Despite its name, salmon poisoning is not so much a poisoning, but an infection. It is a highly fatal infection caused by a bacteria called Neorickettsia helminthoeca, that lives in a fluke (a parasitic flatworm) called N. salmincola. It is found throughout in the Pacific Northwest, extending from northern California to central Washington and as far inland as the Cascade mountain range. The infection occurs when a dog ingests raw salmon that carries the fluke infected with the bacteria.
The fluke acts as the vector for the bacteria and harbors it for its entire life. The fluke must live in three different hosts to complete its lifecycle. First is a river snail in which the fluke develops as a larva. It exits the snail when developed to find its second host, a fish. It burrows into the skin of the fish and disperses itself throughout its circulatory system and into major organs. Its final host is typically a canine but it has been known to live in bears, raccoons and fish-eating birds. The fluke matures in this host, where it attaches to the intestine. The bacteria is subsequently released from the fluke and travels to the host’s circulatory and lymphatic system.
The clinical signs a dog will show are high fever, anorexia, lethargy, diarrhea and vomiting. It typically only takes about a week for clinical symptoms to show. The first step in diagnostics is to run a stool test, which shows if the fluke’s eggs are present, but because an infection of the fluke does not definitively indicate an infection of the bacteria, the most common course of action is to start the dog on antibiotics and see if he/she responds. A definitive diagnosis is very difficult to obtain; special equipment is needed that is often not available in a veterinary medical setting, and it is very costly. Apart from antibiotics, patients are given IV fluids to rehydrate after vomiting and diarrhea. The only way to prevent this infection is to prevent your dog(s) from eating dead or alive salmon. Even in a dead salmon, the bacteria can remain alive for months.
Morgan Pintler is a nurse at St. Francis Pet Clinic.