Author: marina02

Effects of a fucoidan-containing functional feed on immune response of Atlantic salmon challenged with Tenacibaculum dicentrarchi.

Tenacibaculum dicentrarchi is a bacterium responsible for causing Tenacibaculosis, one of the most significant bacterial diseases affecting farmed salmon worldwide. This study aimed to evaluate whether a fucoidan-based diet could boost the immune response of Atlantic salmon and reduce mortality associated with Tenacibaculosis. In the experiment, the fish were tagged and divided into two groups. One group was fed a functional diet containing a fucoidan-rich extract for one month, while the other group received a control diet without fucoidan. After this phase, both groups were fed the control diet for another month (the resting period). Following the resting period, both groups of fish were challenged with the bacteria on day 0. Peripheral blood leukocytes (PBL), head kidneys, and spleens were collected at various points: after the first month of fucoidan feeding (60 days prior to infection), after the resting period (30 days prior to infection), and on 0-, 2-, 7-, and 15-days post-infection. The samples were used for RNA extraction, and the expression of selected immune-related genes was analyzed. The transcript levels of Cathelicidin (CATH)2, Tumoral necrosis factor (TNF)-α, Interferon-gamma (IFN-γ), Interleukin (IL-10), and Transforming growth factor (TGF)-β were measured in each sample. Additionally, immune cells were quantified using flow cytometry in both the PBLs and spleen on days 0, 2, 7, and 15 following the infection.

The results indicated that fish fed a fucoidan-based diet experienced reduced mortality compared to those fed the control diet. Additionally, infected fish that were fed a fucoidan diet exhibited an increase in CATH2 transcripts in both the spleen and head kidney, particularly on day 2 after infection. IFN-γ transcript levels also increased on day 2, but only in the head kidney. Similarly, TGF-β rose on day 2 in PBL and head kidney. In contrast, TNF-α and IL-10 transcripts increased after infection (2- or 7-days post-infection) in PBL and head kidney but only in the group receiving the control diet. Regarding immune cell populations, CD4+ and IgM+ cells increased in infected fish that were fed the fucoidan-based diet compared to those on the control diet. These findings showed that a fucoidan-based diet for Atlantic salmon significantly enhances an optimal and early immune response against T. dicentrarchi and, thereby regulating the immune response soon after infection. Altogether, this study indicated that a diet rich in fucoidan enhances survival rates in Atlantic salmon infected with T. dicentrarchi and significantly modulates the immune response shortly after infection.

1. BENAVIDES, ALMENDRA, UNIVERSIDAD DE SANTIAGO DE CHILE, Author
2. MONTERO, RUTH, NORWEGIAN UNIVERSITY OF LIFE SCIENCES, Author
3. MORALES-LANGE, BYRON, NORWEGIAN UNIVERSITY OF LIFE SCIENCES, Author
4. ROCHA, SERGIO D.C., NORWEGIAN UNIVERSITY OF LIFE SCIENCES, Author
5. MUÑOZ, JOHN, UNIVERSIDAD DE SANTIAGO DE CHILE, Author
6. MANCILLA, MARCOS, ADL DIAGNOSTIC CHILE SPA, Author
7. MERCADO, LUIS, PONTIFICIA UNIVERSIDAD CATÓLICA DE VALPARAÍSO, Author
8. ØVERLAND, MARGARETH, NORWEGIAN UNIVERSITY OF LIFE SCIENCES, Author
9. IMARAI, MONICA, UNIVERSIDAD DE SANTIAGO DE CHILE, Presenter

Assessment of gill health in exposed aquaculture

The Norwegian salmon farming industry is increasingly focused on developing innovative technologies to address sustainability challenges related to salmon lice and the scarcity of new production sites. One possible solution is to develop technology that can be used further out to sea where there is less infection risk and free space available. The “Ocean farm” is an example of one such technology. This study examines the development of gill health of Atlantic salmon under exposed aquaculture conditions at the Ocean – farm vs at a nearby traditional farm with traditional sea cages.

Atlantic salmon with the same genetics, origin and life history were studied over a period of 8 months at the Ocean farm and a nearby site with traditional sea cages. The Ocean farms is located at an exposed site in the outer part of the Lofoten islands, while the traditional farm is located 33 km further inn, at a sheltered fjord location.  Welfare assessment and sampling of gill tissue were performed every second week at both production sites for further analysis such as rt-qPCR and histology.

