Ceratomyxa shasta) is a myxosporean parasite that infects salmonid fish on the Pacific coast of North America.

It was first observed at the Crystal Lake Hatchery, Shasta County, California, and has now been reported from Idaho, Oregon, Washington, British Columbia and Alaska.

Clinical indications of infection in salmons include lethargy, loss of body mass, darkening of the skin, ascites, exophthalmia and kidney pustules, These symptoms vary from one salmonid species to another, and also depend on life stage of the host.

[2][4] Internally, infection with C. shasta affects entire digestive tract, liver, gall bladder, spleen, gonads, kidney, heart, gills, and muscle tissues.

[6] The dams on the river Klamath resulted in the colonization of large areas with polychaete worms which are a secondary host of C. shasta.