Here in the Pacific Northwest "Salmon Poisoning" is a common infectious disease with severe consequences. It seems as if everyone has heard of it, or knows someone whose dog has been afflicted by it.
The life cycle of the infectious agents which cause Salmon Poisoning is a fairly complicated one. The disease is caused by a rickettsial bacteria (Neorickettsia helminthoeca) which resides in a parasitic fluke (Nanophyetus salmincola) that infects a freshwater snail. When that doubly-infected snail is ingested by fresh water trout or salmon, the fluke encysts itself into the muscles of the fish. Infection of dogs is accomplished when they eat raw salmon or trout. Once ingested, the encysted fluke will attach itself to the intestinal lining of the dog, causing severely debilitating clinical signs.
The severity of the signs varies with each patient. Typically a patient will begin to show clinical signs 7-10 days after exposure to an infected fish. A dog may present with a history of anorexia, vomiting, bloody diarrhea, fever, and enlarged lymph nodes. Many times the dog will be dehydrated and depressed.
The diagnosis of salmon poisoning is typically made via microscopic inspection of fecal matter from an infected patient. Finding the fluke ova is diagnostic for the disease. However, due to the nature of the disease and depending on the time of presentation to a veterinarian, fecal results can be negative for the parasite ova and that is why treatment can be instituted with just the clinical history and physical examination findings. Fine needle aspiration and cytologic examination of the enlarged lymph nodes can also be diagnostic in some cases.
If your dog presents with salmon poisoning, they may need to be hospitalized with IV fluid therapy to correct their dehydration. Supportive care to aid in nausea and decrease the fever may also be instituted. Treatment of the rickettsial bacteria is done with an antibiotic while concurrent treatment for the fluke is done with antiparasitic medications.
If discovered and treated early enough, the prognosis for a full recovery is good. However, if left to its own devices, untreated salmon poisoning can be fatal. If you suspect your dog has been exposed to an infected fish, it is important to seek proper veterinary care so that they will have the best fighting chance for a full recovery. It is also important to remember that just because your dog has been infected once with the fluke, does not mean that they are completely immune to future infections!
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