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Veterinarians: Blue-Green “Algae” — Cyanobacteria — Is Toxic For Dogs

Patricia WuestVice President of Media Strategy, NAVC

Veterinarians: Blue-Green “Algae” — Cyanobacteria — Is Toxic For Dogs
When cyanobacteria oxygenated Earth’s atmosphere over 2 billion years ago they helped create an environment that changed the course of the evolution of animal life. Today, they produce toxins that are lethal to dogs. Photo: Shutterstock.com | PJ Photography

“Toxin ingestion is a near-everyday occurrence in veterinary practice,” wrote Courtney Waxman, CVT, VTS (ECC), VetMed Emergency and Specialty Hospital in Phoenix, Ariz., in the Spring 2019 issue of Today’s Veterinary Nurse. “Companion animals are susceptible to several potentially life-threatening toxicants, ranging from human food and medication to animal medication, common plants, illicit drugs, routine household products, and more.”

When several dogs died this past summer after swimming in water contaminated by blue-green algae, the veterinary community began warning clients about the danger blue-green algae poses to their pets, particularly dogs. Most of the deaths occurred in the southern United States (North Carolina, Texas, Tennessee, and Georgia), but Minnesota and Colorado also reported dog deaths suspected to be the result of toxic blue-green algae.

When three dogs owned by the same pet owners died after playing in water containing the toxic blue-green algae, a local veterinarian’s office in Wilmington, N.C., sent out an email warning pet owners that dogs who ingest algae often face death:

“Please be aware of the current bloom of blue-green algae in our area. Blooms of blue-green algae can be toxic to canines and most often fatal. If you feel your pet has been in contact with blue-green algae please rinse with freshwater and seek veterinary help immediately.”

What Is Blue-Green Algae?

Toxic algae blooms can occur throughout the U.S. and Canada, according to the U.S. Environmental Protection Agency. They are not always blue-green but can be red and brown, and can occur in freshwater or saltwater. The “algae” or “pond scum” is actually cyanobacteria. These bacteria can produce toxins (such as microcystins and anatoxins) that affect dogs as well as people, livestock and other pets that swim in and drink from algae-contaminated water. Cyanotoxins are powerful natural poisons, including ones that can cause rapid death by respiratory failure.

Though cyanobacteria isn’t visible to the naked eye, it looks like algae when it clumps together in bodies of water. Toxic algae can also bloom in backyard pools and decorative ponds if they aren’t cleaned regularly.

Toxic blooms can result from more than 30 species of cyanobacteria, which produce four types of toxicity:

Hepatotoxin (damages the liver)
Neurotoxin (destroys nerve tissues)
Nephrotoxin (destroys cells of the kidneys)
Dermal toxin (causes hives or a rash)

Signs/Symptoms Your Patient May Have Ingested Blue-Green Algae

The rapid onset of signs of cyanobacteria illness does not leave much time for treating the animal. Symptoms can begin anywhere from 15 minutes to several days after exposure. Clinical signs of poisoning are dependent on the toxin involved.

Microcystin is a hepatotoxin. Microcystins can result in liver damage or failure. Signs of liver injury include:

Blood in stool or black, tarry stool
Pale mucous membranes

Anatoxins are a neurotoxin that result in neurotoxicity. Signs of neurotoxicity include:

Excessive secretions (e.g., salivation, lacrimation, etc.)
Muscle tremors
Muscle rigidity
Blue discoloration of the skin and mucous membranes
Difficulty breathing

Diagnosis and Treatment for Dogs That Have Been Exposed to Blue-Green Algae

Unfortunately, there is no antidote for the toxins produced by blue-green algae, and the prognosis for an affected dog is poor. Aggressive and immediate veterinary treatment is necessary to help treat the patient. Sadly, in some cases, euthanasia is the only option. According to the VCA Hospitals website:

“…Induce vomiting to remove the algae from the stomach…. Give oral activated charcoal to absorb the toxin… Perform gastric lavage on your dog or cat (pump the stomach). Treatment is limited to supportive care focused on affected organ systems.

“Aggressive therapy including intravenous fluids and plasma may replenish electrolytes, regulate blood glucose, support organ function, and prevent shock. Muscle relaxers may help animals with muscle tremors. Anti-seizure drugs are administered if convulsions occur. Atropine may reduce excess salivation and tearing. Nutraceuticals may be needed to support waning liver function.”

Recovery of Cyanobacteria in Dogs

Recovery can makes weeks or months. Dogs who do recover from cyanobacteria will usually have lingering liver damage, as well as other possible complications, but with the support of the veterinary team, the patient can have a good quality of life.

Learn More

How to Take a Toxin Exposure History


Guide to Managing Toxin Ingestion

Visit the Toxicology Archives of Today’s Veterinary Nurse.