Blue-Green Algae: A Lurking Danger for Pets

Have you heard of cyanobacteria? You may know it by its common name: blue-green algae. This is an extremely dangerous algae that typically lives in warm, nutrient-rich water. Cyanobacteria can make both people and pets very sick. 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 most often occur in summer and early fall, but they can happen anytime the water temperature goes over 75°F. Many local authorities and newscasts will alert people when a body of water has been contaminated, and some post signs. However, it can be easy to miss these updates. The EPA has a map here with cyanobacteria resources for every state. This is definitely something you want to check before taking Fido swimming!


Blue-green algae typically looks like pea soup or green paint. It can also cause a swampy 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. Err on the side of caution here: if in doubt, just stay out!


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.


Blue-green algae can make any pet sick, but 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, and can be fatal. Warning signs include panting, respiratory problems, vomiting, diarrhea, dizziness/disorientation, seizures, and excessive drooling. If your pet shows any of these warning signs, call your veterinarian immediately.


As always, prevention is worth much more than cure. Be very careful when choosing Fido’s swimming holes, and 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 in Powdersville, SC, today!

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