Whirling Disease: Reviews and Current Topics

<EM>ABSTRACT </EM>The effect of pH, total hardness, salinity, and dissolved oxygen on viability of the triactinomyxon (TAM) stage of the Myxozoan parasite <em>Myxobolus cerebralis </em>was evaluated. The vital stains propidium iodide and fluorescein diacetate were used to determine if TAMs were alive or dead. Tests were conducted at 9°C and 14°C. Experiments were conducted at salinities of 5, 10, 15, 20, and 30 ‰, at pH from 4 to 10, at total hardness of 10 or 650 mg/L, and dissolved oxygen at 0–0.5 mg/L. Viability was not significantly affected by low dissolved oxygen or the total hardness levels tested. Few differences were observed related to temperature. Viability decreased over time in controls to roughly half after 72 h at either temperature. Salinity significantly affected mortality, even after 1 h. For disinfection, 20–30 ‰ salinity for at least 6 h would be required to effectively kill all TAMs. The further pH moved from circum-neutral, the more TAM viability decreased. Differences in water quality, especially pH, could partially explain differences observed in severity of whirling disease among geographic regions.