Numerous reports in the literature describe cases of fish poisoning occurring due to ingestion of several species, some of the most important being:

• Shellfish - Poisoning from this fish stems from the effects of saxitoxin, a compound found in butter clams, geoducks, mussels, and other bivalve mollusks that are eaten by shellfish [1] [2] [3]. It is a very potent molecule capable of producing symptoms within several hours after being introduced into the gastrointestinal tract [2] [3]. Because saxitoxin blocks voltage-gated sodium channels, neurological symptoms are a constitutive feature of this type of fish poisoning; circumoral paresthesia, numbness and a tingling sensation of the extremities, ataxia, weakness, and altered consciousness are principal findings [2] [3]. In severe cases, hypertension and tachycardia may be accompanied by a severe muscular and respiratory paralysis, thus the term paralytic shellfish poisoning is often used [2] [3]. In rare cases, the effects of another toxin found in shellfish (brevetoxin) can cause temperature-related dysesthesia [1].
• Pufferfish - Ingestion of pufferfish is a potentially life-threatening clinical entity and is known as fugu poisoning. Tetrodotoxin (TTX), similarly to saxitoxin, impairs the transmission of neuromuscular impulses [4] [5]. Lightheadedness, weakness, vomiting, and a rapidly ascending paralysis, eventually affecting respiratory muscles, may be fatal within 6-24 hours [5]. Diaphoresis, excessive salivation, dysphagia, convulsions, hypotension, bradycardia, and fixed dilated pupils are other notable symptoms of pufferfish poisoning [4] [5].
• Scombroid species - Initially described from tuna, mackerel, and other fish belonging to the Scombridae family, and later with sardines and anchovies, scombroid fish poisoning arises in the setting of improper storage or processing, resulting in the accumulation of histamine [6] [7]. Thus, typical symptoms resemble an acute allergic reaction - disseminated erythema (without wheals) and flushing are accompanied by abdominal cramping, diarrhea, and vomiting [6] [7]. Headaches, palpitation, and dizziness are frequently reported [7]. Furthermore, bronchospasm and respiratory distress in conjunction with an unstable blood pressure can appear as well [6]. Symptoms develop shortly after consuming the fish (in the first hour and a half) and resolve within 36 hours [6].
• Reef fish - Ciguatera fish poisoning (CFP), named after ciguatoxins that produce gastrointestinal (vomiting, diarrhea, abdominal pain), neurologic (paresthesias, pruritis), and musculoskeletal (myalgia, arthralgia, and weakness) symptoms in a period of hours, is primarily seen after consumption of fish species residing in coral reefs [1]. Dysesthesia is a constitutive feature of ciguatera fish poisoning as well, and it may be confused with shellfish poisoning [1].

• Vomiting

  Lightheadedness, weakness, vomiting, and a rapidly ascending paralysis, eventually affecting respiratory muscles, may be fatal within 6-24 hours. [symptoma.com]

  The diagnosis usually is made by the presence of gastrointestinal symptoms, nausea, vomiting, and diarrhea, and of neurological symptoms such as paresthesias, paresis, and pruritus. [ncbi.nlm.nih.gov]

  Do not induce vomiting or give syrup of Ipecac. Ipecac was formerly used to induce vomiting in poisoned patients where there was a chance to get the toxin out of the body. [medicinenet.com]

  After eating contaminated clams or mussels, you will most likely experience nausea, vomiting, and diarrhea. [medlineplus.gov]

• Nausea

  Symptoms of poisoning may include paralysis, respiratory failure, numbness, paraesthesia, nausea and ataxia. Health professionals should be aware of the condition so as to institute early and appropriate management. [ncbi.nlm.nih.gov]

  Abdominal cramps, nausea, vomiting, and diarrhea last 6 to 17 h; then, pruritus, paresthesias, headache, myalgia, reversal of hot and cold sensation, and face pain may occur. [merckmanuals.com]

• Food Poisoning

  Find out more in our viral food poisoning section. [medic8.com]

  When consumed, this substance causes a food poisoning reaction similar to an allergic reaction. Food poisoning from raw fish can also occur as a result of contamination of the fish with infectious organisms. [livestrong.com]

  What Is the Most Common Way to Get Food Poisoning From Fish? There are actually two ways in which you can get food poisoning from consuming fish. [healthguidance.org]

  The treatment of this food poisoning is supportive, although intravenous mannitol is reported to be safe and effective. The prognosis is good and complete recovery is to be expected. [ncbi.nlm.nih.gov]

• Abdominal Pain

  OBJECTIVE: We describe the case of a young man who suffered from diarrhea and abdominal pain after eating raw fish and who also developed severe ataxia with spontaneous downbeat and perverted head-shaking nystagmus. [ncbi.nlm.nih.gov]

  In addition, individuals may experience burning or swelling of the mouth, abdominal pain, or a metallic taste. Most people experience mild symptoms which should resolve on their own within 12 hours. [bouldercounty.org]

• Hypersalivation

  48 hours, while neurological symptoms–which develop later and can last for weeks or months after the initial exposure–include tingling, trouble with cold perception, headache, dental pain, metallic taste, vertigo, lack of coordination, itching, and hypersalivation [sea.edu]

