Category Archives: Brevetoxin

Hong Kong – Food Safety Bulletin 95th Issue

Posted on January 18, 2024 by | Leave a comment

CFS

Feature Article

Shellfish Poisoning

The Centre for Food Safety (CFS) received in April 2023 a referral from the Centre for Health Protection of a suspected case of diarrhoetic shellfish poisoning in which the affected persons developed diarrhoea, nausea, vomiting and abdominal pain within an hour after consuming venus clams at a restaurant.  This article gives a brief introduction on shellfish poisoning.

What is Shellfish Poisoning?

Shellfish poisoning is caused by shellfish toxins produced by certain species of algae.  When shellfish eat toxin-producing algae, the toxins can accumulate in their tissue.  Consumption of shellfish containing shellfish toxins by humans can cause a variety of gastrointestinal and neurological illnesses, known as shellfish poisoning.  Examples of shellfish that have been involved in shellfish poisoning include mussels, clams, oysters, scallops and geoducks.

Numerous shellfish toxins have been discovered around the world; they could cause different types of shellfish poisoning.  Five major types of shellfish poisoning are discussed below:

(i) Paralytic shellfish poisoning (PSP) — caused by paralytic shellfish toxins (PSTs), which are a group of water-soluble alkaloid neurotoxins, including saxitoxins (STXs).

(ii) Diarrhoetic shellfish poisoning (DSP) — caused by diarrhoetic shellfish toxins (DSTs), which are a group of lipid-soluble polyether toxins, including okadaic acid (OA).

(iii) Neurotoxic shellfish poisoning (NSP) — caused by neurotoxic shellfish toxins (NSTs), which are a group of lipid-soluble polyether toxins, including brevetoxins (BTXs).

(iv) Amnesic shellfish poisoning (ASP) — caused by amnesic shellfish toxins (ASTs), including the water-soluble amino acid domoic acid (DA).

(v) Azaspiracid shellfish poisoning (AZP) — caused by azaspiracid shellfish toxins (AZTs), including the lipid-soluble toxin azaspiracid (AZA).

Characteristics of Shellfish Toxins

Different groups of shellfish toxins display multifarious chemical structures, which can be broadly classified into amino acids (DA), alkaloids (STXs) and polyketides (OA, BTXs and AZA).

The reasons why some algae produce shellfish toxins remain unknown.  These toxins are secondary metabolites with no explicit function for the algae.  They are probably used by the algae to compete for space, defence against predators or prevent the overgrowth of other organisms.

In general, shellfish toxins are heat stable, odourless, tasteless and not destroyed by cooking, freezing or other food preparation procedures.  It is hard to distinguish between toxic and non-toxic shellfish visually.

Bioaccumulation of Shellfish Toxins in Bivalve Molluscs

Algae are part of the natural diet of bivalve molluscs.  After shellfish has ingested shellfish toxin-producing algae, shellfish toxins will accumulate and concentrate in their internal organs, such as hepatopancreas of bivalves (Figure 1).  Generally speaking, the adductor muscle contains only a low level of shellfish toxins.

Figure 1: Internal parts of a scallop

Symptoms of Shellfish Poisoning

Shellfish toxins can cause a wide variety of symptoms in humans, depending on the type and amount of toxins ingested.  Symptoms of different types of shellfish poisoning are summarised below:

Safety Levels of Shellfish Toxins

The toxicity of various shellfish toxins was evaluated by a joint expert working group of the Food and Agriculture Organization of the United Nations (FAO), the World Health Organization (WHO) and the Intergovernmental Oceanographic Commission of UNESCO in 2004.  Acute reference doses (ARfDs) (i.e. the amount of toxins that can be ingested in a period of 24 hours or less without appreciable health risk) have been established for these shellfish toxins.  In addition, the Codex Alimentarius Commission (Codex) has established the maximum levels (MLs) for shellfish toxins in edible parts (the whole or any part intended to be eaten separately) of live bivalve molluscs.  While the ARfDs are critical in assessing the safety of food in terms of the level of shellfish toxins contained, Codex MLs are the levels recommended by Codex to be permitted in shellfish.

*An estimate of toxicity of the toxin made by mouse bioassay.

Key Points to Note

  • Shellfish toxins are heat stable, odourless, tasteless and not destroyed by cooking, freezing or other food preparation procedures.
  • It is hard to distinguish between toxic and non-toxic shellfish visually.
  • In general, shellfish toxins accumulate and concentrate in the internal organs of bivalves. 

Advice to Consumers 

  • Purchase shellfish from reliable sources.
  • To reduce the health risk of shellfish poisoning, remove and discard all internal organs of shellfish where possible before consumption.
  • Seek medical attention immediately if you feel ill after eating shellfish.

