How to identify blue-green algae (and why it's toxic)

You may have seen this green, thick layer at your local pond or river and assumed it was just regular, safe algae. But it could be blue-green algae—a type of bacteria called cyanobacteria. It's toxic for dogs, us, and basically everything else.

It's more commonly found when it has the right conditions, like hot weather and non-flowing water. But it can be found year-round.

We recommend that you know what blue-green algae looks like and how to avoid it, especially if your dog truly believes they're part otter.

Blue-green algae in dogs is a serious issue. If you're here because your dog has swallowed water with algae, contact your vet immediately.

We discuss what blue-green algae looks like, what it is, why it's toxic, and the importance of avoiding contaminated water. 

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What's blue-green algae?

As mentioned, blue-green algae is a type of bacteria called cyanobacteria. It's not actually algae; it just looks like it.

It grows in water and flourishes under certain conditions:

• Non-flowing water (ditches, lakes, ponds, puddles, rivers, steams, or wet walls)

• Hot weather

• Little to no wind

When the conditions are right, it causes a "blue-green algae bloom." The result can be a thick, gloopy burst of green that's easily mistaken for algae.

As mentioned, it's toxic and fatal for pets. It can also make humans very ill. It’s a real risk, especially if you have a dog breed that loves swimming.

Sometimes, in extreme cases, you'll see dead fish and other aquatic animals around it. Never let your dog enter this water.

Normal algae have the same or similar appearance from a distance, meaning it can be hard to tell the difference. 

If you can see that the algae has distinguishable leaves or roots, then it is likely to be a harmless plant called duckweed. If the algae is a green, stringy substance that drapes over a stick, then this is green algae.

Blue-green algae tends to be gloopy and often mixes in with the water. It can take on many forms, looking like a scum or paint spill on the surface of the water or foam at the edges of ponds or lakes. We’ll explore this further later on.

If you're unsure, it is best to keep your dog away.

Interestingly, not all blue-green algae are actually toxic; out of the 2000 species of blue-green algae, just 40 of them are harmful.

But you can't tell which is safe and which isn’t, so don’t take any risks.    

Why is blue-green algae dangerous for dogs?

Toxic blue-green algae causes liver damage and neurological symptoms if it's ingested, leading to a variety of serious symptoms. Even getting it on the coat can cause problems, as your pet may lick it off of themselves while grooming.

Unfortunately, it's almost always fatal to dogs. Dogs that survive may have long-term health problems.

Symptoms of blue-green algae poisoning

• Breathing problems

• Diarrhea

• Drooling

• Liver failure

• Muscle problems

• Problems with walking and mobility

• Seizure

• Tremors

• Vomiting

Identifying blue-green algae

As mentioned, you cannot always reliably spot blue-green algae with the naked eye. But it does have a few characteristics.

Appearance

A thick, gloopy texture that looks a little like pea soup.

Smell

Some people report a garbage-like smell. It's likely due to the phosphorus content from blue-green algae.

Texture

Blue-green algae tend to break apart and have a string-like texture. For example, if you tried to catch some with a stick, it would break apart into small bits.  

Locations

As mentioned, it tends to stick to bodies of water with little flow. Areas like ditches, ponds, puddles, lakes, rivers, streams and wet walls.

Generally, avoiding blue-green algae follows similar steps to avoiding contaminated water.

Recognizing and avoiding contaminated water

Your dog can still get ill from waterborne bacteria even if large amounts of algae aren't seen. Each type of contamination is different, but generally, look out for water that has:

• A cloudy, murky appearance

• A foul smell

• Poor water clarity

• Scum, foam or algae build-up

• Dead animals or fish

• Not much plant life

It's important to be a bit more aware when conditions are right for bacterial growth, like still summer days.  

We recommend that you stay cautious if you think something has contaminated the water or if you're unsure about any algae present. If you have any reservations, don't let your dog jump, swim, paddle or drink from it.

You can report any contaminated water to the US Environmental Protection Agency's (EPA) National Response Center hotline at 1-800-424-8802.

Sometimes warning signs will be placed near polluted water sources, so pay attention to what they say.

Precautionary measures for dog owners

Generally, as a dog owner, we recommend that you:

• Avoid high-risk areas, particularly in summer.

• Keep up-to-date with local advisories and warnings, which should give you information on water quality and any outbreaks.

• Become familiar with the signs of contaminated water, particularly if you're visiting a new area for the first time.

• Err on the side of caution, especially when it comes to algae.

• Keep your dog on a leash near water until you’ve checked whether it is safe.

• Always have fresh, clean drinking water on hand.

• Keep your dog completely away from bodies of water that you suspect are contaminated.

• Don't let your dog drink from contaminated water. Algae tend to build up on the edge of lakes, for example.

• Report any suspected contamination by calling 1-800-424-8802.

We also recommend becoming familiar with some general dog swimming tips.

What to do if your dog is exposed

It's stressful when your dog is exposed to contaminated water, but try not to panic. There are steps you can take.

First, seek veterinary advice immediately and call your vet.

Before you take them to the veterinary hospital, rinse your dog well with fresh, clean water, and don't let them lick their fur.

Note any symptoms and when your dog was exposed to the water. Note down what the water was like and get your dog to a professional as soon as possible.

There's no cure for blue-green algae poisoning. Your vet may be able to induce vomiting to get your dog to bring up some of the contaminated water.

Treatment is supportive with intravenous fluids, oxygen therapy and anti-seizure medication. Your dog’s prognosis will depend on the type of toxins your pet has been exposed to.

Sadly, some dogs can die or have long-term health issues from blue-green algae poisoning, despite everyone's best efforts.

Supportive treatment must be started promptly to give your pet the best chance of survival.

Stay prepared

Overall, many dogs love to swim, and most fresh water is safe for them. But staying prepared and knowing the dangers can make the difference.

We recommend you stay informed about your local water quality and pay attention to any warning signs or notices, which can help keep your swimming buddy safe.

And while you're at it, learn how dog insurance can help reimburse you for the cost of treating your pet in the event of an unexpected accident or illness:

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