Salmonid Whirling Disease

Whirling disease is a parasitic infection of trout and salmon by the myxosporean protozoan Myxobolus cerebralis (Syn. Myxosoma cerebralis). This parasite has selective tropism for cartilage; infection can cause deformities of the axial skeleton and neural damage that results in 'blacktail.' The disease is named for the erratic, tail-chasing, 'whirling' in young fish that are startled or fed. Heavy infection of young fish can result in high mortalities or unmarketable, deformed individuals.

Although the parasite was first reported in 1903 in central Europe (Hofer 1903), its complete life cycle was not described until the early 1980's.