Two dogs swimming after a tennis ball.

The Risks of Blue-Green Algae for Pets

Picture this. After a streak of warm days, you are finally rewarded with a day off from work and you decide to spend it outside with your trusty canine companion. You opt for a hike on a nearby trail, one with beautiful scenery wrapping around a large lake. Sounds perfect, right?

It can be, if you keep your pet’s safety in mind. Excessive heat, exposure to ticks and mosquitoes, and musculoskeletal injuries are some of the more obvious health risks to your pet. However, there’s one hazard hiding in the water that can pose an even greater, more life-threatening danger.

Background on Blue-Green Algae

Cyanobacteria, more commonly referred to as blue-green algae, tend to flourish in ponds, rivers, lakes, and brackish (mixed fresh and salt) waters around the globe. These bacteria have been dubbed blue-green algae due to the blue-green color pigment that is commonly released when the algal cells decompose and die.

Under certain environmental conditions, an overgrowth of the algae, also known as an algal bloom, may be witnessed. These circumstances generally involve warm, stable weather and high amounts of light. Additionally, water currents and winds can contribute to congregation of the algae in certain areas, typically along the shoreline or at an inlet. The combination of a bloom along with movement to more accessible areas along the water’s edge increases the chances that an animal or person may become exposed, either in dipping their head down for a drink or going for a swim. Consequently, stories of pets becoming sick and passing away following blue-green algae exposure typically hit the news in late summer, when the weather is warm and pets have a greater potential to be exposed to contaminated water.

Cyanobacteria themselves are not harmful, but the toxins they may create or harbor can be. Not all of these toxins are dangerous, and of those that are it is often dependent on the level of algae breakdown and the method and quantity of exposure. Because blooms typically contain more than one algal species, we must assume that a bloom can potentially expose an animal to more than one toxin.

Affected Species

Reports of severe illness and fatalities have been confirmed in livestock, pets, wildlife, and people. With regards to domestic pets, the reports of toxicity are most commonly seen in dogs as compared to cats, likely because cats have a decreased affinity for swimming and are more discriminate with the types of water they drink.

Risk of Exposure to Blue-Green Algae

Contact with contaminated water, whether it be used for agriculture, recreation, or aquaculture, can result in toxin exposure. This can be through purposefully drinking the water or accidental ingestion when swimming. There have also been reports of dogs becoming exposed after licking their contaminated haircoat.

Clinical Signs

Clinical signs associated with blue-green algae exposure are dependent on the specific toxin(s) produced by the algae. These signs may be primarily associated with liver failure or neurologic signs. Certain toxins may be associated with kidney failure or skin irritation, although there appear to be fewer reports of this in the news and scientific literature. Depending on the toxin, signs may occur between minutes and days after the exposure. Typically, the patient’s signs are accompanied by reported contact with potentially contaminated water. For instance, a pet owner may report a recent swimming event or drinking from a pond.

Clinical signs associated with hepatotoxins, or those toxins resulting in liver failure:

Clinical signs associated with neurotoxins, or those toxins resulting in neurologic signs:

Clinical signs associated with nephrotoxins, or those toxins resulting in kidney failure:

Clinical signs associated with dermal toxins, or those toxins resulting in skin irritation:


Because the clinical signs develop quickly, a test to confirm the diagnosis is not typically performed prior to initiation of treatment. Therefore, veterinarians often diagnose a patient based on history of exposure, clinical signs, and associated laboratory findings.

Nevertheless, the veterinarian will likely request toxicological testing of bodily fluids (for instance, vomit) to evaluate for blue-green algae toxins. Knowing whether or not blue-green algae caused your pet’s symptoms will be very important in order to reduce exposure to other animals and people in the community.

Treatment of Algal Poisoning

Unfortunately, there is no specific treatment for blue-green algae toxicity. However, if there is even a remote possibility that your pet has come into contact with blue-green algae, it is imperative you act fast and take them to the veterinarian as soon as possible, so that supportive care can be initiated.

The first thing your veterinarian may do is attempt to rid the body of any potentially contaminated material. This can be done by making your dog vomit, pumping the stomach (gastric lavage), and/or administration of medications to absorb toxins (such as activated charcoal).

The most common treatment protocols reported are those for hepatotoxin or neurotoxin exposure. If a hepatotoxin is suspected, your veterinarian may need to treat for potential bleeding disorders since the liver, which typically makes things in the body to help blood clot normally, may not be working as efficiently. Your veterinarian may also administer antioxidants to help protect the liver. If a neurotoxin is suspected, your veterinarian may initiate treatment for muscle tremors, seizure activity, and any other neurologic signs. If a patient is having trouble breathing due to respiratory failure, oxygen supplementation may also be warranted.

Less is reported on nephrotoxin and dermal toxin exposure, but such toxicities will require supportive care and treatment of any allergic reactions.


For both hepatotoxin and neurotoxin exposure in pets, death is highly probable. Pets exposed to hepatotoxins may have a slightly greater chance at surviving than those exposed to neurotoxins, but this is only in cases where early supportive care is initiated.

Preventative Measures

The first thing you can do to reduce blue-green algae toxicity in your pets is being aware of the risks. Equipping yourself with this knowledge will help you take the appropriate steps to reduce exposure.

It is important to prohibit pets from accessing potentially contaminated bodies of water, particularly during warmer months when blooms are most common. This will help prevent pets from coming in contact with contaminated water and either drinking it, accidentally ingesting it, or contaminating their fur. Additionally, pay close attention to your local health department and any alerts they may be issued regarding blue-green algae contamination in your community.

Public Health Implications

Exposure to blue-green algae and its toxins is not limited to companion animals. As previously mentioned, we can see side effects from ingestion in livestock, wild animals, and humans. Often, we see the signs in animals before we see them in people, and this may act as a warning in the community. It is very important for veterinarians, pet owners, and local public health officials to work together to identify whether or not a pet is suffering from blue-green algae toxicity. This will allow for quick identification of the toxin source so that appropriate prevention and control measures can be put in place, ultimately reducing the risk to all community members.

What to Do if Your Pet has Been Exposed to Blue-Green Algae

If you suspect that your pet may have been exposed to blue-green algae, it is best to err on the side of caution and take your pet to the veterinarian as soon as possible for evaluation. In the case of blue-green algae toxicity, time is of the essence and those who have the best chance of survival are those treated immediately.

If you are unable to access a veterinarian, various poison hotlines exist where you can obtain more information on the possible exposure and treatment options.