Oregon Officials Warn Toxic Bacteria in Klamath Refuge Water Can Be Fatal to Dogs

Extremely high levels of the toxin, microcystin, have been found in the Barnes Unit of the Upper Klamath National Wildlife Refuge.

Waterfowl Hunters and Dog Owners Urged to Exercise Caution

The Oregon Health Authority (OHA) is urging dog owners and waterfowl hunters to exercise caution when visiting the area, which is currently open for the 2025-26 waterfowl hunting season.

The OHA says exposure can cause acute liver damage in humans and can be fatal to dogs. Dogs can die from water intoxication if they drink too much water while swimming or while fetching objects. The OHA has also warned hunters not to use contaminated water for cleaning gear or when handling harvested birds.

Since July 9, people have been warned that recreational activities, such as swimming, boating, and angling, may not be safe in or around the Upper Klamath National Wildlife Refuge.

Microcystin is a toxin produced by certain types of blue-green algae that grow in lakes, rivers, and reservoirs, especially during warm weather when harmful algal blooms form.

Take Heed of Symptoms

Symptoms of microcystin exposure are similar to food poisoning, with humans experiencing stomach cramps, diarrhea, nausea, and vomiting. Serious symptoms include numbness, tingling, dizziness, and shortness of breath, and require immediate medical attention.

Dog owners must also seek immediate veterinary assistance if their canines display signs of weakness, difficulty walking, lethargy, loss of appetite, and seizures. Canines displaying these symptoms should be seen by a veterinarian immediately.

For more information about the advisory issued for waterfowl hunting in the Barnes Unit of the Upper Klamath National Wildlife Refuge, visit the Oregon Department of Fish and Wildlife (ODFW) news website.

For health information or to report an illness, contact OHA at 1-877-290-6767, or visit OHA’s Cyanobacteria (Harmful Algae) Blooms website.