Risks of Blue-green Algae To Dogs

Blue-green algae has killed dogs throughout the United States and Canada this summer. The algae is actually a cyanobacteria which is extremely toxic to humans and dogs. Cyanobacteria contain chlorophyll which is why the bacteria looks like a plant and is confused with algae.  Blue-green algae outbreaks occur in the summer. The combination of stagnant water and warm temperatures create the perfect condition for the cyanobacteria to grow. Toxic blooms float on the water’s surface. They can be blue, brown or red as well as green. Unfortunately, clear water does not mean the water is safe. As the cyanobacteria breaks down, it sinks to the bottom leaving clear water that is still toxic.

Clinical signs in animals, as well as humans, starts with vomiting, weakness, rash, eye irritation, coughing and diarrhea. It progresses quickly to collapse, muscle tremors, severe salivation and dilated pupils. Dogs are particularly susceptible to cyanobacteria because they swallow a lot of water when swimming and retrieving balls. Symptoms may start within minutes of exposure. Even with aggressive treatment, many animals will die because there are no specific antidotes for cyanobacteria. Treatment is supportive which means treating symptoms as they occur and also trying to neutralize the toxin. If your pet is exposed, seek veterinary attention right away. This is not something that can be treated at home.

Please avoid stagnant warm water whether it is clear or scummy. Before going to the lake, check with state officials for beach or lake closings for blue-green algae. If there are warnings for any part of the lake, avoid the lake all together. Better yet, hit the pool instead.


-Fiala, J. Veterinarians warn of toxic blue-green algae dangers: Cyanobacteria proliferate; dogs sickened, often fatally. Veterinary Information Network, August 16, 2019.

-Harmful algal blooms: Summertime in Minnesota: when in doubt, best keep out! Minnesota Department of Health, Pollution Control Agency, March 2017.