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Blue-green Algae Poisoning

Cyanobacteria Toxicity

Blue-green algae, also known as cyanobacteria, are a diverse group of oxygenic photoautotrophic gram-negative bacteria, some of which are capable of producing deadly cyanotoxins. Cyanotoxins are secondary metabolites which are toxic to most of the eukaryotic organisms including algae, plants, animals and humans. Although there are several types of cyanotoxins, they primarily affect the animal’s liver (Microcystin, Nodularin, Cylindrospermopsin) or nervous system (Anatoxin-a, Saxitoxin).

Cyanobacterial blooms occur worldwide in freshwater sources, usually nutrient-rich calm waters such as that found in ponds and dugouts. The occurrence of toxic cyanobacterial blooms has increased in frequency and severity. They are often associated with hot, dry weather.

Chickens are poisoned through ingestion of contaminated water. Symptoms of poisoning vary depending on the type of toxin ingested. Neurotoxic cyanotoxins (associated with the nervous system) will result in muscle tremors, decreased movement, difficulty breathing, convulsions, or in many cases sudden collapse and death.

Hepatotoxic cyanotoxins (associated with the liver) will cause weakness, bloody diarrhea, pale comb and wattles, mental derangement, and eventually death.

Clinical Signs

Blue green color stains
Difficulty breathing
Pale comb
Bloody diarrhea
Weight loss
Muscle tremors
Sudden death


  • History
  • Clinical signs
  • Physical exam
  • Laborary tests - detection of algal toxins in water samples and GI contents


Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own chicken "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Activated Charcoal2.8 g/kg administered orally as needed, to help absorb ingested toxinsK Marx



  • Regularly clean water sources, especially during hot and humid weather conditions
  • Prevent chickens' access to potentially contaminated natural or man-made stagnant or slow moving water sources (ponds, lakes, bogs, etc.)



Scientific References

Risk Factors

  • Algae growth in stagnant water sources during warm weather
  • Access to a natural water source
  • Not cleaning waterers