An overview of disruptive technologies for aquaculture

Infectious diseases represent a major threat for the sustainable development of fish farming. Efficient vaccines are not available against all diseases, and growing antibiotics resistance limits the use of antimicrobial drugs in aquaculture. It is therefore important to understand the basis of fish natural resistance to infections to help genetic selection and to develop new approaches against infectious diseases. However, the identification of the main mechanisms determining the resistance or susceptibility of a host to a pathogenic microbe is challenging, integrating the complexity of the variation of host genetics, the variability of pathogens, and their capacity of fast evolution and adaptation. Multiple approaches have been used for this purpose: (i) genetic approaches, QTL (quantitative trait loci) mapping or GWAS (genome-wide association study) analysis, to dissect the genetic architecture of disease resistance, and (ii) transcriptomics and functional assays to link the genetic constitution of a fish to the molecular mechanisms involved in its interactions with pathogens. To date, many studies in a wide range of fish species have investigated the genetic determinism of resistance to many diseases using QTL mapping or GWAS analyses. A few of these studies pointed mainly toward adaptive mechanisms of resistance/susceptibility to infections; others pointed toward innate or intrinsic mechanisms. However, in the majority of studies, underlying mechanisms remain unknown. By comparing gene expression profiles between resistant and susceptible genetic backgrounds, transcriptomics studies have contributed to build a framework of gene pathways determining fish responsiveness to a number of pathogens. Adding functional assays to expression and genetic approaches has led to a better understanding of resistance mechanisms in some cases. The development of knock-out approaches will complement these analyses and help to validate putative candidate genes critical for resistance to infections. In this review, we highlight fish isogenic lines as a unique biological material to unravel the complexity of host response to different pathogens. In the future, combining multiple approaches will lead to a better understanding of the dynamics of interaction between the pathogen and the host immune response, and contribute to the identification of potential targets of selection for improved resistance.

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Combining Multiple Approaches and Models to Dissect the Genetic Architecture of Resistance to Infections in Fish

Development of fish vaccine in Southeast Asia: A challenge for the sustainability of SE Asia aquaculture.

Immunoglobulins (Igs) are complex glycoproteins that play critical functions in innate and adaptive immunity of all jawed vertebrates. Given the unique characteristics of mucosal barriers, secretory Igs (sIgs) have specialized to maintain homeostasis and keep pathogens at bay at mucosal tissues from fish to mammals. In teleost fish, the three main IgH isotypes, IgM, IgD and IgT/Z can be found in different proportions at the mucosal secretions of the skin, gills, gut, nasal, buccal, and pharyngeal mucosae. Similar to the role of mammalian IgA, IgT plays a predominant role in fish mucosal immunity. Recent studies in IgT have illuminated the primordial role of sIgs in both microbiota homeostasis and pathogen control at mucosal sites. Ten years ago, IgT was discovered to be an immunoglobulin class specialized in mucosal immunity. Aiming at this 10-year anniversary, the goal of this review is to summarize the current status of the field of fish Igs since that discovery, while identifying knowledge gaps and future avenues that will move the field forward in both basic and applied science areas.

Mucosal immunoglobulins of teleost fish: A decade of advances.

The effect of dietary combined herbs extracts (oak acorn, coriander, and common mallow) on growth, digestive enzymes, antioxidant and immune response, and resistance against Aeromonas hydrophila infection in common carp, Cyprinus carpio

Fish immunization has been carried out for over 50 years and is generally accepted as an effective method for preventing a wide range of bacterial and viral diseases. Vaccination efforts contribute to environmental, social, and economic sustainability in global aquaculture. Most licensed fish vaccines have traditionally been inactivated microorganisms that were formulated with adjuvants and delivered through immersion or injection routes. Live vaccines are more efficacious, as they mimic natural pathogen infection and generate a strong antibody response, thus having a greater potential to be administered via oral or immersion routes. Modern vaccine technology has targeted specific pathogen components, and vaccines developed using such approaches may include subunit, or recombinant, DNA/RNA particle vaccines. These advanced technologies have been developed globally and appear to induce greater levels of immunity than traditional fish vaccines. Advanced technologies have shown great promise for the future of aquaculture vaccines and will provide health benefits and enhanced economic potential for producers. This review describes the use of conventional aquaculture vaccines and provides an overview of current molecular approaches and strategies that are promising for new aquaculture vaccine development.

https://www.mdpi.com/2076-2607/7/11/569/pdf

A Review of Fish Vaccine Development Strategies: Conventional Methods and Modern Biotechnological Approaches.

