When juvenile salmon migrate to the Pacific Ocean, the second host releases a stage infective to salmon. The parasite is then carried in the salmon until the next spawning cycle. The myxosporean parasite that causes whirling disease in trout has a similar life cycle.[1] However, as opposed to whirling disease, the Henneguya infestation does not appear to cause significant incapacitation of the host salmon — even heavily infected fish tend to return to spawn successfully.