the coral reefs of tropical and sub-tropical waters.

In the Northern Territory (NT), these fish are in the Gove and Groote Eylandt areas, such as:

• the south end of Bremer Island
• East Bremer islets
• Bonner Rocks
• Miles Island
• Cape Arnhem area
• Nhulunbuy (Gove)
• Connexion Island off Groote Eylandt.

They may also be in other NT waters.

Fish species with ciguatera

There are more than 300 fish species that have been suspected to cause ciguatera poisoning.

These include:

• chinamanfish
• tripletail maori wrasse
• humphead maori wrasse
• red bass
• paddletail
• giant moray
• pickhandle barracuda
• coral rockcod
• coral trout
• kingfish
• mackerel (various including spanish mackerel)
• giant queenfish
• red emperor
• reef cods
• lined bristletooth (surgeon fish)
• spangled emperor
• trevally
• tuskfish.

Symptoms

Symptoms can appear 3 to 6 hours after eating fish with ciguatera. But they can also start up to 30 hours later.

They can appear as food poisoning symptoms such as:

• tiredness and lethargy
• nausea and vomiting
• diarrhoea
• stomach cramps.

Other typical symptoms are:

• joint and muscle pain and weakness
• tingling or numbness around the lips, in the hands or feet
• severe itching, made worse by drinking alcohol
• headache
• feeling that teeth are loose or aching
• reversal of temperature sensation:
  • hot water feels freezing cold
  • cold drinks feel hot
• heart palpitations
• low blood pressure and slow pulse
• difficulty in breathing in severe cases.

Some of these typical symptoms can last up to 3 months and in some cases, several years. They can be made worse by stress or drinking too much alcohol.

Diagnosis

There is no test for ciguatera poisoning. You will be diagnosed based on your symptoms and food history.

Sometimes, leftover fish is sent to laboratories for research purposes. The results take time and are not relevant for your diagnosis.

Treatment

As soon as your symptoms start, you should see your GP or nearest health centre for treatment.

Treatment will not get rid of the toxin but it will ease your symptoms.

If you’ve experienced vomiting and diarrhoea, you may become dehydrated and need extra fluids.

It’s rare to die from ciguatera poisoning. This happens only in very severe cases from respiratory paralysis or cardiovascular shock.

You are not immune if you’ve already had ciguatera poisoning. You may even be more sensitive to the toxin the next time you get it.

Prevention

To prevent ciguatera poisoning, you should:

• not fish in known ciguatera areas
• avoid eating fish species with suspected ciguatera that weigh more than 2.5kg
• eat small portions of warm water ocean fish, no bigger than 200g
• not eat the head, roe, liver or other viscera (guts) of warm water ocean fish, as the toxin is concentrated in these parts.

You must also remember that any fish spoilage can give you food poisoning. Fish must be cleaned and stored at safe temperatures.

Last updated: 24 November 2022

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Fact sheet
– Food safety, Queensland Government.

Ciguatera
poisoning is a form of food poisoning. It is caused by eating warm water ocean
finfish that carry ciguatera poison (a toxin). This poison is produced by a
very tiny organism called a dinoflagellate, which attaches itself to algae
growing in warm ocean water reef areas. Small plant-eating fish eat this toxic algae and in
turn are eaten by larger predatory fish which are eaten by humans.

Public health management guidelines

The Queensland Health
guidelines for this condition are currently under review. Clinicians should
contact their local public health unit for public health advice if they require it.

Notification

Notification resources

• List
  of all Pathological,
  clinical and provisional diagnosis notifiable conditions
• List of Public
  Health Unit contacts
• Notifiable conditions report form for Queensland doctors/clinicians (PHA S70) or person in charge of a Hospital (PHA S71) (PDF, 77kB) – if faxing notification, follow up by phone.
• Notification criteria for
  pathology laboratories (PDF, 55kB)
  

Enhanced surveillance for public health units

• Suspected ciguatera fish
  poisoning questionnaire (PDF, 143kB)
  – used by public health units to collect and manage more detailed information
  for enhanced case surveillance.

