Dog owners: look out for toxic algae

If you're making the most of Level 2 by taking your dog on an autumn walk, take care to look out for potentially toxic algae in the waterways. It can make dogs (and people) very sick.

The warm, stable conditions in Canterbury this autumn have been great for recreation but unfortunately, also ideal for the persistent growth in some of our rivers and lakes of potentially toxic cyanobacteria (also called blue/green algae, or toxic algae). This can be deadly for dogs.

Shirley Hayward, our Principal Scientist Water Quality and Ecology, said the combination of the mild autumn weather and stable river flows has created favourable conditions for potentially toxic cyanobacteria to continue growing in some of our rivers.

Summer monitoring complete

Our recreational water quality monitoring is now complete for this summer. This means that many of our popular swimming spots are not being regularly monitored in the cooler months and warning signs may not be in place.

"That's why we ask dog owners to be vigilant around lakes and rivers in our region and to learn how to recognise potentially toxic cyanobacteria for themselves. If in doubt, keep the dogs out," said Hayward.

Algae is attractive to dogs

Sadly, the odour of algae is extremely attractive to dogs who may knowingly or accidentally consume cyanobacteria.

"Only a teaspoon of potentially toxic cyanobacteria can have fatal consequences if ingested. Also, cyanobacteria mats can accumulate on the river edges which increases the exposure risk for dogs and river users," said Hayward.

How to spot potentially toxic algae

In Canterbury we have two types of cyanobacteria that can be harmful to dogs and people: mats (benthic), which grows on the bed of rivers and streams; and free floating (planktonic), which is suspended in the water column of slow-moving waters (such as lakes).

Identifying river cyanobacteria

  • It appears as dark brown/black mats attached to rocks along the riverbed.
  • It often has a strong earthy or musty smell.
  • High river levels will remove the algal bloom, however detached mats can accumulate along the river edge and increase the risk of exposure to toxins.

Identifying lake/pond/lagoon cyanobacteria

  • If the water is cloudy, discoloured (especially blue-green coloration, or has scums or small globules suspended in it) avoid all contact.
  • Not all cyanobacterial blooms are visible to the naked eye and toxins can persist after the blooms disappear.

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

Watch our video on how to spot potentially toxic algae.

Knowing the symptoms

Symptoms of cyanobacteria toxin poisoning in animals include:

  • lethargy
  • muscle tremors
  • fast breathing
  • twitching
  • paralysis
  • and convulsions.

In extreme cases, death can occur 30 minutes after symptoms first appear.

If you are concerned, contact a veterinarian immediately. You or your vet can report to us any animal illness resulting from contact with cyanobacteria.

Cyanobacteria can also be harmful for people. If you have been in contact with water which may contain cyanobacteria and contract tingling or numbness around the fingertips and/or mouth, breathing difficulties, gastrointestinal symptoms or skin rashes, please seek medical advice from your doctor or contact Healthline on 0800 611 116.

More information