It appears you're asking about whirling disease in fish, which is caused by a specific parasite.
Whirling disease is caused by Myxobolus cerebralis, a microscopic parasite that affects salmonid fish such as trout, salmon, and whitefish. This parasite has a complex lifecycle requiring both a salmonid fish and an aquatic worm (Tubifex tubifex) as hosts. The name "whirling disease" comes from the abnormal swimming behavior often displayed by infected fish.