Epidemiological data and reports

Last updated: 5/06/2023 14:56:31 PM

Condition information

Search this database of all notifable conditions and find:

• control guidelines
• notification requirements
• health alert information
• Resources

Quick links

• List of notifiable conditions
• Notifiable Conditions Report Form for Queensland Doctors/Clinicians (section 70 PHA) or person in charge of a Hospital (section 71 PHA) (PDF, 77kB)
• COVID-19 Notifiable conditions report form PHA S71 for Queensland Public Hospitals (PDF, 162kB)
• Time out poster (PDF, 160kB) – guidelines for minimum exclusion periods for cases and contacts attending schools, pre-schools and child care centres.
• Public health unit contact details
• Queensland notification criteria guidelines for laboratories (PDF, 459kB) – identifies the results pathology laboratories should notify to the Queensland Notifiable Conditions Register
• Public Health Act 2005 – including Child Health – contagious conditions
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Causes, Symptoms, Diagnosis and Treatment

Ciguatera is a disease that occurs when certain types of reef fish are eaten. The most common symptoms are neurological manifestations, such as paresthesia of the face, limbs, hallucinations, headache, loss of consciousness, delirium. Neuropsychological, cardiovascular, gastrointestinal disturbances are not uncommon. Diagnosis consists in the detection of a toxin in food, the characteristic symptoms of the disease. Treatment is pathogenetic and symptomatic; etiotropic therapy of ciguatera has not been developed, therapeutic measures are aimed at detoxification of the body.

General information

Ciguatera (fish food poisoning) – toxicosis associated with the action of the biological poison ciguatoxin. For the first time, the symptoms of ciguatera are found in the written sources of doctors of Ancient China (VII century AD), the clinic was described in more detail by the Englishman Locke in 1675. The toxin was isolated by the Hawaiian professor Scheuer (1967). More often, poisoning occurs in regions with a tropical, subtropical climate, water areas of the Indian, Pacific Oceans, and the Caribbean. It is believed that no more than 20% of cases of ciguatera are recorded annually, the real number of poisonings is not known for certain.

Ciguatera

Causes

The source of infection is phytoplankton, the dinoflagellate Gambierdiscus toxicus, which is food for small fish, which, in turn, are eaten by predatory relatives. The poison accumulates mainly in the liver and other internal organs of fish. Ciguatoxin is odorless and tasteless, and is not neutralized by heat treatment and freezing. To date, three species are known: Indian, Caribbean and Pacific ciguatoxin; the latter is more common and studied.

Main risk factors: eating reef fish species larger than 10 kg caught after the storm; viscera and heads are especially toxic. The destruction of reefs caused by typhoons and hurricanes significantly increases the toxicity of fish. The most dangerous include Spanish mackerels, yellow moray eels, sea bass, barracudas, sea basses, hamfeads. The danger of ciguatera increases significantly for the elderly, those with heart and arterial diseases, and obesity.

Pathogenesis

The pathogenesis is not fully understood. The main action of toxins (ciguatoxin, meitotoxin) is associated with disruption of the sodium channels of cell membranes, neuronal edema, blockage of potassium channels, which ultimately leads to impaired conduction of the nerve impulse. Uncontrollable and repetitive action potentials occur due to a single stimulus. Ciguatoxin is implicated in calcium channel dysregulation, nitrous oxide induction by cells.

Peripheral nervous system, sensory neurons, skeletal muscle, heart, gray matter become targets for exposure. It has been shown in an animal model that venom administration can lead to neuronal excitotoxicity of the cerebral cortex. It has been suggested that polyneural edema caused by the activity of the toxin and leading to degradation of the myelin sheath may be the cause of autoimmune neuronal aggression.

Symptoms

The incubation period of ciguatera is 1-24 hours. In a typical course, there is a feeling of numbness in the mouth, toothache, burning of the skin upon contact with cold water, a feeling of “loose” teeth. The disease is accompanied by nausea, spastic abdominal pain, vomiting, loose stools, severe muscle weakness. Often there is temperature dysesthesia – hot seems cold, and vice versa.

