Diseased Fish Research Articles

Preparation of Platinum Nanoparticles of Biophytum reinwardtii and Evaluation of Neuroprotective Activity of MPTP-induced Parkinson’s Disease in Zebra Fish

Aim: To evaluate the Neuroprotective activity of Biophytum reinwardtii Platinum nanoparticles Methods: Biophytum reinwerdtii platinum nanoparticles were subjected to evaluation of the neuroprotection activity in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine induced zebra fishes. Experimental fishes are divided into 5 groups, each containing 8 fishes. Group I is considered a normal group; Group II is a toxic group means treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine 225 mg/kg, i.p. for 5 days; Group III, IV, and V are treatment groups means treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (225 mg/kg) with 0.3 µmol, 0.4µmol, and 0.5 µmol of Biophytum reinwardtii Platinum nanoparticles respectively for 5 days. Results: In the in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine group, locomotor activity and complex I activity are decreased, Malondialdehyde levels increased, antioxidants, and catecholamines levels decreased, whereas Biophytum reinwardtii Platinum nanoparticles treated fishes exhibit significant locomotor and increased levels of antioxidants and catecholamines. Conclusion: These results suggest that Biophytum reinwardtii Platinum nanoparticles. Showed significant neuroprotection activity in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine -induced Parkinson’s zebra fishes.

Unpredictable Repeated Stress in Rainbow Trout (Oncorhynchus mykiss) Shifted the Immune Response against a Fish Parasite.

Farmed fish are regularly subjected to various stressors due to farming practices, and their effect in the context of a disease outbreak is uncertain. This research evaluated the effects of unpredictable repeated stress in rainbow trout challenged with the ciliate Ichthyophthirius multifiliis, known to cause white spot disease in freshwater fish. Before and after the pathogen exposure, fish were handled with a random rotation of three procedures. At 7 days post-infection (dpi), the parasite burden was evaluated in fish and in the tank's water, and the local and systemic immune responses were investigated in the gill and spleen, respectively. The fish mortality was recorded until 12 dpi, when all the fish from the infected groups died. There was no statistical difference in parasite burden (fish and tank's water) and infection severity between the two infected fish groups. The immune gene expression analysis suggested a differential immune response between the gill and the spleen. In gills, a T helper cell type 2 immune response was initiated, whereas in spleen, a T helper cell type 1 immune response was observed. The stress has induced mainly upregulations of immune genes in the gill (cat-1, hep, il-10) and downregulations in the spleen (il-2, il-4/13a, il-8). Our results suggested that the unpredictable repeated stress protocol employed did not impair the fish immune system.

Activation of adenosine A2a and A2b receptors augments the skin wound healing in juvenile grass carp

Wounded fish skin leads to the impairment of internal tissue homeostasis and provides an opportunity for pathogens to invade, resulting in the occurrence of fish diseases. Accordingly, skin wound healing has been investigated in many fishes. In the present study, we found that the concentration of adenosine increased in grass carp skin wounds and antagonization of adenosine receptors aggravated the skin wound closure, implying that adenosine receptor activation played a role in fish skin wound repair. After the expression of adenosine A2a receptor (A2aR) and A2bR in grass carp skin was verified, the effects of two adenosine analogs, ZM241385 and CGS 21680, on grass carp A2aR and A2bR activation were examined by a dual-luciferase assay. The results showed that 500 nM of ZM241385 could antagonize the activation of both receptors by adenosine and 5–5000 nM of CGS 21680 could stimulate both receptors. In this scenario, these two compounds were administrated to the skin wounds of juvenile grass carp weighting about 8.0 g each, showing that 0.5, 2.5, 12.5 μg/tail of ZM241385 dose-dependently delayed while 0.8 and 2.4 μg/tail of CGS 21680 accelerated closure of the wounds when compared to the control group treated with the solvent. The thickness and cell proliferation of the epithelial layer in the wounds were decreased by 2.5 μg/tail of ZM241385 but increased by 0.8 μg/tail of CGS 21680 at 3 days post wounding compared to the control group. To our knowledge, this is the first report demonstrating the effects of adenosine receptor activation on skin re-epithelization in vertebrates. Moreover, the effects of ZM241385 and CGS 21680 on granulation formation including fibroblast migration and collagen deposition in grass carp skin wounds were also investigated in the present study. The results revealed that these two compounds oppositely regulated fibroblast migration and collagen deposition in grass carp skin wounds. These results implied that activation of grass carp A2aR and A2bR improved granulation formation in the wound, leading to enhancement of skin wound repair in juvenile grass carp. These results provide the new clues and mechanisms on the skin wound healing in fish species.

