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This study aimed to investigate the potential causes of the summer mortality syndrome affecting the earthen pond cultured Nile tilapia, Oreochromis niloticus in some Egyptian farms. A total of 100 moribund O. niloticus showing non-specific clinical signs of septicemia and mortality (30- 65%) were collected from five farms at Tolombat 7, Kafr El-Sheikh, Egypt, during June 2019. All the fish farms share the same water source and perform some bad management practices. Inadequate water quality measures were noticed in all the investigated farms. Molecular detection of tilapia lake virus (TiLV) using PCR confirmed the non-existence of the TiLV in all examined specimens. A total of 19 pathogenic bacterial isolates were obtained from moribund O. niloticus: Streptococcus agalactiae (14), Aeromonas hydrophila (3), and Vibrio cholera (2). The predominance of Streptococcus agalactiae infections points to its intense involvement in such mortalities. S. agalactiae was confirmed by 16s rRNA gene sequencing and phylogenetic analysis. The PCR detection of virulence genes showed existence of Hyl, cylE, scpB and camp genes in all S. agalactiae strains. Isolates of S. agalactiae showed variable susceptibility to the tested antibiotics with high resistance against ampicillin, amoxicillin and gentamycin. Infections were associated with several pathological alterations in naturally infected fish. The pathogenicity of S. agalactiae was confirmed in O. niloticus (90 % cumulative mortality). The data in the present study proved that the tilapia summer mortality syndrome is multifactorial. Thus, good managemental practices and water quality measures are recommended to minimize fish mortality. [ABSTRACT FROM AUTHOR]

In the present research, samples of Solea solea (Linnaeus) were randomly collected from Qarun Lake, Egypt, for routine parasitological, microbiological, and histopathological examinations. The parasitological analysis revealed that 6.70% of the examined samples were infested with the cymothoid isopod Livoneca redmanii. This parasite was isolated as females from the branchial cavity and as juveniles from the skin of the affected fish. Bacteriological examination identified Aeromonas species isolated from the gills, kidney, and liver of S. solea. Morphological, biochemical characterization, and molecular analysis confirmed the isolate as Aeromonas veronii. The isolated strain produced brown colonies on tryptic soy agar (TSA) supplemented with 3% NaCl. The drug susceptibility test indicated that Aeromonas veronii was sensitive to gentamicin, erythromycin, and trimethoprim/sulfamethoxazole, while exhibiting resistance to nalidixic acid, ampicillin, oxolinic acid, and tetracycline. Histopathological examination of the affected gills revealed edema, leukocyte infiltration, and hyperplasia of mucous cells. The infested skin exhibited sloughing and detachment of the lining epithelium, along with edema and degeneration of the muscles at the site of isopod attachment. [ABSTRACT FROM AUTHOR]

The prospective effect of beetroot extract (Beta vulgaris L.) to resist the toxic effect of lead (Pb) and enhance the immune status and antioxidant enzyme of the Nile tilapia (Oreochromis niloticus) was studied. Fish specimens were divided into 4 groups: C (control group), Pb (group subjected to lead), T1, and T2 (groups injected intraperitoneal with 100 and 150mg/ kg of beetroot extract 2 weeks before being subjected to Pb, respectively). The effects were addressed on the humoral immune parameters, (antiproteases, lysozyme total protein, and globulin) and antioxidant enzymes [Glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) activities], as well as some biochemical parameters. Pb accumulation was studied in gills, liver, and muscle tissues. The results revealed a significant enhancement in some immune parameters viz. a lysozyme and total protein in T1 groups compared to other groups, especially with the Pb group which showed the lowest significant values (P< 0.05). The groups injected with beetroot extract showed the lowest significant values (P< 0.05) of Pb accumulation in tissues compared to Pb group. While, T1 group recorded a significant increase (P< 0.05) in hepatic protein content, GST, SOD, CAT, and POX, respectively, compared to the Pb group. Moreover, Pb group showed a significant decrease compared to the control group. Most of the biochemical parameters, including glucose, cholesterol, AST, and uric acid recorded the highest values in Pb group compared to the other groups, but without significant difference. The albumin value of T1 group showed the highest significant values compared to other groups. To conclude, the injection of the Nile tilapia with 100mg/ kg of beetroot extract may contribute to protecting fish from the harmful effects of lead by enhancing the immune system and antioxidant enzymes, and improving the general fish health. [ABSTRACT FROM AUTHOR]

Immune and antioxidant-related genes reflect the immune response of fish against different ecosystem circumstances around it. The present study is concerned with the effect of industrial and sewage effluents in some water drainages on immune and antioxidant-related genes of the Nile tilapia (Oreochromisniloticus). Fish specimens were collected from three different places; the first group was collected from El-Rayah El-Towfeky stream, Tokh, which receives loads of sewage and agricultural effluents (site A). The second group was collected from El-Sharkawia stream, Shoubra El-Khama, which receives industrial wastes (site B). The third group (site C) was collected from a fish farm in Al-Fayoum City (supplied with clean water) and was considered the control group. The expression of some immune-related genes (inf1a, csf1r, igmh, and il1b) and antioxidant genes (sod, cat, and gr) was determined in the liver and head kidney of the fish. The results revealed that the highest expression of most immune-related genes in the liver and kidney of the Nile tilapia was recorded in fish collected from site B. Regarding antioxidant genes, the highest catalase (cat) expression was recorded in the liver and kidney of the Nile tilapia maintained in sites A and B, respectively. Again fish from site B showed the highest superoxide dismutase (sod) and glutathione reductase (gr) expression in the kidney compared to the fish from other sites (although the differences were not statistically significant). The only highest expression found in fish in site C was reported in superoxide dismutase (sod) and glutathione reductase (gr) expression in the liver. Interestingly, the results revealed the positive influence of industrial pollution in some drainages on the Nile tilapia health. [ABSTRACT FROM AUTHOR]

Fish in the Suez Canal region, a highly diverse ecosystem where many different species of fish interact, are at risk of mixed infections caused by multiple pathogens, including parasites and bacteria. This study highlighted the naturally occurring process of parasitic bacterial co-infections, specifically involving the parasite Livoneca redmanii and the bacterium Pseudomonas aeruginosa in the fish Pomadasys stridens. A total of 80 P. stridens fish were randomly collected from the Suez Canal coasts in Egypt over a period from September to November 2022. The fish samples were tested using standard parasitological and microbiological procedures to identify the presence of L. redmanii and P. aeruginosa. To definitively identify the parasite Livoneca redmanii, its mitochondrial Cytochrome Oxidase subunit I gene was sequenced, and the sequence was deposited in GenBank under the accession number OR051043. Furthermore, the presence of P. aeruginosa was isolated from the infested fish samples with isopods, and its identification was confirmed by molecular techniques. The prevalence of L. redmanii was 48.75%, while P. aeruginosa in the infested P. stridens fish with isopods was 69.23%. These findings shed light on the complex dynamics of parasitic bacterial co-infections among fish species in the region. [ABSTRACT FROM AUTHOR]

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