The severity of symptoms depends on the amount of toxin that has entered the body, and the duration of the disease usually does not exceed 4 days. There are frequent cases of a prolonged drop in blood pressure, accompanied by weakness and the impossibility of active actions in an upright position. In severe cases, shortness of breath appears, a decrease in the patient’s contact reaction to stimuli.

If the symptoms of the disease last 2-6 months or more, it is possible to talk about chronic ichthyotoxicosis. Manifestations of chronic ciguatera are mainly neurological (paresthesia, dysesthesia, cold allodynia, pruritus, headache), psychiatric (cognitive dysfunction, sleep disturbance, anxiety, memory loss, depression) and systemic (myalgia, severe asthenia, arthralgia).

Complications

The most common complication of ciguatera is acute cardiovascular failure, less often respiratory failure. With large fluid losses, dehydration shock and renal dysfunction develop. In severe cases, cerebral edema rapidly increases with the danger of wedging into the foramen magnum. Among 20% ​​of patients, there is a long course and subsequent chronicity of the pathology.

Due to the accumulation of toxin in adipose tissue and the slow rate of its excretion, recurrence of the disease is possible. Most often this is due to repeated intake of fish dishes, caffeine, chicken, nuts, alcohol, prolonged dehydration, stress. To the probable complications of the long course of ciguatera, modern infectology includes multiple sclerosis, chronic fatigue syndrome and brain tumors.

Diagnosis

Verification of the diagnosis of toxicosis and treatment is carried out by infectious disease specialists, often in intensive care units. Other medical specialists are involved according to indications. It is important to collect an epidemiological history, including stay in endemic areas, the nature of nutrition (eating fish). The main clinical, instrumental and laboratory signs of ciguatera are:

• Physical data. Physical examination reveals symptoms of dehydration, diffuse abdominal tenderness, bradycardia, hypotension, severe muscle weakness, less commonly dyspnoea, and forced posture. The degree of impaired consciousness can change to coma, dysphoria is detected. Be sure to evaluate the presence of meningeal symptoms, the nature of vomiting and feces, the amount of urine.
• Laboratory tests . There are no specific laboratory markers for ciguatera. With pronounced fluid losses in the general blood test, symptoms of hemoconcentration increase, the ratio of electrolytes changes, the activity of ALT, AST increases. General clinical analysis of urine – with signs of toxic damage in the form of proteinuria, microhematuria, increased concentration of urinary sediment.
• Detection of infectious agents . There is only a toxicological analysis of probably toxic fish products; in some cases, a biological test on laboratory animals is used for differential diagnosis. A bacteriological examination of feces, washings, preserved suspicious food should be carried out.
• Instrumental methods . Ultrasound examination of the internal organs is shown to exclude urgent surgical pathology, abdominal radiography to confirm or refute the symptoms of an acute abdomen; ECG, EEG – with a differential diagnosis with a gastric form of myocardial infarction and neurological pathologies, respectively.

Differential diagnosis is carried out with various poisonings, in which the only way to determine the source of the toxin is laboratory analysis. Pathologies of the central nervous system are rarely associated with a particular food. The clinic of ciguatera is similar with food poisoning, gastrointestinal salmonellosis, in which there is no neuronal dysfunction, and botulism, characterized by transient “top-down” lesions of the cranial nerves.

Treatment

There are currently no established protocols for the management of patients with ciguatera symptoms. Patients who are indicated for inpatient treatment are the elderly, pregnant women, people with chronic pathology of the heart and blood vessels, children, people with severe dehydration. Before contacting a doctor, it is recommended to wash the stomach, take medicinal sorbents, and perform siphon enemas to get rid of toxic food residues, provided that the patient is conscious.

Bed or semi-bed rest is prescribed. Specific nutrition for ciguatera has not been developed, it is recommended to exclude alcohol, nicotine, heavy, indigestible food, especially saturated with fats. The use of large amounts of water, detoxifying polyionic oral solutions is required for detoxification purposes, as well as to replenish fluid losses – which can be done in the absence of contraindications.