Survey of the invasive alien pink salmon (Oncorhynchus gorbuscha) for infective agents in the Fennoscandian Rivers Tana and Neiden

Pink salmon (Oncorhynchus gorbuscha, Walbaum 1792) is an invasive alien species in the Fennoscandian rivers, and its growing populations cause concern for their impact on the native salmonids and river ecosystems. One of the major concerns is fish diseases and the potential ability of pink salmon to transmit pathogens to the native salmonid species. In this study, pink salmon were sampled during their spawning migration in the Rivers Tana and Neiden in northern Norway and Finland in 2021. The fish were surveyed for viral hemorrhagic septicemia virus (VHSV), infectious pancreatic necrosis virus (IPNV), infectious salmon anemia virus (ISAV), salmonid alphavirus (SAV), piscine orthoreovirus (PRV), Renibacterium salmoninarum, and Gyrodactylus salaris. No viral diseases or infections with R. salmoninarum or G. salaris were detected. However, 23 % of the fish were found infected with a parasitic roundworm, Hysterothylacium aduncum. Additionally, external anomalies, such as hemorrhages or lesions in the skin, were observed in 35 % of the fish studied, and some of the fish exhibited degenerative myopathy. Based on this study, pink salmon appears not to pose a high infection risk to the native salmonid fish populations in the Rivers Tana and Neiden. Nevertheless, the results demonstrate that pink salmon have the potential to carry salmonid pathogens. More information on the susceptibility of pink salmon to different pathogens and on the overall effect this invasive species has on native fish species is needed. As the number of migrating pink salmon in the Fennoscandian rivers appears to increase, the potential risk of parasites and other pathogens spreading between fish species will also rise.

Mass mortality associated with carpione rhabdovirus in golden pompano (Trachinotus ovatus) in China: First report

From August to November 2023, a severe epizootic outbreak occurred in an offshore cultured golden pompano (Trachinotus ovatus) population in Zhanjiang City, Guangdong Province, China, resulting in a cumulative mortality rate of 65–82 %. The diseased fish showed clinical signs of lethargy, anorexia, whirling movements, and hemorrhage at the base of the fins and in the upper and lower jaws before mass mortality. A rhabdovirus strain, designated as CARPV2023, was successfully isolated using fathead minnow (FHM) cells. The cytopathic effects of the tissue filtrate from the diseased golden pompano on FHM and epithelioma papulosum cyprini (EPC) cell monolayers were characterized by rounded cells, grape-like cluster formation, detachment, and lysis. Histopathology revealed congestion, hemorrhage, and necrosis in the spleen, liver, trunk kidney, and intestinal tissues of naturally and experimentally infected golden pompanos. Electron microscopy showed that bullet-shaped viral particles, measuring 183.5–217.6 nm in length and 57.3–82.7 nm in width, budded from the cell membrane or aggregated around the infected FHM cells. The virus remained stable for 7 d at 4–33 °C and replicated optimally at 28 °C. Whole-genome sequencing and subsequent phylogenetic analysis further indicated that the carpione rhabdovirus (CARPV)2023 strain is a new carpione rhabdovirus, and is related to novirhabdoviruses, however, is thus far unclassified. A specific nested reverse transcription-polymerase chain reaction assay confirmed the presence of CARPV in the affected golden pompano. Significantly higher mortality was observed in challenged golden pompanos than that in the controls through intraperitoneal injection and immersion infection. Fluorescence in situ hybridization showed showed positive reactions for RNA in multiple tissues (liver, spleen, trunk kidney, brain, heart, gill, and muscle) from infected fish. The highest expression level was confirmed in the spleen through qPCR. This is the first study to report natural CARPV infections in marine fish.

