A fish pathogen similar to one previously found in the United States only in Pacific salmonids -- salmon and trout species -- has been identified for the first time in the eastern United States and in a non-salmon species, according to new research by the U.S. Geological Survey.

A 2015 sampling effort found the pathogen, Dermocystidium, within cysts on the bodies of Blue Ridge sculpin, although it can cause cysts in the gills and internal organs of infected fish as well, and sometimes death. Before this new study, infections of this pathogen in the U.S. were restricted to Pacific salmonid species in west coast rivers, although it has been reported in other species in Europe.

“The infection was found on Blue Ridge sculpin during fish community surveys in Catoctin Mountain Park, Maryland, in 2015,” said Vicki Blazer, a research fish biologist and lead author of the study. “In portions of the watershed where the infection was observed, sculpin numbers were lower than expected. And a nearby stream lacked sculpin altogether, though they are typically common in the region. The lack of sculpin indicates the possibility of regional effects.”

Dermocystidium is a protist belonging to the phylum Mesomycetozoea, which are mostly found on fish and amphibians. Mesomycetozoea is considered an emerging threat to aquatic and terrestrial animals because they are not species specific, are opportunistic and can be carried as chronic sub-lethal infections.

“Sculpin can be found in many watersheds throughout the Chesapeake drainage and are an important part of the fish community,” said Blazer. “It is currently not known if other fish species may be affected, or if the pathogen will have significant effects on sculpin populations.”

More fieldwork, in collaboration with the National Park Service and Maryland Department of Natural Resources, is planned to monitor fish populations in the affected stream as well as nearby watersheds.

The study, “Dermocystidiumsp. Infection in Blue Ridge Sculpin Cottus caerulomentum Captured in Maryland, USA,” is available online in the Journal of Aquatic Animal Health.