Most cases of salmon poisoning disease are presumptively diagnosed based on a history of the dog’s recent consumption of raw fish and/or exposure to lakes, rivers or streams in an area that is known to be a natural habitat for Neorickettsia helminthoeca bacteria, Nanophyetus salmincola flukes and Oxytrema silicula snails. In a nutshell, this is the Pacific northwestern part of North America, up to but not including Alaska. Many veterinarians will treat a dog that meets this profile on the presumption that it has eaten infected fish. The dog’s positive response to treatment is often the most common way that a diagnosis of salmon poisoning is made.
Routine blood and urine tests performed on dogs with salmon poisoning disease are usually unremarkable, which means that they tend to be pretty normal. X-rays (radiographs) of the dog’s chest or belly usually show nothing out of the ordinary, unless something else is going on besides salmon poisoning. Samples taken from enlarged lymph nodes by a procedure known as fine needle aspiration may reveal the infective bacteria. Microscopic examination of fresh fecal samples may also reveal eggs of the fluke vector, Nanophyetus salmincola.