Search

Stress inevitably occurs during any fish handling and manipulation in culturing, research, or clinical examination situations that require capture and removal of fish from water. Different stress factors can affect the changes in the relative numbers and function of cells of the fish immune system. Catching, transportation and over-crowding caused stress-induced changes in the total number of leukocytes and thrombocytes, as well as changes in the leukocyte formula in Prussian carp (Carassius gibelio, Bloch, 1782) presented here. Cytochemical characterization of leukocyte cell types was performed by applying Myeloperoxidase (MPO), Periodic Acid Schiff (PAS) and Sudan Black B (SBB) staining of Prussian carp blood smears. Cytochemical characterization is a rapid and efficient method for white leukocyte differentiation and insight in their functional status. Comparison and analysis in Prussian carp hematological parameters from fish with and without exposure to stressful conditions such as capture, manipulation, transport and holding, revealed significant differences between stressed and non-stressed fish. Significant reduction in the total number of thrombocytes and lymphocytes and the increase in total neutrophil count were observed in stressed animals. However, differences in total leukocyte number and the number of monocytes were not observed. Deviations from the estimated reference intervals for Prussian carp hematological parameters clearly indicated the presence/absence of a stress reaction and to some extent its intensity. Estimated reference intervals and characterization of morphological and cytochemical appearance of blood cells form a solid basis for further research of the cellular immune function and hematology changes in Prussian carp.

Organically modified clinoptilolite (member of the zeolite family of minerals; MinazelPlus®) feed additive, with an average weight of 30 ± 2 g, was used to prevent mycotoxicosis in Nile tilapia (Oreochromis niloticus) through its supplementation for 42 days to the diet contaminated with multiple mycotoxins: aflatoxin B1 (40 µg/kg), fumonisin B1 and B2 (600 µg/kg), zearalenone (50 µg/kg), and deoxynivalenol (150 µg/kg). The fish were divided randomly into four experimental groups (basal diet control—C; fed 2 g/kg MinazelPlus®—MZ; fed multiple mycotoxins—MT; and fed a combination of MinazelPlus® and multiple mycotoxins—MZ + MT). Each group consisted of triplicate aquarium setups, with six fish in each replicate. Sampling was performed in weeks 2, 4, and 6. The lymphocyte count was significantly higher in the MZ group compared with the MT group and the MT + MZ group in week 6. An overall decrease in the neutrophil count was observed in the experimental groups. Histopathological analysis was performed in weeks 2 and 6, revealing significant changes in the liver, intestines, kidney, and spleen of fish from the MT group, while the MT + MZ and MZ groups were similar to the control. The addition of 2 g/kg MinazelPlus® has the ability to prevent and reduce the adverse effects of chronic exposure to low concentrations of multiple mycotoxins in juvenile Nile tilapia. [ABSTRACT FROM AUTHOR]

Featured Application: Although this is a fundamental microbiological study, its results indicate the necessity of changing the approach to fish ponds maintenance and focusing all hygiene measures on the eradication of biofilms and not on a simple disinfection. Also, the practical laboratory approach to testing biofilms of A. salmonicida subspecies salmonicida should be changed. Biofilm formation of clinical isolates of Aeromonas salmonicida subspecies salmonicida was compared using scarce (minimal M9 and ABTG w/o amino acids) and enriched nutrient media (Tryptone Soya broth) at 8 °C, 16 °C, and 25 °C using direct enumeration of viable cells in biofilm (log CFU), crystal violet staining (ODc) of the formed biofilm biomass, and liquid–air border biofilm formation (pellicle test). Whole-genome sequencing (WGS) was performed with the usage of an Oxford nanopore system by Genomics and Transcriptomics Labor Düsseldorf (Heinrich-Heine-Universität Düsseldorf, Germany). A bioinformatic analysis was performed with the usage of Geneious Prime® 2023.0.4 (Biomatters, Inc., Boston, MA, USA). All data were analyzed using Statistica software version 13.0, and changes in biofilm production in correlation to changes in the type of nutritional medium and temperature were compared between groups using a one-way ANOVA analysis and Tukey's test. All isolates formed biofilms in minimal M9 at 8 °C and 16 °C, and nine isolates failed to form biofilms in minimal M9 at 25 °C. In an ABTG medium, all isolates produced biofilms at 8 °C; however, three isolates at 16 °C and seven isolates at 25 °C failed to form any biofilms. Significant biofilm formation was observed in TSB at all temperatures. Some strains that formed a good biofilm in solid–liquid interface did not have the ability to form a pellicle (liquid–air border biofilm), and vice versa. In all cases of nutritional medium and temperature changes, there were statistically significant differences in the intensity of biofilm production, especially in the detected number of viable cells inside biofilms (log CFU, p < 0.005). Multiple biofilm-production genes, including polar flagella (filM) LuxR family (transcriptional regulators) and VapA family of histidine-kinase-associated genes, were sequenced from all studied isolates. Genetic differences based on geographical origin were not observed among the isolates. Significant variations in isolates' ability to form biofilms were observed, possibly due to epigenetic factors. The optimal temperature for biofilm formation of A. salmonicida subspecies salmonicida in scarce media was 8 °C, and the majority of isolates were not capable of biofilm formation at 25 °C without enriched nutrient media. [ABSTRACT FROM AUTHOR]

