If you have dogs that love water, beware: Dogs visiting rivers, lakes, ponds and marshes, both freshwater and saltwater, are increasingly being exposed to blue-green algae. It’s an aquatic plant that produces toxins that can kill a dog within an hour! It recently happened to one dog owner in North Carolina who took her three dogs to a pond to play and cool off, and watched ALL of them die within hours. And cases of dog algae deaths have also been reported in Georgia and Texas.

Blue-green algae contains toxins that can trigger liver and brain damage and respiratory paralysis. It’s dangerous to humans, but dogs are especially at risk, because they drink the water, and lick their wet fur.

Blue-green algae tends to thrive in hot weather, and can range from bright blue-green to reddish-brown. It can look like a film, scum, streaks, grass-clippings, green cottage cheese or puff-balls on the water or shoreline. Contaminated water is usually murky, and smells bad. But veterinary toxicologist Dr. David Dorman says you can’t always spot contaminated water, because wind can clear algae away, leaving safe-looking, but still-toxic water behind. To protect your pets:

Check local news websites for algae advisories before visiting water areas.

And if your dog gets into toxic water, rinse them off immediately, and seek medical attention. If they haven’t ingested too much toxic algae, a vet might be able to save their life.