Dangers of Blue-Green Algae

Written by: Alison Laurie, Senior Consultant, Crown Vets Inverness

Blue-Green Algae is a term used to describe a group of bacteria, called cyanobacteria. They are not actually algae, they got this name because they often give the appearance of algae when they clump together in bodies of water. The cyanobacteria cannot be seen with the naked eye unless they clump together. When this happens, they can look like frothy, green flakes or bundles of brown-green dots on a pond, loch or stream. When the bacterium “blooms”, it can give the appearance of a blue-green “scum” on the surface of the water. It sometimes looks a bit like frothy, green pea soup. “Blooms” of the organisms often build up around the edges of still water. It is most common in still fresh water such as lochs and ponds during hot, dry weather, when there is less rainfall.

The “blooms” of the blue-green algae can produce harmful toxins which can cause acute Liver failure. Sadly, exposure to the toxic organisms is often fatal, and may also cause long term health problems in dogs that do survive after ingestion. Some types can kill a dog a very short time after drinking contaminated water. Dogs swimming in contaminated water can also get the algae caught in their fur, and then ingest them while licking and cleaning themselves afterwards.

Concentrations of the algae vary throughout the year and may not always be harmful however you can’t tell simply by looking at them whether or not they are dangerous. It is best not to run any risk of allowing your dog to come into contact with water bodies in hot, dry weather where the organisms may be present.

If your dog shows any of the following signs after drinking from, or swimming in water, then contact the surgery immediately:

  • Vomiting/being sick
  • Diarrhoea, often with blood
  • Seizures/fitting
  • Weakness/collapse/unconsciousness
  • Disorientation/confusion
  • Drooling or Frothing at mouth
  • Breathing difficulties

These symptoms are commonly seen with other illnesses too, but you should always call us if you are worried that your pet is suddenly sick after having access to water bodies. Sadly there is no antidote for the toxins produced by the cyanobacteria.  If caught early enough, we may try to make your dog sick and attempt to flush the toxins from the body by giving intravenous fluids and administer gut protecting treatments. Sadly though, even with urgent Veterinary help, this poisoning is often fatal.

Do keep your dog well away from water that you know, or suspect, may contain blue-green algae. They should not be allowed to drink, swim or paddle in such water. Note that the wind often blows “blooms” of algae to the edges of ponds or lochs, so higher concentrations of the toxin are more likely to be present at the water’s edge where your dog may stop to drink. 

Take note of signs warning of the known presence algae during dog walks and do take heed of any information given.  Note blue-green algae is also toxic to cats.

If you think you may have spotted blue -green algae in a water body and you cannot see any warning signs around, please report this to the Environment Agency, Incident Hotline Tel: 0800807060.