Some fish species must be considered unpalatable or non-comestible. The main culprit in Malta is the Mediterranean Puffer Fish Legocephalus legocephalus. The toxin of the Puffer Fish can be very potent causing a mortality rate as high as 50% depending on the physical condition of the individual, and the amount of fish eaten. The poison present in the flesh or viscera of the fish apparently exerts its primary effect on the peripheral nervous system, but the physiologic mechanism is as yet unknown. The toxicity is dependant on the feeding pattern of the fish.

While the Puffer Fish is poisonous during most of the year, other species such as the Moray Eel Muraena helena are poisonous only during a part of the year. This snake-like fish has blood which when fresh is toxic to both humans and animals. Poisoning can occur even during handling of an injured animal in the presence of cuts on the hands. When cooked to a temperature of 75C, the toxin looses its poisonous properties and the fish becomes safe to be eaten. Its bite can also produce toxic manifestations. Coma and death can occur in about 12% of cases.

Fish normally considered edible [e.g. grouper, pompano, barracuda, mackerel, butterfly fish, snapper, sea bass, perch, wrasse, etc.] can become sporadically poisonous giving rise to fish poisoning manifestations known as: -

Ciguatera fish poisoning.

• Clinical Features:

• Symptoms of acute poisoning begin 30 minutes to 4 hours after ingestion.
• They include numbness and tingling of the face and lips which spreads to the fingers and toes.
• This is followed by nausea, vomiting, diarrhea, malaise, dizziness, abdominal pain, and muscular weakness.
• In severe cases, the symptoms can progress to foaming at the mouth, muscular paralysis, dyspnoea, or convulsions. Death may occur from convulsions or respiratory arrest within 1-24 hours.
• After recovery from the immediate symptoms, muscular weakness and paresthesias of the face, lips, and mouth may persist for weeks. Typically, these paresthesias consist of reversed temperature sensations - i.e. cold food cause a searing pain, while hot food feels cold.

Another type of fish poisoning is that caused after consumption of improperly prepared tuna and other scombroidei from the growth of surface organisms in fish stored at ambient temperatures. This type of poisoning is referred to as:-

Scombroid fish poisoning.

• Clinical Features:

• Some of the toxic effects may be the result of the release of histamine-like amines during bacterial decomposition.
• Symptoms of include nausea, vomiting, cramps, diarrhea, facial flushing, headache, and burning in the mouth.

 

• Treatment: 

• Treatment of both Ciguatera and Scombroid fish poisoning is symptomatic.
• Remove the ingested fish by gastric lavage or emesis
• Maintain an adequate airway and treat respiratory failure
• Manage convulsions and treat for shock.
• Antihistaminics have been reported useful to relieve some of the symptoms of Scombroid fish poisoning.