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Pacific Veterinary Hospital

Blue Green Algae Facts You Should Know

A Gray/White Cat Lying Down on Hardwood Flooring Indoors

What is it?

  •   Cyanobacteria – literally blue/green bacteria

  •   Creates “blooms”

    •  ​​​colonies that give the water a pea-soup appearance

    •  can also look like blue or green paint on the surface of the water 

    • Very thick – mats can be blown to the shore   

Where is it found?

  •   How/why does it grow/what conditions are needed

    • Most abundant during hot weather – only grows in high water temps     

      • ​​​​​​​​​​​​​​Spring/summer

      • Nutrient-rich water – run-off from fertilized fields

      • Most actually don’t produce toxins, but all should be considered toxic

        • Don’t know w/o testing

    • What areas of the country/state are at risk?

      • EVERYWHERE!!!

How is it toxic?

  • What species are affected?

    • Cats, Dogs, Horses, Cows/sheep/goats/llamas, Birds

      • Ruminants and birds are more susceptible

      • Dogs more sensitive to neurotoxins

      • Need to ingest it

      • Can lick it off the fur/hair too!

    • People – contact dermatitis

  • Types of toxins

    • Microcystins – harmful to the liver

    • Anatoxins – harmful to the nervous system

  • Not toxic unless dense surface bloom present

Clinical signs

  • Microcystins

    • Malaise/lethargy

    • Weakness

    • Inappetance

    • Vomiting

    • Diarrhea

    • Blood in stool or black, tarry stool

    • Pale mucous membranes

    • Jaundice

    • Seizures

    • Death

    •    First signs in a few hours of microcystins

      • Hepatotoxicosis 

      • Death within 12-24 hours

  • Anatoxins

    • Inability to walk

    • Disorientation

    • Coma

    • Shock

    • Excessive secretions (e.g., salivation, lacrimation, etc.)

    • Neurologic signs (including muscle tremors, muscle rigidity, paralysis, etc.)

    • Blue discoloration of the skin and mucous membranes

    • Difficulty breathing

    • Death

    • First signs w/in 30-60 min if anatoxin – neuro signs

      • Respiratory paralysis/arrest

      • Death can occur within 30 min, usually a few hours


  • Limited and rarely effective

  • Supportive care only

    • IV fluids, electrolytes, control seizures/muscle tremors

    • Activated charcoal

    • Out of direct sunlight

Prevention of exposure is key!!

  • Can treat water supplies, water mixing techniques for livestock


  • Very poor for animals

  • Good for people, but need medical attention