Brown dog by a lake with blue green algae

Blue-green algae is extremely dangerous for dogs: Find out why!

© Elena Grigorieva - Shutterstock

Blue-green algae poisoning in dogs: Watch your pet near water!

By Emilie Heyl Content Writer

Published on the

Blue-green algae is extremely dangerous for dogs. So if your furry friend loves to swim, paddle or even walk around water, be extra cautious! Protect your dog against this bacteria, especially during warmer months.

During warmer months, many dog owners prefer to walk by lakes, ponds or rivers. Although this may seem like a good idea to refresh your pet, some waterways are contaminated with cyanobacteria (blue-green algae) that can dangerously affect your dog's general condition, or even poison them.

Blue-green algae is a serious concern for many pet owners and because some types of blue-green algae can kill a dog in just 15 minutes, it’s really important to know how to recognise infected water, what symptoms to look out for if your dog has been in contact with this bacteria and how to act. In this guide, you will find everything you need to know about cyanobacteria and we’ll give you tips on how to protect your dog from blue-green algae.

What is blue-green algae and what does it look like?

The term 'algae' is confusing, as they are actually a special type of microorganism, which share properties with algae and bacteria. Blue-green algae are also called cyanobacteria.

Because of their rapid growth, some people refer to them as "blooms", but this pretty name hides a very dangerous reality: cyanobacteria secrete toxins that can paralyse the respiratory muscles and cause neurological disorders. These bacteria grow in deep water, or stagnant water. This includes freshwater lakes, ponds or wetlands.

To describe what a blue-green algae looks like, people talk about broccoli soup, pea puree or a green or turquoise paint spill. These algae are present on the surface of the water and give it a very intense blue-green colour. They also form pellets that cling to rocks or gravel.

When they clump together on the banks, they turn brownish-black and their smell seems to attract dogs.

Blue-green algae present in water ©PJ photography - Shutterstock

Is blue-green algae toxic to dogs?

Yes, blue-green algae is extremely toxic to dogs. Cyanobacteria are responsible for extremely serious or even fatal intoxications in dogs that have ingested contaminated water. Dogs are particularly sensitive to cyanobacteria because they drink and bathe in these waters. Be extra vigilant with your dog! Don't let your dog go near an area infected with blue-algae.

We humans are not spared from cyanobacteria either... They can also be responsible for certain disorders observed each year in several cases, but these intoxications are less serious than in our dogs.

How quickly does blue green algae affect dogs?

If your dog has been swimming in water with cyanobacteria and has been exposed to these toxins, symptoms should appear 30 to 60 minutes after the exposure.

Other symptoms could take up to 12 to 24 hours to appear, therefore it’s extremely important to take your dog to a vet as soon as possible.

What are the signs of blue-green algae poisoning?

If your dog has been swimming, paddling or drinking water and you are concerned about blue-green algae being ingested by your pet, you should keep a close eye on these different symptoms. Indeed, by releasing their toxins, cyanobacteria can cause severe poisoning in your dog, which can be fatal within minutes. Your dog may experience the following symptoms:

  • Digestive problems: nausea, vomiting, diarrhoea
  • Nervous disorders: loss of balance, tremors, hyper salivation
  • Breathing difficulties
  • Fever

In the event of suspected poisoning, it is essential to take your dog to your vet as soon as possible so that he can receive emergency first aid and stabilise his general condition.

What should I do if I think my dog has been poisoned by blue-green algae?

If your dog shows signs of weakness, vomiting or diarrhoea when returning from a walk near a dubious water source, make an urgent appointment with your vet. These symptoms of poisoning are a veterinary emergency and you will have to go and see an emergency veterinarian.

The key is to act fast! Indeed, by taking your dog to the vet immediately and seeking immediate treatment for your pet, this could help improve its chances of survival. Blue-green algae often needs rapid treatment, so it is important that your dog sees a vet straight away.

If it’s possible, you should get someone to call your vet while you are on your way, this will give them time to get prepared when your dog arrives.

Sadly, there is no specific treatment or antidote for dogs that have been poisoned by blue-green algae. Your vet will treat the symptoms that exist at the time of diagnosis.

How can I protect my dog from blue-green algae?

Your dog (and yourself) love walking by the water? You shouldn’t stop going if that is the case but you will have to be more cautious in the warmer months and keep an eye open when letting your dog go for a swim or drink water as there could be blue-green algae present. Here are a few tips to help you protect your dog from blue-green algae:

  1. Avoid going to areas where swimming is not recommended (sometimes there will be a notice board to alert you)
  2. Inspect the water before letting your dog go for a swim. Now you know how to recognise blue-green algae and also where to find it, so you’ll have to check the surface of the water, rocks and banks.
  3. If you are walking in a contaminated area, keep your dog on a lead and don’t let your pet approach the water.
  4. If your dog has been in contact with contaminated water, immediately wash and rinse your furry friend.
Did someone just come back from a swim? ©dezy - Shutterstock

What time of year is blue-green algae most common?

Blue-green algae is most often found during or after hot and sunny periods and especially after heat waves. But the amount of cyanobacteria changes throughout the year. Many pet owners have found blue-green algae in spring and autumn.

Is blue-green algae a health risk to humans?

Of course, blue-green algae isn’t only toxic to dogs, cats or any other animals but to humans too. Anyone who swims in contaminated water is also likely to be poisoned. Skin and eye irritation, stomach cramps, vomiting, diarrhoea, fever, headaches, muscle pain... The symptoms can vary, but require rapid treatment in hospital. Children are more at risk than adults because they like to drink water when swimming.

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