Deltamethrin increased susceptibility to Aeromonas hydrophila in crucian carp through compromising gill barrier

Pyrethroids serve as a significant method for managing and preventing parasitic diseases in fish. Among these, deltamethrin (DEL) is used extensively in aquatic environments. Our previous work has been confirmed that DEL exposure can induce oxidative stress and immunosuppression on the gill mucosal barrier of crucian carp (Carassius auratus). However, it is not clear whether DEL affects the susceptibility of farmed fish to bacterial infection. In this study, fish was pre-exposed to different DEL concentration (0, 0.3 and 0.6 μg L−1) and then challenged by immersion with Aeromonas hydrophila (1.0 × 10^8 CFU mL−1). After immersion challenge, fish pre-exposed to DEL developed prominent lipopolysaccharides level in gill and serum and had a significantly lower survival rate compared to the control group. In DEL pre-exposure fish after immersion, the gill apoptosis levels were significantly higher and disrupted the tight junction barrier by downregulating the zo1 and claudin12. Furthermore, fish pre-exposed to DEL exhibited increased activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malonaldehyde (MDA) levels in the early stage after immersion but experiencing decreased activities of glutathione peroxidase (GPx) and lysozyme (LZM) in the later stage after immersion. And this process was regulated by the NRF2 pathway. Additionally, fish pre-exposed to DEL after immersion had significantly lower mRNA levels of immune-related genes tlr4, myd88, tnfα, and il-1β. Overall, these findings indicate that DEL damaged the gill barrier, weakened the immune response, raised LPS levels, and heightened vulnerability to A. hydrophila infection in crucian carp, resulting in mortality. Thus, this work will help social groups and aquaculture workers to understand the potential risk of DEL exposure for bacterial secondary infection in cultured fish.

Identification of a novel circovirus associated with turbot (Scophthalmus maximus) acute hemorrhage disease

Turbot (Scophthalmus maximus) is an economically important farming fish in China. However, an emerging disease named turbot acute hemorrhage disease (TAHD) has been affecting turbot farms since November 2019. TAHD is characterized by severe bleeding in the fish fins and may lead to significant mortality in one or two weeks, with accumulated mortality exceeding 90 %. The TAHD spread rapidly across the major turbot farming regions in China and resulted in significant economic losses. Virome sequencing was utilized in the diseased fish to discover a novel turbot circovirus (TCV). The TCV particle is ∼30 nm in size and is located in the fish spleen and kidney. The TCV genome is 1774 bp long, with three open reading frames (ORFs) encoding the replication protein (Rep), capsid protein (Cap), and ORF3 of unknown function. The identity of the TCV Rep sequence was <53 % compared to the reported circovirus sequences. Phylogenetic analysis of the Rep and Cap protein sequences revealed that TCV is a novel circovirus. The polymerase chain reaction detection method was used to analyze the clinical TAHD samples from 2019, which were all TCV-positive. Various cell lines, including turbot kidney, epithelioma papilloma cyprinid, Chinook salmon embryo, and spotted halibut kidney, were used for TCV isolation. However, no cytopathic effect or replication was observed. The diseased fish tissue homogenate filtrate was used for experimental infection. As a result, all of the infected turbot showed signs of natural infection, with increasing numbers of cap gene copies post-infection. Based on these results, it was hypothesized that the novel circovirus TCV is closely associated with TAHD. Our research also indicated that the circovirus represents a significant threat to fish and more attention should be paid to it in aquaculture.