Viral infections in animals continue to pose a significant challenge, affecting livestock health, welfare, and food safety, and, in the case of zoonotic viruses, threatening global public health. The control of viral diseases currently relies on conventional approaches such as inactivated or attenuated vaccines produced via platforms with inherent limitations. Self-assembling ferritin nanocages represent a novel vaccine platform that has been utilized for several viruses, some of which are currently undergoing human clinical trials. Experimental evidence also supports the potential of this platform for developing commercial vaccines for veterinary viruses. In addition to improved stability and immunogenicity, ferritin-based vaccines are safe and DIVA-compatible, and can be rapidly deployed in response to emerging epidemics or pandemics. This review discusses the structural and functional properties of ferritin proteins, followed by an overview of the design and production of ferritin-based vaccines, the mechanisms of immune responses, and their applications in developing vaccines against animal and zoonotic viruses. [ABSTRACT FROM AUTHOR]

Outbreaks of furunculosis cause significant losses in salmonid aquaculture worldwide. With a recent rise in antimicrobial resistance, regulatory measures to minimize the use of antibiotics in animal husbandry, including aquaculture, have increased scrutiny and availability of veterinary medical products to control this disease in production facilities. In such a regulatory environment, the utility of autogenous vaccines to assist with disease prevention and control as a veterinary-guided prophylactic measure is of high interest to the producers and veterinary services alike. However, evolving concepts of epidemiological units and epidemiological links need to be considered during approval and acceptance procedures for the application of autogenous vaccines in multiple aquaculture facilities. Here, we present the results of solid-state nanopore sequencing (Oxford Nanopore Technologies, ONT) performed on 54 isolates of Aeromonas salmonicida ssp. salmonicida sampled during clinical outbreaks of furunculosis in different aquaculture facilities from Bavaria, Germany, from 2017 to 2020. All of the performed analyses (phylogeny, single nucleotide polymorphism and 3D protein modeling for major immunogenic proteins) support a high probability that all studied isolates belong to the same epidemiological unit. Simultaneously, we describe a cost/effective method of whole genome analysis with the usage of ONT as a viable strategy to study outbreaks of other pathogens in the field of aquatic veterinary medicine for the purpose of developing the best autogenous vaccine candidates applicable to multiple aquaculture establishments. [ABSTRACT FROM AUTHOR]

New technological progress and increased demands for fish as a source of animal protein are driving significant growth of aquaculture production. Intensification of production increases the severity and frequency of infectious disease outbreaks, and so requires significant effort to prevent and control disease. Because of the global crisis of bacterial resistance to antibiotics, the use of antibiotics in aquaculture is increasingly subjected to strict control and regulatory measures, leading to potential misuse. The lack of availability of approved veterinary medical products for use in aquaculture, combined with the risk of drug resistance development and antibiotic residues in fish flesh or water, support the development of preventive actions, including vaccines. However, the diversity of species and aquaculture production methods, including epidemiological units and their links, results in economic challenges for commercial vaccine development and authorization. As a possible response to the increasing demand for less antibiotic use in fish farms, and to the expenses associated with novel veterinary product development, there is a need for increased use of safe and effective autogenous vaccines in aquaculture. Regulatory processes for autogenous vaccine production, approval and application should recognize the specificities of epidemiological units and their links in aquatic animal production facilities. The joint efforts of regulatory authorities, producers, and veterinary services to follow veterinary biosecurity principles, including risk analysis, surveillance, and selection/prioritization of pathogens, are essential to provide maximum safety and efficacy of autogenous vaccines as disease prevention and control tools within larger areas, such as compartments and zones, and allow for reductions in antibiotic use.

Self-assembling protein nanoparticles are used as a novel vaccine design platform to improve the stability and immunogenicity of safe subunit vaccines, while providing broader protection against viral infections. Infectious Hematopoietic Necrosis virus (IHNV) is the causative agent of the WOAH-listed IHN diseases for which there are currently no therapeutic treatments and no globally available commercial vaccine. In this study, by genetically fusing the virus glycoprotein to the H. pylori ferritin as a scaffold, we constructed a selfassembling IHNV nanovaccine (FerritVac). Despite the introduction of an exogenous fragment, the FerritVac NPs show excellent stability same as Ferritin NPs under different storage, pH, and temperature conditions, mimicking the harsh gastrointestinal condition of the virus main host (trout). MTT viability assays showed no cytotoxicity of FerritVac or Ferritin NPs in zebrafish cell culture (ZFL cells) incubated with different doses of up to 100 µg/mL for 14 hours. FerritVac NPs also upregulated expression of innate antiviral immunity, IHNV, and other fish rhabdovirus infection gene markers (mx, vig1, ifit5, and isg-15) in the macrophage cells of the host. In this study, we demonstrate the development of a soluble recombinant glycoprotein of IHNV in the E. coli system using the ferritin self-assembling nanoplatform, as a biocompatible, stable, and effective foundation to rescue and produce soluble protein and enable oral administration and antiviral induction for development of a complete IHNV vaccine. This self-assembling protein nanocages as novel vaccine approach offers significant commercial potential for non-mammalian and enveloped viruses. [ABSTRACT FROM AUTHOR]