Ciguatera is a disease that occurs when eating certain types of reef fish. The most common symptoms are neurological manifestations, such as paresthesia of the face, limbs, hallucinations, headache, loss of consciousness, delirium. Neuropsychological, cardiovascular, gastrointestinal disorders are not uncommon. Diagnosis consists in the detection of a toxin in food, 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.
Poisoning by the sequatera T61.0
Ciguatera (food poisoning by fish) is a toxicosis associated with the action of the biological poison ciguatoxin. For the first time, the symptoms of ciguatera are found in 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 Hawaiian Professor Scheuer (1967). Poisoning is more common in regions with a tropical, subtropical climate, aquatic areas of the Indian, Pacific Oceans, and the Caribbean Sea. It is believed that no more than 20% of cases of ciguatera are recorded annually, the real number of poisonings is not reliably known.
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 has no smell and taste, is not neutralized during heat treatment and freezing. To date, three species are known: Indian, Caribbean and Pacific ciguatoxin; the latter is more widespread and studied.
The main risk factors: the consumption of reef fish species larger than 10 kg caught after a storm; the insides 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 mackerel, yellow moray eels, sea bass, barracudas, sea bass, humphead. The danger of ciguatera increases significantly for the elderly, people with heart and artery diseases, and obesity.
The pathogenesis is not fully understood. The main effect of toxins (ciguatoxin, meitotoxin) is associated with disruption of the sodium channels of cell membranes, neural edema, blocking of potassium channels, which eventually leads to a violation of the conduction of the nerve impulse. Uncontrolled and repetitive action potentials arise due to a single stimulus. Ciguatoxin is involved in the dysregulation of calcium channels, the induction of nitrous oxide by cells.
The targets for exposure are the peripheral nervous system, sensory neurons, skeletal muscle, heart, gray matter. In an animal model, it was shown that the introduction of poison can lead to neuronal excitotoxicity of the cerebral cortex. It has been suggested that polyneurial edema caused by the activity of the toxin and leading to degradation of the myelin sheath may be the cause of autoimmune neural aggression.
The incubation period of ciguatera is 1-24 hours. With a typical course, there is a feeling of numbness in the mouth, toothache, burning of the skin when in contact with cold water, a feeling of “loosening” teeth. The disease is accompanied by nausea, spastic abdominal pain, vomiting, the appearance of loose stools, pronounced muscle weakness. Temperature dysesthesia often occurs – hot seems cold, and vice versa.
The severity of symptoms depends on the amount of toxin ingested, 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 inability to take 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 the chronization of ichthyotoxicosis. The manifestations of chronic ciguatera are mainly neurological (paresthesia, dysesthesia, cold allodynia, itching, headache), psychiatric (cognitive dysfunction, sleep disturbance, anxiety, memory loss, depression) and systemic (myalgia, severe asthenia, arthralgia).
The most common complication with ciguatera is acute cardiovascular insufficiency, less often respiratory. With large fluid losses, dehydration shock and renal dysfunction develop. In severe cases, swelling of the brain rapidly increases with the danger of wedging into the large occipital foramen. Among 20% of patients, there is a long course and subsequent chronization of pathology.
Due to the accumulation of the toxin in adipose tissue and the slow rate of its excretion, a relapse of the disease is possible. Most often this happens due to repeated intake of fish dishes, caffeine, chicken, nuts, alcohol, prolonged dehydration, stress. Modern infectology includes multiple sclerosis, chronic fatigue syndrome and brain tumors as possible complications of the long-term course of ciguatera.
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 staying in endemic territories, the nature of nutrition (eating fish). The main clinical, instrumental and laboratory signs of ciguatera are:
- Physical data. An objective examination reveals symptoms of dehydration, diffuse abdominal pain, bradycardia, hypotension, pronounced weakness in the muscles, less often shortness of breath and forced posture. The degree of disturbance of consciousness can change to coma, dysphoria is detected. The presence of meningeal symptoms, the nature of vomiting and feces, and the amount of urine are necessarily assessed.
- Laboratory tests. There are no specific laboratory markers of ciguatera. With pronounced fluid losses in the blood test, the symptoms of hemococentation increase, the ratio of electrolytes changes, the activity of ALT and AST increases. General clinical analysis of urine – with signs of tosic lesion in the form of proteinuria, microhematuria, increased concentration of urinary sediment.
- Identification 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. It is necessary to conduct a bacteriological study of feces, washing water, preserved suspicious food.
- Instrumental methods. Ultrasound examination of internal organs is shown to exclude urgent surgical pathology, abdominal organs x-ray in order to confirm or refute the symptoms of acute abdomen; ECG, EEG – for differential diagnosis with gastritic 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 rarely have a connection with a certain food. The ciguatera clinic is similar to food poisoning, gastrointestinal salmonellosis, in which there is no neuronal dysfunction, and botulism, characterized by transient “top-down” lesions of the cranial nerves.
There are currently no developed protocols for the management of patients with symptoms of ciguatera. Patients who are shown inpatient treatment are the elderly, pregnant women, people with chronic pathology of the heart and blood vessels, children, people with severe dehydration. Before going to the doctor, gastric lavage, taking medicinal sorbents, setting up siphon enemas to get rid of toxic food residues is recommended, provided the patient is conscious.
Bed rest or semi-bed rest is assigned. Specific nutrition for ciguatera has not been developed, it is recommended to exclude alcohol, nicotine, heavy, hard-to-digest food, especially saturated fats. The use of large amounts of water, detoxifying polyionic oral solutions is required for detoxification purposes, as well as to replenish liquid losses, which can be carried out in the absence of contraindications.
The treatment of ciguatera is non-specific; many groups of pharmaceuticals have been proposed, while etiotropic agents have not yet been developed. It is necessary to begin supportive measures in the first hours and days after the patient’s treatment with suspected ciguatera; thus, manifest symptoms of severe heart muscle damage are found among 43% of patients. Most often, poisoning therapy is carried out using:
- Pathogenetic treatment. It is carried out by the use of infusion detoxification measures with succinate-containing, glucose-salt, polyionic solutions, cardioactive, vasopressor agents. In the chronic course, antidepressants, cholestyramine, antiepileptic medicinal formulas, as well as nonsteroidal anti-inflammatory drugs are indicated. Calcium channel blockers have proven themselves well. Plasma substitutes and dopamine preparations are used for shock therapy.
- Symptomatic therapy. Antiemetic, antispasmodic drugs are used, with severe diarrhea – astringents, sorbents; vitamins of group B are widely used. Sedatives, antihistamines and desensitizing agents are indicated for skin itching. Treatment with steroid hormones, opiates, barbiturates has a weak therapeutic potential with ciguatera.
Previously widely recommended and shown to be highly effective in in vitro experiments, mannitol, according to modern research, should be applied no later than 24 hours from the onset of symptoms. When intravenous mannitol is prescribed later, its effect is comparable to the introduction of saline solution, respectively, the risk of side effects of the drug also increases.
It is noted that mannitol helps to reduce swelling of nerve cells due to exposure to ciguatoxins, and also acts as an absorber of free radicals generated when exposed to cells by these poisons. Treatment of symptoms of paresthesia in ciguatera is carried out by physiotherapeutic methods (diadynamic currents, electrophoresis, magnetotherapy), course use of antihypoxants and antioxidants.
The locals of the South Pacific traditionally use a decoction of the leaves of silver argusium (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 drug is recognized as the most effective only when taken immediately after the appearance of 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.
Specific prevention of ciguatera has not been developed. Non-specific measures are considered abstinence from eating meat and entrails (liver, milk, caviar) of large predatory reef fish, especially during 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.