title: Evaluating the effect of synchronized sea lice treatments in Chile.
abstract: The sea louse is considered an important ectoparasite that affects farmed salmonids around the world. Sea lice control relies heavily on pharmacological treatments in several salmon-producing countries, including Chile. Among options for drug administration, immersion treatments represent the majority of antiparasitic control strategies used in Chile. As a topical procedure, immersion treatments do not induce a long lasting effect; therefore, re-infestation from neighbouring farms may undermine their efficacy. Synchronization of treatments has been proposed as a strategy to improve immersion treatment performance, but it has not been evaluated so far. Using a repeated-measures linear mixed-effect model, we evaluated the impact of treatment synchronization of neighbouring farms (within 10km seaway distance) on the adult lice mean abundance from weeks 2 to 8 post-treatment on rainbow trout and Atlantic salmon farms in Chile, while controlling for external and internal sources of lice before the treatments, and also for environmental and fish-related variables. Results indicate that treatment synchronization was significantly associated with lower adult lice levels from weeks 5 to 7 after treatment. This relationship appeared to be linear, suggesting that higher levels of synchronization may result in lower adult sea lice levels during these weeks. These findings suggest that synchronization can improve the performance of immersion delousing treatments by keeping sea lice levels low for a longer period of time. Our results may be applicable to other regions of the world where immersion treatments are widely used.
authors.affiliation: Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada. Electronic address: garriagada@oceanografia.udec.cl.
authors.forename: G
authors.initials: G
authors.lastname: Arriagada
authors.affiliation: Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Stryhn
authors.affiliation: Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Sanchez
authors.affiliation: Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Vanderstichel
authors.affiliation: Instituto Tecnológico del Salmón, Av. Juan Soler Manfredini 41, Of. 1802, Puerto Montt, Chile.
authors.forename: J L
authors.initials: JL
authors.lastname: Campistó
authors.affiliation: Land and Sea Systems Analysis Inc., 14 rue Long, Granby, Quebec, J2G 6S8, Canada.
authors.forename: E E
authors.initials: EE
authors.lastname: Rees
authors.affiliation: Instituto Tecnológico del Salmón, Av. Juan Soler Manfredini 41, Of. 1802, Puerto Montt, Chile.
authors.forename: R
authors.initials: R
authors.lastname: Ibarra
authors.affiliation: Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PE C1A 4P3, Canada.
authors.forename: S
authors.initials: S
authors.lastname: St-Hilaire
mesh_terms: D000818:Animals; D017756:Aquaculture / Q000379:methods; D002677:Chile; D003140:Communicable Disease Control / Q000379:methods*; D033342:Copepoda / Q000187:drug effects* / Q000502:physiology; D004478:Ectoparasitic Infestations / Q000469:parasitology / Q000517:prevention & control / Q000662:veterinary*; D005393:Fish Diseases / Q000469:parasitology / Q000517:prevention & control*; D016014:Linear Models; D017686:Oncorhynchus mykiss; D020317:Salmo salar
keywords: Antiparasitic treatment; Atlantic salmon; Azamethiphos; Chile; Linear mixed models; Pyrethroids; Sea lice; Treatment coordination; Treatment synchronization