Tuesday, February 27

Marine biotoxins: how they reach shellfish and how serious they are

The marine biotoxins they are natural chemicals caused by various species of microscopic algae, collectively defined as phytoplankton. Specifically, they are dinoflagellate algae, plant cells capable of moving in the water thanks to a flagellum. Normally, their concentrations are too low to be harmful, but under favorable environmental conditions, they form in large quantities and are toxic.

These algae proliferate above all when a combination of warm temperatures, sunlight, and nutrient-rich waterswhich has favored in recent years the accumulation of toxins from marine algae in marine organisms for consumption.

This gives rise to different conditions and degrees of intoxication, depending on the nature of the toxin that has been consumed, its concentration and the characteristics of the consumer. The proliferation of algae colors the water, almost always red, which multiply and give name to what is known as red tidessmall algae that reproduce in a very generalized way until they cover the entire surface of the water.

Marine biotoxins: what foods are they found in?

The toxins can be transmitted through the consumption of products that contain them. The foods most at risk of being contaminated by marine biotoxins are filter-feeding marine organisms, such as bivalve molluscs (clams, mussels, oysters, and scallops), gastropods, and crustaceans.

This is so because bivalve molluscs are very sensitive to the quality of the water in their marine environment. Because they feed by filtering microscopic organisms from the water, harmful bacteria, viruses, and marine biotoxins from their environment can accumulate in their tissues and cause illness in people who consume them.

The lobsters and crabs They can also accumulate marine biotoxins by feeding on bivalve molluscs that are contaminated. None of these filter feeder fish and shellfish are affected by these substances.

How marine biotoxins affect us

Marine biotoxins, in low concentrations, do not produce harmful effects. However, in large amounts they are harmful to humans and can cause severe symptoms. The most common toxins are:

  • Amnesic toxins (ASP): Cause shellfish amnesia with nausea, abdominal cramps, short-term amnesia, dizziness, or headaches.
  • paralyzing toxins (PSP): cause paralysis, tingling or numbness, temporary blindness, motor weakness, motor incoordination, nausea, vomiting, diarrhea or respiratory distress.
  • Neurotoxic toxins (NSP): cause neurotoxicity in the form of reduced respiratory rate, decreased body temperature, chills, sweating, tingling, vomiting, diarrhea, cramps, etc.
  • Azaspiracids (AZA): cause a characteristic intoxication with nausea, severe diarrhoea, vomiting and stomach cramps.

Dinoflagellates can also be the cause of ciguatera poisoning, which is caused by the consumption of reef fish that feed on microalgae and usually causes vomiting, nausea, localized itching, tingling of the lips and extremities, weakness, cramps, diarrhoea, breathing difficulties or joint pain. The toxin is heat stable. Tropical species that feed on dinoflagellates are prohibited in the European Union.

As we have already mentioned, the symptoms will vary depending on the biotoxin and its concentration, although in most cases the most common are diarrheal, neurotoxic, paralytic and anamnestic.

European regulations (European Regulation 853/2004) requires the destruction of any fishery product that is contaminated with marine biotoxins due to their toxicity. For AZA group toxins, for example, it sets a limit of 160 micrograms of eq. AZA/kg.

The European Food Safety Authority (EFSA) established in 2009 a Acute Reference Dose (ARfD) for some biotoxins, which is the maximum amount of biotoxin in a food that can be eaten in 24 hours or less without risk to people.

A year later, in 2010, he evaluated the exposure to biotoxins through the consumption of shellfish taking into account the reference doses, and concluded that the limits for some types were safe, but for others such as AZA or PST they might not be safe. case of excessive consumption of shellfish.

How can we protect ourselves from marine biotoxins?

It is important to remember that all of these toxins are heat stable, that is, cooking does not destroy them, unlike what happens with other contaminants. Therefore, it is very important to avoid eating animals that may contain this toxin.

As warned by the Basque Foundation for Food Safety, Elika, the biotoxins that accumulate in shellfish and fish cannot be eliminated. The key is to buy shellfish that come from establishments that assure us that they have been harvested in authorized farming areas.

It is also advisable to maintain the cold chain during the transport of raw foods, as well as to follow good hygiene practices to avoid contamination by other biological agents such as bacteria and viruses.

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