The results showed a gradual worsening of the macroscopic gill score of the Atlantic salmon reared in both technologies during the autumn months. Histological analysis revealed similar results, however certain histopathological changes such as lamellar epithelial hyperplasia were more prompt at the exposed aquaculture production site compared to the traditional aquaculture production site. In addition, a decreasing ct-value of Ca. Branchiomonas cysticola and Costia was detected during the autumn months with rt-qPCR of gill samples at both production sites.

Although the Atlantic salmon reared in the traditional and the exposed technology had similar seasonal development of gill health, the analyses revealed more severe changes at the exposed site. This suggests that exposed aquaculture gives added risk for poor gill health, and that one therefore must pay extra attention to that this technology is deployed at sites with good oxygen conditions and water exchange.

1. Seem, Julie, NORDLAKS HAVBRUK AS, Presenter
2. Stien, Lars Helge, Institute of Marine Research, Author
3. Bergvik, Sindre, UiT-The Arctic University of Norway, Tromsø, Author
4. Hansen, Rebekka Marie, UiT-The Arctic University of Norway, Tromsø, Author
5. Lader, Pål, NTNU-Norwegian University of Science and Technology, Author
6. Johansen, Bjarne, Nordlaks Havbruk AS, Author
7. Seternes, Tore, UiT-The Arctic University of Norway, Tromsø, Author

In vivo evaluation of a diet enriched with plant-based essential oils against Sparicotyle chrysophrii

Introduction

Sparicotyle chrysophrii poses a significant economic burden in net pen-based farming of gilthead sea bream (GSB) across the Mediterranean. Current control methods rely on formalin baths, which are costly and raise environmental and safety concerns, highlighting the need for sustainable alternatives. Dietary delivery of antiparasitic compounds, particularly plant-derived essential oils (EOs), offers advantages such as ease of administration, reduced stress to fish, and lower environmental impact.

This study evaluated three EOs: Salvia rosmarinus, Cinnamomum zeylanicum, and Origanum vulgare -as in-feed antiparasitic agents during an experimental S. chrysophrii challenge in GSB.

Methodology

The in vivo trial was conducted in closed recirculation aquaculture systems (RAS), with four challenged groups fed EOs-enriched or control diets, and a non-challenged group. Each group was tested in duplicate tanks. Blood, gill, liver, and muscle samples were collected to detect EO bioactive compounds using Gas Chromatography-Flame Ionization Detector.

Results and Conclusions

Biometric and hematological parameters showed no significant differences among the four challenged groups, indicating good dietary acceptance. However, significant differences were observed between challenged and non-challenged fish, confirming the detrimental impact of the infection. Notably, correlation analysis revealed a significant negative association between serum iron levels (Fe²⁺/³⁺) and infection intensity (p = 0.005), providing evidence of the hematophagous behavior in adult S. chrysophrii.

Survival analysis showed significant differences between diets, with Origanum vulgare-enriched diet significantly reducing mortality risk compared to the control (p = 0.0035).

Regarding parasite variables, most fish were heavily infected; however, many individuals exhibited signs of severe anaemia despite having a low parasite burden. This was interpreted as a result of adult parasite migration from severely affected fish, highlighting the difficulties in establishing reproducible and standardized distribution models for this parasite. Overall, final infection intensity did not differ significantly among treatments. Nevertheless, the infective pressure applied during the challenge, combined with substantial variability and uncertainty in parasite distribution, may have masked some differences.

In conclusion, this study contributes valuable data on the biology and impact of S. chrysophrii while providing promising preliminary evidence supporting the potential use of EOs in functional feed as alternative control strategies.

