Administration of Drugs by Hyperosmotic or Vacuum Infiltration or Surfactant Immersion Ineffective for Control of Intradermally Encysted Ichthyophthirius multifiliis

Eight protozoacidal compounds were ineffective in destroying Ichthyophthirius multifiliis trophozoites encysted in the skin of fishes when administered by hyperosmotic or vacuum infiltration or surfactant immersion procedures. The compounds used were Enheptin, formalin, Furacin, Furoxone, malachite green, methylene blue, quinine sulfate, and Tramisol. Histological studies indicated only superficial penetration of methylene blue into the mucous layer of fish subjected to hyperosmotic infiltration. Enheptin and Tramisol were effective in killing excised trophozoites of I. multifiliis in vitro.