U.S. Fish and Wildlife Service



August 28, 1996

Andy Anderson 970-867-3773
Sharon Rose 303-236-7905

Parasitic Protozoan DNA Detected at Ennis National Fish Hatchery

Using an extremely sensitive test procedure known as polymerase chain reaction or PCR, fishery scientists detected the DNA of the microsporidian parasite, Nucleospora salmonis (also known as Enterocytozoon salmonis), in the Kamloop strain of rainbow trout broodstock at the Ennis National Fish hatchery in Ennis, Montana. Five other strains of rainbow trout raised at the Ennis facility tested negative for the parasite s DNA. To date, there has been no detectable symptoms or mortality caused by this parasite at the Ennis facility.

"This discovery at Ennis," said Regional Director Ralph Morgenweck, "underscores once again how technology can outpace the boundaries of our biological knowledge. This finding wouldn't have been possible even last year because we simply didn't have access to the new technology."

The Ennis Hatchery, one of the Service's largest egg producing facilities, incubates 25 million rainbow trout eggs annually for shipment to Federal, State and Tribal hatcheries in 27 states. It also distributes a limited number of eggs to private aquaculturists for seedstocks.

Upon confirmation of the findings in May, the Service sent letters to scheduled future egg recipients notifying them of the presence of Nucleospora salmonis DNA and advised them by phone or letter of the known status of research on the parasite. Similarly, those who have received eggs from Ennis over the past 12 months were notified. Acceptance of Ennis eggs and fish will be the discretionary decision of each recipient.

Fishery scientists believe that the parasite is transmitted from fish to fish. Investigations to determine if the parasite can be transmitted with fish eggs are continuing.

Does this parasite pose a significant threat to fish? "Fish at Ennis remain healthy and are feeding and performing well," said Andy Anderson, Regional Fish Health Manager for the Fish and Wildlife Service. Anderson added that while the Service does not wish to raise unfounded fears, nevertheless as its technological capabilities to detect parasites increase, it has the responsibility to keep partners and cooperators fully informed.

"We felt it was essential to inform the fisheries community of our new findings, especially in light of recent public concerns regarding impacts of diseases on recreational trout fisheries," he said. He also noted that recent discussions with West Coast fish health specialists who have dealt with this parasite for over five years generally indicate only slight concerns and they advise against overreacting to the finding of Nucleospora salmonis in inland trout populations.

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