1. PIROLLO, TERESA, UNIVERSITY OF BOLOGNA, Presenter
2. LEON, ANA MARIA, Instituto de Acuicultura Torre de la Sal (IATS, CSIC), Author
3. CAFFARA, MONICA, UNIVERSITY OF BOLOGNA, Author
4. CANESCHI, ALICE, Società Italiana per la Ricerca sugli Oli Essenziali (SIROE), Author
5. GU, JINNI, BioMar AS, Trondheim, Norway, Author
6. ESTENSORO, ITZIAR, Instituto de Acuicultura Torre de la Sal (IATS, CSIC), Author
7. SCOZZOLI, MAURIZIO, APA-CT srl, Forlì, Italy, Author
8. SITIJA’-BOBADILLA, ARIADNA, Instituto de Acuicultura Torre de la Sal (IATS, CSIC), Author
9. PALENZUELA, OSWALDO, Instituto de Acuicultura Torre de la Sal (IATS, CSIC), Author

Time-dependent effects of dietary methionine supplementation on immune status and antioxidant defenses in European seabass (Dicentrarchus labrax)

When assessing dietary supplements designed to modulate the immune system, it is important to consider the impact of different feeding durations. While short-term dietary methionine supplementation has been shown to enhance immune status in European seabass (Dicentrarchus labrax), the effects of long-term intake remain poorly explored. Therefore, the present study investigated the impacts of 12 weeks of dietary methionine supplementation on immune status, hepatic antioxidant defenses and disease resistance in juvenile seabass (15.92 ± 2.02g). Fish were randomly assigned to six tanks in a recirculating water system. Following a three-week acclimation, triplicated tanks were fed either a control diet (CTRL), formulated to meet species-specific amino acid requirements, or a CTRL-based diet supplemented with 1% methionine (MET). Blood, plasma, head-kidney and liver samples were collected after 4, 8 and 12 weeks of feeding. The remaining fish were bath-challenged with Tenacibaculum maritimum (7.5 × 10⁵ CFU/ml) to assess disease resistance. Hematological profile, leukocyte differential counts, plasma innate immune parameters, gene expression in head-kidney and liver, and hepatic antioxidant defenses were evaluated. After 4 weeks, MET-fed fish showed a transient increase in erythrocyte counts and a reduction in MCH levels, along with trends towards increased leucocyte numbers and enhanced hepatic antioxidant capacity. However, expression of the pro-inflammatory gene il6 in the head-kidney was consistently reduced in this group. By week 12, MET-fed fish exhibited significantly lower plasma lysozyme activity, reduced expression of the apoptotic gene casp8 and the DNA methylation-related dnmt1 in the head-kidney, and diminished hepatic glutathione levels, coinciding with increased susceptibility to T. maritimum, evidenced by a 48% cumulative mortality rate compared to 23% in CTRL-fed fish. Overall, these findings suggest that the immunomodulatory effects of methionine supplementation may be both dose- and time-dependent, with short-term supplementation tending to support immune and antioxidant defenses, while prolonged intake at the tested level appeared to impair host defenses. Furthermore, decreased dnmt1 expression in the head-kidney indicates that prolonged methionine supplementation, under these experimental conditions, may influence epigenetic regulation in this tissue. Further studies are needed to elucidate the underlying mechanisms and determine optimal supplementation strategies.

This work was supported by the European Union’s Horizon Europe research and innovation programme (GA No.101079467 project GRINNAQUA) and national funds by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through project IMMUNAA (reference PTDC/CVT-CVT/7741/2020). IC, DP, MH, MM and BC were supported by FCT, Portugal (2021.04867.BD, UI/BD/150900/2021, 2023.07575.CEECIND/CP2848/CT0014, 2022.03304.CEECIND and 2020.00290.CEECIND, respectively).

1. Carvalho, Inês, CIIMAR/ICBAS, Presenter
2. Cunha, André, CIIMAR/ICBAS, Author
3. Peixoto, Diogo, CIIMAR/ICBAS, Author
4. Santos, Paulo, CIIMAR/ICBAS, Author
5. Hinzmann, Mariana, CIIMAR, Author
6. Ferreira, Inês, CIIMAR/ICBAS, Author
7. Machado, Marina, CIIMAR, Author
8. Costas, Benjamín, CIIMAR/ICBAS, Author

The impact of louse barriers on Atlantic salmon (Salmo salar) gill health

Introduction

The salmon industry is challenged with a difficult balancing act, managing parasitic lice levels while ensuring fish health. Chemical resistance and welfare concerns have driven a shift from reactive to preventive strategies, e.g. barriers. Barriers physically block infectious copepodids concentrated near the surface, reducing host-parasite interactions. While effective at lowering lice burden, barriers restrict water exchange, impacting dissolved oxygen replenishment and waste removal. Farmers must weigh the benefits of lice control against potential deleterious effects, specifically worsened gill health. A deeper understanding of interactions between environmental conditions, barrier use, and gill health is essential to assessing the risks associated with lice prevention.

