Toxic Algae Harmful to Pets and People Detected in Willamette River

ALERT: Do not let dogs swim in or drink from the Willamette River due to current toxic algae bloom.

On Thursday, August 5, 2021, Oregon Health Authority (OHA) and the Department of Environmental Quality (DEQ) informed Multnomah County Health Department about an algal bloom developing on the Willamette River harmful to pets. On August 31, 2021, OHA and DEQ issued an advisory for humans and pets. The affected area of the river stretches from Sauvie Island to Ross Island. The official advisory was issued for Ross Island Lagoon and Holgate Channel.

Read the August 31 Advisory from OHA

Lab results from samples show toxin levels that can be very harmful to people and pets - especially small children and dogs. Cyanotoxins are created by the algae blooms and can be lethal to dogs within hours of ingestion

There's no clear end to when the blooms will go away, and they could last for weeks to months. Blooms develop in rivers when the water becomes slack and warm, and may last until weather and rains cool the water levels to a point where the blooms can no longer propagate.

About blue-green algae toxin poisoning

Blue-green algae toxin poisoning, also known as cyanobacterial poisoning, is an acute, sometimes fatal, condition caused by the ingestion of water containing high concentrations of cyanobacteria.

In Oregon, dogs have become very sick, and some have died after swimming in and swallowing water affected by toxic algae.

Poisonings are most likely to occur during warm, sunny weather when algae blooms are more intense, and dense surface scums are present. If you find thick, brightly colored foam or scum at a lake, pond or river, don’t let your pet drink or swim in the water.

If your pet is exposed

If your pet goes in the water:

  1. Don’t let your pet lick its fur. 
  2. Wash your pet with clean water as soon as possible.
  3. If your dog shows symptoms such as drooling, weakness, vomiting, staggering and convulsions after being in bloom-affected water, seek immediate veterinary care

Acute, life-threatening symptoms from cyanobacterial toxins often develop rapidly. Death can occur within 4 to 24 hours after exposure.

For more information, or to report potential exposure, pet owners are encouraged to visit, call toll free 1-877-290-6767, or e-mail

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