Is blue-green algae poisonous to dogs?

Posted by justinelee in Animal Safety, Blog, Pet Health

If you let your dog jump in the water, please heed! If your dog is exposed to blue-green algae, it can be fatal… even with just a few licks. As the dog days of summer sadly come to an end, I wanted to write to warn you to be more discriminating about what lakes you let your dog swim in this summer.

Maybe I’m just a bit paranoid, but when it comes to swimming in lakes, you want to make sure to avoid ones that have that green scum layer on top of the lake. Why? It’s because during really hot summers and fall, there’s an increased likelihood of the lake developing a thick “bloom” of algae, which float on the surface of the lake. So, why do I worry about this as a toxicologist?

Because of blue-green algae.

Blue-green algae, which is called cyanobacteria, is a microscopic bacteria found in freshwater ponds, lakes, streams, and brackish water ecosystems. Note that not all types of algae are poisonous, but some types can produce toxins called microcystins and anatoxins. These toxins are so dangerous that they are actually poisonous to other species too: humans, cattle, horses, cats, etc. For this reason, you shouldn’t allow your dog (or child) to swim or drink water that has been potentially contaminated with blue-green algae.

While it’s impossible to be able to  tell if it’s benign or poisonous algae on the pond or lake, it’s best to heed caution and avoid allowing your dog to swim in any body of water that has visible algae on the surface. That’s because even small exposures (as little as 1-2 licks), can potentially result in fatal poisoning.

Signs of blue green algae:
Clinical signs of blue-green algae poisoning depend on what type of toxin (e.g., microcystin vs. anatoxin) is present. Clinical signs typically include:

With the blue-green algae that produce microcystins, symptoms include:

• Malaise/lethargy
• Weakness
• Not eating
• Vomiting
• Diarrhea
• Black-tarry stool
• Collapse
• Pale gums
• Jaundice (yellow) gums
• Shock
• Seizures
• Death

With the blue-green algae that produce anatoxins, symptoms include:

• Inability to walk
• Hypersalivating
• Excessive (eye) tearing
• Tremors
• Muscle rigidity
• Difficulty breathing or blue gums
• Death

How do you prevent blue-green algae poisoning in dogs?
The best way to prevent blue-green algae poisoning? Stomp around the lake first before you let your dog dive in, and make sure to avoid it if it has blooms of algae floating on the surface.

The last saddest case that I treated? A dog that had never been out to a lake. But he ended up dying of liver failure. The cause? The owners left a used, old empty fish tank out on the deck. Over months, it accumulated rain water. One day, the dog drank out of this moldy, algae-filled tank, and unfortunately was accidentally poisoned by blue-green algae this way.

When in doubt, whether you’re at the lake or not, make sure your dog always has a bowl of fresh water available so he or she isn’t tempted to drink from contaminated sources.

What’s the prognosis if my dog gets into blue-green algae?
Unfortunately, with blue-green algae, the prognosis is very poor, and some dogs actually pass away before being able to get to a veterinarian. For this reason, if you suspect that your dog was exposed to blue-green algae, get to a veterinarian immediately. Unfortunately, there is no antidote for the toxins produced by blue-green algae.

With any poisoning, the sooner you seek treatment the better the prognosis. With blue-green algae, immediate veterinary attention is important. When in doubt, you can always call your veterinarian, emergency veterinarian, or ASPCA Animal Poison Control Center for life-saving care at 888-426-4435.