Non-infected Fish Research Articles

AI-Driven Realtime Monitoring of Early Indicators for Ichthyophthirius multifiliis Infection of Rainbow Trout.

A novel video-based real-time system based on AI (artificial intelligence) was developed to detect clinical signs in fish exposed to pathogens. We selected a White Spot Disease model involving rainbow trout as the experimental animal and the parasitic ciliate Ichthyophthirius multifiliis as a pathogen. We compared two identical fish tank systems: one tank was infected by co-habitation, whereas the other tank was kept non-infected (sham infection). The two fish tanks were separately video monitored (full top and side view) during the course of infection, during which fish were removed whenever they developed clinical signs (direct visual inspection by the observer). Image analysis (object detection, classification and tracking) was used to track behavioural changes in fish (in every recorded video frame), focusing on movement patterns and spatial localisation. Initially, the two fish groups (infected and non-infected) exhibited similar behaviour and non-infected fish did not change behaviour during the 15 d observation period (from 5 d before infection until 10 dpi). At 4, 7, 8, 9 and 10 dpi some infected fish showed clinical signs (equilibrium disturbance, gasping and lethargy) and were removed from the experiment. Anorexia occurred from 5 dpi and a gradual progression of gasping behaviour was noted, whereas the frequency of fish flashing (rubbing/scratching against objects) was low. Equilibrium disturbances and the development of white spots in the skin appeared to be a much later (8-10 dpi at this temperature) indicator of infection. The video analysis showed a general distribution of non-infected fish in all parts of the fish tank during the entire experiment, whereas infected fish already at 4-5 dpi moved towards higher water currents in the top and bottom positions. This change of fish positioning within the tank appeared as a promising early indicator of infection. The study suggests that continuous monitoring of fish behaviour using AI can potentially optimise the timing of humane endpoints, indicate disease signs earlier and thereby improve animal welfare in both animal experimentation and in aquaculture settings.

Biochemical contents of tapeworm Proteocephalus osculatus and its definitive host, Silurus triostegus

The current study dealt with the determination of the concentration of some biomolecules in the tissues of the tapeworm and the intestinal tissue of its definitive host (fish). At the probability level (P≤0.05) a sig-nificant difference was noticed in the concentration of proteins, glycogen and lipids in the intestinal tissue of non-infected fish compared to the infected fish. The concentration of proteins and glycogen in the tissues of the tapeworm was (9.95 and 7.33) mg/g of fresh weight respectively, it was lower than that in the intestinal tissues of its infected definitive host, which amounted to (22.06, 12.33) mg/g of fresh weight, respectively, while lipids appeared in a higher concentration in the tapeworm tissues (19.17) mg/g of fresh weight com-pared to its concentration in the intestine of its infected definitive host (17.10) mg/g of fresh weight. As for the concentration of urea and creatinine, it was found a significant difference at the level of probability (P≤0.05) in the serum of infected and non-infected fish, as both urea and creatinine showed a significant relative increase in the serum of infected fish (12.30, 2.31) mg/dl respectively than in non-infected fish (10.66 and 1.07) mg/dl respectively. Keywords: creatinine; glycogen; lipid; protein; Silurus triostegus; tapeworm; urea

Effect of parasitic infection on microplastic ingestion in a native leuciscid hybrid species (Alburnus derjugini x Squalius orientalis) from Kürtün Dam Lake, Türkiye

Microplastic (MP) pollution is currently one of the most serious environmental issues. MPs were investigated in the Kürtün Dam Lake in healthy individuals of the native leuciscid hybrid (Alburnus derjugini x Squalius orientalis) species and individuals infected with the Ligula intestinalis parasite. Although MP abundance appeared to be higher in non-infected fish (NIF) than in L. intestinalis (L) and infected fish (IF), the MP abundance in IF was higher, because the parasite theoretically belongs to IF. In addition to the observation of MPs in the gastrointestinal tract (GIT) of fish, the diffusion of MPs by parasites settled in the body cavity indicates that MPs are not only present in the GIT. Therefore, predation on existing fish by birds causes MP dispersion. In the present study, the most common MP shape was fiber (100% for NIF and IF, 85.7% for L), the MP color was black (57.1% for IF and L) and orange (50% for NIF), and the polymer type was polyamide (57.1% for IF, 50% for NIF) and polyethylene terephthalate (28.5% for L). These MP compositions led us to believe that textile effluents and aquaculture operations in dam lakes could be sources of pollution. Therefore, this study provides insights for future research to elucidate the connection between MP consumption and parasite infection.

