Will Water Algae in Ponds Make Dogs Sick?

When algae blooms rest on the surface of the pond, keep your dog away from the water.
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While a sip from a pond during a hike or a swim on a hot day is not always a problem for your dog, water algae, especially blue-green algae, can break down and produce natural toxins, which can be deadly to your canine companion. No antidotes to these toxins are known, so poisoning in large amounts is often fatal. Knowing what to look for and what to do in the case of accidental exposure is essential.


Cyanobacteria, or blue-green algae, are typically found in fresh, brackish or marine water. Most of the time, these bacteria are too small to be seen. However, during hot months towards the end of summer, cyanobacteria grow rapidly, creating blooms. These blooms float on the top of the water, typically giving it a blue-green, fuzzy carpetlike appearance. The blooms can be brown or red and can look like soap scum or foam. Many of these blooms do not produce toxic substances -- but determining which ones may prove toxic, without testing, is impossible. Toxins released include microcystins and anatoxins.


Symptoms after exposure vary based on the toxin. Microcystins often result in liver damage of failure, causing symptoms such as vomiting, diarrhea, bloody stool, weakness, pale gums, jaundice, seizures, coma and shock. Within days of exposure, complete liver failure can occur. Anatoxins cause neurological symptoms, such as excess salivation, muscle tremors, paralysis and difficulty breathing. Breathing issues often reduce oxygen intake, resulting in bluish coloring of the lips and skin. Symptoms can begin within 15 to 20 minutes after exposure.

Water Exposure

Drinking the water is not the only way your dog can be exposed to these toxins. When he jumps in for a swim, the algae clings to his fur and skin. Any open wounds or cuts in the skin allow bacteria to enter. When he licks his fur, he ingests the bacteria. If your dog makes a dash for an algae-filled pond for a swim, get him out of the water immediately and rinse him off with clean water. (ref 1)


No antidotes for cyanobacteria toxins exist, so treatment focuses on symptoms. If you believe your dog has been exposed to these toxins or is suffering from any symptoms, seek veterinary care immediately. The toxins act quickly; death can occur within the first four to 24 hours. The sooner your veterinarian can begin addressing symptoms the better the prognosis should be. Activated charcoal can help to absorb toxins if administered soon after exposure.