Blue-Green Algae and Dogs: What is it, why is it dangerous, symptoms of poisoning and treatment

While this is a perfectly healthy activity, it’s important to be aware of the potential risks associated with freshwater environments.

A recent study has revealed that when dogs enter bodies of water, their skin, and fur can release active ingredients from flea and tick treatments, chemicals that are harmful to aquatic wildlife, including birds that feed on them.

The study recommends that dog owners avoid letting treated dogs swim for at least a month after application, to help reduce the release of harmful pesticides into lakes, rivers, and ponds.

But while dogs may unintentionally harm lakes, the threat can also go the other way.

Blue-green algae, a toxic substance commonly found in still or slow-moving freshwater during warmer months, has been responsible for numerous dog fatalities in recent years.

In response to these risks, Sean McCormack, Head Vet at Tails.com, has explained how to identify blue-green algae and why it poses such a serious health risk to dogs.

He explained: “As we move into summer and sunlight becomes more abundant, the conditions for algal blooms become increasingly favourable. Warm, stagnant water combined with nutrient-rich environments creates the ideal setting for blue-green algae to thrive.

“This makes the warmer months the most high-risk period for toxic algal blooms, particularly in lakes, ponds, and other still bodies of water.”

Here’s everything you need to know.

What is blue-green algae, and how does it differ from green algae?

Although the names sound similar, blue-green algae and green algae are quite different. Blue-green algae is a type of bacteria known as cyanobacteria, and in many cases, it isn’t visible to the naked eye.

However, when blue-green algae blooms and forms clumps, it can often be recognised by the water taking on a distinctive pea-green, soup-like appearance. Green algae, by comparison, usually looks like stringy plant matter that can be lifted out of the water or found draped over sticks.

If you come across water affected by blue-green algae, it is generally best to avoid contact, for both people and pets. While not all blue-green algae is toxic, certain strains can produce harmful substances that may cause skin irritation, nausea, vomiting, or more serious health issues if ingested or inhaled.

Why is blue-green algae dangerous to dogs?

As we approach the warmer months and spend more time outdoors with our canine companions, it’s essential for dog owners to understand the potential risks blue-green algae can pose.

While it may not look particularly threatening, especially when water simply appears green, blue-green algae can be extremely toxic to dogs if they swim in or drink contaminated water. This is due to the harmful toxins produced by blue-green algae blooms, which can interfere with a dog’s liver function.

In some cases, exposure to the bacteria can sadly be fatal, or cause serious long-term health problems, depending on the quantity ingested and how quickly veterinary care is accessed.

If you’re planning to take your dog swimming or walking near open water this summer, it’s important to stay vigilant. Avoid letting them come into contact with any water that may look suspicious. Even if you're unsure whether the green substance is blue-green algae, it’s better to be cautious than risk your dog’s health. We all know how curious dogs can be when exploring new environments.

For a safer alternative, consider visiting a dog-friendly swimming pool or lido where the water is regularly checked and treated, allowing your dog to enjoy a splash without the added risk.

What should you do if your dog has encountered blue-green algae?

If you suspect your dog has come into contact with blue-green algae or ingested contaminated water, contact your vet immediately.

Unfortunately, there is currently no specific antidote for blue-green algae poisoning in dogs. Prompt treatment is vital to reduce the chances of serious or lasting health effects.

The treatment your vet offers will depend on the severity of the symptoms. They may induce vomiting to expel the toxins if caught early, while more serious cases (such as those involving seizures or collapse) may require intensive care.

Tragically, blue-green algae can cause fatal liver failure, so prevention is always the best approach. If you suspect a body of water may be contaminated, avoid it altogether to protect your pet.

What are the signs and symptoms that your dog has ingested blue-green algae?

When dogs come into contact with blue-green algae, they may display some of the same symptoms as humans, such as vomiting. However, the effects on dogs can be significantly more severe.

The most common symptoms include:

• Vomiting
• Loss of appetite
• Diarrhoea
• Seizures or fitting
• Weakness, collapse, or unconsciousness
• Disorientation or confusion
• Excessive drooling
• Difficulty breathing