Therapeutic effects of white poplar (Populus alba) leave extract on hepatorenal, stress, and antioxidant-immune parameters of Oreochromis niloticus challenged with Aeromonas veronii

Herbal plants have gained enormous interest due to their immune, antioxidant, and antibacterial activities. The present study proposed that white poplar (Populus alba) leave extract (WPE) might provide a promising alternative to traditional antibiotics to treat Aeromonas veronii infection in Nile tilapia (Oreochromis niloticus). WPE showed an in vitro antibacterial activity [22 ± 0.45 mm inhibition zone, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 60 µg/mL] against A. veronii. For the in-vivo study, a factorial (2 × 2) design was used to investigate the therapeutic effects of WPE on the antioxidant/immune status and blood biochemical parameters of Nile tilapia challenged with A. veronii. One-hundred sixty fish (33 ± 1.5 g) were assigned into four experimental groups, each with four replicates (4 glass tanks/group, 40 fish/group, 10 fish/tank) for 10 days. In the first (1st) and 2nd groups, 0 and 1.5 mg/L WPE were applied in tank water, respectively, without fish being challenged. In the 3rd and 4th groups, 0 and 1.5 mg/L WPE were applied in tank water, respectively, with fish intraperitoneal inoculated with 0.2 mL of A. veronii (0.5 × 107 CFU). Aeromonas veronii infection significantly diminished the survivability, hepatic catalase, lysozyme activity, nitric oxide, immunoglobulin M, phagocytic %, total protein, albumin, and globulin. Moreover, a significant rise in the hepatic malondialdehyde, serum hepatorenal function indicators, cortisol, and glucose levels were consequences of A. veronii challenge. Interestingly, the interaction between bacterial challenge and WPE application increased the survivability, antioxidant activity, and immune responses and reduced ALT levels of fish treated with WPE during the bacterial challenge. The serum creatinine, cortisol, and glucose levels were decreased in fish treated with WPE during the infection but still higher than in the non-infected fish either treated or not treated with WPE. In conclusion, WPE (1.5 mg/L) can be used as an antibacterial substance in fish farming to alleviate the detrimental impacts of A. veronii infection by enhancing the antioxidant/immune status of the infected fish. These outcomes could help reduce antibiotic usage in fish farms, which is conducive to the sustainable development of aquaculture.

Cytotoxicity and immunological impact of Trypanosoma sp. infection on blood parameters of wild African catfish, Clarias gariepinus

Fish trypanosomiasis is a common blood parasitic disease transmitted by aquatic invertebrates, such as leeches. This study aims to shed light on the cytotoxicity of Trypanosoma sp. on erythrocytes and its impacts on the innate immune response (serum lysozyme activity, nitric oxide production, phagocytic activity, serum total protein, and globulin) in wild African catfish, Clarias gariepinus. One hundred catfish were examined using blood smears stained with Giemsa and confirmed with PCR. The prevalence of infection was found to be 10% by microscope detection and 15% by PCR. The morphological identification of Trypanosoma as Trypanosoma mukasai was determined. Additionally, this study included previously undescribed features of Trypanosoma, such as the width of the anterior and posterior body, the length of the posterior pale region, and the number of folds. Various alterations in erythrocytes were observed, totaling 54.57%. Nuclear abnormalities, including fragmented nuclei, eccentric nuclei, and micronuclei, were also reported. Infected fish showed a reduction in serum total protein and globulin levels, while nitric oxide production, lysozyme activity, and phagocytic activity exhibited a significant increase compared to non-infected fish. We believe that our findings will contribute valuable data to the morphological and molecular identification of Trypanosoma sp. in African catfish, as well as their cytotoxic impact.

