Immunological response profiles to salmon lice infections in Atlantic salmon : modulation by nutrition and selective breeding

Infections with the salmon louse Lepeophtheirus salmonis (L. salmonis) represent one of the most important limitations to sustainable Atlantic salmon (Salmo salar) farming today. The parasite exerts negative impacts on health, growth and welfare of farmed fish, and there are concerns of the impact on wild salmon populations. Current control relies heavily on the use of a few chemical in-feed or bath treatments and an increasing number of reports states their reduced efficiency. Increased mortalities during treatments are also frequently reported. The narrow treatment repertoire is also a consequence of the difficulty in developing novel anti-parasitic chemical treatments that are efficient against lice, environment-friendly and posing no risk for the consumers. Functional feeds and selective breeding are considered two promising alternative approaches for management of salmon lice infections, and understanding the molecular basis of protection against lice is expected to help in their successful application in Atlantic salmon aquaculture.Infeksjoner med lakselus (Lepeophtheirus salmonis) er en av de største utfordringene i dagens oppdrettsnæring, spesielt relatert til påvirkningen på dyrevelferd, resistensutvikling av de antiparasittære midlene brukt, økt infeksjonstrykk på villfisk, redusert vekst og slaktekvalitet. I dag kontrolleres lusenivået i all hovedsak ved hjelp av medisiner, som kan medføre økt mortalitet i seg selv. Behandlingsalternativene er begrenset, fordi det er vanskelig å utvikle nye medisiner mot lus som er både effektive, miljøvennlige og trygge for konsumentene. Behovet for å finne alternative strategier for å håndtere lakselusproblemet for fremtiden er stort, der både funksjonelle fôr og selektiv avl regnes som lovende alternativer. Dette krever en god forståelse av de molekylære responsmekanismene hos atlantisk laks ved lakselusinfeksjoner

A pathomorphological description of cross-stitch vertebrae in farmed Atlantic salmon (Salmo salar L.)

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Nutrigenomic effects of glucosinolates on liver, muscle and distal kidney in parasite-free and salmon louse infected Atlantic salmon

BACKGROUND: Reduction of Lepeophtheirus salmonis infection in Atlantic salmon achieved by glucosinolates (GLs) from Brassica plants was recently reported. However, wider application of functional feeds based on GLs requires better knowledge of their positive and adverse effects. METHODS: Liver, distal kidney and muscle transcriptomes of salmon exposed to the extreme dose of GLs were profiled by microarray, while qPCR analysis followed up selected hepatic and renal responses under the extreme and moderate GLs dose during the L. salmonis challenge. Transcriptional analysis were complemented with measurements of organ indices, liver steatosis and plasma profiling, including indicators of cytolysis and bilirubin. Finally, the third trial was performed to quantify the effect of lower GLs doses on growth. RESULTS: The extreme GLs dose caused a decrease in hepatic fat deposition and growth, in line with microarray findings, which suggested tissue remodeling and reduction of cellular proliferation in the skeletal muscle and liver. Lower GLs inclusion levels in a follow-up trial did not show negative effects on growth. Microarray analysis of the distal kidney pointed to activation of anti-fibrotic responses under the overexposure. However, analyses of ALT, CK and AST enzymes in plasma provided no evidence of increased cytolysis and organ damage. Prevalent activation of phase-2 detoxification genes that occurred in all three tissues could be considered part of beneficial effects caused by the extreme dose of GLs. In addition, transcriptomic evidence suggested GLs-mediated iron and heme withdrawal response, including increased heme degradation in muscle (upregulation of heme oxygenase-1), decrease of its synthesis in liver (downregulation of porphobilinogen deaminase) and increased iron sequestration from blood (hepatic induction of hepcidin-1 and renal induction of intracellular storage protein ferritin). This response could be advantageous for salmon upon encountering lice, which depend on the host for the provision of iron carrying heme. Most of the hepatic genes studied by qPCR showed similar expression levels in fish exposed to GLs, lice and their combination, while renal induction of leptin suggested heightened stress by the combination of extreme dose of GLs and lice. High expression of interferon γ (cytokine considered organ-protective in mammalian kidney) was detected at the moderate GLs level. This fish also showed highest plasma bilirubin levels (degradation product of heme), and had lowest number of attached lice, further supporting hypothesis that making heme unavailable to lice could be part of an effective anti-parasitic strategy. CONCLUSIONS: Modulation of detoxification and iron metabolism in Atlantic salmon tissues could be beneficial prior and during lice infestations. Investigation of anti-lice functional feeds based on low and moderate GLs inclusion levels thus deserves further attention. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13071-016-1921-7) contains supplementary material, which is available to authorized users

Additional file 1: Table S1. of Nutrigenomic effects of glucosinolates on liver, muscle and distal kidney in parasite-free and salmon louse infected Atlantic salmon

An overview of samples and analysis methods applied in Trial 1, 2 and 3. Table S2. Scoring of liver steatosis in individual sections based on [88]. Table S3. Primer list. (DOCX 20 kb