Sea food toxins 

Introduction

Food poisoning caused by the use of toxin containing sea food has been major concern for a long time. This has become wide spread today due to the proliferation of toxic organisms developed by the environmental changes in sea. At the same time it should be noted that significant progress has been achieved in the isolation, identification and control of factors which cause food poisoning in many sea food items.

Sea food toxins found in fishes are known as icthyotoxins and the same in shell fishes are called shell fish toxins. Ciguatera toxin, tetradotoxin, scomberotoxin, saurine etc are some of the icthyotoxins and saxitoxin, okadaic acid,maitotoxin, domic acid etc are some of the shell fish toxins.

Shell fish toxins

Most of the Shell fish toxins are caused by the accumulation of toxins from some types of micro algae formed at the time of algal blooms in the shell fishes. These types of algal blooms which contain toxic algae are called HAB or Harmful Algal Blooms. Toxins of human health importance occur usually in three classes of unicellular algae namely dinoflagellates, diatoms and cyanobacteria. 

The impact of these toxins in human health is primarily through the use of sea food. Filter feeding shell fish, zoo plankton and herbivorous fishes work as vectors. The major sea food poisoning syndromes due to shellfish consumption are paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP) and diarrhetic shellfish poisoning (DSP). The mortality rate by the use of toxic shellfish is about 8.5 percent but is less than 1 percent in developed countries. In a major outbreak in Guatemala in 1987, the mortality rate in children was 50 percent and in adults it was 7 percent.

Paralytic shellfish poisoning (PSP)

Paralytic shellfish poisoning (PSP) is the most occurring and dreaded algal shellfish poisoning today. It is resulting from eating bivalve mollusks like mussels, clams, oysters, and scallops that have consumed toxigenic dinoflagellates. PSP toxins are produced by dinoflagellates coming under the genera Alexandrium, Gymnodinium, and pyrodinium. The toxins are assimilated and temporarily kept by the shellfishes.

Pharmacology

The toxins causing PSP are called saxitoxins which are group of heterocyclic guanidines. The saxitoxins (STX) are a group of water soluble neurotoxins and are some of the most potent toxins. STX is a white colored solid which is hygroscopic in nature and highly soluble in water, partly soluble in methanol and ethanol, but insoluble in solvents like ethyl and petroleum ethers. Chemically it is an alkaloid which can be extracted with acidic water.