The Toxic Effects of Pond Algae on Your Dog's Health

Updated: September 14, 2015
Published: October 31, 2013
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The pond at my local dog park has just been drained for the season… a few weeks earlier than normal. The reason behind the closure was an impressive algal bloom that developed, I suspect, as a result of a summer’s worth of heavy use and warmer than normal fall temperatures.

Let’s face it. Dogs don’t have the best understanding of what constitutes proper sanitation. During my times at the park, I’ve seen dogs urinating and defecating directly in the pond where even the best intentioned owners are unable to clean up. Add those incidents to the contaminated runoff from the areas where unobservant owners (I’m giving them the benefit of the doubt) leave their dogs’ piles, and the nutrient content of that water had to be impressive. Mix in some sunny days and warm temperatures and it was algae city.

The type of algae that grew was especially disturbing. It was non-filamentous; in other words, not the slimy gunk that grows in so many relatively still bodies of fresh water that you can pick up with a stick. This stuff looked like a layer of paint floating on the surface of the water and was a bright, artificial looking green color. This fits the description of some types of potentially deadly blue-green algae blooms (other colors are also possible, including blue-tinged, brown, and a combination of red and green).

Not all types of blue green algae (or cyanobacteria as they are also called) are toxic. The only way to determine exactly what type of algae is involved in a bloom is for an expert to examine the organisms under a microscope. I don’t know if that was done in the case of my dog park or if the city simply drained and closed the pond to be on the safe side.

Toxic blue-green algae are nasty little buggers. They produce a variety of harmful substances that can adversely affect the nervous system, liver, skin, and gastrointestinal tract. The neurotoxins are especially scary. They can start to produce symptoms like weakness, unsteadiness, muscle cramps, twitching, and difficulty breathing within 15 to 20 minutes of an animal ingesting contaminated water. Severely affected animals can develop seizures, heart failure, paralysis, and die even with prompt and appropriate treatment.

If that weren’t bad enough, animals who don’t immediately become ill are not out of danger. The effects of hepatotoxins (liver toxins) can take hours or even a day or two to become evident. When ingested, the hepatotoxins produced by blue green algae can result in acute liver failure and its associated clinical signs of vomiting, diarrhea, abdominal pain, loss of appetite, abnormal behavior, and yellowing of the skin and mucus membranes. The liver is a resilient organ and can regenerate itself if enough tissue remains healthy, but too often so much damage has been done that a large percentage of these patients eventually die or are euthanized.

If you are ever out with your dog (or other animal for that matter) and see a body of water that looks like it could be contaminated with blue green algae, immediately head in the opposite direction. For everybody’s sake, report the situation to your local health department or other appropriate government agency.

Dr. Jennifer Coates

Image: Thinkstock

Last reviewed on September 14, 2015