Shellfish Harvesting Halted Amidst Toxin Threat

authorities have issued urgent bans on shellfish harvesting and sales across a wide swathe of France’s western coastline, stretching from Vendée to Finistère. This action comes in response to a rapid proliferation of toxic algae, posing a significant health risk to consumers. The timing is particularly concerning, coinciding with exceptionally high tides that typically draw large numbers of recreational fishermen to the shores.

Widespread Bans Implemented

The prefecture of Loire-Atlantique was among the first to act, issuing a blanket prohibition on all shellfish-related activities within the department. This includes fishing, collecting, transporting, storing, and marketing shellfish intended for human consumption, applying to both commercial and recreational activities. Similar restrictions are now in effect in specific areas of neighboring departments, including the Baie de Bourgneuf, the western coast of Noirmoutier Island, and Yeu Island in Vendée, as well as the Baie de Plouharnel, Rivière d’Etel, Rade de Lorient, and Belle-Ile in Morbihan. The southern coast of Finistère, notably the bays of Concarneau and Douarnenez, is also affected.

The Culprit: pseudo-nitzschia australis

The source of the problem is a surge in the population of the micro-algae pseudo-nitzschia australis. This particular species produces domoic acid, a potent neurotoxin known to cause Amnesic Shellfish Poisoning (ASP).

This prohibition follows the rapid and significant proliferation of the pseudo-nitzschia Australis alga which produces amnesiating toxin (…) capable of causing potentially serious neurological disorders in the consumer of shellfish.

Health Risks and Symptoms of ASP

Consuming shellfish contaminated with domoic acid can lead to severe health consequences. Initial symptoms often include gastrointestinal distress,followed by a range of neurological disorders. These can manifest as disorientation, confusion, memory loss, and in severe cases, convulsions, coma, and even death. Symptoms can appear anywhere from 15 minutes to 48 hours after ingestion. Crucially, the toxins produced by Pseudo-nitzschia australis are resistant to cooking, meaning that customary planning methods offer no protection.

The severity of ASP can vary greatly depending on the amount of toxin ingested and the individual’s sensitivity. Vulnerable populations, such as the elderly and those with pre-existing neurological conditions, are at higher risk of experiencing severe complications.

Amnesic Shellfish Poisoning: A Past Outlook

ASP first came to global attention in 1987 following a major outbreak in canada. The incident involved over 150 reported cases linked to contaminated mussels, resulting in 19 hospitalizations and four fatalities. This tragic event underscored the potential dangers of domoic acid and led to increased monitoring efforts worldwide.

Called ASP (Amnesic Shellfish Poisoning), the disease caused by this micro-alga had been highlighted in 1987 in Canada, after a massive episode of 150 cases, including 19 hospitalizations and four dead, following the ingestion of contaminated molds.

Understanding Algal Blooms: Environmental Factors

According to experts, blooms of Pseudo-nitzschia and other harmful algae are often triggered by a combination of factors. These include rising water temperatures, increased sunlight, and an abundance of nutrients in the water.Springtime conditions, with their warming temperatures and increased daylight, are particularly conducive to algal growth. Moreover, nutrient runoff from agricultural fertilizers can exacerbate the problem, providing additional fuel for algal proliferation.

While the link between climate change and algal blooms is an area of ongoing research, some scientists believe that changing ocean conditions could contribute to the frequency and intensity of these events in the future. However, long-term trends are still being investigated.

These micro-algae proliferate in spring with the increase in temperature and sunshine…just after winter, seawater is naturally quite rich in nutrients.

Call for Caution During High Tide Season

With exceptionally high tides expected over the coming days, authorities are urging recreational fishermen to exercise extreme caution.The tidal coefficients, reaching as high as 114, create ideal conditions for shoreline foraging, but also increase the risk of exposure to contaminated shellfish. The public is strongly advised to consult official websites for the latest information on prohibited areas and safety guidelines.