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Abstract
Finfish aquaculture in freshwater and marine environments is continuously expanding globally, and the potential for a substantial further increase is well documented. The industry is supplying fish products for human consumption to the same extent as capture fisheries, and new fish species for domestication are still being selected by the industry. The challenge faced by all aquacultured species, classical and novel, is the range of pathogens associated with each new fish type. A fish host in its natural environment carries a series of more or less specific parasites (specialists and generalists). Some of these show a marked ability to propagate in aquaculture settings. They may then elicit disease when infection intensities in the confined aquaculture environment reach high levels. In addition, the risk of transmission of parasites from aquaculture enterprises to wild fish stocks adds to the parasitic challenge. Control programmes of various kinds are needed and these may include chemotherapeutants and medicines as the farmer's first and convenient choice, but mechanical, biological, immunological and genetic control methods are available solutions. New methods are still to be developed by scrutinizing the life cycle of each particular parasite species and pin-pointing the vulnerable stage to be targeted. As parasites exhibit a huge potential for adaptation to environmental changes, one must realize that only one approach rarely is sufficient. The present work therefore elaborates on and advocates for implementation of integrated control strategies for diseases caused by protozoan and metazoan parasites.
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Tschesche C, Bekaert M, Bassett DI, Boyd S, Bron JE, Sturm A. Key role of mitochondrial mutation Leu107Ser (COX1) in deltamethrin resistance in salmon lice (Lepeophtheirus salmonis). Sci Rep 2022; 12:10356. [PMID: 35725748 PMCID: PMC9209418 DOI: 10.1038/s41598-022-14023-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 03/30/2022] [Indexed: 12/01/2022] Open
Abstract
The pyrethroid deltamethrin (DTM) is used to treat Atlantic salmon (Salmo salar) against salmon louse (Lepeophtheirus salmonis) infestations. However, DTM resistance has evolved in L. salmonis and is currently common in the North Atlantic. This study aimed to re-assess the association between DTM resistance and mitochondrial (mtDNA) mutations demonstrated in previous reports. Among 218 L. salmonis collected in Scotland in 2018–2019, 89.4% showed DTM resistance in bioassays, while 93.6% expressed at least one of four mtDNA single nucleotide polymorphisms (SNPs) previously shown to be resistance associated. Genotyping at further 14 SNP loci allowed to define three resistance-associated mtDNA haplotypes, named 2, 3 and 4, occurring in 72.0%, 14.2% and 7.3% of samples, respectively. L. salmonis strains IoA-02 (haplotype 2) and IoA-10 (haplotype 3) both showed high levels (~ 100-fold) of DTM resistance, which was inherited maternally in crossing experiments. MtDNA haplotypes 2 and 3 differed in genotype for 17 of 18 studied SNPs, but shared one mutation that causes an amino acid change (Leu107Ser) in the cytochrome c oxidase subunit 1 (COX1) and was present in all DTM resistant while lacking in all susceptible parasites. We conclude that Leu107Ser (COX1) is a main genetic determinant of DTM resistance in L. salmonis.
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Affiliation(s)
- Claudia Tschesche
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Michaël Bekaert
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - David I Bassett
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Sally Boyd
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - James E Bron
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK
| | - Armin Sturm
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, FK9 4LA, UK.
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Hamoutene D, Oldford V, Donnet S. Drug and pesticide usage for sea lice treatment in salmon aquaculture sites in a Canadian province from 2016 to 2019. Sci Rep 2022; 12:4475. [PMID: 35296749 PMCID: PMC8927096 DOI: 10.1038/s41598-022-08538-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 03/08/2022] [Indexed: 12/04/2022] Open
Abstract
We used 4 years of publicly available data (2016–2019) on chemical usage at salmon sites with information on production, stocking, locations and environmental conditions to explore patterns of anti-sea lice treatments in a Canadian province. Results show that sequential chemical treatments are prevalent, emamectin benzoate (EMB) with azamethiphos being the most used combination with a decrease in ivermectin usage. Relatively high rates of usage of EMB per fish biomass may point to potential lice resistance patterns with information needed on mechanisms and local populations. Lower or no chemical usage at some sites indicate less sea lice infestations likely influenced by localized site conditions (coves), and a lessened need for medication due to the usage of cleaner fish and possibly other non-chemical methods (not documented in this report). The year/climate influenced chemical input only in sites with higher treatment levels likely due to effects on sea lice growth and reproduction. Observed differences between years are warmer surface temperature in the fall, a higher freshwater input in spring, and stronger wind conditions for 2017 and 2018 with more medication usage for these two years. The lack of significant effect of site distances calculated in zones of influence based on 24 h potential connectivity patterns highlight the need to refine the resolution of hydrodynamic processes.