• Orthostatic Hypotension

  PURPOSE: The purpose of this study was to investigate the pathophysiology of persistent orthostatic hypotension in a patient with ciguatera fish poisoning. [ncbi.nlm.nih.gov]

  Orthostatic hypotension in ciguatera fish poisoning. Arch Intern Med 1992;152:2131-3. [ PUBMED ] [ FULLTEXT ] 5. Lewis R, Hoy A, McGiffin D. Action of ciguatoxin on human atrial trabeculae. Toxicon 1992;30:907-14. 6. Marquais M, Sauviat M. [heartviews.org]

• Pruritic Rash

  A 25-year-old woman presented to the emergency department (ED) with one hour of tongue and face swelling, an erythematous pruritic rash, and dyspnea with wheezing after consuming a tuna sandwich. [ncbi.nlm.nih.gov]

• Suggestibility

  Oculomotor findings suggested dysfunction of the vestibulocerebellum, especially the flocculus. CONCLUSION: These findings suggest that both the peripheral and the central nervous systems can be involved in ciguatera. Copyright 2012 Elsevier Inc. [ncbi.nlm.nih.gov]

• Impulsivity

  Tetrodotoxin (TTX), similarly to saxitoxin, impairs the transmission of neuromuscular impulses. Lightheadedness, weakness, vomiting, and a rapidly ascending paralysis, eventually affecting respiratory muscles, may be fatal within 6-24 hours. [symptoma.com]

• Auditory Hallucination

  A 40-year-old man experienced mild digestive troubles and terrifying visual and auditory hallucinations after eating a specimen of Sarpa salpa in a restaurant. [ncbi.nlm.nih.gov]

• Headache

  Amitriptyline demonstrated resolution of most symptoms except for heat/cold reversal in one patient and heat/cold reversal, pruritus and headache in the second patient. [ncbi.nlm.nih.gov]

  Signs and symptoms Symptoms include: tingling and burning around the mouth facial flushing and sweating nausea, vomiting and diarrhoea headache palpitations and dizziness rash. [sahealth.sa.gov.au]

• Nystagmus

  OBJECTIVE: We describe the case of a young man who suffered from diarrhea and abdominal pain after eating raw fish and who also developed severe ataxia with spontaneous downbeat and perverted head-shaking nystagmus. [ncbi.nlm.nih.gov]

• Neurologic Manifestation

  Serious neurological manifestations of ciguatera: is the delay unusually long? J Neurol Neurosurg Psychiatry. 1998;64:688-89. [rarediseases.org]

Because of the rapid onset of symptoms seen in the mentioned types of fish poisoning, a prompt diagnosis can be life-saving. A proper patient history is the single most important step in the workup. Data regarding recent consumption of fish, the development of similar symptoms in friends or other persons who ate the same food (or have been in the same restaurant) can be crucial for a presumptive diagnosis of intoxication [1] [5] [7]. The physical examination is an important component of the workup, during which the severity of complaints and their progression should be defined, mainly in order to consider the optimal therapeutic approach. Despite the scarce availability of commercial tests for specific toxins found in fish, recent introduction of novel biochemical tests might be useful for detecting the concentration of ciguatera toxin, histamine, tetrodotoxin, and saxitoxin in respective fish species; this confirming the presumed source [1] [2] [3] [5] [6]. An assessment of histamine concentration in blood or its metabolites in urine might also be a useful diagnostic tool [6].

• Slow Nerve Conduction Velocities

  However, intraperitoneal injection of ciguatoxin in rats increases neuronal refractory period and slows nerve conduction velocity. Treatment with mannitol fails to correct these effects. [ncbi.nlm.nih.gov]

1. Friedman MA, Fleming LE, Fernandez M, et al. Ciguatera Fish Poisoning: Treatment, Prevention and Management. Mar Drugs. 2008;6(3):456-479.
2. Hurley W, Wolterstorff C, MacDonald R, Schultz D. Paralytic Shellfish Poisoning: A Case Series. West J Emerg Med. 2014;15(4):378-381.
3. Centers for Disease Control and Prevention (CDC). Paralytic shellfish poisoning - Southeast Alaska, May-June 2011. MMWR Morb Mortal Wkly Rep. 2011;60(45):1554–1556.
4. Lago J, Rodríguez LP, Blanco L, Vieites JM, Cabado AG. Tetrodotoxin, an Extremely Potent Marine Neurotoxin: Distribution, Toxicity, Origin and Therapeutical Uses. Long P, ed. Mar Drugs. 2015;13(10):6384-6406.
5. Centers for Disease Control and Prevention (CDC). Tetrodotoxin poisoning associated with eating puffer fish transported from Japan--California, 1996. MMWR Morb Mortal Wkly Rep. 1996;45(19):389-391.
6. Stratta P, Badino G. Scombroid poisoning. CMAJ. 2012;184(6):674.
7. Feldman KA, Werner SB, Cronan S, et al. A large outbreak of scombroid fish poisoning associated with eating escolar fish (Lepidocybium flavobrunneum). Epidemiol Infect. 2005;133(1):29-33.