Albendazole is effective in controlling monogeneans in Colossoma macropomum (Serrasalmidae): therapeutic baths and their physiological and histopathological effects.

In aquaculture worldwide, most of the chemotherapeutic agents used for disease control and treatment are unregulated chemical products derived from agriculture. In this study, we investigated the efficacy of therapeutic baths with albendazole against the monogeneans Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri, which infest the gills of Colossoma macropomum, and the hematological and histopathological effects of this anthelmintic agent on these fish. Albendazole at a concentration of 500 mg/L was used in three baths of 24 hours each, with intervals of 24 hours between these baths. Three replications of this treatment were used, and the control group consisted of water from the cultivation tank. Afterwards, hematological, histopathological and parasitological analyses were conducted. We found that the therapeutic baths with albendazole at 500 mg/L presented high efficacy (94.9%) against monogeneans de C. macropomum and caused few physiological or histopathological alterations. Therefore, baths with albendazole at 500 mg/L, as used in this strategy, can be recommended for controlling and treating infections by monogeneans in C. macropomum.

Synthetic antimicrobial Nkl and Dic peptides are immunomodulatory but only Dic peptide can be therapeutic against nodavirus infection.

Aquaculture is a prosperous economic sector threatened by viral infections. Among the viruses threatening fish culture, Betanodavirus (NNV) is extremely important in the Mediterranean Sea affecting to highly traded species as European sea bass. In this context, application of antimicrobial peptides (AMPs) has arisen as a potential biotechnological tool. The aim of this work was to evaluate the therapeutic application of two European sea bass-derived AMPs, NK-lysin (Nkl) and dicentracin (Dic), against NNV infections. Synthetic Dic peptide was able to significantly reduce NNV-induced mortalities while Nkl failed to do so. Although neither Dic nor Nkl peptides were able to alter the transcriptional levels of NNV and the number of infected cells, Nkl seemed to increase the viral load per cell. Interestingly, both Nkl and Dic peptides showed immunomodulatory roles. For instance, our data revealed an interplay among different AMPs, at both gene and protein levels. Otherwise, Nkl and Dic peptides provoked an anti-inflammatory balance upon NNV infection, as well as the recruitment of macrophages and B cells to the target site of the infection, the brain. In conclusion, Dic can be proposed as a therapeutic candidate to combat NNV.

Copaiba oil's bactericidal activity and its effects on health and zootechnical performance for Nile tilapia after oral supplementation.

Tilapia is one of the most important farmed fish in the world and the most cultivated in Brazil. The increase of this farming favors the appearance of diseases, including bacterial diseases. Therefore, the aim of this study was to evaluate the bactericidal activity of copaiba oil, Copaifera duckei, against Streptococcus agalactiae and Flavobacterium columnare and the dietary effect of copaiba oil on zootechnical performance, hematological, biochemical, immunological, and histological analysis before and after an intraperitoneal infection (body cavity) with S. agalactiae in Nile tilapia. For this, fish were randomly distributed into 15 fiber tanks in five treatments (0, 0.25, 0.50, 0.75, and 1.0%) and fed with a commercial diet supplemented with copaiba oil for 30 days. After this period, the fish were randomly redistributed for the experimental challenge with S. agalactiae into six treatments (T0, T1, T2, T3, T4, and T5), the fish were anesthetized, and blood samples were collected to assess hematological, biochemical, immunological, and histological parameters. Copaiba oil showed bactericidal activity against Streptococcus spp. and Flavobacterium spp. in vitro. In addition, concentrations of 0.75 and 1.0% of copaiba oil have an anti-inflammatory effect and improve hematological and immunological parameters, increasing leukocyte numbers, albumin, and serum lytic activity. Furthermore, there is an increase in the intestinal villus length and tissue damage in groups at concentrations of 0.75 and 1.0% of copaiba oil. In conclusion, copaiba oil presented bactericidal activity against Streptococcus spp. and Flavobacterium spp. in vitro, and oral supplementation at concentrations of 0.75 and 1.0% compared to the control group enhanced non-specific immune parameters and digestibility in Nile Tilapia.

Anti-parasitic activity of garlic (Allium sativum) and onion (Allium cepa) extracts against Dactylogyrus spp. (Monogenean) in Nile tilapia (Oreochromis niloticus): Hematology, immune response, histopathological investigation, and inflammatory cytokine genes of gills.

