title: Toxicity of peracetic acid (PAA) to tomonts of IIchthyophthirius multifiliis.
abstract: The free-living infective theront of Ichthyophthirius multifiliis historically has been thought to be the only stage susceptible to treatment. Here we introduce a technique to determine the toxicity of compounds to the newly released tomont, the encysted tomont and the developing tomites within the tomont that emerge as theronts. The toxicity of Wofasteril E400 (40% peracetic acid, PAA) to free-living forms of I. multifiliis was determined shortly after tomonts were physically removed from the surface of the fish and at 2.5 and 24 h after removal. Results indicate that 0.6 to 0.9 mg l(-1) PAA killed 39 to 82% of the newly released tomonts within 48 h when treated immediately. In a second experiment, tomonts were allowed to settle for 2.5 h after sampling from the skin and then treated for 12 h; concentrations > or =0.5 mg l(-1) PAA produced significantly fewer theronts than the controls. In a third experiment, encysted tomonts that were exposed to PAA 24 h after sampling from the skin and treated for 2 or 4 h produced a variable amount of theronts, but the concentrations tested (0.5 to 3.0 mg l(-1)) did not halt theront production. This research demonstrates that encysted I. multifiliis are less susceptible to chemical treatments.
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany. meinelt@igb-berlin.de
authors.forename: T
authors.initials: T
authors.lastname: Meinelt
authors.forename: S
authors.initials: S
authors.lastname: Matzke
authors.forename: A
authors.initials: A
authors.lastname: Stübert
authors.forename: M
authors.initials: M
authors.lastname: Pietrock
authors.forename: A
authors.initials: A
authors.lastname: Wienke
authors.forename: A J
authors.initials: AJ
authors.lastname: Mitchell
authors.forename: D L
authors.initials: DL
authors.lastname: Strauss
mesh_terms: D000818:Animals; D000977:Antiparasitic Agents / Q000633:toxicity*; D016770:Ciliophora Infections / Q000517:prevention & control; D005393:Fish Diseases / Q000517:prevention & control; D006054:Goldfish / Q000469:parasitology; D016803:Hymenostomatida / Q000187:drug effects*; D008018:Life Cycle Stages; D010463:Peracetic Acid / Q000633:toxicity*; D013997:Time Factors
chemical_list: D000977:Antiparasitic Agents; D010463:Peracetic Acid