Methodology

We tested a dynamic parasite management strategy combining barriers, oxygenation, and behaviour modification to optimize cage conditions while minimizing lice infestations. Fish were sampled monthly throughout a commercial production cycle to assess welfare, lice infestation and gill health. Additionally, gill histology was collected, and gill, mucus and water samples were qPCR tested for pathogens associated with amoebic gill disease (AGD) and complex gill disease (CGD) (P. perurans, B. cysticola, P. theridion, salmon gill poxvirus, Tenacibaculum spp., and M. viscosa). Environmental sensors continuously monitored temperature, salinity, and dissolved oxygen to assess correlations between environmental fluctuations and gill health. Generalised linear mixed models were used to evaluate changes in gill condition in relation to environmental and production variables.

Results

Barriers delayed the need for delousing by two months, reducing the overall number of treatments compared to control cages. Although oxygen levels did not differ significantly between groups (110 ±12.1, 114 ± 13.1), gross gill scores in test cages were twice as high as controls at the peak of AGD infection (0.74, 0.25). Gill pathogen loads mirrored those in the water but were considerably higher. In contrast with AGD results, pathogen loads for CGD did not differ in control and test cages in autumn, suggesting pathogens alone are not solely responsible for the severity of gill disease.

Conclusions

A deeper understanding of the onset and progression of gill disease in Atlantic salmon offers valuable opportunities to enhance early detection and management of outbreaks. Identifying key environmental and biological indicators linked to disease progression, makes it feasible to monitor outbreak risk in real time and implement timely mitigation measures. This knowledge supports farmers in maintaining gill health but also enables the optimisation of lice prevention strategies—ensuring they effectively control parasites while minimising potential drivers of gill disease.

1. Sutton, Jade, University of Sydney, Presenter
2. Oldham, Tina, Havforsknings Instituttet, Author
3. Samsing, Francisca, University of Sydney, Author

FIGHTING GILL POLYOPISTHOCOTYLEANS IN GILTHEAD SEABREAM (Sparus aurata): SCREENING PHARMACOLOGICAL, PHYTOGENICS AND ESSENTIAL OILS FOR CANDIDATE TREATMENTS

Sparicotyle chrysophrii is a blood-feeding ectoparasite threatening the health of farmed gilthead seabream (Sparus aurata), a species of high economic relevance in Mediterranean aquaculture. Therapeutic options remain limited, with formalin baths representing at the moment the sole approved treatment within Western Europe. However, their application in sea cages is logistically complex, costly, and raises safety concerns, emphasizing the pressing need for effective, safe, and practical antiparasitic alternatives.

We shortlisted candidate active ingredients (AIs) against S. chrysophrii, including a range of anthelmintic drugs and their fingerprints, small molecules selected by computational virtual screening of chemical libraries.  We also evaluated commercial phytogenic formulas marketed as food additives, and a range of vegetal essential oils (EOs), as non-pharmaceutical approaches to the drugs. An in vitro dose-response assay was designed to determine their parasiticidal effectiveness. Adult S. chrysophrii were harvested from the gills of experimentally infected gilthead seabream. Specimens were placed in 24-well plates (10 worms per well) and exposed to the treatments in duplicates. Worm survival was assessed at different times post-exposure. Survival data were analyzed using nonlinear regression models fitted to normalized dose-response curves. Lethal doses 50 (LD50), were calculated for 1,2, 4, 6, 20 and 24h post-exposure (p.e).

Salicylanilides were the most effective pharmacological family, including the top three AIs: niclosamide (LD50_2h=0.07 µM), closantel (LD50_2h=2.3 µM), and ME1.62 (fingerprint of closantel; LD50_2h=0.09 µM). Niclosamide, with the strongest parasiticidal effect, was over 1400-times more effective than other anthelmintics like praziquantel (LD50_2h=100 µM), which is considered a reference chemotherapy against fish poliophistocotylans. Salycilanilides provoked rapid worm paralysis and contraction in vitro. Regarding phytogenic additives and EOs, several compounds presented remarkable parasiticidal activity, with Cinnamomum zeylanicum, Origanum vulgare and Salvia rosmarinus LD50_2h ranging between 14-54 ppm.

