Optimization and field use of a bioassay to monitor sea lice Lepeophtheirus salmonis sensitivity to emamectin benzoate

Westcott, Jillian D.; Stryhn, Henrik; Burka, John F.; Hammell, K. Larry

doi:10.3354/dao01887

Cited by 51 publications

(90 citation statements)

References 32 publications

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“…Activity, along with other physiological or reproductive parameters, is commonly used to determine potentially successful parasiticide candidates, or to monitor the development of resistance to treatments. A clearly defined set of observational characteristics can help reduce inter-observer error (Westcott et al 2008). Capturing video images of normal and abnormal motility can also help reduce such errors, since the videos can be used both to train observers, and to record findings so that multiple observers can evaluate the same results.…”

Section: Resultsmentioning

confidence: 99%

“…The copepod, Lepeophtheirus salmonis, exhibited uncoordinated movement and inability to attach to the substrate when exposed to emamectin in vitro (Westcott et al 2008). Two main morphologic or behavioral effects have been observed when avermectins are applied to nematodes in vitro: (1) inhibited pharyngeal pumping, followed by a generalized, rapid paralysis (Geary et al 1993, Gill et al 1995, Keane & Avery 2003.…”

Section: Avermectinsmentioning

confidence: 99%

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In vitro effect of seven antiparasitics on Acolpenteron ureteroecetes (Dactylogyridae) from largemouth bass Micropterus salmoides (Centrarchidae)

Reimschuessel¹,

Gieseker²,

Poynton³

2011

Dis. Aquat. Org.

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Few drugs are approved by the United States Food and Drug Administration for treating parasite infections in minor species such as fish, due in part to the high cost of developing such drugs and to a relatively small market share for drug sponsors. Because in vivo effectiveness trials for antiparasitic drugs are costly, time consuming, and use many animals, a systematic in vitro screening approach to describe parasite motility could help find promising drug candidates. We evaluated the effects of 7 antiparasitics on the activity and survival of the endoparasitic monogenean Acolpenteron ureteroecetes (Dactylogyridae) collected from the posterior kidneys of juvenile largemouth bass Micropterus salmoides (Lacepede, 1802) (Centrarchidae) held in the laboratory. Tests were conducted in 12 well tissue culture plates; each well had 3 parasites, and we tested 3 concentrations and 1 control for each of the 7 antiparasitics. The parasites were observed immediately after adding the drug, at 1 to 3 h, and 17 to 26 h, and video recordings were made. Drug effects were recorded by documenting morbidity (reduced movement, tremors, contracted body, abnormal morphology) and mortality. A. ureteroecetes was strongly affected by the quinoline praziquantel, the imidazothiazide levamisole, and the organophosphates dichlorvos and trichlorfon. The parasites were moderately affected by the macrocyclic lactones ivermectin and emamectin, and generally unaffected by the benzimidazole mebendazole. Our study demonstrates the utility of characterizing in vitro responses with video microscopy to document responses of fish parasites for initial screens of drug effects on a fish monogenean.

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Section: Resultsmentioning

confidence: 99%

Section: Avermectinsmentioning

confidence: 99%

In vitro effect of seven antiparasitics on Acolpenteron ureteroecetes (Dactylogyridae) from largemouth bass Micropterus salmoides (Centrarchidae)

Reimschuessel¹,

Gieseker²,

Poynton³

2011

Dis. Aquat. Org.

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“…Bioassays have been used in New Brunswick (Westcott et al 2008), as well as in other salmon farming regions around the world for monitoring sea lice sensitivity to therapeutic agents (Sevatdal & Horsberg 2003, Sevatdal et al 2005, Bravo et al 2008. Westcott et al (2008) In conclusion, this analysis presents evidence of a reduction in emamectin benzoate treatment effectiveness over time and between geographical locations for the period of time examined, 2004 to 2008. These results correspond with the clinical picture witnessed in the field of a decline in treatment effect, which became a concern in 2008 (Chang et al 2011).…”

Section: Discussionmentioning

confidence: 99%

“…A decline in efficacy was reported in Scotland during the years examined, 2002 to 2006 (Lees et al 2008a,b). On the east coast of Canada, a recent investigation using laboratory bioassays found increases in EC 50 (effective concentration) values for emamectin benzoate in L. salmonis from southwestern New Bruns wick collected in 2011 (Igboeli et al 2012) compared with values from 2002 to 2005 (Westcott et al 2008). A reduction in the sensitivity of Caligus rogercresseyi to emamectin benzoate based on laboratory bioassays has been documented in Chile (Bravo et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of emamectin benzoate for treatment of Lepeophtheirus salmonis on farmed Atlantic salmon Salmo salar in the Bay of Fundy, Canada

Jones¹,

Hammell²,

Dohoo³

et al. 2012

Dis. Aquat. Org.