BACKGROUND: Gills monogenean infestation causes significant mortalities in cultured fishes as a result of respiratory manifestation. Medicinal plants are currently being heavily emphasized in aquaculture due to their great nutritional, therapeutic, antimicrobial activities, and financial value. METHODS: The current study is designed to assess the effect of garlic (Allium sativum) and onion (Allium cepa) extracts as a water treatment on the hematological profile, innate immunity, and immune cytokines expression besides histopathological features of gills of Nile tilapia (Oreochromis niloticus L.) infected with gills monogenetic trematodes (Dactylogyrus sp.). Firstly, the 96-hour lethal concentration 50 (96 h-LC50) of garlic extract (GE) and onion extract (OE) were estimated to be 0.4 g/ L and 3.54 g/ L for GE and OE, respectively. Moreover, the in-vitro anti-parasitic potential for (GE) was found between 0.02 and 0.18 mg/mL and 0.4 to 1.8 mg/mL for OE. For the therapeutic trial, fish (n = 120; body weight: 40-60 g) were randomly distributed into four groups in triplicates (30 fish/group, 10 fish/replicate) for 3 days. Group1 (G1) was not infected or treated and served as control. G2 was infected with Dactylogyrus spp. and not exposed to any treatment. G3, G4 were infected with Dactylogyrus sp. and treated with 1/10 and 1/5 of 96 h LC50 of OE, respectively. G5, G6 were infected with Dactylogyrus sp. and treated with 1/10 and 1/5 of 96 h LC50 of GE, respectively. RESULTS: No apparent signs or behaviors were noted in the control group. Dactylogyrus spp. infected group suffered from clinical signs as Pale color and damaged tissue. Dactylogyrus spp. infection induced lowering of the hematological (HB, MCH, MCHC and WBCs), and immunological variables (lysozyme, nitric oxide, serum Anti- protease activities, and complement 3). the expression of cytokine genes IL-ß and TNF-α were modulated and improved by treatment with A. sativum and A. cepa extracts. The obtained histopathological alterations of the gills of fish infected with (Dactylogyrus spp.) were hyperplasia leading to fusion of the gill filament, lifting of epithelial tissue, aneurism and edema. The results indecated that G4 and G5 is more regenarated epithelium in compare with the control group. CONCLUSION: A. sativum and A. cepa extracts enhance the blood profile and nonspecific immune parameters, and down-regulated the expression level of (IL-1ß and TNF-α).

Antiviral effects of umbelliferone against viral hemorrhagic septicemia virus in olive flounder (Paralichthys olivaceus).

Viral hemorrhagic septicemia virus (VHSV) poses a significant threat to global aquaculture, prompting ongoing efforts to identify potential drug candidates for disease prevention. Coumarin derivatives have recently emerged as a promising class of compounds effective against rhabdoviruses, which severely impact the aquaculture industry. In this study, we assessed the anti-VHSV activity of umbelliferone (7-hydroxycoumarin) in fathead minnow (FHM) cells and olive flounder Paralichthys olivaceus. Umbelliferone exhibited an EC50 of 100 µg/mL by reducing cytopathic effect, with a maximum cytotoxicity of 30.9 % at 750 µg/mL. Mechanistic analyses via a time-course plaque reduction assay revealed that direct incubation with the virus for 1 h resulted in 97.0 ± 1.8 % plaque reduction, showing excellent direct virucidal activity. Pretreatment for 4 h resulted in a 33.5 ± 7.8 % plaque reduction, which increased with longer incubation times. Cotreatment led to a 33.5 ± 2.9 % plaque reduction, suggesting interference with viral binding, whereas postinfection treatment proved less effective. Umbelliferone was prophylactically administered to the olive flounder through short-term (3 days) and long-term (14 days) medicated feeding, followed by a 4-day postinfection period. Short-term administration at 100 mg/kg body weight (bw)/day resulted in the highest relative percent survival (RPS) of 56 %, whereas long-term administration achieved a maximum RPS of 44 % at 30 mg/kg bw/day. Umbelliferone administration delayed mortality at these doses. Additionally, umbelliferone significantly inhibited the expression of the VHSV N gene during viral challenge, with no observed toxic effects in fish up to an administration dose of 30 mg/kg bw/day for 28 days. Our findings suggest that the protective mechanism of short-term administration of 100 mg umbelliferone against VHSV infection may involve the overexpression of TLR2, MDA5, STAT1, and NF-κB at 24 h postinfection (hpi). IL-8 and IFN II expression was upregulated, whereas TNF-α, IL-1ß, and IFN I expression was suppressed at 24 hpi. The upregulation of ISG15 at 48 hpi may contribute to the inhibition of VHSV replication, whereas the downregulation of Caspase 3 expression at 96 hpi suggests a possible inhibition of virus-induced apoptosis at later infection stages. Overall, umbelliferone exhibited anti-VHSV activity through multiple mechanisms, with the added advantage of convenient administration via medicated feed.

