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Posted by Tony Bithell on Jan 07, 2013

The effect of blue-green algae upon dogs

Blue-green algae also known as Cyanobacteria is extremely poisonous to dogs, cats, horses, cows and birds.

Blue-green algae is a microscopic bacteria that can be found in freshwater lakes, streams and ponds. This algae produces a toxin that can affect livestock or pets that drink (or swim in) any algae-contaminated water.

The blue-green algae can be found at any time of the year, yet tends to be more prominent in hot weather and is most likely to be found in nutrient-rich waters. The algae is more prominent in times of drought when water levels are low, however not all blue-green algae carries the poisonous toxins! It’s true to say that without testing, there is no definite way of finding out whether the toxins are present.

It’s important to be aware that hunting dogs that swim or play in lake water are more likely to be at risk of infection and, should they become ill, without immediate treatment the microcystins toxins can have a fatal affect on your dogs, as a result of damage to their liver or perhaps liver failure.

Kansas City District Lakes - Sept. 7, 2011

Example of blue-green algae (Photo credit: Kansas City District)

Signs of dog poisoning

The signs of dog poisoning will depend on whether it is triggered by nervous system toxins or liver toxins.

Signs of liver toxins:

  • Weakness
  • Pale mucous
  • Bloody diarrhoea
  • Disorientation

Signs of nervous system toxins:

  • Muscle tremors
  • Convulsions
  • Laboured breathing
  • Difficulty moving around

Other signs to look out for:

  • Coma
  • Weakness
  • Jaundice
  • Seizures
  • Blood in stool or black stools
  • Vomiting


Sadly, without treatment, death is likely to occur within a couple of days. Therefore, immediate veterinary treatment is necessary to ensure a full recovery. If you suspect your dog or pet has been exposed to blue-green algae, then seek advice from a veterinary practice immediately! In order to make an effective diagnosis, the vet will need to have a clear understanding of the dogs history and will need to know where the dog has recently been. So be prepared to give as much detail as possible!

Likely “after affects” of algae poisoning

If you suspect your pet has algae poisoning, hopefully you will be able to get it to the vet quickly enough to guarantee its survival. However, your pet may still experience lasting effects which could include:

  • ultra sensitivity to sunlight
  • chronic low weight problems
  • lethargicity

Preventing algae poisoning

Do not allow your dog or pet to drink from stagnant water such as ponds, lakes or puddles, especially if the water has a blue-green scum on the surface or around the water edge.

Consider taking with you a collapsible water bucket/bowl and a bottle of water to make sure your dog has fresh water at all times.

In addition, if you find that you have contaminated water on or around your property, then you should fence off the section immediately and treat the algae with copper sulphate. Always obtain advice from your local pond supply store before trying to treat your pond or water supply.

In conclusion

Do not allow your dog to drink stagnant water when out and about. Try to carry a fresh supply of water for yourself and your pets. If you suspect your dog has drank contaminated water then seek veterinary advice immediately.