The Dangers of Blue-Green Algae to Dogs

Blue-green algae is commonly found in streams, lakes, and rivers around the UK. As certain types release dangerous toxins, it can cause dogs serious harm, and in the worst cases, it can even be deadly.

To help keep your furry friend safe, we’ve put together a guide on how to identify blue-green algae, what to do if you encounter it, spotting symptoms, and more below.  

What is blue-green algae?  

Despite its name, blue-green algae isn’t actually algae.

Blue-green algae, also known as ‘cyanobacteria’, is a term used to describe a group of bacteria that thrives in nutrient-rich water. When clumped together, these dense growths of bacteria can give the appearance of algae and turn water green or blue-green - hence the name!

Blue-green algae can grow rapidly and form large “blooms” that contaminate and pollute water. Certain types are dangerous because they release toxins and can cause harm to dogs, humans, and other wildlife.

Where can you find blue-green algae?

Blue-green algae is commonly found in nutrient-rich water such as streams, lakes, rivers, and ponds.  

The amount of blue-green algae found in water may change throughout the year, however, because this bacteria thrives in warm temperatures and sunlight, it tends to reproduce rapidly during summer and early autumn, especially during or after hot sunny periods, and especially after heat waves.   

Important: Never let your dog drink or swim in water known or even suspected to be contaminated with blue-green algae. Dogs can be affected by this toxic substance very quickly.

What does blue-green algae look like?

Blue-green algae tends to bloom in stagnant or slow-flowing water. It usually floats to the surface and can be several inches thick near the shoreline. It’s commonly known for giving water the appearance of pea soup!

Because blue-green algae is a form of bacteria and not true algae, it can appear to be part of the water, rather than in it like a clump of algae that can easily be picked up. It can also have a musty or earthy smell.

How to spot blue-green algae:

While it can be difficult to spot, keep an eye out for: 

  • Blue-green scum on the surface of the water (like pea soup)

  • Blue-green, green, or green-brown paint on the surface of the water

  • Cloudy water with a green/blue/brown appearance

  • Foam around the edges of ponds and lakes

  • Warning signs near bodies of water

  • Dead fish/wildlife in the water

In water where there is a high concentration of blue-green algae, you may spot dead fish. Remember to never let your dog drink from any water source that you notice contains dead animals.

Note: While not all types of blue-green algae are harmful, as it’s impossible to tell simply by looking at it, it’s important to always keep your dog away from water you suspect is contaminated.

Why is blue-green algae dangerous to dogs? 

As blooms of blue-green algae can produce harmful toxins, dogs are at risk if they drink or swim in contaminated water. Your dog is also at risk if they get contaminated water on their fur, as they may ingest it when cleaning themselves. 

Exposure to toxic blue-green algae can be extremely dangerous for dogs and cause organ failure, severe illness, and in the worst cases, death.

Symptoms of blue-green algae poisoning

Blue-green algae poisoning can take anything from 15 minutes to a few days to develop. Symptoms can vary but they can include:  

  • Vomiting (sometimes with blood)

  • Diarrhoea

  • Convulsions

  • Breathing problems

  • Collapse

  • Increased thirst

  • Drooling

What to do if you think your dog has been poisoned by blue-green algae

If your dog has been exposed to blue-green algae, contact your vet immediately.

It’s always better to be safe than sorry, and the sooner you seek treatment the better chance your dog has at getting better.

Is blue-green algae dangerous to humans?

It’s not just animals that are affected by blue-green algae. The dangerous toxins in this bacteria are harmful to humans too.

Symptoms can include:

  • Vomiting

  • Diarrhoea

  • Skin rashes

  • Eye irritations

  • Fever

  • Pains in muscles and joints

If you or your dog come into contact with water you suspect is contaminated with blue-green algae, you should seek immediate medical or veterinary advice.

What to do if you spot water contaminated by blue-green algae

If you’re out walking your dog or you come across a body of water that you suspect contains blue-green algae, stay clear of it. Don’t touch it yourself, and don’t let your dog drink from or swim in it.

Sightings of blue-green algae should be reported to the Environment Agency on their incident hotline on 0800 80 70 60.

You can also report your sightings on the Bloomin’ Algae App. This app is a useful tool for recognising blue-green algae, plus it’ll show other sightings of blue-green algae in your area.

Yappy to help

We hope that you’ve found this blog post helpful and feel more clued-up on the dangers of blue-green algae, especially to our furry friends.

For more guidance on looking out for your best bud, check out our blog post on why dogs eat grass, and for the low-down on dogs and sunscreen, click here!

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