Pet Safety Alert – Blue-Green Algae

Pet Safety Alert – Blue-Green Algae

By Don Hanson, PCBC-A, BFRAP

< A version of this article was published in the AUG25 issue of Downeast Dog News>

< A version of this article was published on Pets and Their People on August 31, 2025 >

< Updated 2025-09-01 >

< The link for this page – https://forcefreepets.com/PetSafetyAlert-BlueGreenAlgae/ >

Blue-green algae, also known as cyanobacteria, are naturally found in most freshwater bodies in the United States. When it rapidly accumulates or “blooms,” it can release neurotoxins and liver toxins that, if ingested, can cause extreme illness and even death. Blue-green algae are most likely to appear in freshwater when the water temperature is above 75°F. The toxins may concentrate near shorelines where animals might drink or swim. Even a small amount of these substances can lead to death in a few hours for a small animal like a dog. Blue-green algae appeared as number 9 on the ASPCA Animal Poison Control Center’s top 10 list of deadliest pet toxins in 2024.

Not everything green in the water is blue-green algae. Typically, blue-green algae are bright green or bluish green in color.. Some describe them as looking like neon green pea soup or paint. They may appear as a large scummy or slimy mass on the water’s surface or be localized in small spots. The water may smell foul or swampy. This graphic in a CDC media kit illustrates what blue-green algae may look like.

In some states, government agencies and private lake associations may monitor blue-green algae blooms. However, warning signs are not always posted, and if one is not present, please do not assume the water is safe. If there is any doubt, stay out of the water!

Symptoms of blue-green algae poisoning include diarrhea, disorientation, excessive drooling, liver failure, panting, respiratory failure, seizures, vomiting, weakness, and death. Symptoms may develop within a few minutes to 12 hours after exposure. If there is any possibility that your dog has been exposed to blue-green algae, please get them to a veterinarian immediately. Their life depends on it.

Recommended Resources

• Algal Blooms in Maine Lakes – https://www.maine.gov/dep/water/lakes/algalbloom.html
• ASPCA Blue-Green Algae Toxicosis: What You Need to Know to Keep Your Pet Safe – https://www.aspca.org/news/blue-green-algae-toxicosis-what-you-need-know-keep-your-pet-safe
• CDC Harmful Algal Blooms: Social Media Toolkit – https://www.cdc.gov/harmful-algal-blooms/toolkit-socialmedia/index.html
• Harmful Algal Blooms (HABs) in Water Bodies – https://www.epa.gov/habs
• Harmful Algal Bloom (HAB)-Associated Illness – https://www.cdc.gov/harmful-algal-blooms/about/index.html
• Preventing Pet and Livestock Illnesses Caused by Harmful Algal Blooms – https://www.cdc.gov/harmful-algal-blooms/prevention/preventing-pet-and-livestock-illnesses.html