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Emamectin benzoate (an avermectin chemotherapeutant administered to fish as an in-feed treatment) has been used to treat infestations of sea lice Lepeophtheirus salmonis on farmed Atlantic salmon Salmo salar in the Bay of Fundy, New Brunswick, Canada, since 1999. This retrospective study examined the effectiveness of 114 emamectin benzoate treatment episodes from 2004 to 2008 across 54 farms. Study objectives were to establish whether changes in the effectiveness of emamectin benzoate were present for this period, examine factors associated with treatment outcome, and determine variables that influenced differences in L. salmonis abundance after treatment. The analysis was carried out in 2 parts: first, trends in treatment effectiveness and L. salmonis abundance were explored, and second, statistical modelling (linear and logistic regression) was used to examine the effects of multiple variables on post-treatment abundance and treatment outcome. Post-treatment sea lice abundance increased in the later years examined. Mean abundance differed between locations in the Bay of Fundy, and higher numbers were found at farms closer to the mainland and lower levels were found in the areas around Grand Manan Island. Treatment effectiveness varied by geographical region and decreased over time. There was an increased risk for unsuccessful treatments in 2008, and treatments applied during autumn months were more likely to be ineffective than those applied during summer months.

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“…The use of such medicines is not only expensive but comes with environmental concerns, as well as increasing evidence that lice populations are becoming tolerant to such treatments (Denholm et al, 2002;Fallang et al, 2004;Sevatdal et al, 2005;Bravo et al, 2008;Lees et al, 2008b). There is a need to better understand the epidemiology of lice infections on farms and to conserve the use of medicines if they are to remain effective (Fallang et al, 2005;Lees et al, 2008c;Westcott et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Use of a mathematical model to describe the epidemiology of Lepeophtheirus salmonis on farmed Atlantic salmon Salmo salar in the Hardangerfjord, Norway

Gettinby¹,

Robbins

Lees

et al. 2011

Aquaculture

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This version is available at https://strathprints.strath.ac.uk/30850/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output.This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. Infestation patterns of the sea louse Lepeophtheirus salmonis from 44 salmon farms in the Hardangerfjord on the south-west coast of Norway over the period 2004 to 2007 were assimilated to create 20-month production cycle profiles for spring and autumn stocked generations. The timing and frequency of in-feed and bath treatments to control sea lice associated with these profiles was considered. Spring and autumn stocked farms were observed to have different patterns of sea lice counts on salmon during the first and second years of production. Spring stocked sites experienced increasing infestation toward the end of the first year and on average counts remained elevated thereafter, whereas autumn stocked sites averaged lower sea lice counts throughout most of the production cycle until the latter part of the second year when these escalated rapidly. In-feed treatments were the predominant form of sea lice control in the first half of the production cycle on spring stocked farms, whereas bath treatments were used exclusively in the second half of the production cycle; a very similar pattern of therapeutant use was observed on autumn stocked farms. Results using the SLiDESim (Sea Lice Difference Equation Simulation) infection model and a range of biological and production parameters showed that modelling resulted in a better fit to the mobile lice profiles for autumn stocked farms compared to spring stocked farms. Some featu...

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Optimization and field use of a bioassay to monitor sea lice Lepeophtheirus salmonis sensitivity to emamectin benzoate

Cited by 51 publications

References 32 publications

In vitro effect of seven antiparasitics on Acolpenteron ureteroecetes (Dactylogyridae) from largemouth bass Micropterus salmoides (Centrarchidae)

In vitro effect of seven antiparasitics on Acolpenteron ureteroecetes (Dactylogyridae) from largemouth bass Micropterus salmoides (Centrarchidae)

Effectiveness of emamectin benzoate for treatment of Lepeophtheirus salmonis on farmed Atlantic salmon Salmo salar in the Bay of Fundy, Canada

Use of a mathematical model to describe the epidemiology of Lepeophtheirus salmonis on farmed Atlantic salmon Salmo salar in the Hardangerfjord, Norway

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