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Posted in Amnesic Shellfish Poisoning, ASP, Azaspiracid Toxin, Brevetoxin, Diarrhoeic Shellfish Poisoning, DOMOIC ACID, DSP, Neurotoxic Shellfish Poisoning, NSP, okadaic acid, paralytic shellfish poisoning, PSP, Saxitoxin, Shellfish, shellfish toxin

Research – ANSES sets value to protect people from emerging toxin in shellfish

Posted on May 13, 2021 by | Leave a comment

Food Safety News

A French agency has proposed a guideline value to protect consumers of shellfish from a group of marine biotoxins.

The French Agency for Food, Environmental and Occupational Health and Safety (ANSES) said brevetoxins (BTX) were first detected in mussels in Corsica in 2018. If ingested by humans, these toxins can cause neurological, gastrointestinal or cardiovascular symptoms.

After this finding a few years ago, ANSES was asked by the Directorate General for Food (DGAL) and Directorate General for Health (DGS) to propose a guideline value to protect the health of people who eat shellfish. The agency has published an opinion and report on the subject in French.

Based on reports of food poisoning in other countries, ANSES has set a guideline value to protect consumers of products such as oysters and mussels. This value is 180 µg/kg of shellfish flesh, expressed in BTX-3 equivalents, with BTX-3 being the form of brevetoxin used as the reference.

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Posted in Algal Toxin, Biotoxin, Brevetoxin, BTX, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Toxin, microbial contamination, Microbiological Risk Assessment, Microbiology, Research, shellfish toxin

USA – Red tide in Southwest Florida – Karenia brevis

Posted on August 9, 2018 by | Leave a comment

File:Karenia brevis.jpgOutbreak News Today 

In an update on the red tide in Southwest Florida, the Fish and Wildlife Conservation Commission says bloom of the Florida red tide organism, Karenia brevis, persists in the area.

Fish kills have been reported over the past week in multiple locations in Manatee County, in Sarasota County, in Charlotte County, in Lee County, and in and offshore of Collier County.

Respiratory irritation was reported over the past week in numerous places along Florida’s west coast.

The National Ocean Service says while many people call these blooms ‘red tides,’ scientists prefer the term harmful algal bloom. One of the best known HABs in the nation occurs nearly every summer along Florida’s Gulf Coast. Red tides have been documented along Florida’s gulf coast since the 1840’s.

This bloom, like many HABs, is caused by microscopic algae that produce toxins that kill fish and make shellfish dangerous to eat. The toxins may also make the surrounding air difficult to breathe. As the name suggests, the bloom of algae often turns the water red.

Karenia brevis was named for Dr. Karen A. Steidinger in 2001, and was previously known as Gymnodinium breve and Ptychodiscus brevis. Karenia brevis is a marine dinoflagellate common in Gulf of Mexico waters, and is the organism responsible for the “tides” (coastal infestations) termed red tides that affect Gulf coasts—of Florida and Texas in the U.S., and nearby coasts of Mexico. It is the source organism for various toxins found present during such “tides”, including the eponymously named brevetoxins.

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Posted in Algal Toxin, Brevetoxin, Karenia brevis, Toxin, Uncategorized

Research – Marine Toxins: 5 Poisons Under the Sea

Posted on March 15, 2018 by | Leave a comment

Pharmacytimes 

Marine toxins originate from microorganisms native to aquatic ecosystems. These molecules eventually find their way into the human gastrointestinal tract through concentrating and bioaccumulating in species such as mollusks, crustaceans, and various fish. Ingestion of marine toxins can generate foodborne illnesses and a constellation of neurologic and gastrointestinal manifestations accompanied by other symptoms.

Ciguatoxin

Ciguatera illness is caused by ciguatoxins, which are compounds that bioaccumulate in shallow, coastal water-dwelling fish.

Saxitoxin

Paralytic shellfish poisoning (PSP) is a foodborne illness brought on by saxitoxin, a chemical compound produced by cyanobacteria of freshwater and by dinoflagellates of marine water. As with ciguatoxin, saxitoxin reaches the human gastrointestinal tract through concentration in species that are higher up in the food chain.

Brevetoxin

Also a result of toxic algal blooms and mollusk consumption, neurotoxic shellfish poisoning (NSP) is thought of as a ‘milder’ case of the paralytic shellfish poisoning described above. Its cause is brevetoxin, a group of more than 10 lipid soluble polyether compounds.

Tetrodotoxin

Tetrodotoxin (TTX) is perhaps the most well known of the marine toxins. Its notoriety arises from the popularity of pufferfish.

Histamine

A red herring in the recognition of fish food poisoning is scombroid syndrome. This illness is commonly mistaken for fish allergy, but instead results from improper storage and transportation of fish belonging to the Scombroidiae family.

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Posted in Algal Toxin, Brevetoxin, Ciguatera, Ciguatera Poisoning, Histamine, Saitoxin, Tetrodotoxin, Uncategorized