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abd elaziz, M., M. Ali, S. yassin, and A. S. raafat and rashad, "Study on the effects of some probiotics on the performance, clinicopathological and histopathological changes of Oreochromis niloticus", Veterinary Medical Journal, vol. 55, no.3 , pp. 879-897, 2007. Abstract

The presen study was carried out to evaluate the use of some probiotics on the growth rate of tilapia fishes and to determine its effect on some hematological and histopathological parameters. Two different commercial probiotics which includes biogen and moreyeast were evaluated for 8weeks. In the experiment, fifty Oreochromis niloticus fishes were classified to 3 groups,Group (1): consisted of 20 fishes which fed diet supplemented by biogen at a dose of 2 kg/ton diet. Group (2): consisted of 20 fishes which fed diet supplemented by moreyeast at a dose of 5 kg/ton diet and Group (3): was control group which consisted of 10 fishes fed diet without probiotics. At the end of the experimental period both biogen and moreyeast administrated groups revealed a significant increase in the body weight gain (W.G.). The results showed significant increase in the values of RBCs, PCV and Hb throughout the experimental period except group 1 (received biogen) at the 6th week of experiment comparing to control group. Fish group received moreyeast (Group 2) had the pronounced effect than group 1. Assessment of leukogram revealed significant leukocytosis allover the experimental period in different groups except during the 2nd week in group 2 (received moreyeast) and at the 6th week in both probiotic administrated groups comparing to control group. Fish group received biogen had pronounced effect comparing to moreyeast administrated group. differential leukocytic picture was recorded. Histopathological examination revealed The biogen and moreyeast administerd groups showed marked activation of the melano-macrophage centers which is a component of reticuloendothelial system and hence part of the defensive system of fish indicating immunoenhancment. the study concluded that: The examined probiotic were safe for the Oreochromis niloticus fish.

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Abd El Aziz, M. A., G. M. Kamel, and M. A. M, "Seasonal study, Histopathological and Treatment Trials on Saproligniosis in some Fish Farms", 1st Scientific Conference of Faculty of Veterinary Medicine . , , Moshtohor- Benha University- Egypt, 2004.
Ali, K. M., E. A. Hassan, M. M. Abuowarda, M. A. Mahmoud, and F. A. Torad, "Bilateral panophthalmia as a late sequel of leishmaniasis in dogs", Pakistan Veterinary Journal, vol. 41, issue 1, pp. 13-18, 2021.
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Ehab, E. E., N. M. Ezz-Eldien, and A. M. Mahmoud, "Nodular cap disease in the red oranda and red cap breeds of gold fish( Crassius auratus) associated with dermocystidium species", Bulletin of the European association of fish pathologists (EAFP), vol. 22, no.1, pp. 7-14, 2002.
Eissa, A. E., M. Abdelsalam, M. A. Mahmoud, N. A. Younis, A. A. A. Mhara, and R. E. A. Zlit, "Cutaneous fibropapilloma in Egyptian-farmed gilthead seabream (Sparus aurata; Linnaeus, 1758)", Aquaculture International , vol. 28, pp. 2081–2091, 2020.
Elgohary, I., J. A. I. Elatief, N. G. Fadel, A. E. Eissa, and M. A. Mahmoud, "Pathological, bacteriological and seasonal prevalence of Aeromonas hydrophila, vibrio vulnificus, Proteus vulgaris and Pseudomonas aeruginosa; infecting Oreochromis niloticus in some Egyptian fish farms", Egyptian Journal of Aquatic Biology & Fisheries, vol. 24, issue 5, pp. 467 – 482, 2020.
Elgohary, I., A. E. Eissa, N. G. Fadel, J. I. A. Elatief, and M. A. Mahmoud, "Bacteriological, molecular, and pathological studies on the Gram-positive bacteria Aerococcus viridans and Enterococcus faecalis and their effects on Oreochromis niloticus in Egyptian fish farms", Aquaculture Research, vol. 52, issue 5, pp. 2220-2232, 2021.
Elsayed, E. E., N. E. E. Dien, and M. A. Mahmoud, "Ichthyophthiriasis: Various Fish Susceptibility or Presence of More than one Strain of the Parasite", Nature and Science, vol. 4 (3), pp. 5-13., 2006. Abstract