The involvement of Pseudoterranova decipiens fish infestation on the shelf-life of fresh Atlantic cod (Gadus morhua) fillet

Zoonotic nematodes of the family Anisakidae are highly common in many marine fish species, which act as paratenic hosts for the third larval stage. In the fish, these parasites may migrate from the fish's gastro-intestinal tract (GI-tract) further to the coelomic cavity and muscles, making them a possible contamination source of bacteria they carry on their cuticle and in their GI-tract. A previous study revealed no apparent effect of Anisakis simplex on spoilage of fish, but the equally common anisakid species Pseudoterranova decipiens has a larger body surface potentially increasing the bacterial load brought into the fish muscle upon migration. As the presence of shelf-life reducing spoilage bacteria in the microbiome of this anisakid species has been demonstrated, the objective of the present study was to assess the potential shelf-life reducing effect of P. decipiens in fresh fish fillets stored in a domestic refrigerator.Atlantic cod was used as a model since members of the cod family are the third most consumed marine fish globally and it has the highest prevalence of P. decipiens infections. Infected and non-infected codfish fillet portions were collected and microbiologically analyzed at day 0 and day 4 of storage in a domestic fridge. Three isolation media were used to enhance maximum bacterial recovery and isolates were identified using MALDI-TOF MS and 16S rRNA gene sequencing. In parallel to the microbiological examination, sensory analysis was performed daily on the cod fillets to evaluate the freshness of the fish.Results revealed the presence of typical spoilage bacteria (e.g., Pseudomonas sp., Photobacterium sp.) in all fish, but based on the total viable counts, total H2S-producing bacteria, and sensory analysis, there were no objective indications to assume an increased fish spoilage rate by the presence and migration P. decipiens. Additionally, a beta-diversity comparison revealed no significant differences in microbiota composition between infected and non-infected fish parts, though individual heterogeneity in microbiome composition among Atlantic codfish individuals was found. As total viable counts did, however, exceed the guideline limits for fresh fish, further research should now focus on the role of the candling step as a potential source of post-harvest contamination. As such, anisakid infection might still accelerate fish spoilage, though now in an indirect way.

Особливості лігульозу ляща (Abramis brama Linnaeus, 1758) та плітки (Rutilus rutilus Linnaeus, 1758) у Дніпровському (Запорізькому) водосховищі

Purpose. Study of the peculiarities of ligula infestation of roach and bream in the Dnipro (Zaporizhzhia) reservoir and the influence of Ligula intestinalis on the morphological and cytometric parameters of infected fish species. Methodology. The work presents the generalized results of studies conducted in 2020-2021 during planned test catches. Sampling was carried out along the shoreline of the Dnieper (Zaporizhzhia) reservoir in the lower part of the villages of Viiskove and Mykilske-na-Dnipri, Dnipropetrovsk region, in the summer-autumn period. The morphological study was carried out by carefully examining the surface of the scales and skin cover. Special attention was paid on fins, the amount of mucus, its consistency, color change, the presence of tumors, hemorrhages, ulcers, cysts, large ectoparasites, and the condition of eyes. The parasitological study was carried out by a complete anatomical dissection of the fish according to the classical method. Blood was collected at the catch site from the heart of the fish using a needle and a syringe into a dry test tube for the biochemical serum analysis. Blood was also collected for the preparation of smears and their subsequent microscopy. Blood smears were fixed with methyl alcohol and stained according to Romanovsky’s method with Giemsa’s standard solution. Blood smears were examined by microscopy at a 40x magnification. Blood smears of non-infected fish were used for comparison. Thirty fields of view were examined in each smear. Findings. In the course of the study, a decrease in the weight and condition factor of infected roach and bream was observed, and irreversible pathological changes in the internal organs caused by the mechanical pressure and migration of parasites were recorded. In addition, deviations from the normal values were found in the formed elements of blood. About 24.3% of erythrocytes in infected specimens of bream and roach were deformed: the cell membrane was not clear, erythrocytes had a slightly inflated shape. In some erythrocytes, the nucleus was faintly visible. Infected specimens had more juvenile forms of erythrocytes compared to non-infected fish. Originality. For the first time, a comparative morphological, cytometric analysis of blood during ligulosis infestation of infected specimens of bream and roach in the Dnipro (Zaporizhzhia) reservoir is presented. Practical value. The study of biological, clinical and epizootic peculiarities of parasitic helminths is of urgent interest for both science and fish farming. The obtained results can be implemented in the practical activity of fish farming and used in the development of measures to limit and prevent the development of parasitic diseases among the ichthyofauna of the Dnipro (Zaporizhzhia) reservoir. Key words: bream, roach, ligula, erythrocytes, albumins.

