Strawberry Disease (SD) is a chronic, nonlethal skin condition that affects Rainbow Trout (Oncorhynchus mykiss) in the United States, several European countries (Scotland, England, Switzerland, Germany, France, among others), Chile and Peru (Sandoval 2017, unpublished report). In Europe it is also known as Red Mark Syndrome (RMS) or Cold-Water Strawberry Disease. The severity of the skin lesions suggests a hypersensitivity response, but hypersensitivity to what?  Affected fish respond well to immune suppressors including corticosteroids, but also to a wide range of antibiotic treatments, suggesting that...