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SEA LICE 2018 blog: Tackling the big challenge

The 12th annual Sea Lice conference takes place this week in Punta Arenas, Chile. IntraFish Correspondent John Evans is on the ground at the event.

Wednesday, Nov. 7 12:39 pm CT

Benchmark's genetic sea-lice resistant eggs shortlisted for Newton Prize 2018

Benchmark’s research on sea-lice resistant genetics funded by Chile and the United Kingdom was shortlisted for the Newton Prize 2018.

Benchmark is using genetic markers to select which fish will be resistant to sea lice species existing in Norway and Chile and is studying the possibilities of developing this technique to select genetics resistant to SRS, the main cause for antibiotic use in the Chilean salmon industry.

The projects are funded by the University of Chile and the UK The Roslin Institute as part of a collaboration program targeting the functional genomic basis of resistance against sea lice and SRS.

"The collaboration between Universidad de Chile, The Roslin Institute and Benchmark Genetics Chile has helped to identify the genetic basis of the resistance to two of the most important diseases affecting Chilean salmon aquaculture and we believe that the findings from this work will help enhance the genetic improvement aimed at generating more robust fish for production," said Jose Manuel Yanez, professor at the University of Chile.

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Wednesday, Nov. 7 12:28 pm CT

Genomic selection shows promise for host resistance to sea lice

Scottish researchers highlight promise in genomic selection to expedite genetic improvement of host resistance to lice in farmed salmon populations.

Researchers evaluated the heritability of host resistance to sea lice in a commercial Chilean population to study the genetic architecture of the trait and to assess potential of genomic selection for enhancing host resistance to represented (imputed ) genotypes.

Genetic selection using imputed genotypes showed increased accuracy compared to pedigree methods, highlighting promise of genetic selection to expedite improvement of host resistance to lice in farmed salmon populations.

Genomic prediction is the most likely use for the work at the current stage, said Ross Houston from the Royal School of Veterinary Studies.

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Wednesday, Nov. 7 12:05 pm CT

Scottish researchers identify sea lice treatment resistant genetic markers

Researchers in Scotland have identified two genetic markers linked to resistance to Emamectin benzoate (EMB) contained in Merck Animal Health's trademarked oral salmon delousing agent Slice.

But so far the identity of the genes involved is still unknown and the SNP markers require further validation in farm populations of lice, David Guidi from Scotland's University of Stirling said.

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Wednesday, Nov. 7 10:50 am CT

Reverse vaccinology shows promise in targeting Chile salmon lice disease

At least one prototype treatment targeting the "caligidosis" disease affecting Chilean salmon farming will be trialed in the field under commercial aquaculture conditions.

The prototype based on the use of "reverse vaccinology" is the fruit of a joint project between Chile's University of Concepción and the Interdisciplinary Center for Aquaculture Research (INCAR).

The genetic technique can slash vaccine development times from 5-15 years to 1-2 years and also reduce costs in the process, said Cristian Gallardo-Escárate from the University of Concepción.

One vaccine prototype reduced the parasitic burden by 97 percent in adult stages.

"Reverse vaccinology provides a unique opportunity to develop novel vaccines against sea lice," Gallardo-Escárate said.

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Wednesday, Nov. 7 10:24 am CT

Cloning used to target sea lice with viruses

Norwegian researchers are working on producing infective viruses targeting sea lice using reverse genetics techniques.

The method, funded by The Research Council of Norway, employs cDNA clones to create wild type and recombinant viruses

As viruses are cultivated in cell culture they can be produced on a large scale, Renate Skoge from the Fish Disease Research Group said.

"We don't actually know if this will actually work in the end. But it's a work in progress and so promising," she said, adding viruses appear to have beneficial effects for the host fish.

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Tuesday, Nov. 6 17:50 pm CT

Lufenuron 10% well tolerated in Elanco trialling

The administration of 10 percent lufenuron in medicated feed at 35mg/kg over 7-14 days trialing was well tolerated and the dosing period had no impact on efficacy, said John McHenery, safety manager at Elanco Animal Health.

IMVIXA (10 percent lufenuron) has been marketed in Chile since 2016 with an indication for prevention and control of (Caligus rogercresseyi) sea lice in farmed salmonids.

Lufenuron is used as a flea treatment for domestic pets.

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Tuesday, Nov. 6 16:20 pm CT

Time response method put forward as alternative in delousing drug sensitivity assays

A new study proposes the monitoring of sea lice at regular intervals, increasing from 1 hour to 24 hours, to assess their susceptibility to delousing drugs.

Joint work on time response toxicity analysis was undertaken by the Laboratory of Biotechnology and Aquatic Genomics, the Interdisciplinary Center for Aquaculture Research (INCAR) and the University of Concepción in Chile.

Among other things, researchers found lower confidence intervals (95 percent) than traditional bioassays.

At the same time, while differences based on gender must be estimated, the estimation of sea lice drug susceptibility should not be restricted to traditional bioassays even when this is the current gold standard for sea lice sensitivity monitoring, Gustavo Nuñez from Chile's Universidad de Concepción said.

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Tuesday, Nov. 6 12:25 pm CT

Trials on recombinant vaccine prototype move ahead

An evaluation of a second prototype of a recombinant vaccine will be carried out following promising trials.

This comes after 'prototype 2' vaccine induced a significant protection and reduction against different stages of C. rogercresseyi sea lice versus an unvaccinated fish group, Abbot Laboratories' Pedro Ilardi said.

