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Diseases of Aquatic Organisms

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DAO 86:51-56 (2009)  -  DOI:

Toxicity of peracetic acid (PAA) to tomonts of Ichthyophthirius multifiliis

T. Meinelt1,*, S. Matzke2, A. Stüber1, M. Pietrock3, A. Wienke4, A. J. Mitchell5, D. L. Straus5

1Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Mueggelseedamm 301, 12587 Berlin, Germany
2Humboldt-University of Berlin, Invalidenstr. 42, 10115 Berlin, Germany
3Toxicology Centre, University of Saskatchewan, 44 Campus Drive, Saskatoon, Saskatchewan S7N 5B3, Canada
4Martin-Luther-University Halle-Wittenberg Medical Faculty Institute of Medical Epidemiology, Biostatistics and Informatics, Magdeburger Strasse 27, 06097 Halle (Saale), Germany
5US Department of Agriculture, Agricultural Research Service, Harry K. Dupree Stuttgart National Aquaculture Research Center, PO Box 1050, Stuttgart, Arkansas 72160, USA

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 ≥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.

KEY WORDS: Ichthyophthirius multifiliis · Peracetic acid · Toxicity · Wofasteril®

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Cite this article as: Meinelt T, Matzke S, Stüber A, Pietrock M, Wienke A, Mitchell AJ, Straus DL (2009) Toxicity of peracetic acid (PAA) to tomonts of Ichthyophthirius multifiliis. Dis Aquat Org 86:51-56.

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