The disease is caused by a bacteria-like organism, Neorickettsia helminthoeca, which is transmitted by the parasitic flatworm (or “fluke”) Nanophyetes salmincola. The fluke affects both trout and salmon in an area roughly north of a diagonal line from Sausalito to Chico, and on the western slope of the Sierra/Cascade mountain range. CDFW raises fish at three hatcheries where the fluke is present either intermittently or continuously: Darrah Springs, Crystal Lake and Mount Shasta. However, CDFW only stocks fish from these hatcheries into waters where the parasites have been present for decades.
Throughout the Pacific Northwest thousands of dogs are infected every year with Salmon Poisoning Disease after eating raw or cold-smoked fish infected with the parasitic fluke. All fish caught or originating from streams in northern California, Oregon and southern Washington could potentially be infected with disease-carrying flukes harmful to dogs.
If your dog has eaten or is suspected of eating raw fish, watch to see whether signs of the disease appear. If signs of the disease appear, promptly take your dog to a veterinarian. Although this disease is relatively easy to cure if diagnosed in time, it will almost certainly kill a dog if left untreated.
Symptoms are similar to distemper and may include some or all of the following: a rise in body temperature, loss of appetite, vomiting, diarrhea, listlessness and/or rapid weight loss.
Dog owners are advised to be cautious and to keep salmon, steelhead, trout and other freshwater fish carcasses away from their dogs. The parasite cannot survive in cooked fish, is not harmful to humans and does not affect pets other than canines.