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Affiliation(s)
- Dounia Hamoutene
- Saint Andrews Biological Station, Fisheries and Oceans Canada, 125 Marine Science Drive, St. Andrews, NB, E5B 0E4, Canada.
| | - Vanessa Oldford
- Northwest Atlantic Fisheries Center, Fisheries and Oceans Canada, P.O. Box 5667, St. John's, NL, A1C 5X1, Canada
| | - Sebastien Donnet
- Northwest Atlantic Fisheries Center, Fisheries and Oceans Canada, P.O. Box 5667, St. John's, NL, A1C 5X1, Canada
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Tschesche C, Bekaert M, Bassett DI, Mitchell C, North B, Boyd S, Carmona-Antoñanzas G, Bron JE, Sturm A. Investigation of deltamethrin resistance in salmon lice (Lepeophtheirus salmonis) provides no evidence for roles of mutations in voltage-gated sodium channels. PEST MANAGEMENT SCIENCE 2021; 77:1052-1060. [PMID: 33001569 DOI: 10.1002/ps.6120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/24/2020] [Accepted: 10/01/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND The pyrethroid deltamethrin is used to treat infestations of farmed salmon by parasitic salmon lice, Lepeophtheirus salmonis (Krøyer). However, the efficacy of deltamethrin for salmon delousing is threatened by resistance development. In terrestrial arthropods, knockdown resistance (kdr) mutations of the voltage-gated sodium channel (Nav ), the molecular target for pyrethroids, can cause deltamethrin resistance. A putative kdr mutation of an L. salmonis sodium channel homologue (LsNav 1.3 I936V) has been identified previously. At the same time, deltamethrin resistance of L. salmonis has been shown to be inherited maternally and to be associated with mitochondrial DNA (mtDNA) mutations. This study assessed potential roles of the above putative kdr mutation as a determinant of deltamethrin resistance in laboratory strains and field populations of L. salmonis. RESULTS The deltamethrin-resistant L. salmonis strain IoA-02 expresses the LsNav 1.3 I936V mutation but was susceptible to the non-ester pyrethroid etofenprox, a compound against which pyrethroid-resistant arthropods are usually cross-resistant if resistance is caused by Nav mutations. In a family derived from a cross between an IoA-02 male and a drug-susceptible female lacking the kdr mutation, deltamethrin resistance was not associated with the genotype at the LsNav 1.3 locus (P > 0.05). Similarly, in Scottish field populations of L. salmonis, LsNav 1.3 I936V showed no association with deltamethrin resistance. By contrast, genotypes at the mtDNA loci A14013G and A9030G were significantly associated with deltamethrin resistance (P < 0.001). CONCLUSION In the studied L. salmonis isolates, deltamethrin resistance was unrelated to the LsNav 1.3 I936V mutation, but showed close association with mtDNA mutations.
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Affiliation(s)
- Claudia Tschesche
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Michaël Bekaert
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - David I Bassett
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | | | | | - Sally Boyd
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Greta Carmona-Antoñanzas
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
- Imegen, Parc Cientific de la Universitat de Valencia, Valencia, Spain
| | - James E Bron
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Armin Sturm
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
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Myhre Jensen E, Horsberg TE, Sevatdal S, Helgesen KO. Trends in de-lousing of Norwegian farmed salmon from 2000-2019-Consumption of medicines, salmon louse resistance and non-medicinal control methods. PLoS One 2020; 15:e0240894. [PMID: 33119627 PMCID: PMC7595418 DOI: 10.1371/journal.pone.0240894] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 10/01/2020] [Indexed: 12/02/2022] Open
Abstract
The salmon louse Lepeophtheirus salmonis has been a substantial obstacle in Norwegian farming of Atlantic salmon for decades. With a limited selection of available medicines and frequent delousing treatments, resistance has emerged among salmon lice. Surveillance of salmon louse sensitivity has been in place since 2013, and consumption of medicines has been recorded since the early 80’s. The peak year for salmon lice treatments was 2015, when 5.7 times as many tonnes of salmonids were treated compared to harvested. In recent years, non-medicinal methods of delousing farmed fish have been introduced to the industry. By utilizing data on the annual consumption of medicines, annual frequency of medicinal and non-medicinal treatments, the aim of the current study was to describe the causative factors behind salmon lice sensitivity in the years 2000–2019, measured through toxicity tests–bioassays. The sensitivity data from 2000–2012 demonstrate the early emergence of resistance in salmon lice along the Norwegian coast. Reduced sensitivity towards azamethiphos, deltamethrin and emamectin benzoate was evident from 2009, 2009 and 2007, respectively. The annual variation in medicine consumption and frequency of medicinal treatments correlated well with the evolution in salmon louse sensitivity. The patterns are similar, with a relatively small response delay from the decline in the consumption of medicines in Norway (2016 and onward) to the decline in measured resistance among salmon louse (2017 and onward). 2017 was the first year in which non-medicinal treatments outnumbered medicinal delousing treatments as well as the peak year in numbers of cleanerfish deployed. This study highlights the significance of avoiding heavy reliance on a few substance groups to combat ectoparasites, this can be a potent catalyst for resistance evolution. Further, it demonstrates the importance of transparency in the global industry, which enables the industry to learn from poor choices in the past.