Diving into the fish pathology of an important commercial fish species: the case of the European hake (Merluccius merluccius Linnaeus, 1758) in the northwest Mediterranean Sea

Diving into the fish pathology of an important commercial fish species: the case of the European hake (<i>Merluccius merluccius</i> Linnaeus, 1758) in the northwest Mediterranean Sea

A Convolutional Neural Network Approach for Precision Fish Disease Detection

Background: Detecting and classifying fish diseases is crucial for maintaining the health and sustainability of aquaculture systems. This study employs deep learning techniques, particularly Convolutional Neural Networks (CNNs), to automate the detection of various fish diseases using image data. Methods: The study utilizes a carefully curated dataset sourced from the Kaggle database, comprising images representing seven distinct types of fish diseases, along with images of healthy fish. Data preprocessing techniques, including resizing, rescaling, denoising, sharpening, and smoothing, are applied to enhance image quality and facilitate accurate disease detection. Data augmentation is employed to increase the model's ability to generalize to unseen data. The CNN architecture is designed with cascading convolutional layers, ReLU activation functions, and pooling operations to extract high-level features associated with fish infections. The model architecture, implemented using the Keras Sequential API, includes convolutional layers, max pooling layers, and densely connected layers for classification. Results: Experimental results demonstrated promising performance across various disease categories, with high accuracy and balanced precision and recall values for most classes. The study also discussed the impact of climate change on fish disease incidence and underscores the importance of effective monitoring and management practices facilitated by technological innovations such as Big Data, IoT, sensors, and robotics in ensuring sustainable fisheries management.

The early life microbiome of giant grouper (Epinephelus lanceolatus) larvae in a commercial hatchery is influenced by microorganisms in feed

Fish health, growth and disease is intricately linked to its associated microbiome. Understanding the influence, source and ultimately managing the microbiome, particularly for vulnerable early life-stages, has been identified as one of the key requirements to improving farmed fish production. One tropical fish species of aquaculture importance farmed throughout the Asia-Pacific region is the giant grouper (Epinephelus lanceolatus). Variability in the health and survival of E. lanceolatus larvae is partially dependent on exposure to and development of its early microbiome. Here, we examined the development in the microbiome of commercially reared giant grouper larvae, its surrounding environment, and that from live food sources to understand the type of bacterial species larvae are exposed to, and where some of the sources of bacteria may originate. We show that species richness and microbial diversity of the larval microbiome significantly increased in the first 4 days after hatching, with the community composition continuing to shift over the initial 10 days in the hatchery facility. The dominant larval bacterial taxa appeared to be predominantly derived from live cultured microalgae and rotifer feeds and included Marixanthomonas, Candidatus Hepatincola, Meridianimaribacter and Vibrio. In contrast, a commercial probiotic added as part of the hatchery’s operating procedure failed to establish in the larvae microbiome. Microbial source tracking indicated that feed was the largest influence on the composition of the giant grouper larvae microbiome (up to 55.9%), supporting attempts to modulate fish microbiomes in commercial hatcheries through improved diets. The marked abundances of Vibrio (up to 21.7% of 16S rRNA gene copies in larvae) highlights a need for rigorous quality control of feed material.

OCCURRENCE OF LAMPROGLENA PULCHELLA (NORDMANN, 1832) (COPEPODA: LERNAEIDAE) IN SOME CYPRINID FISH FROM OHRID LAKE (MACEDONIA)

