Please take the time to read this important information!

For more information or to report an incident contact Lynda Knobeloch, Ph. D. Senior Toxicologist, Madison, WI 


About Blue Green Algae Toxicity in Dogs

Incidents of blue green algae toxicity in dogs were widely reported due to the drought that plagued a great portion of the USA in 2007. Reports from the Minnesota lake regions alone included as many as 40 cases of canine algae poisoning. At the time, four deaths had been reported in that region, but this number only pertains to the known cases. There could have been more deaths that were not attributed to algae poisoning because pet owners were not aware their dogs had been exposed to the contamination.

Dogs develop algae poisoning when they drink from contaminated water sources. The algae produce toxins that affect the dog's internal organs, and depending on the concentration of algae in the dog's stomach, the animal can die immediately or succumb later from a variety of symptoms.


Dogs are particularly susceptible to blue-green algal poisoning because scums can attach to their coats and be swallowed during self-cleaning. If you suspect that your animals are showing any of these symptoms you should seek veterinary advice.


What Causes Blue Green Algae Outbreaks?

In times of drought, lowered water levels and low air circulation combine to boost production of algae into overdrive. Normally, algae are equally distributed throughout the water, but large blooms are often followed by large die offs. The gas produced by these die offs pushes the algae colony up to collect at the water's surface, creating a dangerous situation.

From this point, even a gentle breeze will serve to push the algae into a concentrated layer of scum, often near the water's edge where dogs and other animals are likely to ingest it while drinking.

Signs of Algae Poisoning

The signs of algae toxicity in dogs vary, depending on whether they are triggered by nervous system toxins or liver toxins.

Signs of the presence of liver toxins include:

*       Weakness and/or lethargy

*       Pale mucous membranes

*       Bloody diarrhea

*       Mental instability

*       Eventual death

Signs of the presence of nervous system toxins include:

*       Muscle tremors

*       Convulsions

*       Labored breathing

*       Difficulty moving

*       Eventual death

Getting a Diagnosis

In order to diagnose algae poisoning, a vet will take into consideration the dog's symptoms and a history of where the dog has recently been. Most dogs will display tell-tale blue green staining on the muzzle if they have recently drunk from an algae contaminated water source, and this can contribute greatly to the diagnosis.


Treating a case of blue green algae poisoning is difficult at best, so it's extremely important to take action quickly if you believe your dog has been exposed.

In some cases, dogs have been given activated charcoal to help bind the toxins and move them out of the dog's system. Forcing the dog to throw up before the toxins leave the stomach has also proven useful.  Atropine is also administered in some cases.

After Affects

If a dog manages to survive a blue green algae poisoning, he will likely experience lasting effects over the rest of his life.

These can include:

*       Ultra-sensitivity to sunlight

*       Chronic low weight problems

*       Failure to thrive

Prevention is the Key

Preventing blue green algae toxicity in dogs is easier than successfully treating it. The best advice is to not allow your dog to drink from stagnant water, ponds or lakes, especially if they have a bluish-green scum on the surface and around the edges.

If you have contaminated water on your property, you should immediately fence the area off so your dog and other animals in the vicinity cannot drink there. Treat the algae bloom by sprinkling copper sulfate over the water surface at a concentration of one part per million (PPM). Your local landscape/pond supply store should be able to help you figure out the dosage needed to treat your water, as well as how to apply it.


Although all blue green algae should be treated with suspicion, there are many strains and not all of them produce toxins. In the long run, it's better err on the side of caution and keep your dog away from any water you have reason to believe is contaminated..

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