The Only Locally-Owned Emergency and Specialty Hospital in Minnesota

Dangers of Blue-Green Algae

What is blue-green algae?
Blue-green algae (cyanobacteria) are photosynthetic bacteria that grow in the slow moving or stagnant waters of lakes, ponds, and wetlands. The bacteria are often called algae because of the way they look when clumped on water. Despite the name, algae can also range in color from olive green to red.

What is an algae bloom?
Blue-green algae grow rapidly during the warm months of summer. They thrive in areas of runoff where water is rich in nutrients. The microscopic bacteria are often blown around by the wind and accumulate along shore lines.  If accumulations are heavy enough, the algae can give the water a blue-green or “pea soup” appearance.  This is an algae bloom.

What are the health risks of blue-green algae?

Not all algae are toxic. However, it is not possible to determine if a bloom is toxic just by looking at it; water testing is required. Therefore, all blooms should be considered potentially toxic. As with any toxin, the extent of symptoms depends on the type of toxin and the level of exposure. Even a few sips of water containing blue-green algae toxin can cause a fatal toxicity. Some toxicities are so severe that dogs don’t even have time to make it to a veterinary hospital for treatment.

Blue green-algae can produce two types of toxins: hepatotoxins and neurotoxins.

  • Hepatotoxins (microcystins)
    • Can cause liver damage or even liver failure.
    • Symptoms may take 12-24 hours to develop.
    • Symptoms include anorexia, vomiting, diarrhea, dark or black stool, icterus/jaundice, disorientation, seizures, and death.
    • Rapid and aggressive veterinary care is needed to provide the dog with the best chance for survival.
  • Neurotoxins (anatoxins)
    • Can cause toxicity to the nervous system.
    • Symptoms are often seen within minutes to hours.
    • Symptoms include disorientation, weakness, inability to walk, muscle tremors, seizures, difficulty breathing, blue gums and sudden death.

What to do if your pet is exposed
If you think your pet has been exposed to blue-green algae, seek veterinary care immediately. There is no specific antidote, and patients who develop signs of toxicity have a poor prognosis.  However, early and aggressive veterinary care can improve the chance that the dog may survive.

As with any toxicity, prevention is best.  Avoid letting your pet swim in water with algae growth or discoloration. If your pet has contaminated fur after swimming, wash him off immediately. Seek veterinary attention immediately if your pet has exposure and is showing signs of toxicity.

If you have any questions about blue-green algae, we encourage you to talk with your family veterinarian. We hope you and your pets have a safe summer!


Subscribe to Blog via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.


  • This field is for validation purposes and should be left unchanged.
Font Resize
Oakdale St. Paul Text Us