White spot disease is one of the devastating protozoal infections affecting freshwater fish. Commonly known as “Ich”, the Ichthyophthiriasis can infect almost all freshwater fish causing devastating losses in susceptible fish. In the present study, an outbreak of Ichthyophthiriasis erupted in one of the holding tanks of two ornamental fish species, Siamese shark (Pangasius sutchi) and goldfish (Carassius auratus var.bicausatus). Initial observation of the outbreak showed that only Pangasius sutchi was affected by typical white spots associated with mortalities. However, Carassius auratus, a known susceptible species for Ichthyophthirius multifiliis (Ich) in the same aquarium showed only mild erythema that disappeared during the course of infection with no mortalities. To confirm the previous observation, an experimental designs was performed in which infection with Ichthyophthirius was induced in Pangasius sutchi species alone. Cohabitation was performed between the Ich-induced Pangasius sutchi and Carassius auratus. Three days after the induction, Pangasius sutchi started showing the typical clinical signs. Mortalities associated with severe infection were recorded in Pangasius sutchi by 7th day after infection. Associated Carassius auratus showed only mild erythema that disappeared by the end of experiment. Histopathological examination of skin from both species in natural and experimental infection was performed to evaluate the severity of infection on the tissue level. Substantial numbers of typical large size trophonts surrounded by layers of fibrous tissue, melanophores and hemorrhages were detected in dermal and epidermal layers. Underlying myodegeneration was also associated the skin lesions in Pangasius sutchi. In contrary, pathological changes in the skin of Carassius auratus were mild and few numbers of immature trophonts were noticed in the epidermal layers. Possible reasons for such infection discrepancies between the two susceptible species are discussed.

Elsayed, E., M. A. Mahmoud, and N. E. ElDien, " Ichthiophthiriasis: Atypical outbreak In Two Suscetible Ornamental Fish Species In Egypt Under The Same Environmental Conditions ", 29th ANNUAL EASTERN FISH HEALTH WORKSHOP, U.S.A., March 22-26, 2004.
Ezz El -Dien, N. M., and A. M. Mahmoud, "Neorhadinorhynchus aspinosum (Acanthocephala: Echinorhynchidae) as a new record among Red Sea fish in Egypt with histopathological studies", J. Egypt. Vet. Med. Ass., vol. 62, no.5, pp. 233-243, 2002. Abstract

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Girgis, S. M., and M. A. Mahmoud, "PROTECTIVE EFFECT OF VITAMIN C AGAINST GENOTOXICITY AND PATHOLOGICAL CHANGES CAUSED BY SOME HEAVY METALS IN OREOCHROMIS NILOTICUS", J. Egyp. Vet. Med. Assoc., vol. 69, no. 4 , pp. 263-285, 2009. Abstract

The present study was carried out to evaluate the protective effect of vitamin C (vit. C) against genotoxic and pathological changes induced by arsenic (As), zinc (Zn) and their mixture in Oreochromis niloticus. Fish of almost the same weight and size were divided into 13 groups (6 groups were exposed for 3 weeks and the other 6 groups were exposed to the same treatment but for 6 weeks) beside the control group (10 fish/group). The 1st group was served as control, the 2nd group was exposed to 2.9 mg/L of As in the form of sodium salt in water for 3 weeks. The 3rd group was exposed to As plus vit. C (10mg/kg diet equivalent to 30 gm/kg bw). The 4th group was exposed to 3mg/L of Zn in the form of zinc sulfate. The 5th group was exposed to Zn and vit. C. The 6th group was exposed to both As and Zn. The 7th group was exposed to As, Zn and vit. C. Five samples from each group were sacrificed at 3rd and 6th week of the experiment, respectively, and subjected to cytogenetical and histopathological examination. Gross lesions were recorded along the time of exposure. The results revealed genotoxicity in O.niloticus exposed to As and/ or Zn for 6 weeks. There was a significant increase of micronuclei (Mn) in all As and/or Zn exposed fish groups, compared to the control, while the treatment with vit. C significantly decreased the frequency of Mn in all As and/or Zn exposed groups. The histopathological examination revealed severe pathological lesions in gills, skin, muscles and liver in case of As toxicity, while in case of Zn toxicity, the changes were common in liver and spleen and other internal organs. In both cases, vit. C protects the tissue against such toxicity. In conclusion, this study proved that As and Zn had genotoxic effect on O.niloticus and that appear in the significant increase in the frequency of Mn induced by these metals, whereas the treatment with vit. C reduced that genotoxic effect especially with long term treatment. In addition, the histopathological lesions were recorded in As and/or Zn exposed groups for 3 w, whereas the alterations were more clear in 6 w exposed groups. Minor or no lesions were noticed in all vit. C treated groups.

