Blue-Green Algae Poisoning in Dogs: Dangers & Signs

Your dog loves going out for a swim, and you love bringing him. But are you practicing caution when it comes to blue-green algae risks?

Sure, you’ve probably seen your fair share of bacterial or algal blooms (also called “pond scum”) on bodies of water in the great outdoors. While these growths come in many toxic and non-toxic forms, it is cyanobacteria or “blue-green algae” that cause the most freshwater blooms of concern for humans and pets alike. Exposed dogs are at particular risk of toxic illness and death.

Although there are some indicators you can look for the help spot cyanobacteria in water (and no, blue-green color isn’t one of them), both the Centers for Disease Control and Prevention (CDC) and the Environmental Protection Agency (EPA) stress that there is no way to visibly distinguish toxic blooms from non-toxic ones.

Treatment for pets exposed to cyanobacteria is possible in many cases, but prevention is key. That’s why it’s important to learn the risks of blue-green algae poisoning in dogs and how to keep pups who love to swim safe in the great outdoors.

What is blue-green algae?

There are a lot of misconceptions about blue-green algae, starting with the name. The term “cyan” means blue-green. But cyanobacteria come in many colors, from deep green to even pinks and reds!

Blue-green algae is also not a type of plant or even an algae. Whereas other algae are eukaryotic organisms, blue-green algae refers to a type of single-celled (prokaryotic) cyanobacteria that obtains energy through photosynthesis. They thrive in slow-moving or stagnant water, like ponds, lakes, reservoirs, and slow-moving streams.

“These bacteria reproduce most rapidly at higher temperatures, and are therefore most common in late summer to early fall,” says veterinarian Dr. Caroline Wilde, DVM. “Not all blue-green algae are toxic, but there are some that produce substances that are toxic to the dog’s liver and nervous system, and there is no way to tell just by looking whether or not the algae is toxic.”

It’s not just dogs who are at risk either. As Trupanion veterinarian Dr. Sarah Nold adds, “[Cyanobacteria] is one of the few toxicants that can result in sudden death in several species, including humans, dogs, and livestock.”

How to detect blue green algae in water

The name comes from the cyanobacteria’s common appearance as a bluish-green film floating along the surface of the water. However, there are other key indicators to look for:

• Foul-smelling water or shoreline
• Seeing dead fish along the water surface or shoreline
• No leaves or roots. Non-plant-like
• Slimy or “spilled paint” appearance
• Flows with the water without chunks or stringy-behavior
• Water may appear cloudy but not dusty. If it’s yellow and dusty, it might be tree pollen.

Nevertheless, Wilde notes that blue-green algae may not always be easy to spot on water surfaces, and the toxins can persist even after the physical blooms are no longer visible.

“Avoid stagnant water where blue green algae proliferates, and if there is any question regarding the safety of the water, I would recommend avoiding it,” Wilde says. “I would also recommend checking local public health websites to see if the body of water has been tested. Although a negative test does not rule out potential exposure.”

How canine blue-green algae poisoning happens

Not every dog who enters a body of water with blue green algae is going to get sick. So, how does algae toxicity actually occur?

“Blue-green algae poisoning in dogs occurs when the toxin is absorbed through the intestines after ingestion of contaminated water,” Wilde explains. “This happens while swimming or through licking their fur after swimming in contaminated water.”

Because blue-green algae toxins can quickly cling to fur or be consumed while your pup is swimming, it can be tough to define a timeline for toxicity to affect your dog. Just because your pal seems fine right after a water activity doesn’t necessarily mean he’s in the clear.

“Signs usually begin 1 to 4 hours following ingestion,” Nold explains. “With death possibly occurring within 24 hours or up to 5 days after.”

Blue-green algae risks aren’t limited to summer

It’s a common misconception that dogs are only at risk of blue-algae poisoning during summer months. While these algal blooms thrive in warm weather, the toxic forms can be spurred by temperature fluctuations in general. They can also grow anywhere there is stagnant water and an influx of phosphorus and nitrogen.

According to Nold, blooms can occur all year long in southern states as long as cyanobacteria’s environmental and nutritional conditions are met. An example of this was a 2021 breakout of blue green algae poisonings in dogs in central Texas, which took place early in the year following a cold snap.

Signs of blue green algae poisoning in canines

Dogs who have been exposed to a toxic form of blue-green algae may not show any signs of poisoning. However, it is crucial to seek emergency veterinary attention if you notice any of the following:

• Weakness
• Collapse
• Shallow or difficulty breathing
• Muscle spasms or tremors (seizures may also occur)
• Paralysis
• Pallor (loss of color) of mucous membranes
• Black or bloody stool
• Vomiting
• Diarrhea
• Lethargy

Sudden death may also occur, as can neurological or liver damage. Regardless, if you believe your dog has been exposed, seek emergency veterinary care immediately. Do not wait for them to start showing signs of illness.

How to treat blue green algae toxicity in dogs

There is no antidote or “cure” for blue-green algae poisoning in canines. According to the Pet Poison Helpline, “aggressive, immediate treatment is necessary to help treat this quick-acting, potentially fatal poison.”

Treatment depends on the severity of your pet’s symptoms and how long it has been since exposure. Along with intravenous fluids and oxygen, anti-seizure medication may be administered.

As Wilde notes, taking steps to prevent canine blue-green algae poisoning in the first place is the best course of action.

“Dogs should be bathed after swimming to wash off any potential algae,” she says. “If you are concerned that your pet has ingested blue green algae, you should seek veterinary care immediately.”

Your pet’s safety comes first

Blue-green algae poisoning can affect dogs of all breeds, sizes, and ages. Always check local advisories before heading out to a local lake or other body of water, and practice caution even if your pal is just wading in. Bring along fresh, clean water from home and try to deter your pet from drinking anything else. Never let your dog eat or approach a dead fish or other creature.

While it might be hard to resist a swim in the nice weather, your pal’s safety should always take precedent. If you haven’t done so already, there’s no better time than the present to enroll your dog in a medical insurance plan to protect him from the unexpected.

Of course, having a good dog insurance policy does not negate the need for everyday safety measures. If you’re at all unsure of the water conditions, it might be a good choice to stay out. Consider another dog-friendly outdoor activity, like taking your pup for a walk, starting up a game of fetch, or even just enjoying some nice rest and relaxation in the comfort of your own home.

Keep your pal safe in all kinds of water! Check out 7 Tips for Walking Dogs in the Rain.