Salmonid whirling disease

John E. Grant jgrant1 at
Mon Feb 6 22:00:19 EST 1995

Recently reports from Montana indicate that a possible reason for the
dramatic decrease in native rainbow trout populations on the Madison
river is the introduction of what is known as Whirling disease.  The
disease is caused by a protozoan parasite that attacks the brain and
spine of trout and salmon.  The fish lose their equilibrium, causing
them to swim in circles until they starve to death or are attacked by

The Protozoan is Myxobolus cerebralis.  It has a multi-stage life cycle
in two hosts, early stages in the tubifex or sludge worm and later stages
in the trout.  It is endemic to Europe, therefore brown trout (also from
Europe) are less susceptible than American rainbows, which are thought to
have 85-95% mortality in infected waters.  If there is any information on
how to control this or related protozoans, it would be greatly
appreciated.  I am a Biology student at Tufts University and an avid fly 
fisherman so I have a double interest in the topic.  Thanks for any help.

John E. Grant		  |"This morning I shot two holes in my freezer,
jgrant1 at | I think I've got cabin fever,
Parrothead logician	  | I've gotta go where it's warm." -J. Buffett

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