Heavy infection of the orange-spotted grouper (Epinephelus coioides) with Huffmanela japonica: morphological, ultrastructural identification, tissue reactions and immunological analysis

This study aimed to determine the causative agent of black spots which observed in the mesentery, adipose tissue and peritoneum of orange-spotted grouper, Epinephelus coioides. The parasitological examination using light and electron microscope confirmed infection with trichosomoidid parasite, genus Huffmanela, which identified as Huffmanela japonica (H. japonica). The examined eggs were present in two stages (stage 1, mature light brown eggs with larva; stage 2, advanced dark brown eggs with grown larva). The histopathological alteration of the infected tissues together with determination of immunological gene expression in different organs demonstrated prominent response of the host tissues against the studied parasite. Pathological examination of the infected fish revealed that the lesions were mainly in the mesenteric and diffuse pancreatic tissues which present in the abdominal fat. Granulomas containing eggs and mononuclear and eosinophilic granular cell infiltrations, together with fat necrosis of the pancreatic tissue, were the most common pathological findings. Migrating larvae and peritoneal adhesions with organised fibrosis were also observed. In the infected tissues as well as in the spleen, liver and kidney, interleukin 1β (IL-1β) and cyclooxygenase (COX)-2 were upregulated than in control non-infected fish. Our results confirmed that H. japonica is infecting orange-spotted grouper caught from the Red Sea in Egypt with prominent tissue specificity in the mesentery, adipose tissue surrounding the intestine, and in the peritoneum.

DNA Barcoding of Argyrops filamentosus (Perciformes: Sparidae) Based on Mitochondrial COI Gene and Histopathological Evaluation of Gills Infected by Monogeneans

Background: Sparidae is a fish family that belongs to the order Perciformes and is commonly known as sea breams and porgies. Many species are included in this family and divided into 71 genera that could be barcoded using mitochondrial DNA genes. These fish are vulnerable to different parasitic taxa that affect fish status. The present study is aimed to confirm the molecular status of Argyrops filamentosus fish via the mitochondrial cytochrome c oxidase (COI) gene and to study the pathological changes of gills infested by monogenean parasites. Methods: Thirty Argyrops filamentosus fish were collected from Jeddah (Saudi Arabia) and identified molecularly via the mtCOI gene. Also, gills were isolated and examined microscopically for presence of monogeneans. Histopathological impacts of monogeneans on fish gills were studied in comparison to the gills of non-infected fish. Result: The DNA of fish species was barcoded and showed highly stringent criteria with the previously Argyrops filamentosus sequence data. The obtained host DNA sequences were deposited in NCBI database under accession number OP975758.1. Examination of the investigated fish gills revealed the presence of three monogenean species Protolamellodiscus senilobatus Kritsky, Jiménez-Ruiz and Sey, 2000, Acleotrema maculatus Morsy, El-Fayoumi and Fahmy (2014) and Haliotrema susanae Soo, 2019. Monogenean parasites penetrated deeply with their haptor to the gill lamella and caused damage and degeneration of epithelial cells leading to the formation of a cup-shaped depression. Therefore, the mtDNA gene has the ability for host identification and heavy monogeneans infections lead to severe damage to fish gills.

Biomonitoring of heavy metals using Contracaecum quadripapillatum (Nematoda) in comparison to its fish host, Lates niloticus, from the Nile River, Egypt

Recently, fish parasites have been used as a biomonitoring tool to indicate the health status of ecosystems. Therefore, this research aimed to evaluate the potential capacity of Contracaecum quadripapillatum larvae as accumulation indicators for metal pollution and compare metal concentrations in host tissues of non-infected and infected fish: Lates niloticus from the Nile River. Accumulations of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in larval nematodes and tissues of the liver, kidney, and muscles of both infected and non-infected fish were determined. All metal concentrations exhibit a significantly higher increase in larval nematodes than the muscles of infected fish and vice versa except Cd in the kidney. On the other hand, only Cd, Mn, Pb, and Zn concentrations were significantly higher in the parasite than in the host liver. Therefore, bioaccumulation factors were most obvious and effective in the muscles of infected fish than in the liver and kidney. Contracaecum larvae accumulate Cd and Pb more than other metals. The infrapopulation size of C. quadripapillatum correlated with metal concentrations in different host tissues, especially the kidney, while the correlations between metal levels in the tissues of both parasite and fish organs exhibit different patterns in each organ. The current work revealed that C. quadripapillatum larvae represent environmental monitors for metal pollution in the freshwater ecosystem.

