Effects of Cyanobacteria toxins (Cyanotoxins) on Humans and Animals
1. How can cyanotoxins affect people?
Humans are susceptible to cyanotoxins, but most people avoid drinking affected water because of the objectionable appearance and odor of a cyanobacteria bloom. This explains the few records of toxicity causing death in humans. The accidental ingestion of blue-green algae during swimming and water skiing can result in fever, headache, dizziness, stomach cramps, vomiting, diarrhea and sore throat. Humans can also suffer skin and eye irritation and swelling, and swollen lips. These symptoms seldom persist for more than two or three days. Children can be more intensely affected because they may spend more time in the water than adults and have lower tolerance to the toxins. Further information can be found in Health Canada’s Guidelines for Canadian Recreational Water Quality – Cyanobacteria and their toxins.
2. Can cyanobacteria toxins harm me?
Although many people globally have become ill from exposure to blue-green algae toxins, poisoning from contaminated drinking water is unlikely to occur given that drinking water supplies are usually effectively managed to control taste, odor and other problems. Low levels of cyanobacteria hepatotoxins can have long-term or chronic effects in humans. Further information can be found in Health Canada’s Cyanobacterial Toxins in Drinking Water.
3. How can cyanotoxins affect animals?
Though not necessarily more sensitive to blue-green algae toxins than humans, many animals, such as dogs and cattle, may enter and ingest water even if there is an obvious bloom occurring. During a bloom, animals may consume large quantities of cyanobacterial cells if they drink the water, and if those cells happen to be producing toxin(s), the animals can become very ill, and even die. Symptoms of cyanotoxin poisoning may range from lethargy and loss of appetite to seizures, vomiting, and convulsions. Dogs are particularly susceptible to cyanobacteria poisoning because the algae can attach to their coats and be swallowed during self-cleaning. If a bloom is visible, do not allow livestock or pets access to the affected water and provide alternative sources of drinking water. Aquatic animals can also be impacted by changes to the water quality that occur during a cyanobacteria bloom. pH and dissolved oxygen can rapidly change during cyanobacteria blooms.