Antibiotic resistance profiles of sentinel bacteria isolated from aquaculture in Cambodia.

The misuse of antibiotics and the emergence of antimicrobial resistance (AMR) is a concern in the aquaculture industry because it contributes to global health risks and impacts the environment. This study analyzed the AMR of sentinel bacteria associated with striped catfish (Pangasisanodon hypophthalmus) and giant snakehead (Channa micropeltes), the two main fish species reared in the pond culture in Cambodia. Phenotypic and genotypic characterization of the recovered isolates from fish, water, and sediment samples revealed the presence of bacteria, such as 22 species belonging to families Aeromonadaceae, Enterobacteriaceae, and Pseudomonadaceae. Among 48 isolates, Aeromonas caviae (n = 2), Aeromonas hydrophila (n = 2), Aeromonas ichthiosmia (n = 1), Aeromonas salmonicida (n = 4) were detected. A. salmonicida and A. hydrophilla are known as fish pathogens that occur worldwide in both fresh and marine water aquaculture. Antibiotic susceptibility testing revealed antibiotic resistance patterns of 24 (50 %) isolates among 48 isolates with higher multiple antibiotic resistance index (> 0.2). All the isolates of Enterobacteriaceae were susceptible to ciprofloxacin. Ciprofloxacin is a frontline antibiotic that is not recommended to use in aquaculture. Therefore, its use has to be strictly controlled. This study expands our knowledge of the AMR status in aquaculture farms which is very limited in Cambodia.

Field evaluation of hydrogen peroxide bath technique for controlling sea lice (Lepeoptheirus spinifer) infestation in snubnose pompano (Trachinotus blochii).

Sea lice infestations can pose significant challenges in the aquaculture sector, affecting fish health and overall production. In the search for effective and eco-friendly solutions, hydrogen peroxide bath treatment has been considered as one of the promising methods. This is the first study to evaluate the field efficacy of hydrogen peroxide bath technique against sea lice infestation on cage-cultured snubnose pompano (Trachinotus blochii). Sea lice was identified as Lepeophtheirus spinifer using morphological description. Naturally-infested snubnose pompano stocked in 2 ×3×2 m3 net cages at 15 fish/cage at the Igang Marine Station of SEAFDEC/AQD, in Guimaras, Philippines were treated in triplicates with two hydrogen peroxide concentrations (1500 and 2000 ppm) in comparison to a control (seawater only) for 20 minutes at 32.8 ± 0.7 ppt and 28.9 ± 0.3 °C and were monitored at 3rd and 7th day post-treatment. The total mean intensity of sea lice, mean intensity per life stages (copepodid, chalimus I, chalimus II, pre-adult I, pre-adult II, adult male and adult female), and the 12-h viability of scraped male and adult female L. spinifer from the treatment groups were evaluated. The total mean intensity of sea lice in the treated groups at 3 day post-treatment was significantly lower than the control group (p<0.001). A possible re-infection of sea lice was observed 7 days post-treatment as explained by the slight increase in the mean intensity in the treated groups. However, no mortalities of pompano were recorded throughout the experiment. In addition, adult female lice were absent in the treated group while adult male lice were only detected in the 1500 ppm treatment group at a very low mean intensity. The viability test also showed that all sea lice were not able to recover after 12 h whereas a 100 % recovery rate was noted in the control group. Results suggest that the 1500 and 2000 ppm hydrogen peroxide concentrations are effective in reducing sea lice infestation on cage-cultured snubnose pompano. However, a long-term effect of hydrogen peroxide treatment on sea lice needs further investigation.

Exogenous NADH promotes the bactericidal effect of aminoglycoside antibiotics against Edwardsiella tarda.