Conservative therapy

Treatment of ciguatera non-specific; many groups of pharmaceuticals have been proposed, while etiotropic agents have not yet been developed. It is necessary to start supportive measures in the first hours and days after the patient presents with suspected ciguatera; thus, manifest symptoms of severe damage to the heart muscle occur among 43% of patients. Most often, poisoning therapy is carried out with the help of:

1. Pathogenetic treatment. It is carried out using infusion detoxification measures with succinate-containing, glucose-salt, polyionic solutions, cardioactive, vasopressor agents. In chronic course, antidepressants, cholestyramine, antiepileptic drug formulas, as well as non-steroidal anti-inflammatory drugs are indicated. Calcium channel blockers have proven themselves well. For the treatment of shock, plasma substitutes, dopamine preparations are used.
2. Symptomatic therapy. Antiemetic, antispasmodic drugs are used, with severe diarrhea – astringents, sorbents; B vitamins are widely used. With skin itching, sedatives, antihistamines and desensitizing agents are indicated. Treatment with steroid hormones, opiates, barbiturates has little therapeutic potential with ciguatera.

Previously widely recommended and highly effective in vitro studies, mannitol should be administered within 24 hours of symptom onset, according to current research. When intravenous mannitol is administered later, its effect is comparable to the introduction of saline, respectively, the risk of side effects of the drug also increases.

Mannitol has been shown to help reduce swelling of nerve cells due to exposure to ciguatoxins and also acts as a scavenger of free radicals generated when cells are exposed to these poisons. Treatment of symptoms of paresthesia with ciguatera is carried out by physiotherapeutic methods (diadynamic currents, electrophoresis, magnetotherapy), course use of antihypoxants and antioxidants.

Experimental treatment

Local people in the South Pacific traditionally use a decoction of the leaves of the silver argusia (Heliotropium foertherianum) to treat the symptoms of ciguatera. In vitro studies have shown that this herbal preparation has the ability to compete with ciguatoxins, limiting their fixation on biological targets, so the remedy is considered most effective only when taken immediately after the first signs of poisoning.

Prognosis and prevention

The prognosis is favorable in most cases. Ciguatera rarely leads to death, however, with a burdened premorbid background and a high dose of toxin that has entered the body, untimely treatment, the lethality of this poisoning is 0.04-0.1%. The duration of neurological symptoms – paresthesia, depression, headaches, memory loss – after recovery can be weeks and months.

No specific prophylaxis of ciguatera has been developed. Non-specific measures are considered to be abstinence from the consumption of meat and viscera (liver, milk, caviar) of large predatory reef fish, especially in periods after natural disasters, spawning; it is necessary to exclude the purchase of fish from private individuals. In endemic zones, states carry out toxicological studies of fish products supplied for official sale.

Causes, Symptoms, Diagnosis and Treatment

Ciguatera is a disease that occurs when certain reef fish are eaten. The most common symptoms are neurological manifestations, such as paresthesia of the face, limbs, hallucinations, headache, loss of consciousness, delirium. Neuropsychological, cardiovascular, gastrointestinal disturbances are not uncommon. Diagnosis consists in the detection of a toxin in food, the characteristic symptoms of the disease. Treatment is pathogenetic and symptomatic; etiotropic therapy of ciguatera has not been developed, therapeutic measures are aimed at detoxification of the body.

General information

Ciguatera (fish food poisoning) – toxicosis associated with the action of the biological poison ciguatoxin. For the first time, the symptoms of ciguatera are found in the written sources of doctors of Ancient China (VII century AD), the clinic was described in more detail by the Englishman Locke in 1675. The toxin was isolated by the Hawaiian professor Scheuer (1967). More often, poisoning occurs in regions with a tropical, subtropical climate, water areas of the Indian, Pacific Oceans, and the Caribbean. It is believed that no more than 20% of cases of ciguatera are recorded annually, the real number of poisonings is not known for certain.

Ciguatera

Causes

The source of infection is phytoplankton, the dinoflagellate Gambierdiscus toxicus, which is food for small fish, which, in turn, are eaten by predatory relatives. The poison accumulates mainly in the liver and other internal organs of fish. Ciguatoxin is odorless and tasteless, and is not neutralized by heat treatment and freezing. To date, three species are known: Indian, Caribbean and Pacific ciguatoxin; the latter is more common and studied.

