Whirling Disease

Infection of fishes with protozoan parasites is possibly more easily recognized than worm parasites. The "Whirling Disease", where fishes lose their equilibrium and "whirl" about dizzily or cannot maintain themselves in their characterized position, is caused by a parasitic protozoan, Lentospora cerebralis. At a stage in the organism's development it penetrates the cartilages of the skull and destroys the part of the brain which controls the balancing power of the fish (the auditory section). Treatment of the whirling disease is practically impossible once the fish has reached the "whirling" stage, and, prior to the manifestation of this symptom, the organism is so deeply imbedded inside the tissues of the fish that treatment would be futile.

Once a fish shows the whirling symptoms, it is best disposed of. The disease itself is not very virulent and is fairly rare.