We have demonstrated the potential of certain salicylanilides as promising candidates for novel pharmacological treatments against S. chrysophrii, alongside the remarkable in vitro activity of several natural alternatives, which may offer more sustainable options and face fewer regulatory restrictions in the short term. Current research is focused on elucidating their mechanisms of action, specifically by assessing the damages to the parasite´s tegument ultrastructure, musculature, and cytoskeleton. Cytotoxicity assessments and in vivo in-feed trials are planned as the next steps.

This work was partially supported by Grant PID2022-136914OB-I00 funded by MICIU/AEI/10.13039/501100011033 and by FEDER, UE. Additional appropriations were obtained through the ThinkInAzul programme supported by MICIU, with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (GVA-THINKINAZUL/2021/022).

1. León, Ana M., IATS-CSIC, Presenter
2. Pirollo, Teresa, UNIBO, Author
3. Estensoro, Itziar, IATS-CSIC, Author
4. Sitjà-Bobadilla, Ariadna, IATS-CSIC, Author
5. Caffara, Monica, UNIBO, Author
6. Gil, Carmen, CIB-CSIC, Author
7. Martínez, Ana, CIB-CSIC, Author
8. Gu, Jinni, Biomar AS, Author
9. Caneschi, Alice, SIROE, Author
10. Scozzole, Maurizio, APA-CT srl, Author
11. Palenzuela, Oswaldo, IATS-CSIC, Author

Role of methionine supplementation in immune modulation and resistance of Atlantic salmon (Salmo salar) to Salmon Louse (Lepeophtheirus salmonis)

Salmo salar aquaculture is severely affected by Lepeophtheirus salmonis infections, resulting in substantial economic losses. In recent years, numerous studies have investigated the host-pathogen interaction in order to develop effective treatments or prophylactic measures against salmon louse. Dietary supplementation with methionine in fish diets has shown to enhance resistance to bacterial infections. However, no studies have been developed to assess the immunomodulatory potential of this amino acid on parasite incidence in aquaculture. The present study aimed to evaluate on the effect of dietary methionine supplementation on the immune response of Atlantic salmon to sea lice infection.

Juvenile fish (±120g) were fed for four weeks with either a control diet (CTRL) or a methionine-supplemented diet (MET, 2x requirement level of L-methionine), and subsequently sampled (n=12/diet). The remaining fish were infected by cohabitation with sea lice (100 copepods/fish) and sampled two weeks post-challenge. Blood, plasma, liver and head-kidney tissues were collected, for haematological analysis, evaluation of the systemic humoral response, oxidative stress parameters, and gene expression analysis, respectively. Additionally, fish skin was collected for proteomic analysis and single-cell RNA sequencing (scRNA-seq) before, and after infection (parasite attachment sites).

Parasite counts per fish revealed that 70% were in the chalimus-II while the remainder were pre-adults stage, with no differences found between diet. At chamilus-II stage, the parasite feeds solely on mucus and skin, which may explain the limited haematological response observed, though infection seems to increase white blood cells counts. These results, together with lack of oxidative stress biomarkers and immune-related genes modulation in the head kidney, suggest that although the presence of the ectoparasite was confirmed, it did not induce a significant systemic response in the host. This is further supported by the absence of lipid peroxidation in tissues. Altogether, this reinforces the notion that at early developmental stages the parasite induces immune responses mainly locally, at the skin. These responses mainly caused by wounds may not impose a systemic response. Nonetheless, plasma protease activity in the MET-diet group increased significantly following infestation when compared to the basal-diet and the non-infected group.

The results of proteomics and scRNA-seq of the skin where lice were attached are currently being analysed in order to gain a better understanding of the immunomodulatory capacity of methionine and the local response involved in resistance to salmon louse.

Work funded by the European Union’s Horizon Europe research and innovation programme (GA No.101079467 project GRINNAQUA).