Metal accumulation capacity of raphidascaridid nematode, Hysterothylacium reliquens, infecting the king soldier bream (Argyrops spinifer)

There are several types of biological markers in the environment. The potential parasites’ ability to serve as bio-indicators of pollution in marine ecosystems was the focus of the current study. Forty samples of the king soldier bream Argyrops spinifer, were collected from the Red Sea (Jeddah, Saudi Arabia) for this study, and they were examined for parasite infections. Only 25 fish samples included one naturally occurring nematode parasite, Hysterothylacium reliquens, which had three of its life-cycle stages (adults, L3, and L4 larvae). The levels of some metals (Fe, Cu, Cd, and Pb) were detected in the parasite stages and the tissues of the fish host tissues (liver, muscle, and intestine). These metals accumulated higher in non-infected fish tissues than in infected ones. The significant parasite capability for metal accumulation rather than fish tissues was validated by bioconcentration factors. Depending on the stage of a parasite’s life, different metals were used. Larval stages are more prone to gathering essential elements (Fe and Cu). Although adults have a greater tolerance to toxic metals (Cd and Pb). The various metal absorption mechanisms were referred to as the differences between parasite stages. This proved that fish nematodes might serve as helpful bioindicators for assessing the extent of heavy metal contamination of aquatic ecosystems.

Parasites either reduce or increase host vulnerability to fishing: a case study of a parasitic copepod and its salmonid host

Parasites generally increase host vulnerability to predators via host manipulation for trophic transmission and reduction of host activities. Predators also select prey depending on the parasite infection status. Despite such parasites' roles in prey-predator interactions in wild animals, how parasites affect human hunting probability and resource consumption remains unknown. We examined the effects of the ectoparasitic copepod Salmincola cf. markewitschi on fish vulnerability to angling. We found that infected fish were less vulnerable compared with non-infected fish when the fish body condition was low, which was probably due to reduced foraging activity. On the contrary, infected fish were more vulnerable when the host body condition was high, probably due to the compensation of parasites' negative effects. A Twitter analysis also suggested that people avoided eating fish with parasites and that anglers' satisfaction decreased when captured fish were parasitized. Thus, we should consider how animal hunting is affected by parasites not only for catchability but also for avoiding parasite infection sources in many local regions.

Transcriptomic response to ISAV infection in the gills, head kidney and spleen of resistant and susceptible Atlantic salmon

BackgroundInfectious Salmon Anaemia virus (ISAV) is an orthomyxovirus responsible for large losses in Atlantic salmon (Salmo salar) aquaculture. Current available treatments and vaccines are not fully effective, and therefore selective breeding to produce ISAV-resistant strains of Atlantic salmon is a high priority for the industry. Genomic selection and potentially genome editing can be applied to enhance the disease resistance of aquaculture stocks, and both approaches can benefit from increased knowledge on the genomic mechanisms of resistance to ISAV. To improve our understanding of the mechanisms underlying resistance to ISAV in Atlantic salmon we performed a transcriptomic study in ISAV-infected salmon with contrasting levels of resistance to this virus.ResultsThree different tissues (gills, head kidney and spleen) were collected on 12 resistant and 12 susceptible fish at three timepoints (pre-challenge, 7 and 14 days post challenge) and RNA sequenced. The transcriptomes of infected and non-infected fish and of resistant and susceptible fish were compared at each timepoint. The results show that the responses to ISAV are organ-specific; an important response to the infection was observed in the head kidney, with up-regulation of immune processes such as interferon and NLR pathways, while in gills and spleen the response was more moderate. In addition to immune related genes, our results suggest that other processes such as ubiquitination and ribosomal processing are important during early infection with ISAV. Moreover, the comparison between resistant and susceptible fish has also highlighted some interesting genes related to ubiquitination, intracellular transport and the inflammasome.ConclusionsAtlantic salmon infection by ISAV revealed an organ-specific response, implying differential function during the infection. An immune response was observed in the head kidney in these early timepoints, while gills and spleen showed modest responses in comparison. Comparison between resistance and susceptible samples have highlighted genes of interest for further studies, for instance those related to ubiquitination or the inflammasome.

