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UI researcher angling for fish vaccine

US - Rainbow trout might be native to Northwest streams, but chefs all over the world revere the fish's firm, mild-tasting flesh. Thanks to aquaculture, fresh trout appears on menus from Tokyo to Tehran.

"In Japan, it sells quite well against the sockeye salmon," said Jim Parsons, senior vice president of Troutlodge Inc. in Sumner, Wash. His company ships rainbow trout eggs for cultivation to 45 countries, including Iran.

In distant fish farms the eggs grow into pan-sized fillets. But each year an elusive killer called coldwater disease causes millions of dollars in losses for fish farmers. The bacterial disease sweeps through rearing ponds, killing vulnerable fingerling trout.

"You can lose 30 percent of them in a short time," said Ken Cain, associate professor of aquaculture and fish health at the University of Idaho.

For the past six years, Cain has worked on developing a vaccine for coldwater disease. By injecting thousands of tiny trout – each weighing slightly more than a quarter coin – Cain and his graduate students determined that trout can build up immunity to coldwater disease, similar to the way that people get protection from flu shots. Cain's now trying to identify which proteins in the bacteria trigger the immune response.