1. Vaz, Mariana, Centro Interdisiplinar de Investigação Marinha e Ambiental (CIIMAR), University of Porto, Portugal, Presenter
2. Øvergård, Aina-Cathrine, SLCR-Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Norway, Author
3. Pinto, Gonçalo, Centro Interdisiplinar de Investigação Marinha e Ambiental (CIIMAR), University of Porto, Portugal, Author
4. Espedal, Per Gunnar, SLCR-Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Norway, Author
5. Kongshaug, Heidi, SLCR-Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Norway, Author
6. Azeredo, Rita, Centro Interdisiplinar de Investigação Marinha e Ambiental (CIIMAR), University of Porto, Portugal, Author
7. Costas, Benjamín, Centro Interdisiplinar de Investigação Marinha e Ambiental (CIIMAR), University of Porto, Portugal, Author
8. Nilsen, Frank, SLCR-Sea Lice Research Centre, Department of Biological Sciences, University of Bergen, Norway, Author
9. Machado, Marina, Centro Interdisiplinar de Investigação Marinha e Ambiental (CIIMAR), University of Porto, Portugal, Author

Effects of particle load in recirculating aquaculture systems on Atlantic salmon health

Recirculating aquaculture systems (RAS) offer potential for intensive fish production with better environmental control, reduced water consumption and potentially greater biosecurity. However, despite the production advantages, RAS production can pose problems with regard to fish welfare and in particular, deterioration of gill health. As part of a program investigating the interactions of particle load, microbiome and fish health and physiology in RAS systems for raising Atlantic salmon, the progressive effects of maintaining fish from freshwater parr to seawater transfer in RAS were studied with respect to the gill health and physiological performance at low total organic suspended solids load (approximately 1 mg/L) compared with a normal/high load of >7mg/L.

There was a progressive increase in the prevalence of gill associated pathology consistent with that seen in commercial RAS systems from the early onset of RAS production for both low and high TSS loads. There were no significant difference of TSS load on the severity or extent of gill pathology in any of the sampled fish. Following transfer to flow-through seawater, there was a marked reduction in gill pathology to pre-experimental levels. There was a tendency for a marginal increase in expression of inflammatory markers IL1b and TNFa in fish exposed to increased suspended solids. These results together suggest that suspended solids load has a limited effect on the occurrence or progression of gill pathology in RAS-raised Atlantic salmon suggesting that other water quality parameters or suboptimal levels of several parameters play a more significant role.  This work was funded through the Fisheries and Aquaculture Research fund of Norway.

1. POWELL, MARK, UNIVERSITY OF ST ANDREWS/RESURGAM CONSULTING AND MEDIA, Presenter
2. Calabrese, Sara, NIVA, Author
3. Hess-Erga, Ole-Kristian, NIVA, Author
4. Paulo, Fernandes, NIVA, Author

Myxobolus cerebralis discovered in cartilage of ribs in wild Atlantic salmon Salmo salar and brown trout Salmo trutta in Norway

Introduction: Myxobolus cerebralis is the causative agent of whirling disease in salmonids. The first discovery of M.cerebralis in Norway was in farmed rainbow trout (Oncorrhyncus mykiss) in earth ponds near Oslo in 1970. Several cases of whirling disease were recorded in pond aquaculture during the 1980ies, while only three Myxobolus sp. cases have been recorded in the Norwegian veterinary Institutes (NVI) journals during the last twenty years. In 2024, NVI received photos of juvenile Atlantic salmon (Salmo salar) with darkened and deformed tails characteristic for Myxobolus sp. infection, from a stock enhancement hatchery in Nordland County, Norway.

Methodology: Formalin-fixed organ samples and whole fish from the hatchery were submitted to NVI for pathological analysis. Subsequently, a PCR assay for M. cerebralis was developed and used in combination with sequencing for species confirmation. In addition, retrospective studies of archived histopathological samples from health monitoring in wild salmonids were initiated. A PCR-based screening was launched to map the occurrence of the parasite in samples from wild salmonids submitted to NVI during late 2024 and early 2025, which mainly comprised healthy salmon parr captured for Gyrodactylus salaris surveillance.

Results: Histopathological examination of deformed Atlantic salmon from the hatchery revealed parasites in the cartilage of ribs (os costae) consistent with Myxobolus spp. PCR and sequencing analysis revealed that the species present was M. cerebralis. Retrospective studies of histopathological samples revealed that parasites resembling Myxobolus sp. was prevalent in ribs of both wild Atlantic salmon and brown trout (Salmo trutta). Subsequent PCR-based screening revealed that M. cerebralis was widespread south of the polar circle, but not detected in Counties Troms and Finnmark in Northern Norway. This may bedue to the distribution of the definitive host Tubifex tubifex. However, the findings of M. cerebralis positive fish were not linked to skeletal deformities. The parasite was not detected in Arctic char (Salvelinus alpinus).

