Blue-Green Algae: A Lurking Danger for Pets

Have you ever heard of cyanobacteria? You might know it by its common name: blue-green algae. This is an extremely dangerous algae that can be found in warm, nutrient-rich water, such as shallow areas of lakes and ponds. Cyanobacteria can make both people and pets very sick, and can even be fatal. It 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 goes over 75°F. Many local authorities and newscasts will put out alerts to let people know when a body of water has been contaminated, and some will post signs and/or close beaches. However, it can be easy to miss these updates. The EPA has a map available here with cyanobacteria resources for every state. This is definitely something you should check before taking Fido swimming.


Blue-green algae looks like pea soup or green paint. It often has a swampy odor. However, you can’t really go by a lake’s appearance or smell. Smaller blooms can still be dangerous, but they may not alter the look or scent of a lake or pond very much. It’s also worth noting that not all algae blooms are harmful. Either way, 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 dangerous. You don’t have to drink contaminated water to get sick: you can also become ill through skin contact or by just 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 our canine pals are particularly at risk, especially those that love to swim or splash around in water. Cyanobacteria can cause very serious neurological problems and/or liver failure, and can be fatal. Some warning signs include panting, respiratory problems, vomiting, diarrhea, dizziness/disorientation, seizures, and excessive drooling. If your pooch shows any of these red flags, call your veterinarian immediately.


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

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