For veterinarians schooled on the East Coast, salmon poisoning disease is simply a strange illness studied in textbooks, but for practicing veterinarians in the Northwest, it’s an illness all too common in pet dogs.
Salmon poisoning is a potentially fatal bacterial disease that occurs when dogs have ingested certain types of raw or undercooked fish that are infected with a fluke worm, which carries the rickettsial bacterium Neorickettsia helmonthoeca. Interestingly, a freshwater aquatic snail plays a vital role in transmission of the bacteria, acting as an intermediate host.
When it comes to the raw fish potentially harboring this pathogen, salmon is the most common culprit, followed by trout and a few other freshwater fish. Salmon poisoning is geographically restricted to Oregon, Washington and southern British Columbia, and thousands of cases pop up every year. The illness is not transmittable to humans.
Dr. Rob Hlavin, a veterinarian, practiced eight years in Portland before taking a position at Columbia Veterinary Hospital in Astoria. He has been at CVH for 2.5 years and is currently treating three suspected cases of salmon poisoning in dogs. He noted that he had seen some cases in Portland, and even though the most frequent times for infection are during the spring and fall salmon runs, these days, cases trickle in all year long.
“For vets moving in from other areas, it’s the nurses in our area who often teach the doctors about this disease, which is unknown in other parts of the country,” he said. “Many people swear that there is no way their dog came into contact with raw salmon, but it can happen easily. Ironically, salmon fishermen are sometimes the ones who swear their dog did not get into salmon, but the dogs somehow came into contact with it.”
Salmon poisoning is a familiar disease to longtime locals in the Northwest, who know the signs and symptoms. But for those who have recently moved to the area, salmon poisoning may look like many other canine illnesses. This can be problematic, as infected dogs can die without swift and properly diagnosed treatment.
Dogs that consume uncooked or undercooked infected fish will develop a high fever and gastrointestinal problems, which can include vomiting and diarrhea. In the later stages of the illness, the symptoms are more pronounced, but often the early stages and symptoms can be less dramatic — such as general lethargy and loss of appetite — and can resemble other maladies. All ages and breeds of dog are susceptible, with Labrador retrievers being highly represented due to their participation in fishing-related activities. Any part of the fish (especially gutted fish, entrails or skin) can be risky for dogs to ingest. Fishermen gutting fish on the docks is a common method of contraction of salmon poisoning, since dogs are attracted to eating the fishy-smelling entrails.
Local dog owner Audrey Pettersen had a puzzling experience with her family dog, Stella, a small terrier-retriever mix in 2015. The Emlen-Pettersen family was fully aware of salmon poisoning when they adopted Stella and took great measures to keep her away from the creek their property paralleled during the fall salmon runs. In the fall of that year, Stella seemed listless, which was puzzling because the dog had never been off leash or near the creek, and the family was very careful.
“Stella wasn’t eating, which made the alarm bells go off for me,” Pettersen said. “Normally she is a total chow-hound, so I just knew something was wrong. I was really glad later that I took the day off of work to see the vet — she could have died had I ignored it.”
It was surmised that a bird or a wild animal had possibly dropped a piece of fish in the family’s field as it was flying by. Hlavin noted that dogs have even picked up the illness from swimming, even when no direct contact with fish had been observed.
Fortunately for Stella, she was treated in the early stages and made a full recovery; shortly after, she accompanied her human family to Crater Lake.
There is a long-held belief around the area that once a dog gets salmon poisoning, they are immune for life. Hlavin doesn’t buy it.
“I suppose it’s possible — but if you got E. Coli from eating raw hamburger, would you eat it twice?” he asked. “Perhaps they learn, unlike us.”
Thankfully, salmon poisoning in dogs is fully treatable if you know the symptoms to look for. Avoid letting your dog eat uncooked, undercooked or kippered salmon or trout. During spring and fall salmon runs, be extra cautious about letting your dog run free around spawning areas. And, if you enjoy fishing, dogs may become infected in areas where fish is gutted and cleaned. Dogs are sneaky about eating things they like, so most importantly, if your dog exhibits unexplained lethargy, sluggishness or loss of appetite, it’s important to consult your local vet.
‘I was really glad later that I took the day off of work to see the vet — she could have died had I ignored it.’