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Abstract:The monosex Nile tilapia, Oreochromis niloticus L., was exposed to subacute concentration (1.46 μ g/l) of a pyrethroid insecticide, deltamethrin for 28 consecutive days. Behavioural, clinical, haematological, serum biochemical and histopathological consequences were assayed at a regular interval of 7 days. The abnormal behavioural responses and toxic symptoms were described. Exposure to deltamethrin not only significantly decreased lymphocyte and basophile percentages, total leucocytic and total erythrocytic counts, haemoglobin percentage and packed cell volume value, but also caused serious effects in the form of hypoproteinaemia, hypoalbuminaemia, hypercholesterolaemia, hyperglycaemia and significantly increased serum aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase activities. Moreover, the histopathological results indicated that the haemobiotic organs were affected by deltamethrin, primarily liver and gills. Our data suggest that subacute exposure to deltamethrin exerts a serious metabolic distress on the fish corresponding to the exposure period. In addition, the assayed parameters and histopathological findings can be as good biomarkers of pyrethroid ecosystem pollution.

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The current study was conducted to analyze the potential benefits of dietary supplementation of synbiotics on water quality, microbial population, growth performance, proximate analysis, non-specific immune response, oxidative status, cytokine gene expression and susceptibility to experimental infection by V. harveyi in L. vannamei juveniles. A total number of 9000 white shrimp (L. vannamei) in post-larval stage (PL 12) with mean initial weight (0.5 ± 0.02 g/ piece) obtained from Barket-Ghalioun fish farm, Kafr El-Sheikh Governorate were used. After the accommodation period, shrimps were randomly distributed into three experimental groups of 3000 post-larvae / each group allotted into three replicates of 1000 post-larvae / each replicate (experimental tanks). Salinity of all tanks was adjusted from 25‰-35‰. The first experimental group (G-I) was kept as control (feed on basal diets with continous change of water and aeration). The second experimental group (G-II) (synbiotic culture treatment) was fed on 50 % basal diets + fermented rice bran with Bacillus subtilis without change of water and high aeration). However, the last experimental group (G-III) was fed on fermented rice bran with Bacillus subtilis (without basal diets and change of water and high aeration). The synbiotic containing probiotic B. subtilis in shrimp diets could significantly improve the growth by enhancing the immune response, antioxidative activity, water quality and biofloc composition. The increase of nonspecific responses of the shrimp fed the synbiotic supplemented diets may suggest that the antioxidant defense system and innate immune system could work synergistically to improve the physiological performance of the shrimp leading to higher resistance against bacterial challenge. This system can play a key role in developing a sustainable aquaculture via better water quality, maintenance decrease in feed requirements and higher production to achieve more profit in shrimp farming. Consequently, the synbiotic could be practically used as a viable alternative dietary supplement.

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A trial was carried out to assess the potential use of chemically synthesized silver nanoparticles (AgNPs) with two concentrations (5 and 10 µg/L) as an antibacterial agent in Oreochromis niloticus and Sparus auratus against Streptococcus agalactiae and Vibrio alginolyticus respectively. All AgNPs were with a mean of 26 nm in diameter.The particles were negatively charged (−30.7 ± 0.45 mV). In different ways, the in vitro AgNP antibacterial activity was investigated against S. agalactiae and V. alginolyticus in different ways showing clear inhibition zones of the two AgNP concentrations dose-dependent manner. In vitro measurement of extracellular proteins of pathogenic S. agalactiae and V. algenolyticus against AgNPs and the ultrastructural interaction between AgNPs and these bacterial pathogens using transmission electron microscopy (TEM) revealed AgNPs have good antibacterial properties. O. niloticus and S. auratus were exposed to AgNPs for 28 days. Some groups were challenged with S. agalactiae and V. alginolyticus respectively. Haematological, biochemical and immunological parameters and phagocytic activity, phagocytic index, respiratory burst activity of neutrophils and serum lysozyme activity were estimated in addition to the concentration of minerals. Histopathological examinations of all fish groups were explored. From the investigation above, we concluded that AgNPs have significant deleterious effects on O. niloticus exposed to 5 and 10 µg/L of AgNPs, appearing a significant decrease in leukocytes, red blood corpuscles (RBCs) count and haemoglobin concentration the fish on day 28 of the trial, with more deleterious effect with challenging fish by S. agalactiae and V. algenolyticus. In addition, AgNPs caused a substantial increase in liver enzymes with a reduction in total protein, albumin and globulin in the fish and considerably decreased the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Additionally, there was a significant decrease in sodium (Na) and potassium (K) content, nitroblue tetrazolium (NBT) and lysozyme activity (LYZ) in all groups of O. niloticus and S. auratus. In addition, lower survival rates disturb histopathological findings; meanwhile, S. auratus exposed to 5 and 10 µg/L of AgNPs showed antibacterial potency and immunostimulatory effects, which appeared in their higher survival rates and induced immune parameters and histopathological findings. In low concentration (5 µg/ml of AgNPs), AgNPs were less cytotoxic, especially in S. auratus, | 6219 MOUSTAFA eT Al.

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Isolation and identification of S. agalactiae from cultured sea bream by different microbiological methods, mortality rate, clinical signs, and postmortem lesions in sea bream in naturally and experimentally inoculated with a field sample of S. agalactiae. The aquarium trial was carried out with sea bream (Sparus auratus) in private fish farm at Borg El-Arab, Alexandria governorate Egypt. At total 50 of sea bream (Sparus auratus) was used during the study. The study lasted 10 weeks, starting with 50 ± 5 gram /fish. Prior to the start of the trial, the fish were fed with a commercial diet (45 percent CP, crude protein). Water quality parameters were monitored during fish acclimatization and throughout the trial. Water temperature, pH and dissolved oxygen remained within acceptable ranges for marine production during the trial. Our results concluded that, Streptococcus spp. (specifically S. agalactiae) is very pathogenic as they can affect sea bream which become a perfect host for Streptococcus infection. In addition, water quality parameter plays an important role in sea bream farming. In more specific, an optimum water quality parameter should be maintained to prevent “stress’’ in fish that can lead to outbreaks of disease. It can be concluded that the medicinal plant can help in prevention and control of bacterial infection in cultured fish, and because of their high resistance, to most antibiotics utilization in the prophylaxis or treatment of S. agalactiae infection should be avoided. The farmers must be used such approach to applied in the protocol of prevention of such infection in stead of chemotherapy.