Nanophyetus Salmincola

Nanophyetus salmincola may be the most common trematode endemic to the United States. In particular, the parasite is a food-borne intestinal trematode prevalent in the coast of the Pacific Northwest.

The life cycle of the N. salmincola requires three hosts. The first intermediate host is an Oxytrema silicula stream snail. The second intermediate host is a salmonid fish, though some non-salmonid fishes also play a role. Lastly, the definitive host is most commonly a canid, though many other mammals are also definitive hosts, including humans. Transmission of N. salmincola to the definitive host occurs upon ingestion of parasite-infected fish.

The parasite is most known for its association with “salmon poisoning disease", which, left untreated, proves to be fatal to dogs and other canids. However, canids are affected by the Neorickettsia helminthoeca bacteria, for which N. salmincola acts as a vector, and not by the parasite itself.

Very few known cases of naturally acquired human infection with N. salmincola are found in the literature, though it is likely that many cases are unreported, since most people are asymptomatic, or symptomatic with non-specific symptoms like gastrointestinal discomfort. Disease caused by N. salmincola, or nanophyetiasis, is easily preventable by thoroughly cooking fish before consumption. There are no known cases of human infection by the Rickettsia bacteria carried by N. salmincola.

A subspecific parasite, Nanophyetus schikhobalowi, is endemic to Siberia, where human cases of nanophyetiasis have been reported in scientific literature since 1931.