Interacting Effects of Sea Louse (Lepeophtheirus salmonis) Infection and Formalin-Killed Aeromonas salmonicida on Atlantic Salmon Skin Transcriptome

Lepeophtheirus salmonis (sea lice) and bacterial co-infection threatens wild and farmed Atlantic salmon performance and welfare. In the present study, pre-adult L. salmonis-infected and non-infected salmon were intraperitoneally injected with either formalin-killed Aeromonas salmonicida bacterin (ASAL) or phosphate-buffered saline (PBS). Dorsal skin samples from each injection/infection group (PBS/no lice, PBS/lice, ASAL/no lice, and ASAL/lice) were collected at 24 h post-injection and used for transcriptome profiling using a 44K salmonid microarray platform. Microarray results showed no clear inflammation gene expression signatures and revealed extensive gene repression effects by pre-adult lice (2,189 down and 345 up-regulated probes) in the PBS-injected salmon (PBS/lice vs. PBS/no lice), which involved basic cellular (e.g., RNA and protein metabolism) processes. Lice repressive effects were not observed within the group of ASAL-injected salmon (ASAL/lice vs. ASAL/no lice); on the contrary, the observed skin transcriptome changes –albeit of lesser magnitude (82 up and 1 down-regulated probes)– suggested the activation in key immune and wound healing processes (e.g., neutrophil degranulation, keratinocyte differentiation). The molecular skin response to ASAL was more intense in the lice-infected (ASAL/lice vs. PBS/lice; 272 up and 11 down-regulated probes) than in the non-infected fish (ASAL/no lice vs. PBS/no lice; 27 up-regulated probes). Regardless of lice infection, the skin’s response to ASAL was characterized by the putative activation of both antibacterial and wound healing pathways. The transcriptomic changes prompted by ASAL+lice co-stimulation (ASAL/lice vs. PBS/no lice; 1878 up and 3120 down-regulated probes) confirmed partial mitigation of lice repressive effects on fundamental cellular processes and the activation of pathways involved in innate (e.g., neutrophil degranulation) and adaptive immunity (e.g., antibody formation), as well as endothelial cell migration. The qPCR analyses evidenced immune-relevant genes co-stimulated by ASAL and lice in an additive (e.g., mbl2b, bcl6) and synergistic (e.g., hampa, il4r) manner. These results provided insight on the physiological response of the skin of L. salmonis-infected salmon 24 h after ASAL stimulation, which revealed immunostimulatory properties by the bacterin with potential applications in anti-lice treatments for aquaculture. As a simulated co-infection model, the present study also serves as a source of candidate gene biomarkers for sea lice and bacterial co-infection.

Changes in the level of oxidative stress markers in Indian catfish (Wallago attu) infected with Isoparorchis hypselobagri

BackgroundHelminth infection and infestation in fishes are detrimental and have a major effect on fish health and fish production. Among various factors, parasitic infections are known to modulate antioxidant defences in fish. Similar to other aerobic animals, fish are also susceptible to the effect of reactive oxygen species and thus have well established intrinsic and efficient antioxidant defences. ‘Oxidative stress markers are an important indicator of the physiological state of the parasite and its host’. Indian catfish,Wallago attu is a freshwater fish that serves as the definitive host of the adult piscine trematode Isoparorchis hypselobagri. Our two years prevalence data signifies the intensity of the problem revealing a minimum of 5.5% and a maximum of 54% I. hypselobagri infection in Indian catfish W. attu (unpublished data). The present study aimed to achieve baseline data attributed to changes in some oxidative markers due to parasitic infection.ResultsDuring the present study, the level of enzyme activities of Catalase (CAT), Glutathione reductase (GR), Glutathione-S-transferase (GST), Glutathione peroxidase (GPx), Superoxide dismutase (SOD) and lipid peroxidation was investigated to explore the pathogenic impact on the fish host. The level of these oxidative stress markers was monitored in the swim bladder, liver, intestine and muscle of the host. We also recorded the enzyme activities in the parasite I. hypselobagri. Analysis of data revealed an elevation in GST, SOD, GR, GPx and CAT activity in the infected host tissue as compared to the non-infected fish. Further, we observed presence of GST, SOD, GR and GPx enzymes in the parasite I. hypselobagri while CAT did not show any enzyme activity.ConclusionsIncreased level of enzyme activity in liver, muscle and intestine of infected host has been recorded which indicates increased oxidative stress in the host due to parasitic invasion. The presence of antioxidant enzymes in the parasites suggests an active antioxidant defence system to avoid immune responses to long term survival and establishment in their host.

