With the increasing popularity of feeding home prepared or raw food diets based on the works of veterinarians Ian Billinghurst and Richard Pitcairn as well as other canine
nutritionists, the issue of feeding raw fish needs to be addressed. For those dog owners living in northern California, Oregon, Washington, Idaho, British Columbia, and parts of southern Alaska the risk of a dog contracting Salmon Poisoning Disease is a very real possibility.
What is Salmon Poisoning Disease?
Salmon Poisoning Disease (SPD) is a misnomer. It
does not result from from ingestion of a toxin, rather it results from infection by a rickettsial organism,Neorickettsia helminthoeca. SPD has been known since the early 19th century in North America. It had been observed that dogs that ate raw salmon frequently died however the connection between the fluke and the rickettsia was not established at this time.(1) It is unusual in that the rickettsial organism does not directly infect the dog but is instead carried by a parasite, a trematode (flatworm or fluke) called Nanophyteus salmincola through two intermediate hosts first: freshwater snails and salmonid fish (salmon, trout,
steelhead).
Nanophyteus salmincola are found to infect freshwater snails particularly Oxytrema plicifer. The infected snail forms part of the salmonid species food web and is ingested. Neither the fluke nor the rickettsial organism act
as pathogens in the fish. The dog is exposed only when it ingests the secondary host - an infected fish. After the dog
ingests the fish, the encysted fluke larvae burst and embed in the dog’s intestinal tract and the rickettsia are introduced. The cycle continues when ova are excreted in dog feces to infect snails.
Transmission by other means (cage to cage or aerosol) is rare. The disease is not breed, age or gender specific. The determining factor for disease prevalence is the
availability of fish.(2)
What are the symptoms, treatment, and prognosis?
Sudden onset of symptoms 5-7 days after ingestion of fish.
Initial symptoms include lethargy and anorexia.
Peaking of temperature between 104-107.6o F in the first two days followed by gradual return to normal.
Onset of persistent vomiting by the fourth day.
Development of bloody diarrhea within a few days of vomiting onset. The diarrhea that is normally seen is a bright yellow color.(3)
Enlarged lymph nodes.
In the acute stages, SPD gastrointestinal symptoms are quite similar to canine parvovirus. Nasal and ocular symptoms can resemble canine distemper. If left untreated, SPD has a
mortality rate of up to 90%. Treatment is supporative therapy
to maintain hydration as well as antibiotic therapy to kill the disease producing organism. Dogs that survive SPD are immune.(4)
How can it be prevented?
Prevention of the disease is quite simple. Avoid feeding dogs fed raw salmonids or cold processed, cold smoked salmonids (cold processing and cold smoking do not
kill the pathogen). If you chose to feed salmonids to a dog, the fish must be cooked or pressure canned. If you hike or camp in areas that are salmonid habitat,keep a watchful eye on your pet to insure that fish carcasses are not ingested. See your vet immediately if your dog develops symptoms resembling SPD and you think your dog may have ingested raw salmonid fish.
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(1) Smith, J.M., Dr. "Nanophyetus salmincola", World of Parasites,
http://martin.parasitology.mcgill.ca/jimspage/biol/NANO.HTM
(2) Ailello, Susan E. B.S., D.V.M, E.L.S. ed. and Mays, Asa, D.V.M.,
M.M.S., Dipl. A.C.L.A.M. The Merck Veterinary
Manual, 8th edition. Merck & Co., Inc. Whitehouse Station, NJ.
1998. pg 565
(3) Gary Olson, DVM, Shelton Veterinary Hospital, Shelton, WA
(4) "Nanophyetus salmincola" Veterinary Parasitology (VPBIO556-557)
http://web.missouri.edu/~vmicrorc/Platyhelminths/Trematodes/Nanophyt.htm
© 2000 Sandra Dunlap (reviewed by Gary Olson, DVM)