The global surge in multidrug-resistant bacteria owing to antibiotic misuse and overuse poses considerable risks to human and animal health. With existing antibiotics losing their effectiveness and the protracted process of developing new antibiotics, urgent alternatives are imperative to curb disease spread. Notably, improving the bactericidal effect of antibiotics by using non-antibiotic substances has emerged as a viable strategy. Although reduced nicotinamide adenine dinucleotide (NADH) may play a crucial role in regulating bacterial resistance, studies examining how the change of metabolic profile and bacterial resistance following by exogenous administration are scarce. Therefore, this study aimed to elucidate the metabolic changes that occur in Edwardsiella tarda (E. tarda), which exhibits resistance to various antibiotics, following the exogenous addition of NADH using metabolomics. The effects of these alterations on the bactericidal activity of neomycin were investigated. NADH enhanced the effectiveness of aminoglycoside antibiotics against E. tarda ATCC15947, achieving bacterial eradication at low doses. Metabolomic analysis revealed that NADH reprogrammed the ATCC15947 metabolic profile by promoting purine metabolism and energy metabolism, yielding increased adenosine triphosphate (ATP) levels. Increased ATP levels played a crucial role in enhancing the bactericidal effects of neomycin. Moreover, exogenous NADH promoted the bactericidal efficacy of tetracyclines and chloramphenicols. NADH in combination with neomycin was effective against other clinically resistant bacteria, including Aeromonas hydrophila, Vibrio parahaemolyticus, methicillin-resistant Staphylococcus aureus, and Listeria monocytogenes. These results may facilitate the development of effective approaches for preventing and managing E. tarda-induced infections and multidrug resistance in aquaculture and clinical settings.

Synergistic effect of green synthesis magnesium oxide nanoparticles and seaweed extract on improving water quality, health benefits, and disease resistance in Nile tilapia.

This study aimed to evaluate the effect of adding liquid extract of algae (Hypnea musciformis, Grateloupia acuminata, and Sargassum muticum) (HGS) and Magnesium oxide nanoparticles (MgO NPs) using this extract to rear water of Oreochromis niloticus, on improving culture water indices, growth performance, digestive enzyme, hemato-biochemical characters, immune, antioxidative responses, and resistance after challenged by Aeromonas hydrophila with specific refer to the potential role of the mixture in vitro as resistance against three strains bacteria (Aeromonas sobria, Pseudomonas fluorescens, P. aeruginosa) and one parasite (Cichlidogyrus tilapia). The first group represented control, HGS0, whereas the other group, HGS5, HGS10, and HGS15 mL-1 of liquid extract, as well as all groups with 7.5 µg mL-1 MgO-NPs added to culture water of O. niloticus, for 60 days. Data showed that increasing levels at HGS 10 and HGS15 mL-1 in to-culture water significantly enhanced growth-stimulating digestive enzyme activity and a significantly improved survival rate of O. niloticus after being challenged with A. hydrophila than in the control group. The total viability, coliform, fecal coliform count, and heavy metal in muscle partially decreased at HGS 10 and HGS15 mL-1 than in the control group. Correspondingly, the highest positive effect on hemato-biochemical indices was noticed at levels HGS 10 and HGS15 mL-1. Fish noticed an improvement in immune and antioxidant indices compared to control groups partially at HGS 10 and HGS15 mL-1. Interestingly, fish cultured in rearing water with the mixture provided downregulated the related inflammatory genes (HSP70, TNF, IL-1ß, and IL-8) partially at HGS15 mL-1. In vitro, the mixture showed positive efficiency as an antibacterial and partially antiparasitic at HGS 10 and HGS15 mL-1. This study proposes utilizing a mixture of (HGS) and (MgO-NPs) with optimum levels of 10-15 mL-1 in cultured water to improve water indices, growth, health status, and increased resistance of O. niloticus against bacterial and parasitic infection.

Antimicrobial efficiency against fish pathogens on the green synthesized silver nanoparticles.

