Paralytic shellfish poisoning: Seafood safety and human health perspectives

Abstract

a b s t r a c tParalytic shellfish poisoning (PSP) is the foodborne illness associated with the consumption of seafood products contaminated with the neurotoxins known collectively as saxitoxins (STXs). This family of neurotoxins binds to voltage-gated sodium channels, thereby attenuating action potentials by preventing the passage of sodium ions across the membrane. Symptoms include tingling, numbness, headaches, weakness and difficulty breathing. Medical treatment is to provide respiratory support, without which the prognosis can be fatal. To protect human health, seafood harvesting bans are in effect when toxins exceed a safe action level (typically 80 mg STX eq 100 g À1 tissue). Though worldwide fatalities have occurred, successful management and monitoring programs have minimized PSP cases and associated deaths. Much is known about the toxin sources, primarily certain dinoflagellate species, and there is extensive information on toxin transfer to traditional vectors -filter-feeding molluscan bivalves. Non-traditional vectors, such as puffer fish and lobster, may also pose a risk. Rapid and reliable detection methods are critical for toxin monitoring in a wide range of matrices, and these methods must be appropriately validated for regulatory purposes. This paper highlights PSP seafood safety concerns, documented human cases, applied detection methods as well as monitoring and management strategies for preventing PSP-contaminated seafood products from entering the food supply.Published by Elsevier Ltd. Paralytic shellfish poisoning toxins and sourcesParalytic shellfish poisoning (PSP) is a common seafood toxicity problem with worldwide distribution, and typically this illness is due to the consumption of contaminated molluscan bivalves and other shellfish. A similar seafood-related syndrome involves puffer fish contaminated with the same family of toxins. To distinguish these puffer fish poisonings from those caused by tetrodotoxin, this food poisoning syndrome is becoming known in the literature as saxitoxin puffer fish poisoning (SPFP; Landsberg et al., 2006;Deeds et al., 2008a). The toxins responsible for both of these seafood-borne illnesses are the neurotoxins known collectively as the saxitoxins (STXs), also referred to as PSP toxins (or PSTs). At least 24 saxitoxin-like congeners have been identified (Fig. 1), with a range of hydroxyl, carbamyl, and sulfate moieties at four sites on the backbone structure. These substitutions result in congeners varying more than three orders of magnitude in potency (Oshima et al., 1993). The carbamate toxins are the most potent, and they include saxitoxin (STX), neosaxitoxin (NEO), and the gonyautoxins (GTX1-4). The decarbamoyl toxins (dcSTX, dcNEO, dcGTX1-4) have intermediate toxicity and are reported in certain bivalves, but are not commonly found in toxic dinoflagellates. The N-sulfocarbamoyl toxins (B1 [GTX5], B2 [GTX6] and C1-4) are less potent. There is a fourth group known as the deoxydecarbamoyl toxins, but their potency has not yet *

First report of the use of a saxitoxin–protein conjugate to develop a DNA aptamer to a small molecule toxin

“…One of the most harmful marine toxins, saxitoxin (STX) is primarily produced by several dinoflagellates as well as certain cyanobacteria (Deeds et al, 2008). Along with dozens of related congeners, STX makes up a suite of neurotoxins, which is referred to as paralytic shellfish toxins (PSTs) and are responsible for the human syndrome paralytic shellfish poisoning (PSP; Etheridge, 2010). Molluscan bivalves represent the major vectors of PSTs to humans given their capacity to filter feed and accumulate high concentrations of the toxins; however, numerous non-traditional vectors such as crabs, lobster, and carnivorous snails have also been identified (Deeds et al, 2008).…”

“…The longstanding regulatory method for testing overall PSP toxicity is the mouse bioassay (MBA, AOAC Official Method of Analysis [OMA] 959.08); however, it has received much criticism for ethical reasons as well as a host of other issues including poor specificity, high cost, and high variability (Etheridge, 2010). Thus, recent emphasis has been placed on developing screening assays for PSTs that could reduce animal usage and provide a means of rapid, high throughput testing.…”

Dinoflagellates: Ecological Approaches and Spatial Distributions in Malaysia Waters

“…Saxitoxins (STX) is the prototype of congeners mainly from Dinoflagellates and responsible of inducing PSP to human [45,46]. The congeners developed from the skeletal structure of 3,4,6-trialkyltetrahydropurine compound into carbamate, decarbamoyl, N-sulfocarbamoyl and hydroxybenzoate with each varied in their toxic potential [47].…”

“…Blocking of sodium conductance eventually generates symptoms of numbness, tingling sensation of the oral parts and nausea to the patient. The after affects took minutes to be expressed depending on the toxins concentrated within the shellfish [46].…”

“…Pyrodinium, Alexandrium and Gymnodinium are the three genus of Dinoflagellates affiliated to cause PSP worldwide [46]. In Sabah, PSP cases have been extensively reported since the first outbreak of Pyrodinium bahamense in 1976 [49].…”