Whole Dog Journal's Blog August 10, 2010

Toxic Blue-Green Algae can be Deadly to Your Dog

Posted at 09:35AM - Comments: (11)

It’s that time of year again – when news reports start coming out of dogs dying after swimming in or drinking from ponds, lakes, and reservoirs polluted with toxic blue-green algae. The component of the algae that produces toxins is called cyanobacteria.

Three dog deaths in July have been attributed to toxic algae at Grand Lake St. Marys in Ohio, but the problem can occur anywhere. In past years, reports of toxic algae blooms have ranged from California to Maine, and Canada to Florida, as well as the UK.

Blue-green algae thrive in warm, shallow water. While algae may be present throughout the year, it is only when there is an extensive “bloom” that problems occur. Most blooms occur in late summer or early fall, but they can occur earlier as well, particularly when the weather is unusually warm and dry. Toxic algae can be blue, bright green, brown, or red.

Signs of toxicity in dogs may start with lethargy, followed by vomiting and diarrhea. Tremors and seizures can occur almost immediately. Additional signs range from excess salivation, skin irritation, and pale gums to severe respiratory, circulatory, or neurological disorders. Convulsions and death can occur as little as four hours after exposure. Treatment may include fluids to prevent dehydration, diazepam (Valium) to control seizures, atropine to counteract the poison, charcoal to absorb toxins from the stomach, and adrenaline to help counteract respiratory failure.

Prevention is the best course of action. Keep your dogs away from stagnant water in warm weather, particularly if you notice any of the following:


  • The water looks like green paint or pea soup, or is cloudy with a green, yellow, or blue-green hue.
  • It smells swampy or musty.
  • You see what looks like foam, scum, or mats on top of the water.


If contact occurs, prevent your dog from licking his feet or coat, and wash him off thoroughly with clean water as soon as possible. If you suspect problems, contact your vet immediately. If your dog becomes ill, be sure to notify authorities so that warning signs can be posted to protect other pets and people.

More information:

Blue-green Algae and Harmful Algal Blooms


San Francisco Bay Area resident Mary Straus has spent more than a decade investigating and writing about canine health and nutrition topics for her website, DogAware.com.

Comments (10)

Cyanobacteria (algae) varies...there are hundreds of species. Everything from the green scum in your aquarium to some types of seaweed. Most can be very toxic if ingested, but there are a select few which are actually very beneficial to one's health.
The alga grown in man-made ponds are commonly known as Spirulina and Chlorella. Another one which grows wild in large enough quantities to harvest is the Aphanizomenon flos-Aquae from Oregon. Several companies harvest it and it is usually freeze-dried and turned into supplement form for smoothies, capsules/tablets. It is a powerhouse of nutrition and if one is skeptical, there is no less than 4 or 5 books have been written about it's nutritional value. But of course, one does have to do their research and make sure you're purchasing from a company which has in impeccable record for testing each batch, and processing it in such a way that it retains it full strength.
I have personally been consuming Super Blue-green Algae since 1994 and also giving it to all of my pets. My dogs have lived long, dis-ease free lives to at least 15 and some have lived to be almost 18 and passed away in their sleep. My own health is phenomenal, and at almost 63 I'm proud to say I have the stamina of someone much younger, and despite travels to some third world countries, I haven't even had a cold or illness this entire time.
So do yourself and your pets a favor, and add this type of blue-green algae to your daily regimen.

Posted by: mhurst | May 13, 2014 11:06 PM    Report this comment

I feed my dogs BioSuperfood, which is made of Blue-green algae ad is an amazing product!

Posted by: soberdog | October 21, 2010 7:48 PM    Report this comment

To Lee G.:
Spirulina is a safe supplement....not the same as the algae discussed in this article.

Posted by: VALERIE H | August 12, 2010 12:38 PM    Report this comment

Several lakes where I live in WA state have been closed for the past four years because of this algae bloom. Seems it doesn't want to go away! Sadly, it took the deaths of two (I believe that was the total) dogs, and several made very ill, to finally close the lake nearest to where I live.

Posted by: VALERIE H | August 12, 2010 12:36 PM    Report this comment

Can it be in small swimming pools too? Like the little plastic kiddie pools?

Posted by: Chelsea E | August 11, 2010 6:43 PM    Report this comment

My dog wades and drinks from a creek with moving water. There is some brown scummy looking stuff at the edge of the water and is attached to rocks in the water is this the same thing???
Very Concerned.

Posted by: Unknown | August 11, 2010 2:53 PM    Report this comment

This article is very timely. Last year a few days after arriving in Maine, our 8+ yr old Lab developed terrible reactions to what we thought was swimming in the (clean, beautiful!) lake....panting, nervous, enflamed red skin, frantic behavior. On a hunch I gave him some Benadryl, which was the correct thing. The local vet said (a day later) yes, it was the "August bloom" on our lake, and prescribed a course of Benadryl for the next week. By the end of our vacation, the water problem, and his allergy to it, seemed to be gone.
We are again in Maine, and once again our dog is exhibiting signs of a reaction. This time we were prepared , but our water-loving dog can't go swimming until the lake issue clears. He's on Benadryl again. I was told this was a red algae problem; my point is that this lake is from all appearances clear, clean and sparkling, yet there remains allergen potential....a neighbor has said that she too gets a reaction from the lake water in late July/early August.

Posted by: Barbara L | August 11, 2010 2:32 PM    Report this comment

Any stagnate water can have cyanobacteria--so that also means anything that may catch water but is not regularly cleaned or treated--so check your yard for anything that may hold water and dump it!

Posted by: HELEN C | August 11, 2010 8:16 AM    Report this comment

years ago this happened to a friend of mine while she was on vacation, the guardians were un-aware of the dog's typical behavior and the dog was not treated in time, therefore died of this nasty problem

Posted by: ShawnM | August 10, 2010 6:46 PM    Report this comment

Wondering about Spirulina as a supplement?

Posted by: LEE G | August 10, 2010 3:17 PM    Report this comment

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