Consequences of reduced effectiveness of salmon lice treatments for lice control

TitleConsequences of reduced effectiveness of salmon lice treatments for lice control
AuthorsStige LC, Huseby RB, Helgesen KO, Aldrin M, Qviller L
TypeJournal Article
Journal NamePreventive veterinary medicine
CitationStige LC, Huseby RB, Helgesen KO, Aldrin M, Qviller L. Consequences of reduced effectiveness of salmon lice treatments for lice control. Preventive veterinary medicine. 2024 Feb 01; 224:106134.


The effective control of ectoparasitic salmon lice, Lepeophtheirus salmonis, in fish farms is challenged by the salmon lice having developed resistance towards several antiparasitic drugs and by the effectiveness of non-medicinal treatments being limited by considerations of fish welfare. When new antiparasitics are introduced to the market, these should be used sparingly to slow resistance development. Using a population model for salmon lice parameterised for salmonid fish farms in Norway, we quantified how reduced treatment effectiveness influences treatment frequency and lice abundance. Furthermore, we investigated when in the production cycle a highly effective lice treatment leads to the largest reduction in the total number of treatments, mean lice abundance and lice larvae production. Results showed that reductions in treatment effectiveness to lower than 50% led to the steepest increases in treatment frequency and mean lice abundance, as well as to increased risk that lice abundance increased beyond control. The timing of the most effective treatment had only moderate effects on the total treatment need and the mean number of adult female lice through the production cycle, but large effect on the production of lice larvae in spring. These findings imply that farmers can optimise the timing of the most effective treatment to reduce the release of lice larvae in the period of year when wild salmonids are in coastal waters, without compromising total treatment need or mean lice levels.

Author Details
Additional information about authors:
1Leif Christian Stige
2Ragnar B Huseby
3Kari O Helgesen
4Magne Aldrin
5Lars Qviller
Additional details for this publication include:
Property NameValue
Journal CountryNetherlands
Publication TypeJournal Article
Language Abbreng
CopyrightCopyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.
Journal AbbreviationPrev Vet Med
Publication Date2024 Feb 01
Publication ModelPrint-Electronic
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PMID: PMID:38325114