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Diseases of Aquatic Organisms

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DAO 70:101-108 (2006)  -  doi:10.3354/dao070101

Randomized clinical trial to investigate the effectiveness of teflubenzuron for treating sea lice on Atlantic salmon

P. J. Campbell1,3, K. L. Hammell1,*, I. R. Dohoo1, G. Ritchie2

1Department of Health Management, Atlantic Veterinary College, 550 University Avenue, Charlottetown, Prince Edward Island C1A 4P3, Canada
2Nutreco Aquaculture Research Centre, PO Box 48, Sjohagen 3, 4001 Stavanger, Norway
3Present address: Inwood Animal Center, 7611 Winchester Avenue, Inwood, West Virginia 25428, USA
*Corresponding author. Email:

ABSTRACT: A double-blind, randomized control clinical trial was performed to investigate the effectiveness of teflubenzuron in controlling sea lice Lepeophtheirus salmonis on farmed Atlantic salmon Salmo salar. A total of 40 sea cages from 3 commercial cage sites in Atlantic Canada were used in this Good Clinical Practice (GCP) trial. The teflubenzuron was administered in the feed at a dosage of 10 mg kg–1 biomass d–1 for 7 d. Medicated and control cages were matched by site, cage size, and pre-treatment mean lice counts using cages as the unit of concern. Post-treatment lice counts and staging of developmental stages were performed at 1 and 2 wk after the end of treatment. Chalimus stages in medicated cages were significantly lower than in control cages at 1 wk (79% reduction in mean lice counts, p < 0.001), and at 2 wk (53% reduction, p < 0.001). Mobile (pre-adult and adult) stages were also significantly reduced in medicated cages at 1 wk (69% reduction, p < 0.01), and at 2 wk (40% reduction, p < 0.01) post-treatment, respectively. Teflubenzuron was proven effective for reducing lice burdens on salmon despite the low parasite levels experienced during the trial and the recruitment of lice from the untreated cages. The use of cage as the unit of concern was an important design component of this trial.

KEY WORDS: Sea lice · Lepeoptheirus salmonis · Teflubenzuron · Atlantic salmon · Salmo salar · Clinical trial · Good Clinical Practice

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