Blue-Green Algae Poisoning in Dogs

Lakes, ponds and rivers can be a fun place for dogs to swim and play. But in warm weather, some bodies of water can develop toxic blooms of blue-green algae. Blue-green algae poisoning in dogs is a true emergency. Some toxins can cause signs within minutes and can be fatal.

What is blue-green algae?

Blue-green algae aren’t true algae. They’re cyanobacteria, tiny organisms that live in fresh and brackish water. When conditions are right, usually in warm, sunny weather with still water and lots of nutrients, they can multiply quickly and form a bloom.

Not all blooms are toxic, and you can’t tell by looking. Some produce dangerous toxins.

What does a toxic bloom look like?

Blue-green algae blooms may:

• Look like pea soup or spilled paint on the water
• Be green, blue-green, brown or red
• Form scum, foam or mats on the surface
• Collect along the shoreline
• Smell bad

Blooms are most common in late summer and early fall, but they can happen any time water is warm.

Why it’s so dangerous for dogs

Dogs are at high risk because they:

• Swim in and drink from lakes and ponds
• Lick algae off their fur after swimming
• Eat mats of algae on the shore

The toxins include:

• Microcystins, which damage the liver
• Anatoxins, which affect the nervous system and can cause death within minutes to hours

Signs of blue-green algae poisoning

Nervous system signs (can start within minutes)

• Drooling
• Muscle tremors or twitching
• Weakness or collapse
• Trouble breathing
• Seizures

Liver signs (can start within hours)

• Vomiting and diarrhea
• Lethargy
• Loss of appetite
• Pale or yellow gums
• Bloody or black stool

Our guide to pet emergency signs explains other urgent symptoms.

What to do if your dog was exposed

1. Get your dog out of the water right away.
2. Rinse your dog thoroughly with clean, fresh water. Wear gloves if you can.
3. Don’t let your dog lick their fur.
4. Contact a vet or emergency clinic immediately, even if your dog seems fine.
5. Take a photo of the water and note where it was.

How is it treated?

There’s no antidote. Treatment is supportive and may include decontamination, IV fluids, medicines to protect the liver, seizure control and oxygen. Quick treatment gives the best chance of survival.

How to protect your dog

• “When in doubt, stay out.” Don’t let your dog swim in water that looks discolored or scummy
• Check local water advisories before outings
• Bring fresh water so your dog doesn’t drink from lakes or ponds
• Rinse your dog after swimming in natural water
• Keep your dog on a leash near water during warm months

Our article on summer pet safety covers other warm-weather risks.

Can cats and people be affected?

Yes. Blue-green algae can harm people, livestock and other pets too. Avoid contact with suspicious water.

Frequently asked questions

Can dogs get sick from algae in a backyard pond?

Yes. Any still, warm water can develop a bloom. Keep ponds clean and well circulated.

Is clear water always safe?

Not always. Toxins can remain after a bloom fades. Follow local advisories.

Worried after a swim? Ask a vet

Talk to a licensed vet 24/7, even on holidays, by chat, voice call or video call. Your first month is free with code FREEMONTH, then US $9.99/month, at NYPTeleVet.com. One membership covers up to 6 pets, and you can cancel anytime.

Our vets can’t prescribe medication, but they’ll tell you what’s likely needed and when an in-person visit is the next step.

Sources

• Blue-Green Algae Toxicosis: What You Need to Know to Keep Your Pet Safe, ASPCA
• Blue-Green Algae, Pet Poison Helpline
• Symptoms Caused by Freshwater Harmful Algal Blooms, Centers for Disease Control and Prevention