Conclusions: Our results show that M. cerebralis infects the ribs of both Atlantic salmon and brown trout, and are widely distributed in both these fish species throughout the southern and middle parts of Norway. Previous diagnostic efforts may have overlooked the presence of M. cerebralis as mainly cranial cartilage were investigated for the presence of spores. These standard procedures for detection are based on tissue distribution in rainbow trout, but based on our results, we now recommend including samples of ribs for screening of M. cerebralis in Atlantic salmon and brown trout.

1. Garseth, Åse Helen, Norwegian Veterinary Institute, Author
2. Erkinharju, Toni, Norwegian Veterinary Institute, Presenter
3. Nilsen, Arve, Norwegian Veterinary Institute, Author
4. Spilsberg, Bjørn, Norwegian Veterinary Institute, Author
5. Gåsnes, Siri Sollien, Norwegian Veterinary Institute, Author
6. Lo, Håvard, Norwegian Veterinary Institute, Author
7. Biering, Eirik, Norwegian Veterinary Institute, Author
8. Hansen, Haakon, Norwegian Veterinary Institute, Author

Revolutionizing Farmed Fish Health Surveillance with non-invasive Multiomics Biomarkers

INTRODUCTION

The growing demand for high-quality animal protein is placing increased pressure on aquaculture to adopt sustainable practices that balance productivity and animal welfare. Climate change adds further stressors, such as temperature shifts and increased handling. In response, the IGNITION project is developing innovative tools to improve fish health and resilience across key aquaculture species, including European seabass (Dicentrarchus labrax), Atlantic salmon (Salmo salar), and rainbow trout (Oncorhynchus mykiss). The identification of a panel of molecular, physiological, and behavioral signatures that identify and predict accurate stress and health status is a priority. By integrating advanced omics technologies combined with machine learning, the project is discovering minimally invasive biomarkers for precise health assessments.

METHODOLOGY

Transcriptomic and proteomic analyses have been conducted on the skin and skin mucus of European seabass, Atlantic salmon, and rainbow trout, respectively, subjected to transport-stress (acute) and temperature variations (chronic). For the first, samples were collected at three time points: before transport, immediately after stress exposure, and following a 24-hour recovery period. For the temperature trial, samples were collected before and after a month period of exposure to 19, 23 and 27 ºC. RNA sequencing and nano liquid chromatography mass spectrometry were conducted, followed by differential expression analyses with edgeR and limma. Features of interest were integrated across the different omics layers and machine learning was employed to determine those with the highest predictive power for key surrogate endpoints (e.g., physiological indicators).

RESULTS

The integrated analysis of genes differently expressed across all trials, showed 35 genes commonly regulated in the skin of all three species in response to both temperature and transport challenges. Concomitantly, a comparison with differentially abundant proteins in the fish skin mucus revealed shared features between the different omics layers, indicating a correlation between transcriptomics and proteomics. Functional annotation of these features indicated that these were mainly involved in transcription regulation, response to stress, fatty acid metabolism and immune related pathways such as cytokines’ release.

CONCLUSIONS

The common regulation across species, challenges and multiomics layers make these biological features a promising panel of transversal biomarkers for fish health assessment. Future research will incorporate the validated biomarkers into cutting-edge biosensors for continuous, non-invasive monitoring. These electrochemical sensors will detect these validated biomarkers in water and skin mucus samples, allowing real-time health surveillance and facilitating early interventions.

1. Raposo de Magalhães, Cláudia, SPAROS, LDA/RIASEARCH, Lda, Presenter
2. Buha, Tonka, SPAROS, Lda/Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Author
3. Simó-Mirabet, Paula, Instituto Universitario de Investigación Marina (INMAR), Author
4. Barreto, André, RIASEARCH, Lda, Author
5. Teixeira, Sofia, Tyndall National Institute, UCC, Author
6. Costas, Benjamin, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR), Author
7. Gonçalves, Ana Teresa, SPAROS, LDA/RIASEARCH, Lda, Author