Fish-borne pathogens such as A. hydrophila and F. aquidurense are the most resistant strains in pisciculture farming. Removing the aforementioned pathogens without antibiotics presents a formidable challenge. To overcome this problem, silver nanoparticles (AgNPs) are synthesized using silver nitrate, water medium, and as an AzadirachtaIndica leaf extract via the green synthesis route. X-ray diffraction (XRD) pattern results authenticate the synthesized material is the face-centered cubic structure of silver. The optical absorption edge of the synthesized product was found at the wavelength of 440 nm from the UV-visible spectra, which is confirmed to relate to the Surface Plasmon Resonance peaks of silver particles. In addition, the optical band gap value of the synthesized Ag sample is measured to be 2.81 eV from the obtained optical absorption spectra. EDX spectrum of the synthesized product also supports confirming the silver particle formation. The FT-IR spectra of the neem extract and silver nanoparticles showed their characteristic functional groups, respectively. The presence of bands between 1000 cm-1 to 500 cm-1 indicates to the formation of silver particles. Spherical particles appeared in the synthesized Ag using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The particle size of Ag NPs was measured as 40 nm and 62 ± 10 nm by TEM and Dynamic Light Scattering (DLS). The zeta potential was also measured as -12 mV showing the synthesized sample's stable nature. Using the DPPH assay, synthesized AgNPs were taken along with the various concentrations of ascorbic acid (20, 40, 60, 80, and 100 µg/mL) to examine the free radical scavenging activity (RSA). RSA value is higher (84 ± 2 %) for synthesized AgNPs at higher concentration (100 µg/mL) than 21 ± 2 % at low concentration (100 µg/mL). The antimicrobial efficacy of the AgNPs against A. hydrophila and F. aquidurense was performed through the agar diffusion method and its results showed the inhibitory zones of the F.aquidurense and A. hydrophila were measured as 25 ± 3 mm, and 28 ± 4 mm respectively. The synthesized Ag particles showed excellent antimicrobial and antioxidant properties confirmed by antimicrobial and DPPH experiments. It implies that the green synthesized silver nanoparticles could be a good alternative for antibiotics in aquaculture farms. The exposure of low concentrations of silver nanoparticles to zebrafish and brine shrimp does not affect the viability and morphology. The exposure of silver nanoparticles in the fisheries in optimized concentration and time could control the fish-borne pathogens without antibiotics.

Preparation and evaluation of microencapsulated delivery system of recombinant interferon alpha protein from rainbow trout.

Diseases caused by viruses pose a significant risk to the health of aquatic animals, for which there are presently no efficacious remedies. Interferon (IFN) serving as an antiviral agent, is frequently employed in clinical settings. Due to the unique living conditions of aquatic animals, traditional injection of interferon is cumbersome, time-consuming and labor-intensive. This study aimed to prepare IFN microcapsules through emulsion technique by using resistant starch (RS) and carboxymethyl chitosan (CMCS). Optimization was achieved using the Box-Behnken design (BBD) response surface technique, followed by the creation of microcapsules through emulsification. With RS at a concentration of 1.27 %, a water­oxygen ratio of 3.3:7.4, CaCl2 at 13.67 %, CMCS at 1.04 %, the rate of encapsulation can escalate to 80.92 %. Rainbow trout infected with Infectious hematopoietic necrosis virus (IHNV) and common carp infected with Spring vireemia (SVCV) exhibited a relative survival rate (RPS) of 65 % and 60 % after treated with IFN microcapsules, respectively. Moreover, the microcapsules effectively reduced the serum AST levels and enhanced the expression of IFNα, IRF3, ISG15, MX1, PKR and Viperin in IHNV-infected rainbow trout and SVCV-infected carp. In conclusion, this integrated IFN microcapsule showed potential as an antiviral agent for treatment of viral diseases in aquaculture.

Centella asiatica extract ameliorates deoxygenation-induced neurological dysfunction in zebrafish larvae.

Background: Oxygen deprivation (OD) is a critical condition that can lead to brain damage and even death. Current hypoxia management approaches are limited in effectiveness. Centella asiatica (CA), known for its neuroprotective properties, offers a potential alternative for OD treatment. Aims: This study aims to investigate the neuroprotective effects of CA on the expression of brain-derived neurotrophic factor (BDNF) and vesicular glutamate transporter 1 (VGLUT1) in zebrafish larvae under oxygen-deficient conditions. Methods: Zebrafish embryos were subjected to low oxygen levels (1.5 mg/l) 0-2 hours post-fertilization (hpf) until 3 days post-fertilization (dpf), simulating the early stages of OD. Subsequent treatment involved varying concentrations of CA (1.25-5 µg/ml) up to 9 days post-fertilization. The expression levels of BDNF and VGLUT1 were measured using PCR methods. Statistical analysis was conducted using a two-way analysis of variance to evaluate the impact of CA on the expression of BDNF and VGLUT1 in zebrafish larvae aged 3 and 9 dpf in oxygen-deprived conditions. Results: CA significantly influenced the expression of BDNF and VGLUT1 under OD (p < 0.001). An increase in BDNF expression (p < 0.001) and a decrease in VGLUT1 (p < 0.01) were observed in zebrafish larvae experiencing OD and treated with CA. There was no significant difference in BDNF and VGLUT1 expression across age variations in zebrafish larvae at 3 dpf and 9 dpf in the treatment groups (p > 0.05). CA concentration of 2.5 µg/ml effectively enhanced BDNF and reduced VGLUT1 in 3-9 dpf zebrafish larvae. Conclusion: CA demonstrates potential as a neuroprotective agent, modulating increased BDNF expression and reduced VGLUT1 under OD conditions. These findings lay a foundation for further research in developing therapies for oxygen deficiency.