Molecular Epidemiology of Anisakis spp. in Wedge Sole, Dicologlossa cuneata (Moreau, 1881), from Fishmarkets in Granada (Southern Spain), Caught in Two Adjacent NE and CE Atlantic Areas.

The presence of third stage larvae (L3) of Anisakis spp. in wedge sole, Dicologlossa cuneata (Moreau, 1881), purchased in fishmarkets in the city of Granada (Andalusia, southern Spain) was assessed. The wedge sole were caught in two FAO zones: area 27.IXa NE Atlantic (SW Spain coast) and area 34.1.11 CE Atlantic (NW Morocco coast). Only Anisakis larvae, type I, were detected in the largest fish (>20 cm) from the CE Atlantic. These were molecularly identified as A. simplex s.s. The prevalence (P) of Anisakis in this area was 12.5% and the mean intensity (MI) was 1. The presence of Hysterothylacium spp. larvae was also detected in the fish from both areas, with the prevalence being approximately double in the CE Atlantic area (12.5 vs. 5.7). A comparison between the Anisakis-infected and non-infected fish from this area showed that the former were significantly longer than the latter (p < 0.01). These results show that Anisakis parasitization of wedge sole sold in the markets of the city of Granada is of low prevalence and intensity (P = 4.5, MI = 1), especially in those from area 27.IXa (P = 0), indicating that the risk of human infection is low, particularly as this fish is traditionally prepared by deep-frying in oil in Andalusia (southern Spain).

Hazardous pollutants in the environment: Fish host-parasite interactions and bioaccumulation of polychlorinated biphenyls

The present paper reports on the interrelationships of fish, parasites and the bioaccumulation of hazardous organic compounds in the Zemplínska Šírava water reservoir in eastern Slovakia, which is heavily polluted with polychlorinated biphenyls (PCBs). The concentrations of these contaminants were measured in various fish matrices (dorsal and abdominal muscle tissues, hepatopancreas, intestine wall and adipose tissue) of the freshwater bream, Abramis brama (Cyprinidae), and in its intestinal parasite Caryophyllaeus laticeps (Cestoda), which was used for the first time as a model for a PCB bioaccumulation study. Regarding the fish, the highest concentrations of PCBs were found in the intestine, followed by hepatopancreas and muscle tissues. The amounts of PCBs were higher in abdominal muscles than in their dorsal parts. Concentrations of ∑PCBs above the limits set by European regulations were detected in both muscle parts in the fish, confirming the persistent unfavorable conditions in this locality and high risk for biota and humans. Based on bioconcentration factor values (BCFs), PCBs reached much higher levels in cestodes compared to bream matrices. Some significant differences in PCB amounts between infected and uninfected bream were determined. Fulton's condition factor (CF) significantly differed in infected and non-infected fish (p ˂ 0.05), with CF values surprisingly lower in fish free of parasites compared to parasitized fish, which suggests a “mutualistic” relationship between the parasite and its host.