The representatives of the class Copepoda are of great importance in fish pathology. Lamproglena pulchella (Nordmann, 1832) (Copepoda: Lernaeidae) is an ectoparasite of many cyprinid fish, widespread in Europe up to the Aral Sea. During the long-term investigations of 12 species of cyprinid fish from the Lake Ohrid, a total of 7 specimens of Lamproglena pulchella was found in 5 fish from 4 fish species: Rutilus ohridanus, Squalius squalus, Scardinius knezevici and Chondrostoma ohridanus. Only fresh fish were subjected to routine parasitological examinations, dissection, and observation methods. Parasite identification was performed morphologically, based on the character of their maxilla, maxilliped, antennae, legs and uropods, using a referent key for determination. The 3 parasite specimens were found in two samples of Rutilus ohridanus, followed by 2 parasite specimens in Squalius squalus and one specimen in Scardinius knezevici and Chondrostoma ohridanus, each. These parasites attach to gills and general body surfaces by their maxilla and maxilliped, causing wounds that become the spots of secondary infection by microbes. The damage caused by this parasite is more pronounced in aquaculture systems. We did not find many parasites, but considering the potential danger that Lamproglena pulchella poses to the fish health, we point out the need to monitor infestations with this parasite and take preventive measures so that the parasite does not spread massively among fish in Lake Ohrid and to prevent its introduction into other waters in Macedonia. The record of Lamproglena pulchella in all four cyprinid fish in the present study is considered as the first from the Ohrid Lake. At the same time, Rutilus ohridanus, Scardinius knezevici and Chondrostoma ohridanus represent new hosts for this parasite, worldwide.

Optimization of iron flocculation for enrichment of CyHV-2 in aquaculture water

Cyprinid herpesvirus 2 (CyHV-2) is an important infectious virus endangering the farmed Carassius species industry. The enrichment and identification of CyHV-2 in the water is a vital means of early warning diagnostics, which is helpful to aquatic diseases prevention and control. In this study, we employed and optimized iron flocculation to enrich the concentrations of CyHV-2 in aquaculture water. Different Fe3+ concentrations (0.5, 1.0, and 10.0 mg/L), various membrane filters (mixed cellulose ester, glass fiber, nylon microporous filter membrane), different elution buffers containing reductants (ascorbate, citrate, DL-malate, and their combinations with EDTA or TE buffer) were compared to check the recovery yield of CyHV-2. Viral genome quantitation was determined using quantitative real-time PCR. The results showed that Fe3+ concentration of 1.0 mg/L, the glass fiber and citrate-TE were determined to have high efficiency and stable recovery yield. To evaluate infectious CyHV-2 viral titres, crucian carps (Carassius auratus) were intraperitoneally injected with CyHV-2. The mortality rate was 100 % at 9 days postinoculation (dpi) with the 96.7 % detection of CyHV-2 in the pooled tissues. The histopathological phenotype showed necrotic cell death in the liver, spleen and kidney. The CyHV-2 genome was ranging from 101.1 to 107.5 copies/μl in the deceased fish, and 101.4 to 103.0 copies/μl in the feeding water at various stages from latent infection to onset of disease. The field samples from Huzhou, Zhejiang Province on June 4th and 7th had higher detection rates, 87.5 % and 100 % respectively, corresponding to higher CyHV-2 detected in the aquaculture water. CyHV-2 viral load in cultured waters tends to increase prior to fish death, which provides a new indicator for the prediction of fish diseases. In summary, we have established a unified operational standard for enrichment of CyHV-2 in the aqueous environment by iron flocculation.

Occurrence of Ectoparasites on Tilapia zillii (Red Belly Tilapia) Gervais 1848 in The Tono Reservoir, Navrongo, Ghana

