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Blue-Green Algae: A Lurking Danger to Pets

June 15, 2021

Have you heard of cyanobacteria? Commonly known as blue-green algae, this is an extremely dangerous type of algae that can be found in warm, nutrient-rich water. Cyanobacteria can make both people and pets very sick. Unfortunately, it can even be fatal. The algae can grow rapidly, or bloom, under the right conditions. Unfortunately, blue-green algae blooms are becoming much more common. A veterinarian discusses cyanobacteria below.

Warning Signs

Blue-green algae blooms usually occur in summer and early fall, but they can happen anytime the water temperature is above 75°F. Many times, local authorities and newscasts will alert people when a body of water has been discovered to be contaminated, and some post signs. However, it can be quite easy to miss these updates. The EPA has put up a map here, with links to cyanobacteria resources for every state. This is definitely something you want to check before taking Fido swimming, especially if you are traveling outside of your local area.


Blue-green algae looks like pea soup or green paint. It can sometimes cause a swampy odor. Keep in mind that smaller blooms are still very dangerous, but they may not alter the look (or smell) of a lake or pond very much. It’s also worth noting that, while not all algae blooms are harmful, you can’t tell by looking at a lake whether it is or isn’t safe. Err on the side of caution here: if there’s any doubt, just stay out!


As mentioned above, blue-green algae is extremely toxic to both you and your pup. You don’t have to drink contaminated water to get sick: you can also become ill through skin contact or by breathing in water droplets or vapors. This sometimes happens when people go swimming, boating, or tubing in afflicted lakes. Cyanobacteria can also stick to pets’ fur, where they can later lick it off.


Blue-green algae can make any pet sick. It’s also a threat to wildlife. Dogs are particularly at risk, though, especially those that love to swim or splash around in water. Blue-green algae can cause very serious and potentially-fatal issues, including neurological problems and/or liver failure. Warning signs include panting, respiratory problems, vomiting, diarrhea, dizziness/disorientation, seizures, and excessive drooling. If your furry friend shows any of these warning signs, call your veterinarian immediately.


As always, an ounce of prevention is worth several tons of cure here. Be very careful when choosing Fido’s swimming holes. Don’t let your pooch drink from lakes or ponds, especially ones with blue-green scum.

Do you have questions about pet care? Contact us, your animal hospital in Peterborough, ON, today!