Toxic algae and dogs

Symptoms of blue-green algae poisoning in dogs

Blue-green algae, or cyanobacteria, can make toxins that attack the nervous system or the liver. Dogs are poisoned far more often than people because they swim in blooms, drink the water, eat scum on the shore and lick algae off their fur afterwards. A small amount can be enough.

Nerve toxins (such as anatoxin)

These act fast, sometimes within minutes of exposure and usually within an hour. Watch for:

• Drooling or foaming at the mouth
• Muscle tremors, twitching or stiffness
• Stumbling, staggering or loss of coordination
• Difficulty breathing, seizures, paralysis or collapse

Liver toxins (such as microcystin)

These usually take a few hours to show, and the damage can keep getting worse over the next days. Watch for:

• Vomiting and diarrhoea
• Weakness, tiredness or not wanting to eat
• Pale gums, and later yellowing of the gums, eyes or skin

Any of these signs after a trip to a lake, pond or river is an emergency. Don't wait to see whether your dog gets better.

What the vet will do

There is no antidote for algal toxins, so treatment aims to remove as much toxin as possible and support the body while it clears. If your dog arrives quickly and is stable, the vet may make it vomit, give activated charcoal and bathe it. Dogs with symptoms often need intensive care: fluids through a drip, oxygen, medicine to control seizures and support for the liver.

Many dogs with severe symptoms don't survive, even with treatment, and dogs that recover from liver toxins can be left with lasting liver damage. That's why the first minutes matter: rinse, call and go.

How to spot a toxic algae bloom

You can't tell toxic algae from harmless algae by eye, so treat any of these as a warning sign:

• Water that looks like pea soup, spilled paint or has green or blue-green streaks
• Scum, foam or a film on the surface, often blown into one corner of a lake or along the shore
• Dark brown, black or green mats on rocks or the bottom of rivers and streams, which dogs sometimes eat
• Dried crusts of algae on the shore or rocks
• A bad smell, or dead fish

California posts "algal mat" signs on rivers for exactly this reason, and several of the reports on this site are for rivers and creeks, not just lakes.

Keeping your dog safe at the lake

• Check before you go. Search for your lake on this site to see the latest official report and how often it has had blooms, then check the state's live map.
• Read the signs at the water. Caution, Warning and Danger signs mean keep your dog out.
• Look at the water every time. Conditions change by the day and from one beach to the next.
• Bring fresh water so your dog doesn't drink from the lake.
• Keep your dog on a lead near water that looks off, and away from scum and dried algae on the shore.
• Rinse your dog after swimming in natural water, before it can lick its coat.

Where and when blooms are most common

Across the 1142 lakes and rivers on this site, 76% of reports were logged between May and September, when warm, calm, sunny weather helps blue-green algae grow. 565 of these lakes have had blooms in three or more different years, so a bloom at a lake you've visited before is a good reason to stay alert there.

New York

Lakes with the most bloom years: Rockland Lake, Chautauqua Lake, Honeoye Lake and Orange Lake. See every lake on the New York algae bloom map.

Florida

Lakes with the most bloom years: Crescent Lake, Blue Cypress Lake, Lake Weir and Lake Okeechobee. See every lake on the Florida algae bloom map.

Oregon

Lakes with the most bloom years: Willow Creek Reservoir, Upper Klamath Lake, South Umpqua River and Willamette River. See every lake on the Oregon algae bloom map.

Kansas

Lakes with the most bloom years: Marion Reservoir, Melvern Outlet Pond, South Park Lake and Milford Lake. See every lake on the Kansas algae bloom map.

California

Lakes with the most bloom years: Clear Lake, Lake Isabella, Discovery Bay and Lake Oroville. See every lake on the California algae bloom map.

Questions about dogs and toxic algae

How quickly does toxic algae affect dogs?

It depends on the toxin. Nerve toxins can cause drooling, trembling, staggering and seizures within minutes to an hour. Liver toxins usually cause vomiting, diarrhoea and weakness within a few hours, and liver damage can get worse over the following days. Don't wait for symptoms: if your dog swallowed water or scum from a bloom, call a vet straight away.

Can a dog survive blue-green algae poisoning?

Some dogs do, especially when they get to a vet quickly, but there is no antidote and many dogs with severe signs die even with intensive care. Dogs that survive liver toxin poisoning can be left with long-term liver damage. Fast treatment gives the best chance.

Is all green algae toxic to dogs?

No, but you can't tell toxic blue-green algae from harmless algae by looking at it. Treat any green, blue-green, brown or red scum, film or mat as dangerous and keep your dog away from it.

Can dried algae on the shore hurt my dog?

Yes. Algae that has washed up and dried on the shore or on rocks can still contain toxins. Dogs that eat or lick dried algal crusts or mats can be poisoned.

Is it safe to let my dog swim if there is no advisory?

No advisory doesn't mean the water is safe. Most lakes are only tested occasionally, and blooms can appear in a day. Look at the water every time, and keep your dog out if anything looks off.