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Hassan, M. A., A. M. Mahmoud, and M. M. Moustafa, "Epizootiological and pathological studies of trypanorhynchiasis among some marine fishes of the Arabian Gulf", J. Egypt. Vet. Med. Ass., vol. 61, no.3, pp. 9-24, 2001.
Hassan, M. A., A. M. Hussien, and A. M. Mahmoud, "Studies on Dermocystidiosis (Yellow Muscle Disease) among Some Marine Fishes of Arabian Gulf and Red Sea Coast, Jeddah, Saudi Arabia", Middle-East Journal of Scientific Research, vol. 22 , issue 4, pp. 478-487, 2014.
Hassan, M. A., E. A. Noureldin, M. A. Mahmoud, and N. A. Fita, "Molecular identification and epizootiology of Aeromonas veronii infection among farmed Oreochromis niloticus in Eastern Province, KSA", Egyptian Journal of Aquatic Research, vol. 43, pp. 161-167, 2017.
Hassan., M. A., W. S. Soliman., M. A. Mahmoud., and M. I. Sami Shabeeb Al-Shabeeb, "Prevalence of Bacterial Infections among Cage-Cultured Marine Fishes at the Eastern Province of Saudi Arabia.", Research Journal of Pharmaceutical, Biological and Chemical Sciences , vol. 6, issue 4, pp. 1112-1126, 2015.
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Ibrahim, M. M., A. I. Shaaban, and A. M. Mahmoud, "Eels vibriosis in Lake Brolos (Egypt)", J. Egypt. Vet. Med. Ass., vol. 61, no.2, pp. 133-142, 2001.
Ibrahim, M. M., and A. M. Mahmoud, "Histopathological observations on oral skin papilloma of cultured O. niloticus at the eastern province of Saudi Arabia", Beni-Suef Vet. Med. J., vol. 11, no.2, pp. 765-771, 2001.
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Karima, M. F., Z. M. Malak, M. A. Mahmoud, and S. M. Sohair, "Genetical studies on melanomas in xiphpphorus fish", Arab J. Biotech,, vol. vol. 4, no.2, pp. 217-228, 2001.
Karima, F. M., K. B. K. Wagdy, and A. M. Mahmoud, "Assessment of toxicity and clastogenicity of sterigmatocystin in Egyptian Nile tilapia", African Journal of Biotechnology , vol. 5 (12), pp. 1180-1189., 2006. Abstract

The increasing presence of genotoxic pollutants in the aquatic environment has led to the development of quick monitoring methods. Sterigmatocystin (Stg) is closely related to mycotoxins and has the carcinogenic potency in the experimental animal models. The exposure to genotoxic agents will give rise to alterations of DNA structure that can lead to abnormal changes of DNA fingerprints. Therefore, we have applied the random amplified polymorphism DNA (RAPD) method to evaluate the genotoxic effects of Stg and to determine if the Egyptian montmorillonite (EM) has a protective effect against Stg. The experiment was conducted in vivo to evaluate the ability of EM at a level 0.5 mg/kg body weight (bw) to prevent the toxicity and genotoxicity induced by Stg in the Nile tilapia fish. Fishes were orally administrated with EM in corn oil with or without Stg (1.6 µg/kg bw) twice a week for 4 weeks. Blood and tissue samples were collected at the end of the treatment. The results revealed that Stg had genotoxic and toxicopathological effects in Oreochromis niloticus fish. The genotoxic effects were indicated by appearance of some changes in polymorphism band patterns including lost of stable bands or occurrence of new bands. There also exists a distinct distance between the band patterns of exposed fish and protected or control fish samples. The effects on the tissues were manifested by different histopathological lesions in different organs including hyperplastic proliferation of branchial epithelium, necrobiotic changes in hepatic tissue and destruction of components of the spleen. These responses were virtually abolished or markedly decreased when fishes were exposed to EM combined with Stg. It could be conclude that addition of EM resulted in the inhibition of the toxicity and clastogenicity of Stg.

