Paralytic toxin detection in bivalve molluscs PSP (PSP: paralytic shellfish poisoning): mouse bioassay.


This test determines the presence of paralytic toxin (PSP: Paralysis Shellfish Poisoning) in shellfish and applies essentially to bivalve molluscs. The test is performed from the fleshy mass of these molluscs, which is subjected to a treatment with hot acid to obtain an extract where the toxin is investigated. Detection is effected by inoculating mice with the extract intraperitoneally. Should this be the toxin mice die, and the time from inoculation to death of the mice, is related to the toxin content in mass mollusk, obtaining the mouse units (UR). From these UR (mouse units) content mg PSP toxin per 100 g body mass mollusc is determined. The maximum accepted limit is 80 mg / 100 g.



Unicellular microalgae of (20 to 200 microns) are an important component feeding shellfish such as mussels, oysters and scallops. Under favorable conditions of light, temperature, salinity, stability of the water column and nutrients, algae populations of a few cells can multiply rapidly, creating masses with millions of cells per liter that can change the color of seawater. Of the 2,000 living species of dinoflagellates, about 30 species produce toxins that can cause human disease by eating shellfish poisoning have been fed with these algae. When people ingest contaminated with these microalgae seafood, they may suffer gastrointestinal or neurological disorders.

Intoxication (poisoning) shellfish is caused by a group of toxins produced by planktonic algae (mostly by dinoflagellates), of which the shellfish feed. Toxins accumulate and sometimes metabolized by the shellfish.

There are four syndromes of poisoning marine products (bivalve molluscs, echinoderms, tunicates and gastropods):

  • Diarrheic shellfish poisoning (DSP: diarrheic shellfish poisoning)
  • Paralytic shellfish poisoning (PSP: paralytic shellfish poisoning).
  • Neurotoxic shellfish poisoning (NSP: neurotoxic shellfish poisoning)
  • Amnesic shellfish poisoning (ASP: shellsish amnesic poisoning)

The 20 toxins responsible for paralytic shellfish poisoning (PSP) derived from saxitoxin. Diarrheal shellfish poisoning (DSP) is presumably caused by a group of high molecular weight polyethers, including okadaic acid, dinophysis toxins, pectenotoxins and Yessotoxin. Neurotoxic shellfish poisoning (NSP) is due to exposure to a group of brevetoxins called polyethers. Amnesic shellfish poisoning (ASP) is caused by an unusual amino acid, domoic acid.

Contaminated seafood show no distinct appearance or have a different flavor to non - contaminated, and cooking and other treatments shellfish does not destroy toxins. Therefore, control areas and shellfish breeding seafood infested with toxic algal species must be performed to detect the presence of such seaweed in water; and when present, tests must be performed to detect toxins in seafood products related thereto.

Paralytic shellfish poisoning (PSP: paralytic shellfish poisoning)

Paralytic shellfish poisoning is usually associated with the consumption of bivalve molluscs. In some places has been associated with the intake of organ meats, mackerel, lobster, crab (Dungeness crab, tanner crabs, red rock crab). Although the viscera of mackerels are usually not eaten, if made with lobster and crab. However, the PSP toxin concentrations in lobsters do not usually cause a health hazard unless large amounts are ingested and come from a contaminated area.

PSP poisoning is caused by many toxic algae Alexandrium, Pyrodinium and Gymnodinium. It is due to a combination of any of toxins 20 (Saxitoxins), depending on the algal species, geographical area and type of seafood involved.

Saxitoxin (STX) is a naturally occurring neurotoxin produced by some marine dinoflagellates (Alexandrium spp., Gymnodinium spp., Pyrodinium spp.) And cyanobacteria (Anabaena spp., Some Aphanizomenon spp., Cylindrospermopsis spp., Lyngbya spp., Planktothrix spp.). Ingestion of saxitoxin is responsible for human disease known as "paralytic shellfish poisoning" and the name is derived saxitoxin clam Saxidomus giganteus in which for the first time its presence was recognized. Saxitoxin, one of the most potent natural toxins known, acts on sodium channels potential of nerve cells, preventing normal cell function, and causing paralysis.

Symptoms develop very fast, between 30 minutes and 2 hours after ingesting shellfish, depending on the amount of toxin ingested.

Symptoms of PSP poisoning include numbness and initially burning, or tingling of the lips and tongue that extends to the face and fingertips. This leads to a general lack of muscular coordination in the arms, legs and neck. In severe cases causes respiratory paralysis, which can lead to death if the patient respiratory support is not provided.


PSP toxin tolerance limits

The amount of PSP (paralytic toxin mollusc) in the edible parts of molluscs, or the entire body or any part edible separate toxin must not exceed 80 micrograms per hundred grams (Decree 116/1995 of 31 March the Ministry of Presidency and public Administration of the Junta de Galicia, by which control of biotoxins in bivalve molluscs and other organisms from fishing, shellfishing and aquaculture) is regulated.

Sample Type: bivalves, enough for 200 grams of fleshy body mass amount.


Preservation and shipment of sample:

Refrigerated (preferred) for less than 2 days.

Frozen: over 2 days.


Cost of the test: