Decryption. Toxic venom, rare presence... What are the physalia, which cause beach closures?

If you're going on vacation to the Southwest, be careful. Several beaches, particularly in Biarritz, Anglet, and Bidart, have been forced to close in recent days due to the presence of physalia . This marine animal, also known as the "sea bladder" or "Portuguese galley," possesses highly toxic venom.

Although their bluish appearance, with its purple and pink highlights, makes you want to touch them, it is better to avoid giving in to temptation: even when washed up on the beach , the physalia remain venomous.

Physalia are often confused with jellyfish . They have a purplish-blue vesicle 10 to 30 centimeters long, filled with gas, which serves as a "float" and allows them to stay on the surface of the water. A deceptive balloon appearance, because under this "float" are long and thin stinging tentacles with very toxic venom. It is these tentacles that allow physalia to feed. The majority of their diet consists of small and medium-sized fish, caught with the help of the tentacles, whose stinging cells paralyze them, indicate observation data for the recognition and identification of underwater fauna and flora ( Doris ).

"The problem with these physalia is that they have extremely long filaments, which can reach up to 20 or 30 meters, so people don't see them immediately. In addition, the floating part of the individual can look like a plastic bottle from a distance," Elvire Antajan, a zooplankton ecology researcher at Ifremer, explained to 20 Minutes in 2023. However, simple contact with these tentacles can trigger intense pain, skin welts and itching, and sometimes even a severe allergic reaction.

The venom of the "Portuguese galleys" is indeed composed of a mixture of toxic proteins. After contact, signs of severity may appear: nausea, vomiting, rapid pulse, chest and abdominal pain, difficulty breathing, muscle and joint pain, dizziness, or even fever, according to the Belgian Poison Control Center.

Severe allergic reactions and serious complications can sometimes occur. "When these symptoms appear, the swimmer should contact the local first aid station or call the Samu Centre 15," recommends the Bordeaux University Hospital , which notes, however, that "no deaths linked to this type of envenomation have been reported to date in France."

Physalia typically live in the warm waters of North America, Central America, or the western Pacific Ocean. However, currents or winds sometimes carry them close to European coasts. Their presence was first detected in metropolitan France in 2008, with the first mass envenomation: 40 victims reported in Biscarrosse (Landes). In 2010, 154 envenomations were reported in the Aquitaine region in three months, which forced the Aquitaine Regional Health Surveillance Institute and the Bordeaux Poison Control and Toxicology Monitoring Center to set up a monitoring system called PhysaTox.

In 2011, 885 cases of physalia poisoning were reported, the majority in the Landes region, according to the Bordeaux University Hospital. Then, there were no further cases between 2014 and 2017. They reappeared in 2023, "with around a hundred people poisoned" during the summer, according to the annual report on bathing water quality from the ARS Nouvelle-Aquitaine. In 2024, new problems with physalia were reported, particularly in Charente-Maritime.

In the event of contact with a physalia, the French Society of Emergency Medicine recommends removing the victim from the water, calming them, preventing them from rubbing themselves, and then removing any visible filaments with forceps or a double glove. The remaining cells should then be trapped with shaving foam or sand and allowed to dry before gently scraping with a stiff piece of cardboard or a credit card to remove any remaining cells. It is then recommended to rinse the skin with seawater, without rubbing.