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Tuesday, Nov. 6 11:45 am CT

Airdome trials to combat sea lice move to industrial scale

Deeper swimming reduces sealice infestation, said Frode Oppedal from Norway's Institute of Marine Research.

Norway Atlantis Subsea Farming plans to carry out industrial-scale trials using an airdome on farmed salmon with the aim of encouraging salmon to refill swim bladders during continuous submergence.

The trial follows a pilot test carried out by Norway's Institute of Marine Research using 10,000 fish. The new trial involves 30,000-50,000 salmon.

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Tuesday, Nov. 6 9:50 am CT

Higher harvest levels offset treatment costs

Salmon production costs increase by around $1.40/kilogram with the presence of caligus sea lice and after treatments, said Miguel Quiroga, an economist and research fellow at Chile's Interdisciplinary Centre for Aquaculture Research (INCAR).

At the same time treatments reduce the cost of caligus sea lice on salmon biomass over the production cycle and treatment costs are offset by higher harvesting levels meaning that production costs are very similar to those without treatment.

All estimated effects differ depending on a farms environmental and spatial conditions, suggesting that cost effective intervention depends on discriminatory regulation under heterogeneous conditions.

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Tuesday, Nov. 6 9:23 am CT

Public opinion underpins sea lice management

Resistance, available technologies and shifts in public opinion on the use of medicines have driven changes in sea lice management, said Kari Olli Helgesen from the Norwegian Veterinary Institute.

The deployment of cleaner fish has risen steeply since 2008, while the number of times fish have been treated has fallen to around once a year.

Much of the change in management techniques took place in 2016 and 2017. Thermal de-licing has become the most widely used and distributed along the Norwegian coast, she said.

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Monday, Nov. 5 4:19 pm CT

State-Space modelling plugs sea lice data gap

A 'state-space' modelling approach developed by Canada's University of Prince Edward Island succeeded in handling data with missing values from farm's multiple production cycles incorporating predictive covariates.

The model predicted juvenile and adult abundances as far ahead of ten weeks with a 'reasonably low' error margin, Adel Elghafghuf from the university outlined.

Sea lice data systems often contain missing values leading errors. Main sources of error are methodology used for sea lice counts and failing to take account of environmental changes or management intervention.

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Monday, Nov. 5, 3:51 pm CT

Sea lice outbreaks may start nearby

Research based on modeling suggests that some larger sea lice outbreaks are influenced by sea lice counts on adjacent salmon farms, professor Fernando Mardones from Chile's School of Veterinary Medicine said.

Piscirickettsiosis, a severe disease that has caused major economic losses in the aquaculture industry since its appearance in 1989, can be driven by sea lice in farms of the same zone or adjacent zones, researchers found.

A combined research project between the Epvivet Research Center (Chile-Spain), the University of Minnesota and Andres Bello University in Chile aims to design surveillance and mitigation strategies to better prevent sea lice in main production areas and area management zones. Future modeling options include looking at seasonal variations on a local scale and in designated zones within those local areas.

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Monday, Nov. 5, 12:48 pm CT

Peptides may disrupt sea lice behavior

Researchers at Chile's Universidad de Concepción say a method to control sea lice infestation by disrupting the host-recognition mechanism shows promise.

The most common approach to control this parasite is with pesticides, but due to their decrease in efficacy and the environmental impact, alternative methods are emerging.

Anti-microbial peptides (AMPs) were selected for use as an attractant peptides. Sea lice were exposed to peptides identified in salmon skin to assess physiological and molecular effects of these molecules on the parasites.

Adult lice were exposed to these chemoattractants and the chemoreceptor activity was measured using neurophysiological methods.

Lice from the infective developmental stage were exposed to these chemicals in seawater and changes in their swimming behavior were analyzed using image processing techniques.

Sea lice exposed to AMPs, which were abundant in salmon skin, exhibited stimulation of the development of its frontal filament.

The peptide altered sealice swimming patterns, increasing their jump distance and swim speed after they were stimulated by a specific signal.

Results were also consistent with gene expression analyses of smell sensory systems.

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Monday, Nov. 5, 11:16 am CT

Insect growth inhibitor shows promise on sea lice

Lufenuron, which is used as a flea treatment for domestic pets, may have an extended effect on sea lice eggs when used in the field, according to Sandra Marin from Chile's Universidad Austral.

Tests showed a reduction in reproductivity levels and egg viability among fish treated with 489ppb in fillet and skin at the time of infestation.

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Monday, Nov. 5, 10:34 am CT

Differences in sea lice behavior between species highlighted

Cargill Innovation Center researchers found slightly less susceptibility to sea lice in coho salmon than in Atlantic salmon in tests during 2014 and 2015.

The growth and presence of sea lice attached to fish reduced as trials progressed in coho compared with Atlantic salmon, said Christopher Hawes, Research Scientist for Cargill Aquaculture Nutrition.

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Monday, Nov. 5, 09:56 am CT

Catching it early

Early surveillance helps us to make prompt decisions, said Alicia Gallardo from Chile's National Marine Fisheries and Aquaculture Service (Sernapesca).

Her organization's programs have identified predictive factors, investigated environmental impacts on sea lice as well as genetic and lifestyle effects.

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Monday, Nov. 5, 09:18 am CT

Climate change may see growth in sea lice

Temperature and precipitation trends forced by greenhouse gases will continue during the 21st century, potentially causing an increase in sea lice expansion.

The magnitude and timing of global climate change depends on greenhouse gas emissions and whether governments stick to international accords such as the Paris Agreement, said René Garreaud, from Universidad de Chile.

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