The therapeutic role of Azadirachta indica leaves ethanolic extract against detrimental effects of Aeromonas veronii infection in Nile tilapia, Oreochromis niloticus.

Bacterial pathogens cause high fish mortalities and in turn economic losses in fish farms. Innovative strategies should be applied to control bacterial infections instead of antibiotics to avoid the resistance problem. Consequently, the present investigation studied the curative potential of Azadirachta indica leave ethanolic extract (AILEE) on Aeromonas veronii infection in Oreochromis niloticus. A preliminary trial was assessed to evaluate the curative dose of AILEE which was found to be 2.5 mg/L. One hundred and sixty fish were divided into equal four groups in four replications, where group 1 and group 2 were non-challenged and treated with 0- and 2.5-mg/L AILEE, respectively. Group 3 and group 4 were challenged with A. veronii and treated with 0- and 2.5-mg/L AILEE, respectively for 10 days. A. veronii infection produced severe clinical manifestations and a high mortality rate in the infected fish. Furthermore, the infected fish exhibited a significant rise in the hepatorenal indices (aspartate aminotransferase, alanine aminotransferase, and creatinine), the oxidant biomarker (malondialdehyde), and the stress indicators (glucose and cortisol). A significant reduction in the protein profile and antioxidant/immune parameters (catalase, immunoglobulin M, lysozyme, nitric oxide, and phagocytic activity) was observed in the infected fish. Water application of the infected group to 2.5-mg/L AILEE notably ameliorated the hepatorenal indices, the oxidant biomarker, and the stress indicators. Furthermore, AILEE improved the antioxidant/immune indices. Water application of 2.5-mg/L AILEE could be useful against A. veronii infection in O. niloticus culture.

Redox profile of silver catfish challenged with Aeromonas hydrophila and treated with hexane extract of Hesperozygis ringens (Benth.) Epling through immersion bath.

The growing increase in the fish farming sector has favored the establishment of bacterial outbreaks caused by Aeromonas hydrophila in several species. The hexane extract of Hesperozygis ringens (HEHR) (Lamiaceae) leaves increased the survival rate of silver catfish (Rhamdia quelen) experimentally infected by A. hydrophila. However, it is noteworthy that no reports have been found on the possible mechanisms of action of this extract in infected fish. This study aimed to evaluate the effect of the HEHR, administered through single immersion bath, on lipid peroxidation and antioxidant defenses in muscle and liver tissue of silver catfish challenged with A. hydrophila. The results showed that the oxidative status of silver catfish was altered, although oxidative stress was not triggered during the experiment. HEHR at 30 mg/L (HEHR30) was not characterized as a pro-oxidant agent in the presence of infection, unlike florfenicol and HEHR at 15 mg/L treatments in some cases. In short, HEHR30 provided an important increase in hepatic catalase activity, characterizing one of the possible mechanisms involved in the greater survival of fish experimentally infected by A. hydrophila. Additionally, HEHR30 did not induce lipid peroxidation, nor reduced antioxidant defenses of silver catfish infected or not by A. hydrophila.

Pseudomonas putida infection induces immune-antioxidant, hepato-renal, ethological, and histopathological/immunohistochemical disruptions in Oreochromis niloticus: the palliative role of titanium dioxide nanogel.