This study was carried out to assess the occurrence of endoparasites in (Tilapia zillii (Gervais, 1848)) from Tono reservoir, Navrongo Ghana. A total of 120 fish samples were collected from the upstream, midstream and downstream regions of the reservoir using cast nets. All the collected fish samples were transported to the research laboratory in the University for Development Studies and examined for ectoparasites during January 2022 to August 2022. Five ectoparasites namely Trichodina sp. of Protozoans ciliates, Dactyolgyrus sp. of Monogenean, Argulus sp. and Lernaea sp. of Crustaceans and the Diplostomum sp were identified. Overall prevalence of the fish parasites was 52.32 %. Intensity of the parasites observed ranged between 1.58% to 3.52%. Highest prevalence 70 % was reported in dry season while lowest (31.67%) was reported in the rainy season. Female fish samples had higher prevalence (64.47 %) than males (27.27 %). Fishes of downstream had highest prevalence (92.5 %) than upstream (17.5 %). Fish samples with maximum length and weight were highly (65.15 %) infected than small sized fish with low body length and weight (33.33 %). It is debatable if the degree of ectoparasite activity found in this study will constitute a serious danger to the local fish population. Yet, in order to stop disease outbreaks brought on by an increase in ectoparasites, the reservoir must be given significant attention by using optimum management strategies. This study shows that dry season affects the fish business and result in poor quality fish meat with risk of diseases infection.

Inactivated LMBV vaccine with nano‑aluminum adjuvant provided immune protection in largemouth bass (Micropterus Salmoides)

Largemouth bass ranavirus (LMBV) has caused severe economic losses in largemouth bass (Micropterus salmoides) aquaculture. Vaccination is acknowledged as an efficient strategy to prevent viral diseases in fish. In this study, an inactivated virus vaccine with nano‑aluminum adjuvant was successfully developed to protect largemouth bass effectively against LMBV. LMBV was inactivated by formalin and mixed with nano‑aluminum adjuvant under moderate agitation. The nano‑aluminum hydroxide adjuvant showed a cuboidal structure under the scanning transmission electron microscope (STEM), scanning electron microscope (SEM), and transmission electron microscope (TEM), and LMBV antigen-adsorbing rate was 39.49 % superior to those of micro‑aluminum hydroxide and IMS1312 adjuvants. The results from both external and internal damage assessments indicated that the nano‑aluminum vaccine had good safety for Micropterus salmoides. The relative percentage of survival was 80 % with a booster immunization in largemouth bass. The expression levels of immune-related genes such as TNF-α, IFN, and IL-8 were significantly up-regulated in the spleen of fish immunized by nano‑aluminum adjuvant vaccine compared to those in inactivated LMBV and control groups. The neutralizing antibody in nano‑aluminum adjuvant vaccine group showed higher abundance and lasted for a longer period. Lymphocytes from the head kidney of largemouth bass in the nano‑aluminum adjuvant vaccine group showed stronger proliferation activity in vitro post-stimulation with ConA. Moreover, stronger migration of the dendritic cells was induced by the nano‑aluminum adjuvant vaccine. Collectively, our findings suggested that the inactivated LMBV vaccine with nano‑aluminum adjuvant could provide efficient protection for largemouth bass against LMBV infection. The nano‑aluminum adjuvant has potential application with inactivated viral vaccines in fish.

Parasites of African catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;) cultured in selected homestead ponds in Rivers State, Nigeria

Fish are a major source of protein to humans and one of the constraints to improved fish production in Nigeria are parasites/parasitic diseases. A study to evaluate the parasites of African catfish (Clarias gariepinus Burchell, 1822) cultured in selected homestead ponds in Rivers State, Nigeria was conducted from January to June, 2023. One hundred and twenty catfish were randomly selected from two homestead ponds (sixty fish per pond) and categorized (sex, weight and length); each fish was analyzed for parasites (ecto and endo) using standard parasitological techniques. Descriptive analyses (mean and percentages) were used to represent data obtained and chi-square test was used to determine the level of significance with a P&lt;0.05 considered significant. An overall parasite prevalence of 30 (25.0%) was recorded in this study (P&lt;0.05) and four parasites were observed; Ichthiphitrius 14 (11.7%), Chilodinella 6 (5.0%), Trichodina 6 (5.0%) and Crytobia 4 (3.3%). Male and female fish had parasite prevalence of 8 (16.0%) and 22 (31.4%) respectively (P&gt;0.05).According to weight, parasite prevalence values of 4 (16.0%), 4 (17.4%), 8 (28.6%), 8 (30.8%) and 6 (33.3%) were recorded for 140 – 160g, 161 – 180g, 181 – 200g, 201 – 220g and 221 – 240g respectively while according to length, parasite prevalence values of 8 (21.1%), 10 (24.4%), 7 (26.9%) and 5 (33.3%) were recorded for 20 – 22cm, 23 – 25cm, 26 – 28cm and 29 – 31cm respectively (P&gt;0.05). Proper management practices should be adhered to in aquaculture to increase yield and reduce the detrimental effects of fish parasites.

