Cyanobacteria blooms in French rivers cause dog deaths, authorities urge caution

The association Cyanobacteries alertes warned that a massive cyanobacteria bloom has spread downstream from Chazey‑sur‑Ain to the confluence of the Ain and Rhône rivers. The alert notes several recent dog fatalities after exposure, including a death in Vaison‑la‑Romaine on 28 July following a swim in the Ouvèze, and other cases reported in Isère, the Rhône department and the Pyrénées, all suspected to involve cyanobacterial toxins.

Cyanobacteria proliferate in warm, stagnant freshwater and can produce anatoxins dangerous to humans and animals. Authorities advise avoiding water that appears green or blue‑green, shows surface foam, or emits a musty odor. Dog owners should keep pets away from such water, prevent them from drinking, bathe only in supervised zones, and obey posted warnings. Local officials may impose temporary bans on swimming, water sports or fishing when toxin levels rise.