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Affiliation(s)
- Elena Myhre Jensen
- Faculty of Veterinary Medicine, Sea Lice Research Center, Norwegian University of Life Sciences (NMBU), Oslo, Norway
- * E-mail:
| | - Tor Einar Horsberg
- Faculty of Veterinary Medicine, Sea Lice Research Center, Norwegian University of Life Sciences (NMBU), Oslo, Norway
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Tackling the Molecular Drug Sensitivity in the Sea Louse Caligus rogercresseyi Based on mRNA and lncRNA Interactions. Genes (Basel) 2020; 11:genes11080857. [PMID: 32726954 PMCID: PMC7464394 DOI: 10.3390/genes11080857] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 07/21/2020] [Accepted: 07/24/2020] [Indexed: 01/05/2023] Open
Abstract
Caligus rogercresseyi, commonly known as sea louse, is an ectoparasite copepod that impacts the salmon aquaculture in Chile, causing losses of hundreds of million dollars per year. This pathogen is mainly controlled by immersion baths with delousing drugs, which can lead to resistant traits selection in lice populations. Bioassays are commonly used to assess louse drug sensitivity, but the current procedures may mask relevant molecular responses. This study aimed to discover novel coding genes and non-coding RNAs that could evidence drug sensitivity at the genomic level. Sea lice samples from populations with contrasting sensitivity to delousing drugs were collected. Bioassays using azamethiphos, cypermethrin, and deltamethrin drugs were conducted to evaluate the sensitivity and to collect samples for RNA-sequencing. Transcriptome sequencing was conducted on samples exposed to each drug to evaluate the presence of coding and non-coding RNAs associated with the response of these compounds. The results revealed specific transcriptome patterns in lice exposed to azamethiphos, deltamethrin, and cypermethrin drugs. Enrichment analyses of Gene Ontology terms showed specific biological processes and molecular functions associated with each delousing drug analyzed. Furthermore, novel long non-coding RNAs (lncRNAs) were identified in C. rogercresseyi and tightly linked to differentially expressed coding genes. A significant correlation between gene transcription patterns and phenotypic effects was found in lice collected from different salmon farms with contrasting drug treatment efficacies. The significant correlation among gene transcription patterns with the historical background of drug sensitivity suggests novel molecular mechanisms of pharmacological resistance in lice populations.
