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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, no.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.

Karima, F. M., K. B. Wagdy, and A. M. Mahmoud, "Assessment of toxicity and clastogenicity of sterigmatocystin in Egyptian Nile tilapia", African Journal of Biotechnology, vol. 5, no.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.

MAI, I. B. R. A. H. E. M. D., H. A. Hussien, and A. M. Mahmoud, "Spring Viraemia of Carp disease: Experimental Infection of Cultured Common Carp (Cyprinus Carpio L.) in Egypt", Veterinary Medical Journal, vol. 54, no.4, pp. 887-898, 2006. Abstract

Experimental oral infection of common carp (C. carpio L.) fish was carried out via stomach tube with 2 local positive samples of Spring Viraemia of Carp Virus (SVCV) at water temperature 14± 20C. Investigation of the pathogenesis of SVCV to common carp (C. carpio L.) revealed that virus was detected in gills at the 3rd day post infection, and in the internal organs one week post infection. Clinical and post mortem examination of experimentally infected fish were recorded. The established infection was confirmed using monoclonal antibodies against SVCV in dot ELISA technique and electron microscopy. Histopathological picture of the experimentally infected common carp (C. carpio L.) showed severe changes in gills, liver and intestine.