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Blue-Green Algae: A Lurking Danger to Pets
July 1, 2021

Do you know what cyanobacteria is? You may have heard of it under its common name: blue-green algae. This is an extremely dangerous algae that typically thrives in shallow, warm, nutrient-rich water. It can grow rapidly, or bloom, under the right conditions. Unfortunately, these blooms are becoming much more common. A veterinarian discusses cyanobacteria below.

 Warning Signs

Blue-green algae blooms will most often occur in summer and early fall, but they can happen anytime that average water temperatures are over 75°F. Many local authorities and newscasts will alert people when a body of water has been contaminated, and some will close lake access or post signs. However, it can be easy to miss these updates. The EPA has a map here with cyanobacteria resources for every state. (Click here for Florida’s.) This is definitely something you want to check before taking Fido swimming, especially if you’re in a strange place.


As mentioned above, blue-green algae is extremely toxic. 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 can happen when swimming, boating, or tubing. Cyanobacteria can also stick to pets’ fur, where they can later lick it off.


Cyanobacteria blooms look like pond scum, and may resemble pea soup or green paint. It can cause a swampy, musty odor. However, you can’t judge by appearance alone. Smaller blooms can still be 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 to swim in. Err on the side of caution here: if in doubt, just stay out! (This is also a good rule of thumb around these parts, even when there are no algae blooms, because of gators.)


Blue-green algae can make any pet sick, and also is a threat to wildlife. As far as pets go, dogs are particularly at risk, especially those that love to swim or splash around in water. Blue-green algae can cause very serious neurological problems and/or liver failure, which can be fatal. Warning signs can come on very rapidly. These include panting, respiratory problems, vomiting, diarrhea, dizziness/disorientation, seizures, and excessive drooling. If your pet shows any of these, contact your veterinarian or an emergency clinic immediately.


As always, prevention is worth much more than cure. Be very careful when choosing Fido’s swimming holes. Finally, don’t let him drink from lakes or ponds, especially ones with blue-green scum. 

Do you have questions about pet care? Contact us, your animal clinic, today!