Harmful Algal Bloom-Related Illness in Animals - Minnesota Dept. of Health

Harmful Algal Bloom-Related Illness in Animals

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Symptoms animals experience during illness depend on the type of toxin present in the water and how the animal is exposed (i.e., ingestion, skin contact, and inhalation). Additionally, the severity of the illness depends on the amount of water and algal cells ingested, the animal’s body size, the amount of food in the animal’s stomach, and the sensitivity of the species and individual animal.

Common symptoms experienced include:

  • vomiting
  • diarrhea
  • rash
  • difficulty breathing
  • general weakness
  • liver failure
  • seizures

In the worst cases, animals may suffer convulsions and die.

Symptoms generally begin minutes to hours after exposure to the toxins.


Pets can be more easily exposed to harmful algal blooms because they do not naturally avoid swimming in and drinking from green, smelly water. Pets can also be exposed to the toxins when they lick algae from their fur while grooming. Their small size means they don’t have to ingest as much water as humans to get sick from the toxins.

Animals can be exposed to microcystin and other cyanotoxins when surface scums or water containing high levels of toxins are:

  • swallowed while drinking or swimming
  • swallowed while licking contaminated fur or hair
  • in contact with skin


There is no way to tell if a blue-green algal bloom is toxic or not just by looking at it, so if you see a bloom in a lake, you and your pets should avoid contact with the water until it goes away. Always remember, “When in doubt, stay out!”

To reduce the risk of harmful algal bloom-related illness in animals:

  • Do not let your pets or livestock swim in or drink from water that is discolored or where you see foam, scum, or mats of algae on the water.
  • Do not let pets lick the algae or scum off their fur.
  • If you think your animal swam in water where a harmful algal bloom is occurring, rinse them off with fresh water immediately.

Do you suspect you are experiencing adverse health effects from a harmful algal bloom? Visit reporting suspected foodborne/waterborne illnesses.

Updated Tuesday, 29-Jan-2019 16:25:14 CST