What is this “Toxic Blue-Green Algae” and how can it harm our dogs and us?

Blue-green algae, or cyanobacteria, can be found in any aquatic habitat but are often found in lakes, streams, ditches, and livestock ponds. Small numbers of the algae are present in many bodies of water, including Green Lake. However a “bloom” of the algae can grow under the appropriate climate and nutrient dense conditions causing an accumulation of scum on the water surface and shore edges. The bloom gives the waters surface a blue-green appearance. Here in the Northwest this may be seen during the late summer and fall months after we have had warm dry weather, although the bloom will dissipate as colder weather arrives.

It should be noted that not all blue-green algae blooms produce toxins, however those that do, cause liver toxicity (Microsystis sp. and Nodularia sp.) and neurologic toxicity (Anabaena sp., Aphanizomenon sp., and Oscillatoria sp.). These toxins are very potent and a very small exposure can cause fatality. Both of these groups of toxins are rapidly absorbed from the intestine after ingestion and symptoms can be seen within 60 minutes of exposure. Clinical signs of the liver toxin include sudden lethargy, weakness, diarrhea, vomiting, pale gums, and death within 24 hours to several days. The toxin essentially causes rapid necrosis (killing off) of liver cells. Six of the neurologic toxin include tremors, weakness, drooling, paralysis, muscle rigidity, involuntary urination and defecation, seizures. Death from respiratory paralysis can occur within 30 minutes from the start of these symptoms.

If you are suspicious your dog has been exposed to blue-green algae it is vital to rush him or her to the nearest veterinarian immediately as time is of the essence. There is no specific antidote for these toxins so your vet will have to treat your dog supportively, which means to provide decontamination procedures and medications to minimize the symptoms as necessary. These may include oxygen, IV fluids, anti-seizure medication, and liver protectants.

King County Lakes and Streams Monitoring Group and Friends of Green Lake take water samples and collect information on water conditions at Green Lake. However, blue-green algae blooms can be very patchy and many areas are not this closely monitored, so if you notice a suspicious area you are advised keep yourself and your dog away from the area and contact the environmental health section of your local health department or the Washington State Department of Ecology.

Maryam R. Salt, DVM, CVA