Main risk factors: eating reef fish species larger than 10 kg caught after the storm; viscera and heads are especially toxic. The destruction of reefs caused by typhoons and hurricanes significantly increases the toxicity of fish. The most dangerous include Spanish mackerels, yellow moray eels, sea bass, barracudas, sea basses, hamfeads. The danger of ciguatera increases significantly for the elderly, those with heart and arterial diseases, and obesity.

Pathogenesis

The pathogenesis is not fully understood. The main action of toxins (ciguatoxin, meitotoxin) is associated with disruption of the sodium channels of cell membranes, neuronal edema, blockage of potassium channels, which ultimately leads to impaired conduction of the nerve impulse. Uncontrollable and repetitive action potentials occur due to a single stimulus. Ciguatoxin is implicated in calcium channel dysregulation, nitrous oxide induction by cells.

Peripheral nervous system, sensory neurons, skeletal muscle, heart, gray matter become targets for exposure. It has been shown in an animal model that venom administration can lead to neuronal excitotoxicity of the cerebral cortex. It has been suggested that polyneural edema caused by the activity of the toxin and leading to degradation of the myelin sheath may be the cause of autoimmune neuronal aggression.

Symptoms

The incubation period of ciguatera is 1-24 hours. In a typical course, there is a feeling of numbness in the mouth, toothache, burning of the skin upon contact with cold water, a feeling of “loose” teeth. The disease is accompanied by nausea, spastic abdominal pain, vomiting, loose stools, severe muscle weakness. Often there is temperature dysesthesia – hot seems cold, and vice versa.

The severity of symptoms depends on the amount of toxin that has entered the body, and the duration of the disease usually does not exceed 4 days. There are frequent cases of a prolonged drop in blood pressure, accompanied by weakness and the impossibility of active actions in an upright position. In severe cases, shortness of breath appears, a decrease in the patient’s contact reaction to stimuli.

If the symptoms of the disease last 2-6 months or more, it is possible to talk about chronic ichthyotoxicosis. Manifestations of chronic ciguatera are mainly neurological (paresthesia, dysesthesia, cold allodynia, pruritus, headache), psychiatric (cognitive dysfunction, sleep disturbance, anxiety, memory loss, depression) and systemic (myalgia, severe asthenia, arthralgia).

Complications

The most common complication of ciguatera is acute cardiovascular failure, less often respiratory failure. With large fluid losses, dehydration shock and renal dysfunction develop. In severe cases, cerebral edema rapidly increases with the danger of wedging into the foramen magnum. Among 20% ​​of patients, there is a long course and subsequent chronicity of the pathology.

Due to the accumulation of toxin in adipose tissue and the slow rate of its excretion, recurrence of the disease is possible. Most often this is due to repeated intake of fish dishes, caffeine, chicken, nuts, alcohol, prolonged dehydration, stress. To the probable complications of the long course of ciguatera, modern infectology includes multiple sclerosis, chronic fatigue syndrome and brain tumors.

Diagnosis

Verification of the diagnosis of toxicosis and treatment is carried out by infectious disease specialists, often in intensive care units. Other medical specialists are involved according to indications. It is important to collect an epidemiological history, including stay in endemic areas, the nature of nutrition (eating fish). The main clinical, instrumental and laboratory signs of ciguatera are:

• Physical data. Physical examination reveals symptoms of dehydration, diffuse abdominal tenderness, bradycardia, hypotension, severe muscle weakness, less commonly dyspnoea, and forced posture. The degree of impaired consciousness can change to coma, dysphoria is detected. Be sure to evaluate the presence of meningeal symptoms, the nature of vomiting and feces, the amount of urine.
• Laboratory tests . There are no specific laboratory markers for ciguatera. With pronounced fluid losses in the general blood test, symptoms of hemoconcentration increase, the ratio of electrolytes changes, the activity of ALT, AST increases. General clinical analysis of urine – with signs of toxic damage in the form of proteinuria, microhematuria, increased concentration of urinary sediment.
• Detection of infectious agents . There is only a toxicological analysis of probably toxic fish products; in some cases, a biological test on laboratory animals is used for differential diagnosis. A bacteriological examination of feces, washings, preserved suspicious food should be carried out.
• Instrumental methods . Ultrasound examination of the internal organs is shown to exclude urgent surgical pathology, abdominal radiography to confirm or refute the symptoms of an acute abdomen; ECG, EEG – with a differential diagnosis with a gastric form of myocardial infarction and neurological pathologies, respectively.