BACKGROUND: Pseudomonas putida is a pathogenic bacterium that induces great losses in fishes, including Nile tilapia (Oreochromis niloticus). Currently, the application of nanomaterials in aquaculture practices has gained more success as it endows promising results in therapies compared to traditional protocols. OBJECTIVE: Therefore, the current perspective is considered the first report to assess the anti-bacterial efficacy of titanium dioxide nanogel (TDNG) against Pseudomonas putida (P. putida) in Nile tilapia. METHODS: The fish (n = 200; average body weight: 47.50±1.32 g) were allocated into four random groups (control, TDNG, P. putida, and TDNG + P. putida), where 0.9 mg/L of TDNG was applied as bath treatment for ten days. RESULTS: Outcomes revealed that P. putida infection caused ethological alterations (surfacing, abnormal movement, and aggression) and depression of immune-antioxidant variables (complement 3, lysozyme activity, total antioxidant capacity, superoxide dismutase, and reduced glutathione content). Additionally, a substantial elevation in hepatorenal biomarkers (aspartate and alanine aminotransferases and creatinine) with clear histopathological changes and immuno-histochemical alterations (very weak BCL-2 and potent caspase-3 immuno-expressions) were seen. Surprisingly, treating P. putida-infected fish with TDNG improved these variables and obvious restoration of the tissue architectures. CONCLUSION: Overall, this report encompasses the key role of TDNG as an anti-bacterial agent for controlling P. putida infection and improving the health status of Nile tilapia.

Biocontrol of multidrug resistant pathogens isolated from fish farms using silver nanoparticles combined with hydrogen peroxide insight to its modulatory effect.

This study was divided into two parts. The first part involved the isolation, and detection of the prevalence and antimicrobial resistance profile of Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio species from Nile tilapia fish and marine aquatic water. One hundred freshly dead Nile tilapia fish were collected from freshwater aquaculture fish farms located in Al-Abbassah district, Sharkia Governorate, and 100 samples of marine aquatic water were collected from fish farms in Port Said. The second part of the study focused on determining the in vitro inhibitory effect of dual-combination of AgNPs-H2O2 on bacterial growth and its down regulatory effect on crucial virulence factors using RT-PCR. The highest levels of A. hydrophila and P. aeruginosa were detected in 43%, and 34% of Nile tilapia fish samples, respectively. Meanwhile, the highest level of Vibrio species was found in 37% of marine water samples. Additionally, most of the isolated A. hydrophila, P. aeruginosa and Vibrio species exhibited a multi-drug resistance profile. The MIC and MBC results indicated a bactericidal effect of AgNPs-H2O2. Furthermore, a transcriptional modulation effect of AgNPs-H2O2 on the virulence-associated genes resulted in a significant down-regulation of aerA, exoU, and trh genes in A. hydrophila, P. aeruginosa, and Vibrio spp., respectively. The findings of this study suggest the effectiveness of AgNPs-H2O2 against drug resistant pathogens related to aquaculture.

Essential Oil of Piper marginatum (Piperaceae) Against Monogeneans, and Its Hematological and Histopathological Effects on Colossoma macropomum.

PURPOSE: This study investigated the anthelmintic efficacy of therapeutic baths with the essential oil of Piper marginatum Jacq against the monogeneans Anacanthorus spathulatus Kritsky, Thatcher & Kayton, 1979, Notozothecium janauachensis Belmont-Jégu, Domingues & Laterça 2004, Mymarothecium boegeri Cohen & Kohn, 2005 and Linguadactyloides brinkmanni Thatcher & Krytsky, 1983 in Colossoma macropomum Cuvier, 1818, and its hematological and histopathological effects on this fish. METHODS: Short six therapeutic baths with 100 mg/L of the essential oil of P. marginatum and two control groups (water from the cultivation tank and water from the cultivation tank + 70% alcohol) were used for 20 min every two days. RESULTS: The therapeutic baths with 100 mg/L of the essential oil of P. marginatum had efficacy of 42.8% against monogeneans of C. macropomum gills. Toxicity was low for C. macropomum, because there were few physiological and histopathological changes that did not compromise the functioning of the gills of this fish. CONCLUSION: Short therapeutic baths with 100 mg/L of the essential oil of P. marginatum had low efficacy for controlling monogeneans in C. macropomum and thus cannot be recommended.

A nanobody-mediated drug system against largemouth bass virus delivered by bacterial nanocellulose in Micropterus salmoides.