Propagation of koi herpesvirus using embryonated chicken eggs: a potential substitute method for fish vaccine production?

Koi herpesvirus disease (KHVD) is caused by a large DNA virus that commonly infects carp, Cyprinus carpio (koi and common carp). KHVD has spread rapidly across the globe and caused high mortality in all ages of common carp and koi. Until now, no effective treatment has been applied to prevent KHV infection impacting the mass production of koi and common carp . An environmentally friendly alternative strategy for controlling fish disease is vaccination. One of the challenges facing conventional viral vaccine production is the requirement for koi or common carp cell cultures, which must be frequently maintained with expensive materials required for virus propagation. This study aims to obtain KHV that has been propagated in embryonated chicken eggs (ECE) to formulate an affordable KHV vaccine for the aquaculture industry. This research consisted of three stages; the first stage was virus inoculation into various parts of eggs (allantoic fluid, chorioallantoic membrane, amniotic fluid, and egg yolk). The second stage was observing viral growth and collecting ECE fluid and membranes. The third stage involved quantitatively determining the viral genomic copy numbers using the quantitative Polymerase Chain Reaction (qPCR) assay. KHV propagation in various parts of ECE resulted in varying viral genomic copy numbers with a high DNA copy number reported in allantoic fluid on the third day after inoculation. Further work is required to monitor virus titer in later passages and optimize methodology for using ECE as the potential alternative to cultured cells as the medium for virus propagation. In the future the system could be developed to produce promising vaccine candidates with more affordable vaccine prices for the Indonesian fish farming industry.

Fish Genomics and Its Application in Disease‐Resistance Breeding

ABSTRACTGlobal aquaculture production has been rising for several decades, with up to 76% of the total production from fish. However, the problem of fish diseases is becoming more and more prominent in today's context of pursuing sustainable aquaculture. Since the first fish genome assembly reported in 2002, genomic approaches have been successfully implemented in fish breeding to enhance disease resistance and reduce economic losses caused by diverse fish diseases. Here, we present a review of the current progress in fish genomics and its application in disease‐resistance breeding. First, assembly data for all publicly available fish genomes were curated and statistical analysis of these data were performed. Subsequently, genomics‐assisted breeding approaches (including quantitative trait loci mapping, genome‐wide association study, marker‐assisted selection, genomic selection, gene transfer, and genome editing) that have been applied in practical disease–resistance breeding programs are outlined. In addition, candidate genetic markers that could possibly be utilized in breeding were summarized. Finally, remaining challenges and further directions were discussed. In summary, this review provides insight into fish genomics and genomics‐assisted breeding of disease‐resistant fish varieties.

Exploration of a model driven by climate to simulate pond water temperature in aquaculture systems