Co-infection with Trichodina (Ciliophora: Trichodinidae) and Aeromonas caviae synergistically changes the hematology and histopathology of Asian seabass Lates calcarifer

Abstract. Sufardin, Sriwulan, Anshary H. 2021. Co-infection with Trichodina (Ciliophora: Trichodinidae) and Aeromonas caviae synergistically changes the hematology and histopathology of Asian seabass Lates calcarifer. Biodiversitas 22: 3371-3382. Consequential interaction contributed by parasitic and bacterial infections in fish has received little attention and impact of co-infection is mostly undescribed. This study identifies and describes notable damage arising from the co-infection of Trichodina and Aeromonas caviae infecting the seabass Lates calcarifer. A completely randomized experiment was performed with 4 infection treatments (healthy fish; fish naturally infected with Trichodina sp.; healthy fish injected with A. caviae; fish naturally infected with Trichodina sp. and injected with A. caviae) and 3 replicates. Fish were obtained from the Takalar Brackish Aquaculture Institute, South Sulawesi, Indonesia. The data were statistically tested using linear regression analysis. The results showed bacterial pathogenicity, lymphocyte percentage, and histopathological quantification were statistically different (P &lt; 0.05). Meanwhile, the number of erythrocytes and leukocytes, the percentages of monocytes and neutrophils were not significantly different (P &gt; 0.05) between treatments. The non-infected fish showed no cell inflammation and necrosis, very little hemorrhage (liver and gills), negligible hemorrhage and melano-macrophages (kidney). Kidneys and liver were the most damaged organs of co-infected fish, with a large number of inflammatory cells, hemorrhages, vacuoles, melano-macrophages, scar tissue, inflammation and necrosis. Infection with Trichodina sp. presented less damage than the co-infection of A. caviae and Trichodina sp. In conclusion, single infection showed a mild pathological impact, meanwhile, the co-infection of Trichodina sp and A. caviae contribute significantly to fish’s health.

Alteration of the Immune Response and the Microbiota of the Skin during a Natural Infection by Vibrio harveyi in European Seabass (Dicentrarchus labrax).

Disease outbreaks continue to represent one of the main bottlenecks for the sustainable development of the aquaculture industry. In marine aquaculture, many species from the Vibrio genus are serious opportunistic pathogens responsible for significant losses to producers. In this study, the effects on the immune response and the skin microbiota of European sea bass (Dicentrarchus labrax) were studied after a natural disease outbreak caused by V. harveyi. Data obtained from infected and non-infected fish were studied and compared. Regarding the local immune response (skin mucus) a decrease in the protease activity was observed in infected fish. Meanwhile, at a systemic level, a decrease in protease and lysozyme activity was reported while peroxidase activity showed a significant increase in serum from infected fish. A clear dysbiosis was observed in the skin mucus microbiota of infected fish in comparison with non-infected fish. Moreover, V. harveyi, was identified as a biomarker for the infected group and Rubritalea for healthy fish. This study highlights the importance of characterizing the mucosal surfaces and microbial composition of the skin mucus (as a non-invasive technique) to detect potential disease outbreaks in fish farms.

PRV-1 Infected Macrophages in Melanized Focal Changes in White Muscle of Atlantic Salmon (Salmo salar) Correlates With a Pro-Inflammatory Environment.

Melanized focal changes in white skeletal muscle of farmed Atlantic salmon, “black spots”, is a quality problem affecting on average 20% of slaughtered fish. The spots appear initially as “red spots” characterized by hemorrhages and acute inflammation and progress into black spots characterized by chronic inflammation and abundant pigmented cells. Piscine orthoreovirus 1 (PRV-1) was previously found to be associated with macrophages and melano-macrophages in red and black spots. Here we have addressed the inflammatory microenvironment of red and black spots by studying the polarization status of the macrophages and cell mediated immune responses in spots, in both PRV-1 infected and non-infected fish. Samples that had been collected at regular intervals through the seawater production phase in a commercial farm were analyzed by multiplex fluorescent in situ hybridization (FISH) and RT-qPCR methods. Detection of abundant inducible nitric oxide synthase (iNOS2) expressing M1-polarized macrophages in red spots demonstrated a pro-inflammatory microenvironment. There was an almost perfect co-localization with the iNOS2 expression and PRV-1 infection. Black spots, on the other side, had few iNOS2 expressing cells, but a relatively high number of arginase-2 expressing anti-inflammatory M2-polarized macrophages containing melanin. The numerous M2-polarized melano-macrophages in black spots indicate an ongoing healing phase. Co-localization of PRV-1 and cells expressing CD8+ and MHC-I suggests a targeted immune response taking place in the spots. Altogether, this study indicates that PRV-1 induces a pro-inflammatory environment that is important for the pathogenesis of the spots. We do not have indication that infection of PRV-1 is the initial causative agent of this condition.