Dogs love to eat fish and fish parts, but in this region they often get sick from eating any part of the Salmonid type fish in its raw state. The disease is called Salmon Poison Disease, Fish Disease, Salmon Infection, Pacific Northwest Fish Fever, and a variety of others. Please note that it is a very different disease from Salmonella.
Salmon Poison Disease (SPD) is very serious and an estimated 90 percent of infected and untreated dogs die. However, it is treatable, and in most cases does very well with the correct therapy. The SPD profile is not completely understood by those who study it, and consequently, there are a lot of rumors surrounding this disease that are not quite accurate. Hopefully reading this article will help dispel these rumors and help more dogs survive and get the help they need.
The vast majority of SPD cases are from Salmonid type fish. This is a large category including Trout, Steelhead, Coho, Chinook, King, Chum, Sockeye and others. There are some reports of non-salmonid fish and salamanders playing a role in this predominantly canine disease. This condition is very complicated and includes the fish (salmonid), a liver fluke (Nanophyetus salmincola), snail (Oxytrema plucifer), and rickettesia bacteria (Neorickettsia helminthoeca). This disease only occurs in the Pacific Northwest and is thought to only occur here due to the habitat range of the snail. The pathway for infection is thought to begin with eating a snail that is infected with a juvenile lifecycle of the liver fluke, which contains the rickettesia bacteria. Any tissue of the fish can be infected, which means the flesh, blood, guts, eyeballs, or slime. Other types of fish can be a factor in this disease, but the tissue that may be infected in other fish may not be what dogs tend to eat (e.g.: only fins), which his why “other fish” are often thought unimportant. Juvenile salmonid fish become infected by eating free-floating liver flukes or snail parts on their way to sea where they reach maturity, therefore the oceanic life cycle phase of the Salmonid fish is thought to be as contagious to domestic dogs as river salmon. This disease is further complicated by the fact that the disease-causing rickettesia comes in several varieties, which allows for dogs to get Salmon Poison Disease more than one time.
As any part of the fish that dogs may eat can be infective, and the concentration that is in the tissue of the fish may mean that only a small amount is eaten, the owner may not notice the dog eating fish, so it is of great importance that if there is ANY CHANCE that the dog ate fish of salmonid origin in the Pacific Northwest the owner MUST alert their veterinarian. Veterinarians who have trained in other parts of the country/world and have relocated here may not think of this as quickly, and often the disease is not caught as early as it could be. This is equally important to those who visit this coastal region, since the dog is infected here but doesn’t show signs until they get back home.
Domestic dogs that are infected by eating fish can become deathly ill very quickly, but often the dogs don’t show clinical signs of being sick for 5-14 days (sometimes as long as 30 days). The sickness can be very generalized with the dog only showing lethargy. More commonly, the dog has enlarged lymph nodes, high fever, vomiting and diarrhea. The diagnostic test that a veterinarian may perform is an Internal Parasite Analysis (aka faecal), which may show liver fluke eggs. It is important to understand that if the dog has eaten fish and there are no fluke eggs in the stool, SPD cannot be ruled out, and a second poop test should be performed a couple days later.
Finding a local veterinarian who is familiar with the Pacific Northwest Fish Fever is very helpful in getting the dog diagnosed and treated quickly. The sooner a veterinarian examines the dog and gets treatment started, the better the chance of survival and subsequent full recovery.