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Dogs

Blue-green algae and dogs: symptoms, risk, and what to do

Dogs are the ones who die from cyanobacteria, and they die fast. A dog that swims through a bloom or laps scummy water can collapse within an hour. This is the one water hazard where minutes matter, so it is worth knowing the signs before you are standing at a lake trying to decide.

If your dog just swam in or drank from water with visible scum: rinse it off with clean water immediately, stop it from licking its fur, and call a vet or emergency animal hospital now. There is no home antidote, and waiting for symptoms can be too late.

Why dogs are so much more at risk than people

Blue-green algae is not algae at all but cyanobacteria, and some blooms release toxins that are among the most potent found in nature. People usually get a warning: the water looks and smells bad, so most adults wade back out. Dogs do the opposite. They wade straight into the scummy shallows where the toxin concentrates, drink the water, and then groom the dried scum off their coat afterward, swallowing a concentrated dose. Their smaller body size means the same amount of toxin hits far harder.

Two families of toxin cause most dog deaths. Neurotoxins such as anatoxin-a attack the nervous system and can stop a dog breathing within minutes to an hour. Liver toxins such as the microcystins work more slowly, over hours to days, but cause fatal liver damage. A single bloom can carry both, and you cannot tell how toxic a bloom is by looking at it.

The symptom timeline

Signs depend on which toxin is present. Watch for these in the hours after any contact with suspect water.

Nerve toxins minutes to one hour

Excessive drooling, watery eyes, vomiting or diarrhea, stumbling and disorientation, muscle tremors or rigidity, weakness, seizures, blue gums, and difficulty breathing. This is the fast, deadly path. Respiratory failure can follow within an hour of exposure.

Liver toxins hours to a few days

Vomiting and diarrhea (sometimes with blood or black, tarry stool), loss of appetite, weakness and lethargy, pale gums, and yellowing of the gums, eyes, or skin as the liver fails. A dog can seem to recover from the first upset and then crash as liver damage sets in, so do not wait it out.

What to do, step by step

  1. 1Get the dog out and away from the water the moment you see scum, foam, or discoloration. Do not let it drink or swim any further.
  2. 2Rinse thoroughly with clean water from a bottle, hose, or tap as soon as you can, coat and paws included, so it cannot lick off the toxin later. Wear gloves or wash your own hands, because the same toxins affect people.
  3. 3Call a vet or emergency animal hospital immediately, even if the dog seems fine. Tell them you suspect blue-green algae. Do not wait for symptoms and do not try to induce vomiting unless a vet tells you to.
  4. 4Treatment is supportive. There is no antidote. Vets manage seizures, protect the liver, and give fluids and oxygen, and the sooner that starts the better the odds. Report the bloom to your state health or environmental agency so others are warned.

Preventing it

  • Keep dogs out of any water that looks like spilled paint, pea soup, or has surface scum, foam, or mats, and away from bright green, blue-green, or brownish streaks along the shore. When in doubt, stay out.
  • Bring clean drinking water so a thirsty dog never has to drink from the lake, and do not let it eat dried algae crusts on rocks or the shoreline, which stay toxic.
  • Rinse your dog after any swim in a natural water body, even one that looked clean, and check the daily read for the water first.
  • Blooms concentrate on the downwind shore, so a lake can be clear on one side and dangerous on the other. Move on if the near shore looks off.

To recognize a bloom on sight, see what blue-green algae looks like, and for the CDC guidance on protecting pets around harmful algal blooms, see the CDC HAB and pets page. For a specific lake, check its verdict on the nationwide map.