Keeping dogs safe from toxic algae

Dog in riverbedCyanobacteria (also called blue-green algae or toxic algae) can make animals extremely sick, sometimes causing death. Dogs are particularly at risk if they swallow the algae or algal mats when swimming and drinking from rivers and lakes.

Unfortunately, dogs love the musty smell of cyanobacteria and are naturally drawn to investigating it – usually by drinking or licking the material. Not all algae in our rivers and lakes are harmful but dogs are not able to tell the difference.

Warning signs are not always in place

During November to March, popular swimming spots in Canterbury are monitored weekly for cyanobacteria and warning signs put in place if required. However, signs may not be at all access points or may not be in place outside of the summer season. That is why it is important for dog owners to know how to identify cyanobacteria and prevent your animals from getting sick.

If health warnings are issued for a lake or river site, these can be found on the Land Air Water Aotearoa (LAWA) website, Community and Public Health's website or on our health warnings page.

Know what to look for

In rivers – how to spot cyanobacteria

This cyanobacteria (called benthic cyanobacteria) grows on the bottom of river beds. It appears as thick dark brown or black mats that have a slimy or velvety texture and musty smell.

Cyanobacteria in riverbed
Cyanobacteria on rocks

In lakes, ponds and lagoons – how to spot cyanobacteria

This cyanobacteria (called planktonic cyanobacteria) is suspended in the water. Water can look cloudy, discoloured, or like it has small globules in it. Planktonic cyanobacteria may not have obvious visual traits.

If you are in any doubt about the water quality, then keep your dog on a leash and away from the water.

Cyanobacteria in lake
Cyanobacteria in pond

Know the symptoms of poisoning

Symptoms of cyanotoxin poisoning in dogs usually occur within 30 minutes. These include:

  • panting
  • lethargy
  • muscle tremors
  • twitching
  • convulsions.

If your dog is showing these symptoms after being in contact with a waterway, contact a veterinarian immediately. You or your vet can report any animal illness resulting from contact with cyanobacteria to us.

Find out more by reading this factsheet on the risks of cyanobacteria to animals (PDF File, 745.85KB). You can also check if there are any current warnings in place.