Emerging marine biotoxins detected in shellfish in France
Brevetoxins (BTX) are marine toxins that augment the transmission of nerve impulses. They can be responsible for neurotoxic shellfish poisoning (NSP) if contaminated shellfish are ingested. This poisoning causes neurological, gastrointestinal and/or cardiovascular symptoms. The most commonly observed symptoms in benign cases are tingling and numbness of the face and extremities. No human deaths related to these toxins have been reported worldwide to date. However, their toxicity to marine fauna is known and can lead to episodes of mass mortality in fish, sea birds, turtles and marine mammals, mainly in the Gulf of Mexico.
BTX are not currently regulated in France or in Europe, where they are considered emerging toxins. However, they pose a proven risk in Florida in particular, as well as in Australia, New Zealand and Mexico, where they have been regulated for many years.
After being added to the work programme of the French network for monitoring the emergence of marine biotoxins in shellfish (EMERGTOX) in 2018, BTX were detected for the first time in France the same year in mussels from a lagoon in Corsica. ANSES was then asked by the Directorate General for Food (DGAL) and the Directorate General for Health (DGS) to propose a guideline value aiming to protect the health of consumers of shellfish (mussels, oysters, etc.).
Based on data from cases of food poisoning having occurred in other countries, ANSES identified minimum doses of brevetoxins associated with symptoms. This work has led the Agency to propose a guideline value of 180 µg/kg of shellfish flesh, expressed in BTX-3 equivalents, with BTX-3 being the form of brevetoxin used as the reference.
The species of BTX-producing microalga in Corsica is not currently known
The origin of this emergence in France is not known to date and should be specifically investigated.
BTX are produced by marine microalgae. The main producer is the Karenia brevis dinoflagellate, which has not been detected by the monitoring network for phytoplankton and phycotoxins (REPHY) in water in metropolitan France.
Other microalgae are also suspected of producing BTX; these include K. papilionacea, K. mikimotoi, K. bicuneiformis, Chattonella marina, Heterosigma akashiwo and Fibrocapsa japonica. While several of them have been found in water in metropolitan France – some since 1987 – their production of BTX has not been confirmed.
Additional work to understand exposure to BTX by skin contact and by inhalation
ANSES continues to undertake expert appraisal work on exposure to BTX via direct contact with contaminated water, associated in particular with swimming, other water activities and inhalation of sea spray. The results will be available at the end of 2021.
A reporting form has also been developed for the poison control centres in the toxicovigilance network to record cases of poisoning associated with the consumption of shellfish contaminated by marine toxins such as brevetoxins. This form will facilitate the identification of poisoning cases and lead to a more precise estimate of the level of health concern related to brevetoxins in France.