Karima, M. F., H. M. Aziza, R. A. Hasnaa, and M. A. Mahmoud, "Inhibition of cadmium- induced genotoxicity and histopathological changes in Nile tilapia fish by Egyptian and Tunisian montmorillonite clay", Ecotoxicology and Environmental Safety, vol. 119, issue 2015, pp. 140- 147, 2015.
Khalil, W. - K. B., M. A. Mahmoud, M. M. Zahran, and K. F. Mahrous, "A sub-acute study of metronidazole toxicity assessed in Egyptian Tilapia zillii.", Journal of applied toxicology , vol. 27, pp. 380- 390, 2007. Abstract

Metronidazole (MTZ), an antiparasitic and antibacterial compound, is one of the world’s most widely used drugs. Despite being considered as a rodent mutagen and a carcinogen, it is still widely used in humans for the treatment of infections with anaerobic organisms. Therefore, the main objective of the current study was to evaluate the in vivo toxicity of MTZ using the micronucleus (MN) assay and random amplified polymorphism DNA (RAPD-PCR) analysis as well as histopathological examination in Tilapia zillii. Moreover, the protective effect of vitamin C (VitC) against toxicity of MTZ was investigated in the present study. Fish were treated with three doses of MTZ (5, 10 and 20 mg/ l) alone or in combination with VitC (200 mg/ kg food) at several time intervals (2 days, 7 days and 14 days). The results of the present study showed a significant effect of MTZ on micronucleus formation and changes in polymorphic band patterns as well as induction of different histopathological alterations in Tilapia zillii. The effects of the drug were reduced when fish were exposed to a combination of MTZ and VitC.

M
Mahdy, O. A., M. A. Mahmoud, and M. Abdelsalam, "Morphological characterization and histopathological alterations of homologs Heterophyid metacercarial coinfection in farmed mullets and experimental infected pigeons", Aquaculture International , vol. 28, pp. 2491–2504, 2020.
Mahmoud, A. M., A. E. R. H. Abeer, and A. - A. A. Nashwa, " Effect Of Confinement Stress On Behaviour, Performance, Clinicopathological And Histopathological Alterations Of Nile Tilapia Challenged With Aeromonas hydrophila With Regard To The Blue Light As Stress Inhibitor ", Veterinary Medical Journal, vol. , 55, no.3 , pp. 687-717, 2007. Abstract

The present study was carried out to assess the effects of blue light as antistressor and its effect on susceptibility of Nile tilapia (Oreochromis niloticus) to Aeromonas hydrophila (A. hydrophila) infection. A total number of (120) O. niloticus was divided into 3 experimental groups (40 fish / group). Group 1 (G1), was exposed to normal day light and considered as control group. Group 2 (G2), was exposed to blue light. Group 3 (G3), was exposed to white light (fluorescent illumination). After 15 days of light exposure, fish in groups 2 and 3 were confined into small area and then challenged with A. hydrophila infection. The obtained data revealed that during exposure to blue light, the fish of (G2) recorded significant lower proportion in behavioural parameters including factors of fright behaviour "creeping, oblique plan position and air-gulping" than those of﴾G3﴿. On the other hand, (G2) showed lower behaviour alterations for fright behaviour during confinement and infection than those of﴾G3﴿. Contrarily, it also had significantly higher proportions of aggressive behaviour during exposure to light, confinement and infection than﴾ G3﴿. SO blue light improved behaviour and fish become more comfortable in (G2) than (G3). Moreover, fish of (G2) showed higher significant growth performance during exposure to blue light and little reduction in growth performance during exposure to both confinement and infection than those of (G3). The clinicopathological studies revealed significant increase in the stress response indicators after exposure to confinement stress in (G.3). Marked elevation in the serum cortisol, glucose levels and significant leukocytosis associated with heterophilia and lymphopenia was observed in group 3 (G3). On the other hand, non significant changes were observed in the measured stress parameters in group (G 2) which exposed to the blue light. Exposure of stressed fish to A. hydrophila infection induced significant leukocytosis with heterophilia, monocytosis and lymphopenia in both (G2&G3). Analysis of serum biochemical constituents showed significant elevation in ALT, AST, BUN, creatinine and glucose while significant reduction in the total proteins, albumen and globulin was achieved. These changes were more pronounced and early detected in A. hydrophila infected stressed fish exposed to white light compared to those exposed to blue light From pathological point of view, fish group which exposed to blue light and infection revealed early positive immune response "activation of melanomacrophage center of spleen" but with time dependent adverse pathological lesion. The lesions were noticed in spleen and gills after 2 weeks. Regeneration of the most observed lesions were detected after 4 weeks. On the other hand, the fish group exposed to white light and infection showed more advanced lesions including diffuse necrosis in hepatic tissue with additional changes in the kidneys. So, the blue light has a protective effect aganist stress in Nile tilapia.

Mahmoud, M. A., M. Abdelsalam, and O. A. Mahdy, "Infectious bacterial pathogens, parasites and pathological correlations * of sewage pollution as an important threat to farmed fishes in Egypt", Environmental Pollution , vol. 219, issue 2016, pp. 939-948, 2016.