Diplostomum spathaceum

ALSO KNOWN AS: Eye Fluke, diplostomum

Diplostomum are digenean trematodes that have complex life cycles that involve birds (usually gulls), snails and fish. Diplostomum species are common parasites throughout North America and Europe. Many fish species can become infected, including both warm water (e.g. channel catfish) and coldwater (salmonids) fishes. Infections have been reported in amphibians, reptiles and humans.

In fish, the parasite infects the eye and can lead to modifications of the host’s behavior, which can make it more likely to be eaten by the parasite’s next host (a fish-eating bird). The parasite also affects marketability of the fish, affecting its feeding and growth, cosmetic appearance and causing blindness. There have been cases of blindness in hatchery populations of coho on the Columbia, in association with the large (and infected) populations of the parasite’s alternate host birds and snails.

Distribution: Widespread in freshwater environments across the Palearctic region

Detection Methods: Microscopic exam – wet mount

Hosts: Over 125 fish species

Target Tissue: Lens of the eye