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Candidate genes for monitoring hydrogen peroxide resistance in the salmon louse, Lepeophtheirus salmonis. Parasit Vectors 2020; 13:344. [PMID: 32650825 PMCID: PMC7350588 DOI: 10.1186/s13071-020-04211-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 07/02/2020] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Hydrogen peroxide (H2O2) is one of the delousing agents used to control sea lice infestations in salmonid aquaculture. However, some Lepeophtheirus salmonis populations have developed resistance towards H2O2. An increased gene expression and activity of catalase, an enzyme that breaks down H2O2, have been detected in resistant lice, being therefore introduced as a resistance marker in the salmon industry. In the present study the aim was to validate the use of catalase expression as a marker and to identify new candidate genes as additional markers to catalase, related to H2O2 resistance in L. salmonis. METHODS A sensitive and an H2O2 resistant laboratory strain (P0 generation, not exposed to H2O2 for several years) were batch crossed to generate a cohort with a wide range of H2O2 sensitivities (F2 generation). F2 adult females were then exposed to H2O2 to separate sensitive and resistant individuals. Those F2 lice, the P0 lice and field-collected resistant lice (exposed to H2O2 in the field) were used in an RNA sequencing study. RESULTS Catalase was upregulated in resistant lice exposed to H2O2 compared to sensitive lice. This was, however, not the case for unexposed resistant P0 lice. Several other genes were found differentially expressed between sensitive and resistant lice, but most of them seemed to be related to H2O2 exposure. However, five genes were consistently up- or downregulated in the resistant lice independent of exposure history. The upregulated genes were: one gene in the DNA polymerase family, one gene encoding a Nesprin-like protein and an unannotated gene encoding a small protein. The downregulated genes encoded endoplasmic reticulum resident protein 29 and an aquaporin (Glp1_v2). CONCLUSIONS Catalase expression seems to be induced by H2O2 exposure, since it was not upregulated in unexposed resistant lice. This may pose a challenge for its use as a resistance marker. The five new genes associated with resistance are put forward as complementary candidate genes. The most promising was Glp1_v2, an aquaglyceroporin that may serve as a passing channel for H2O2. Lower channel number can reduce the influx or distribution of H2O2 in the salmon louse, being directly involved in the resistance mechanism.
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Major KM, Brander SM. The Ecological and Evolutionary Implications of Pyrethroid Exposure: A New Perspective on Aquatic Ecotoxicity. THE HANDBOOK OF ENVIRONMENTAL CHEMISTRY 2020. [DOI: 10.1007/698_2019_432] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Carmona-Antoñanzas G, Helgesen KO, Humble JL, Tschesche C, Bakke MJ, Gamble L, Bekaert M, Bassett DI, Horsberg TE, Bron JE, Sturm A. Mutations in voltage-gated sodium channels from pyrethroid resistant salmon lice (Lepeophtheirus salmonis). PEST MANAGEMENT SCIENCE 2019; 75:527-536. [PMID: 30062864 DOI: 10.1002/ps.5151] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 06/22/2018] [Accepted: 07/19/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Parasitic salmon lice (Lepeophtheirus salmonis) cause high economic losses in Atlantic salmon farming. Pyrethroids, which block arthropod voltage-gated sodium channels (Nav 1), are used for salmon delousing. However, pyrethroid resistance is common in L. salmonis. The present study characterized Nav 1 homologues in L. salmonis in order to identify channel mutations associated to resistance, called kdr (knockdown) mutations. RESULTS Genome scans identified three L. salmonis Nav 1 homologues, LsNav 1.1, LsNav 1.2 and LsNav 1.3. Arthropod kdr mutations map to specific Nav 1 regions within domains DI-III, namely segments S5 and S6 and the linker helix connecting S4 and S5. The above channel regions were amplified by RT-PCR and sequenced in deltamethrin-susceptible and deltamethrin-resistant L. salmonis. While LsNav 1.1 and LsNav 1.2 lacked nucleotide polymorphisms showing association to resistance, LsNav 1.3 showed a non-synonymous mutation in S5 of DII occurring in deltamethrin-resistant parasites. The mutation is homologous to a previously described kdr mutation (I936V, numbering according to Musca domestica Vssc1) and was present in two pyrethroid-resistant L. salmonis strains (allele frequencies of 0.800 and 0.357), but absent in two pyrethroid-susceptible strains. CONCLUSIONS The present study indicates that a kdr-mutation in LsNaV 1.3 may contribute to deltamethrin resistance in L. salmonis. © 2018 Society of Chemical Industry.
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Affiliation(s)
- Greta Carmona-Antoñanzas
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
- Imegen, Parc Científic de la Universitat de València, Paterna, Spain
| | - Kari O Helgesen
- Department of Epidemiology, Norwegian Veterinary Institute, Oslo, Norway
| | - Joseph L Humble
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Claudia Tschesche
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Marit J Bakke
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Sea Lice Research Centre, Oslo, Norway
| | - Louise Gamble
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Michaël Bekaert
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - David I Bassett
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Tor E Horsberg
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Sea Lice Research Centre, Oslo, Norway
| | - James E Bron
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
| | - Armin Sturm
- Institute of Aquaculture, Faculty of Natural Sciences, University of Stirling, Stirling, UK
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