Diseases caused by pathogens severely hampered the development of aquaculture, especially largemouth bass virus (LMBV) has caused massive mortality and severe economic losses to the culture of largemouth bass (Micropterus salmoides). Considering the environmental hazards and human health, effective and environmentally friendly therapy strategy against LMBV is of vital importance and in pressing need. In the present study, a novel nanobody (NbE4) specific for LMBV was selected from a phage display nanobody library. Immunofluorescence and indirect ELISA showed that NbE4 could recognize LMBV virions and had strong binding capacity, but RT-qPCR evidenced that NBE4 did not render the virus uninfectious. Besides, antiviral drug ribavirin was used to construct a targeted drug system delivered by bacterial nanocellulose (BNC). RT-qPCR revealed that NbE4 could significantly enhance the antiviral activity of ribavirin in vitro and in vivo. The targeted drug delivery system (BNC-Ribavirin-NbE4, BRN) reduced the inflammatory response caused by LMBV infection and improved survival rate (BRN-L, 33.3 %; BRN-M, 46.7 %; BRN-H, 56.7 %)compared with control group (13.3 %), ribavirin group (RBV, 26.7 %) and BNC-ribavirin (BNC-R, 40.0 %), respectively. This research provided an effective antiviral strategy that improved the drug therapeutic effect and thus reduced the dosage.

Drug delivery system based on metal-organic framework improved 5-Fluorouracil against spring viremia of carp virus.

Spring viremia of carp virus (SVCV), as a high pathogenicity pathogen, has seriously restricts the healthy and sustainable development of cyprinid farming industry. In this study, we selected 5-Fluorouracil (5-Fu) as the drug model based on zeolitic imidazolate framework-8 (ZIF-8) to construct a drug delivery system (5-Fu@ZIF-8), and the anti-SVCV activity was detected in vitro and in vivo. The results showed 5-Fu@ZIF-8 was uniform cubic particle with truncated angle and smooth surface, and the particle size was 90 nm. The anti-SVCV activity in vitro results showed that the highest inhibition rate of 5-Fu was 77.93% at 40 mg/L and the inhibitory concentration at half-maximal activity (IC50) was 20.86 mg/L. For 5-Fu@ZIF-8, the highest inhibition rate was 91.36% at 16 mg/L, and the IC50 value was 5.85 mg/L. In addition, the cell viability was increased by 18.1% after 5-Fu treatment. Similarly, after 5-Fu@ZIF-8 treatment, the cell viability increased by 27.3%. Correspondingly, in vivo experimental results showed the viral loads reduced by 18.1% on the days 7 and the survival rate increased to 19.4% at 80 mg/L after 5-Fu treatment. For 5-Fu@ZIF-8, the viral loads reduced by 41.2% and the survival rate increased to 54.8%. Mechanistically, 5-Fu inhibits viral replication by regulating p53 expression and promoting early apoptosis in infected cells. All results indicated that 5-Fu@ZIF-8 improved the anti-SVCV activity; it may be a potential strategy to construct a drug-loaded system with ZIF-8 as a carrier for the prevention and treatment of aquatic diseases.

Identification and florfenicol-treatment of pseudomonas putida infection in gilthead seabream (Sparus aurata) fed on tilapia-trash-feed.

The present study aimed to determine the major cause of the high mortality affecting farmed gilthead seabream (Sparus aurata) and controlling this disease condition. Fifteen diseased S. aurata were sampled from a private fish farm located at Eldeba Triangle, Damietta, fish showed external skin hemorrhages, and ulceration. Bacterial isolates retrieved from the diseased fish were identified biochemically as Pseudomonas putida and then confirmed by phylogenetic analysis of the 16 S rRNA gene sequence. P. putida was also isolated from three batches of tilapia-trash feed given to S. aurata. Biofilm and hemolytic assay indicated that all P. putida isolates produced biofilm, but 61.11% can haemolyse red blood cells. Based on the antibiotic susceptibility test results, P. putida was sensitive to florfenicol with minimum inhibitory concentrations ranging between 0.25 and 1.0 µg mL- 1, but all isolates were resistant to ampicillin and sulfamethoxazole-trimethoprim. Pathogenicity test revealed that P. putida isolate (recovered from the tilapia-trash feed) was virulent for S. aurata with LD50 equal to 4.67 × 107 colony forming unit (CFU) fish- 1. After intraperitoneal (IP) challenge, fish treated with 10 mg kg- 1 of florfenicol showed 16.7% mortality, while no mortality was recorded for the fish group that received 20 mg kg- 1. The non-treated fish group showed 46.7% mortality after bacterial challenge. HPLC analysis of serum florfenicol levels reached 1.07 and 2.52 µg mL- 1 at the 5th -day post-drug administration in the fish groups received 10 and 20 mg kg- 1, respectively. In conclusion, P. putida was responsible for the high mortality affecting cultured S. aurata, in-feed administration of florfenicol (20 mg kg- 1) effectively protected the challenged fish.