When it comes to things that make our pets sick in this country, there are no hard and fast rules. There are diseases that affect both dogs and cats throughout the country (rabies, for example), some that affect only one species of pet (dog OR cat) throughout the country (like parvo or feline leukemia), and some that affect pets only in a particular part of the country.
Salmon poisoning falls in the latter category—it affects only dogs living in the Pacific Northwest states. Summer is a good time to talk about salmon poisoning, because it tends to occur more when the weather is warmer and people (and their pets) are venturing outdoors more, but salmon poisoning can certainly happen any time of the year.
As its name implies, salmon poisoning occurs in dogs who eat contaminated raw salmon. It’s not exclusive to salmon, however—trout, shad, sturgeon and any other fish that spends time in the coastal rivers and streams can cause this potentially deadly disease.
It’s not strictly the fish’s fault, though, and not all of these fish can cause salmon poisoning. You see, some fish can harbor a kind of parasitic flatworm known as a fluke. And sometimes this fluke can be infected with a bacterial organism called Neorickettsia helmonthoeca. When the stars align this way (or misalign, I should say), dogs can then contract salmon poisoning disease.
When fish infected with flukes are ingested, the larval flukes release the Neorickettsia helmonthoeca organisms in the intestines of the dog. From there, the organisms spread through the blood to the lymph nodes, liver, lungs and brain of the poor soul who only thought he was getting a tasty fish treat.
It usually takes about a week for dogs who have eaten infected fish to show signs of salmon poisoning. Clinical signs include fever, lethargy, weakness, decreased appetite, vomiting and diarrhea (often with blood).
Diagnosis can be tricky—signs of salmon poisoning disease mimic other more common diseases, like parvovirus infection. A history of eating raw fish is key to helping make the diagnosis, so be sure to mention to your veterinarian if you and your dog have been fishing lately or if your dog is a known “dumpster diver” who loves getting into trash.
Finding fluke eggs in a fecal exam can lead a veterinarian down the path to diagnosing salmon poisoning disease, but because not all flukes harbor the infectious agent that causes salmon poisoning disease, sometimes the presence of fluke eggs is a red herring. Samples obtained from the lymph nodes of infected dogs can show the bacterial organism, or infection can be confirmed through a PCR assay.
Salmon poisoning can be fatal without treatment, with death occurring as soon as two weeks after exposure. However, with prompt treatment, the disease is rarely life threatening. Antibiotic therapy is usually quite effective, with clinical signs improving dramatically in as little as 24 hours. Because dogs can be quite ill with salmon poisoning disease, many affected patients will require hospitalization for supportive therapy as they recover.
Salmon poisoning disease sounds quite scary, and it is, especially without treatment. Luckily, it is pretty rare, and also very specific geographically. If you’re one of the lucky ones who gets to live in the beautiful Pacific Northwest, do your dog a favor by keeping your fishing haul to yourself. If you must share, though, be sure to cook your catch first!
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