Oregon’s Success

Prompt Cyanotoxin Testing and Outreach at Oregon Lake Allow for Successful Triathlon and Increase Awareness of Cyanobacterial Blooms

Dog Becomes Ill After Swimming in Oregon Lake

In early July 2021, a dog became ill shortly after playing fetch in a lake in northwestern Oregon. The dog was in the water for nearly 2.5 hours and then developed neurological symptoms. She lost control of her back legs, could not walk, and slipped into a coma in transit to the closest veterinary emergency hospital. When she did not respond to several treatments, she had to be put to sleep. The owner then posted on social media, suggesting cyanotoxins (toxins produced by cyanobacteria) had caused the death. This prompted several people to report to the Oregon Health Authority (OHA) that they had become ill after visiting the lake two days earlier.

State and Local Agencies Test for Cyanotoxins

OHA quickly began investigating the cause of the dog’s death. The dog’s symptoms were consistent with exposure to cyanotoxins. However, no visitors to the lake, including the dog owner, had seen a cyanobacterial bloom before or around the time of the dog’s illness. OHA was concerned that a cyanobacterial bloom may have been growing under the water in the “benthic” zone (near the bottom of the water) or on rocks nearby. This type of bloom would have been harder to see.

The lake provides drinking water to approximately 450,000 people. Additionally, over 420 people were scheduled to swim in it two days later as part of an upcoming triathlon. OHA collaborated with the Oregon Department of Environmental Quality (DEQ), the Washington County Health Department, the City of Hillsboro Water Department, and the Washington County Parks Department to collect water samples from several popular recreational areas at the lake, including the swim area for the triathlon. The City of Hillsboro Water Department and the Joint Water Commission shipped water samples to a laboratory for cyanotoxin testing, including samples from the area where the dog had swum. In the interim, DEQ fast-tracked analysis of a sample collected from this area and did not detect anatoxin or saxitoxin, two cyanotoxins associated with symptoms similar to those the dog had experienced. The agencies worked together to develop risk messages to share with the public.

Rapid Response Enables Triathlon to Occur and Raises Awareness About Animal Health

State and local agencies acted quickly to collect water samples, but there was a delay during the shipment to the laboratory. Even so, DEQ’s lab confirmed before the triathlon that no cyanotoxins were detected in the water where the dog had played.

To reassure the public and inform lake visitors on how to reduce their exposure to blooms and toxins, OHA developed a public statement, issued a press release, and coordinated with partners to provide consistent information through as many traditional and social media outlets as possible. Information was also available on OHA’s Cyanobacteria (Harmful Algae) Bloom websiteexternal icon and posted on other agency websites, including the Sheriff’s Office website.

Parks department management updated the triathlon organizer so the organizer could decide whether to proceed with the event. The management shared the information from OHA and other agencies about blooms and potential risks and noted that there was no visual identification of blooms, either by the water department or swimmers practicing before the triathlon. The triathlon went ahead as planned.

OHA determined that no swimmers in the training group had become ill prior to the triathlon, and participants reported no illnesses after the event. Laboratory results available after the triathlon showed that none of the cyanotoxins analyzed (microcystins, cylindrospermopsin, anatoxin-a, and saxitoxin) were found in the water.

To further understand whether benthic cyanobacteria could have been responsible for the dog’s illness and death, OHA sent the dog’s stomach contents to the University of California Davis, California Animal Health and Food Safety Lab for analysis. No cyanotoxins were found. Based on the full investigation, OHA believes that the dog swallowed a large amount of water (water intoxication) while playing fetch. This can be dangerous to dogs, causing the same symptoms as neurotoxin exposure.

To help keep dogs safe, OHA updated their education and communication materialsexternal icon with information about outdoor risks, such as water intoxication and heat stroke, that cause similar symptoms as cyanotoxin-associated illnesses. For lake visitors, Washington County Parks Department now posts signs at popular access areas around the lakes explaining human and animal risks of exposure to cyanotoxins and promoting health and safety in and around water.

For more information about animal illnesses caused by cyanobacteria and how to protect pets and livestock, visit CDC’s Cyanobacterial Blooms: Information for Animal Owners and Cyanobacterial Blooms: Information for Veterinarians.

Page last reviewed: April 28, 2022