IntroductionInterannual climate variability in the Asian mega deltas has been posing a wide range of climate risks in the aquaculture systems of the region. Water temperature variation is one of the key risks related to disease outbreak, fish health, and loss and damage in fish production. However, Climate information can improve the ability to predict changes in pond water quality parameters at the farm level using publicly available weather and climate data. Little research has been done to translate weather data into water temperature forecasts using mechanistic models in order to provide farmers with relevant forecasting information in the context of climate services.MethodsThe advantage of mechanistic models over statistical models is that they are based on physical processes and can therefore be used in a wider range of environmental conditions. In this study, we used an energy balance model to investigate its ability to simulate pond water temperature at daily and seasonal timescales in the southwest and northeast regions of Bangladesh. The model was able to adequately simulate pond water temperature at a daily timescale using publicly available weather data, and the accuracy of the model was lower at the study site with very heavy rainfall events.ResultsSensitivity analyses showed that the model was also able to simulate the impact of air temperature cold and hot spells on the pond water temperature. Connecting the model with seasonal air temperature forecasts resulted in very small variations in the forecasted seasonal pond water temperature, in large part due to the low variability observed in water temperature at seasonal scale in the study sites.DiscussionClimate information can improve the ability to predict changes in pond water quality parameters at the farm level using publicly available weather and climate data. Hence, these improved predictions are important to help fish-farmers make informed decisions for managing associated climate risks.

Investigation of vibriosis caused by Vibrio anguillarum in rainbow trout (Oncorhynchus mykiss).

Identifying pathogenic microorganisms causing disease is important for epidemiological research, antimicrobial therapy, and control. The current study was carried out to use different methods for the identification of Vibrio anguillarum from diseased rainbow trout (Oncorhynchus mykiss) obtained from Türkiye (Muğla-Fethiye), the damage caused by the pathogenic microorganism in the tissues and organs, and the determination of the antibiotic effective against the pathogen. Hemorrhagic and ulcerative skin lesions and diffuse petechial hemorrhage in the internal organs were clinically detected in diseased fish obtained from the rainbow trout farm. Bacteria isolated from diseased fish were subjected to analysis using conventional bacteriological methods, a commercial bacterial identification test kit (API), an automated bacteria identification system known as Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS), BD Phoenix™, and 16S rRNA sequence analysis. All isolated bacteria were identified as V. anguillarum by API 20E and conventional bacteriological method. These results have been confirmed with 16S rRNA sequence analysis. However, the isolated bacteria were identified as Grimontia hollisae (syn. Vibrio holisae) with the BD Phoenix system. Histologically, tissue damage such as melano-macrophage centers and necrosis in the kidney and spleen, hyperemia and mononuclear cell infiltration in the liver, as well as mononuclear cell infiltration on muscles, talengectiasis in the gill tissue was observed. In addition, it has been determined that the most effective antibiotic against the pathogen was enrofloxacin. When comparing all identification methods used for this pathogen causing tissue damage, it was demonstrated that the MALDI-TOF MS provides better results than other methods in terms of cost and identification time, and it could be used as an alternative to the conventional method to the identification of V. anguillarum.

Characterization of novel marine bacteria isolated from deep Atlantic Ocean in Morocco as a source of natural bioactive compounds to control infections in aquaculture

With the rapid expansion of aquaculture production, there has been a concomitant increase in fish diseases, generally combatted by the utilization of chemicals and antibiotics. However, their overuse leads to the emergence of drug-resistant microorganisms and the appearance of oxidative stress. Consequently, antibiotics contribute to a reduction in fish immune defense. In this work, eight marine bacteria were characterized using physiological, biochemical and microbiological tests, and were evaluated for their safety by studying their haemolytic and gelatinase activities. Then, we evaluated their ability to produce active biomolecules and tested their in vitro antibacterial activities against five bacterial pathogens that are highly prevalent in aquaculture. Moreover, we evaluated their antioxidant potential using DPPH, ABTS and ferric reducing power tests. The obtained results revealed that cell-free supernatants were effective, they exhibited good antioxidant and antibacterial activities. Their biomolecules showed good stability under different temperatures ranging from 60 to 121 °C and were found to be chemically composed of peptides, exopolysaccharides and polyphenols. Therefore, the secreted bioactive substances are of great biotechnological interest and constitute a promising eco-friendly alternative to antibiotics and chemical agents in the context of sustainable aquaculture.