Abstract

Uronemiasis is a disease of warm- and cold-water marine fishes caused by opportunistically pathogenic scuticociliates of Uronema sp. The disease can be devastating in aquaria and aquacultural environments where Uronema marinum is most often incriminated as the causative agent. Little is known about the prevention, diagnosis, and treatment of disease caused by this organism. Thus, the objectives of our studies were 1) to identify potential environmental factors associated with uronemiasis using an in vitro system and 2) to identify potential treatment modalities for uronemiasis using an in vitro system. For the first objective we looked at the survival, proliferation, and behavioral responses of U. marinum to temperature, salinity, and pH.

U. marinum survived at a wide variety of specific gravities, pH values, and temperatures. However, low specific gravity and warm temperatures severely depressed growth, and low pH caused rapid death. Thus, changes in water specific gravity, temperature, and pH potentially could be used to control the proliferation of Uronema. For the second objective, U. marinum was cultured with various concentrations of formalin, methylene blue, malachite green, metronidazole, chloroquine, and H₂O₂. Formalin, malachite green, chloroquine, and H₂O₂ all appeared useful for killing Uronema in water and on the surface of fish as long as the appropriate doses and treatment durations were used. H₂O₂ was a very effective water treatment for killing Uronema at concentrations as low as 250 ppm. Chloroquine has potential as a systemic drug for the parenteral treatment of uronemiasis in individual fish.