KLAMATH FALLS, Ore. – Oregon Health Authority (OHA) urges caution for dog owns and waterfowl hunters after extremely high microcystin levels were detected in the Barnes Unit of the Upper Klamath National Wildlife Refuge.
The sample was taken from an area currently open for waterfowl hunting during the 2025–2026 season. The Upper Klamath National Wildlife Refuge has been under a recreational advisory since July 9.
Microcystin is a cyanotoxin produced by certain harmful algal blooms. Exposure can cause acute liver damage in people and is often fatal to dogs. Hunters should avoid using contaminated water for cleaning gear or handling harvested birds.
Dogs are at increased risk for exposure because of their size and level of activity. They can become extremely ill and die from water intoxication after drinking excessive amounts of water while swimming or fetching objects for long periods of time.
Symptoms
Symptoms of microcystin exposure may be similar to food poisoning such as stomach cramping, diarrhea, nausea and vomiting. Symptoms may also be more serious, such as numbness, tingling, dizziness and shortness of breath. These symptoms may require medical attention.
Dogs can experience weakness, difficulty walking, seizures, lethargy, loss of appetite and more. If a dog exhibits symptoms, veterinary treatment should be sought as quickly as possible.
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.