Salmonid diseases caused by infections of Flavobacterium psychrophilum, the causative agent of bacterial coldwater disease, remain difficult to manage as novel, pathogenic strains continue to emerge in aquaculture settings globally To date, much of the research regarding treatment options and vaccine development has focused on rainbow trout (Oncorhynchus mykiss), but other inland-reared salmonids are also impacted by this Gram-negative bacterium As such, Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) were injection-challenged with a variety of previously reported F psychrophilum strains isolated from disease diagnostic cases in salmonids, as well as a standard and well-studied F psychrophilum strain (CSF 259-93) known to be virulent in rainbow trout In three separate virulence assessments (Trials A, B and C), strains US063 (isolated from lake trout; Salvelinus namaycush) and US149 (isolated from Atlantic salmon) caused a significantly higher cumulative per cent mortality (CPM) relative to other strains in Atlantic salmon (p <001 for all trials), with US149 causing significantly greater mortality than US063 in Trials A (CPM 97% vs 65%, p =008) and B (CPM 96% ± 23% vs 8133% ± 48%, p =014) Trial C used a lower dose (186 × 108  CFU/mL) for US149, resulting in a lower mortality (7867% ± 933%) relative to Trials A and B CSF259-93 did not cause significant mortality in any trials In brook trout, the strain 03-179 (originally isolated from steelhead trout; Oncorhynchus mykiss) was significantly more virulent than any other (CPM 100% ± 0%, p <001), followed by US063 (73% ± 38%) and US149 (40% ± 61%,) respectively Again, CSF259-93 did not cause significant mortality relative to a mock challenge treatment Results provide information about the applicability of strain selection in F psychrophilum virulence testing in Atlantic salmon and brook trout, demonstrating the high virulence of US063 and US149 for these salmonid species This information is applicable for the development of therapeutics and vaccines against F psychrophilum infections and demonstrates the reproducibility of the experimental challenge model

Assessment of Flavobacterium psychrophilum-associated mortality in Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis).

Burbot (Lota lota maculosa) are a potential new species for commercial aquaculture As burbot culture expands, there is a need to further define pathogen susceptibility and characterize aspects of the burbot immune response in an effort to assess fish health A recent clinical diagnostic case from juvenile burbot reared at a commercial production facility resulted in the isolation and identification of Flavobacterium columnare along with several Aeromonas spp The F columnare isolate was assigned to genetic group 1 via multiplex PCR, a genetic group commonly associated with columnaris disease cases in rainbow trout (Oncorhynchus mykiss) Virulence of the F columnare isolate was assessed in vivo in both juvenile burbot and rainbow trout Additionally, several of the Aeromonas sp case isolates were identified via sequencing (16S rRNA, gyrB and rpoD) and a putative A sobria isolate (BI-3) was used to challenge burbot, along with a known virulent Aeromonas sp (A141), but BI-3 was not found to be virulent Burbot were refractory to F columnare when challenged by immersion, and it is likely that this is a secondary pathogen for burbot Although refractory in burbot, the identified F columnare isolate (BI-1) was found to be virulent in rainbow trout

Evan M. Jones

Papers

A Review of Fish Vaccine Development Strategies: Conventional Methods and Modern Biotechnological Approaches.

Assessment of Flavobacterium psychrophilum-associated mortality in Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis).

Isolation and experimental challenge of cultured burbot (Lota lota maculosa) with Flavobacterium columnare and Aeromonas sp. isolates