Amnesic Shellfish Poisoning

Amnesic shellfish poisoning was first recognized in 1987 as the result of an outbreak in Canada. This outbreak, involving ingestion of mussels from Prince Eward Island, was associated with more than 100 cases and at least four deaths. Amnesic Shellfish Poisoning is the result of an unusual neurotoxic amino acid (domoic acid) that contaminates shellfish.

The domoic acid is produced by a plankton in the genus Pseudo-nitzschia, the first example of a toxin-producing diatom. When shellfish accumulate domoic acid in high concentrations during filter breeding, the toxin can be passed on to humans that eat them.

Amnesic Shellfish Poisoning is characterized by gastrointestinal symptoms and unusual neurologic abnormalities.

Domoic acid is related structurally to the excitatory amino acid neurotransmitter glutamate. Within 24 hours of eating contaminated shellfish, the symptoms begin: vomiting and diarrhea, severe headache, abdominal pain and a host of neurological problems, including confusion, memory loss, disorientation, seizure and coma.
Amnesic Shellfish Poisoning

Paralytic Shellfish Poisoning

Paralytic shellfish poisoning is a serious illness caused by eating shellfish contaminated with dinoflagellate algae that produce harmful toxins. The toxicity of paralytic shellfish poisoning toxins is estimated to be 1,000 times greater than cyanide and symptoms appear soon after consuming toxic shellfish.

Only a few marine animals accumulate these toxins. Shellfish, including hard-shell clams, soft-shell clams, oysters, mussels, and scallops, are particularly prone to contamination as they feed by filtering microscopic food out of the water.

At lease there are 21 molecular forms of paralytic shellfish poisoning toxins. Collectively, these paralytic shellfish poisoning toxins are termed saxitoxins, deriving the name from the butter clam, Saxidomus giganteus, where saxitoxins were originally extracted and identified.

Clinical illness is characterized by neurological symptoms such as paresthesia and/or paralysis involving the mouth, face, neck and extremities, which may be accompanied by gastrointestinal symptoms, which usually resolve within a few hours to a few days. In severe cases, ataxia, dysphonia, dysphagia and muscle paralysis with respiratory arrest and death may occur within 12 hours.

Who is most at risk? Anyone who eats non-commercially harvested shellfish is at risk for Paralytic shellfish poisoning.
Paralytic Shellfish Poisoning

Tetrodotoxin of puffer fish poisoning

Puffer fish poisoning is results from ingestion of the flesh of certain species of fish belonging to the Tetraodontidae. These fish can be found in both fresh and salt water and can inflate their bodies to a nearly spheric shape using air or seawater.

The toxin involved is called tetrodotoxin and was originally believed to be a true ichthyosarcotoxin produced by the fish itself. Puffer fish, the most common source of tetrodotoxin, is eaten as the delicacy fugu in some Southeast Asian countries.

Although tetrodotoxin is concentrated in the fish’s skin and internal organs, all parts of the fish may contain it. Most poisonings occur in Japan, where sushi chefs must be licensed in the proper technique of preparing puffer fish owing to risk of death with improper preparation.

Tetrodotoxin blocks the action potentials in nerves by binding to the pores of the voltage-gated, fast sodium channels in nerve cell membrane.

The symptoms of puffer fish poisoning are similar to those described for paralytic shellfish poisoning, including initial tingling and numbness of lips, tongue and fingers leading to paralysis of the extremities; ataxia,; difficulty on speaking; and finally death buy asphyxiation due to respiratory paralysis. Nausea and vomiting are common early symptoms.
Tetrodotoxin of puffer fish poisoning

Pufferfish

A pufferfish or puffers is a bit like an underwater balloon. When in danger the pufferfish swells up to many times its usual size. The pufferfish fool its predator into thinking it is a fish that is much too big to eat.

Pufferfish have large eyes so they can see well. They also have sharp, powerful teeth and this part of the body is often referred to as beak.

Most pufferfish swim in warm ocean waters. Many live near coral reefs. There are more than 120 different kinds of pufferfish.

 Some pufferfish are very small. Others are longer than human arm. The smallest is just 1 inch (2.5 cm) long. The biggest pufferfish are more than 3 feet (1 m) long. Some pufferfish have stripes or spots on their skin. Some are very colorful.

While pufferfish are almost never targeted, they are frequently captures by young or very inexperienced anglers, some of whom want to keep them.

All pufferfish species are highly toxic and should never be consumed, no matter how well they are cleaned. All pufferfish species are highly toxic and should never be consumed, no matter how well they are cleaned.
Pufferfish

Histamine poisoning

This type for food poisoning may result from eating fish of the scombroid group as well as related fish tuna. Their flesh normally contains large amounts of free histidine.

Also called scombroid food poisoning, scombroid is a type of food poisoning caused by eating foods with elevated levels of histamine.

Initially, the disease was associated with consumption of scombroid fish such s tuna, mackerel, bonito and saury.

Now, other types of fish have also have been identified as causing the intoxication, including mahimahi, bluefish, jack, mackerel, amberjack, herring, sardine and anchovy. 

As much as 1 percent histidine on wet-weight basis can exist in the muscle tissue of such fish. The worldwide network for harvesting, processing and distribution of fish and fish products has made scombroid poisoning a global problem.

Numerous species of bacteria readily decarboxylate histidine, resulting in the accumulating of histamine. The histamine production is fish is a consequence of improper handling and storage of fish after capture.

If fish are stored incorrectly e.g. at too high a temperature for a long period, bacteria naturally occurring in the product can form histamine and other biogenic amines by hydrolysis of fish proteins and subsequent decarboxylation of the formed amino acids.

Histamine is a blood vessel dilator, and the consumption of excessive quantities can produce allergic-type poisoning symptoms.

Symptoms include headaches, rash, and increase blood pressure, which can progress to gastrointestinal problems and hospitalization in high risk group.

In the United States, scombroid fish poisoning has been caused dominantly by mahimahi, tuna and bluefish.
Histamine poisoning