Differential diagnosis is carried out with various poisonings, in which the only way to determine the source of the toxin is laboratory analysis. Pathologies of the central nervous system are rarely associated with a particular food. The clinic of ciguatera is similar with food poisoning, gastrointestinal salmonellosis, in which there is no neuronal dysfunction, and botulism, characterized by transient “top-down” lesions of the cranial nerves.

Treatment

There are currently no established protocols for the management of patients with ciguatera symptoms. Patients who are indicated for inpatient treatment are the elderly, pregnant women, people with chronic pathology of the heart and blood vessels, children, people with severe dehydration. Before contacting a doctor, it is recommended to wash the stomach, take medicinal sorbents, and perform siphon enemas to get rid of toxic food residues, provided that the patient is conscious.

Bed or semi-bed rest is prescribed. Specific nutrition for ciguatera has not been developed, it is recommended to exclude alcohol, nicotine, heavy, indigestible food, especially saturated with fats. The use of large amounts of water, detoxifying polyionic oral solutions is required for detoxification purposes, as well as to replenish fluid losses – which can be done in the absence of contraindications.

Conservative therapy

Treatment of ciguatera non-specific; many groups of pharmaceuticals have been proposed, while etiotropic agents have not yet been developed. It is necessary to start supportive measures in the first hours and days after the patient presents with suspected ciguatera; thus, manifest symptoms of severe damage to the heart muscle occur among 43% of patients. Most often, poisoning therapy is carried out with the help of:

1. Pathogenetic treatment. It is carried out using infusion detoxification measures with succinate-containing, glucose-salt, polyionic solutions, cardioactive, vasopressor agents. In chronic course, antidepressants, cholestyramine, antiepileptic drug formulas, as well as non-steroidal anti-inflammatory drugs are indicated. Calcium channel blockers have proven themselves well. For the treatment of shock, plasma substitutes, dopamine preparations are used.
2. Symptomatic therapy. Antiemetic, antispasmodic drugs are used, with severe diarrhea – astringents, sorbents; B vitamins are widely used. With skin itching, sedatives, antihistamines and desensitizing agents are indicated. Treatment with steroid hormones, opiates, barbiturates has little therapeutic potential with ciguatera.

Previously widely recommended and highly effective in vitro studies, mannitol should be administered within 24 hours of symptom onset, according to current research. When intravenous mannitol is administered later, its effect is comparable to the introduction of saline, respectively, the risk of side effects of the drug also increases.

Mannitol has been shown to help reduce swelling of nerve cells due to exposure to ciguatoxins and also acts as a scavenger of free radicals generated when cells are exposed to these poisons. Treatment of symptoms of paresthesia with ciguatera is carried out by physiotherapeutic methods (diadynamic currents, electrophoresis, magnetotherapy), course use of antihypoxants and antioxidants.

Experimental treatment

Local people in the South Pacific traditionally use a decoction of the leaves of the silver argusia (Heliotropium foertherianum) to treat the symptoms of ciguatera. In vitro studies have shown that this herbal preparation has the ability to compete with ciguatoxins, limiting their fixation on biological targets, so the remedy is considered most effective only when taken immediately after the first signs of poisoning.

Prognosis and prevention

The prognosis is favorable in most cases. Ciguatera rarely leads to death, however, with a burdened premorbid background and a high dose of toxin that has entered the body, untimely treatment, the lethality of this poisoning is 0.04-0.1%. The duration of neurological symptoms – paresthesia, depression, headaches, memory loss – after recovery can be weeks and months.