Attempts to control Ichthyophthirius multifiliis Fouquet (Ciliophora: Ophryoglenidae) by chemotherapy and electrotherapy

Abstract. New methods were studied for the control of Ichthyophthirius muttifiliis Fouquet, one of the most serious parasites of fish. Totals of 272 fish, 354 I. Multifiliis trophozoites and 562,500 tomites were used in the screening of amprolium, ronidizole, and silver nitrate for parasite control. In addition, 1,465 trophozoites and 600 tomites were subjected to pulsed DC electrotherapy trials. Silver nitrate at 0·67 ppm was 100% effective in eradicating tomites, while ronidizole at 750 ppm gave 100% and 97% control of trophozoites and tomites, respectively. Amprolium and electrotherapy were both ineffective against trophozoites and tomites. Silver nitrate has promise as a safe and effective alternative to chemicals currently used to control I. multifiliis .