Dog Safety: The Dangers of Blue-Green Algae Poisoning

Heading to a lake or pond this summer? Beware of this type of algae that can be toxic to dogs.

by Sheila Pell
June 1, 2021
Black Lab playing in creek
Brandon Herrell // Stocksy

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Blue-green algae and the dangers it poses for dogs are back in the news: Recently, three dogs died in Washington state after swimming in a river allegedly contaminated by blue-green algae. 

While most algae are harmless, some species of blue-green algae produce toxins that can kill a dog within minutes. Dogs that survive (who are often exposed to low levels of toxins) may develop health problems such as chronic liver disease and possibly tumors—damage that may go unnoticed until it’s severe. 

Researchers suspect many deaths are missed because people don’t even realize their dogs were exposed. Vets may not recognize the symptoms, and tests to detect the toxins can be costly and complex. (Blue-green algae can be harmful to humans, too, but deaths are rare.) 

In recent years, cases of blue-green algae poisoning in dogs have surged due to nutrients like phosphorous and nitrogen being washed into waterways from agriculture, lawns, and other sources. Climate change also plays a role. Below, learn how to keep your dog safe from blue-green algae this summer.

How to Spot Blue-Green Algae

Also known as cyanobacteria, blue-green algae thrives in fresh bodies of water during warm weather. There are plenty of ways to differentiate blue-green algae from harmless green, brown, and other kinds of algae. 

For one thing, its color isn’t always blue-green. It can also be reddish-purple or brown, and other hues. Normally, algae are equally distributed throughout the water. But blue-green algae produces large blooms that are often concentrated along the water’s edge (it may look like slimy paint). These can still taint the water after it looks clear. Blooms may last for a week; their toxins may last three weeks.

Even when blue-green algae isn’t floating on the surface, it may lurk below, moving up and down with available light and nutrients. At night, it often floats to the top, forming a scum. 

Wind and waves can then concentrate toxic blooms in shallow areas or at the water’s edge—right where dogs like to splash, wade or drink. The water doesn’t taste bad, vets say, so dogs will lap it up. Some like to gobble down dried algae mats.

How to Protect Your Dog from Blue Green Algae 

The Environmental Protection Agency recommends that outings with pets to lakes, rivers and streams include an algae check. Dogs should not drink, swim or wade in water that is discolored, smells bad, or where there are mats of algae, foam or scum.
If your dog does get into scummy water, rinse them off with tap water immediately, making sure they don’t lick algae from their fur. The toxins can also be absorbed through their skin. If a dog shows signs of poisoning, seek veterinary treatment right away. 

Here are the signs of blue-green algae poisoning to lookout for: 

  • Vomiting

  • Diarrhea

  • Weakness or staggering

  • Difficulty breathing

  • Drooling

  • Convulsions 

Finally, be sure to report any blue-algae incidents to your state’s Public Health Department to prevent other dogs from getting sick.

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Sheila Pell

Sheila Pell is a freelance journalist who frequently writes about environmental issues. Her work has appeared in The Washington Post, Modern Farmer, San Diego Reader, The Bark, and American Forests. She lives in northern California with her husband and two large dogs.