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Klamath Worm Epidemic Baffles Salmon Biologists

Trout Biosecurity Welfare +5 more

CALIFORNIA, US - Researchers struggling to understand an epidemic of parasites infecting the Klamath River's salmon raised questions and offered some answers at a gathering of biologists Tuesday.

Among the findings were that significantly more young salmon died faster from the parasite called Ceratomyxa shasta during tests in the river's disease hot spots in 2008 than the year before, writes John Driscoll for the Times-Standard.

According to the news report, Rich Holt with Oregon State University told a conference that chinook and coho salmon exposed to the parasite in the most infested areas below Iron Gate Dam to the Scott River, then taken to a lab, died faster than even rainbow trout with no immunity. A higher proportion of salmon died, too, nearly twice that of 2007, Holt said.

C. shasta targets the intestines of salmon and trout. Adult fish release the parasite's spores when they die, and the spores then move into an interim host, a tiny polychaete worm. The worm then releases spores that are taken in by young salmon, which often die from the parasite.

The worm is especially prevalent just below Iron Gate Dam, and the percentage of polychaete worms infected by C. shasta are also highest in the reach around Beaver Creek and the Seiad Valley. Exactly why the stretch is so rife with the parasite isn't known, said OSU researcher Jerri Bartholomew, but it's possible that the large number of adult fish that spawn just below the dam spread huge amounts of spores.

”We have a situation whether the host-parasite balance is out of synch,” Bartholomew said.

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