الفهرس 
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Abstract
In this study about 180 collected from 30 farms of O. niloticus and Common carp in Alex., Kafr El Shikh and Behera Governorates. Fishes were transferred to the Dept. of Poultry and fish diseases. Fac. of Vet. Alex. Univ. and kept in glass aquaria untile examined.
For viral diagnosis, conformation and identification of the virus by using cell line from Carp ovary to study the CPE, specific monoclonal antibody for immunohistochemistry and EM were done.
The isolated virus was used for experimental infection. Clinical signs, PM lesions and histopathological change were recorded.
The results of this work revealed that :
The clinical signs & P.M. lesions of naturally infected fish were in the form of skin darkening, tail & fin rot with the P.M findings of generalized hyperemia and congesion of all internal organs and distended gall bladder in most of examined fishes . The above mentioned clinical signs and P.M. lesion which accompanied with naturally infected samples appeared in the fish are due to the causes other than the bacteria, mycotic and parasitic agents . which may be due to viral infection.
In the present study, cell culture from ovary of mature Common carp was prepared and used for primary isolation of the virus and study the CPE of tissue suspension collected from naturally infected fish .
The degree of CPE formation correlated positively with the degree of the virulent virulence and dilution rate of the virus as the high concentration of the viruses the high amount of CPE formation and the low concentration of the virus the lower number of CPE formation and it confirmed the presence of the viruse in the tissue.
The mortality pattern in experimentally infected fish indicated that the mortality rate in O. niloticus was higher than that of Common carp (19/30 and 15/30) for the O. niloticus and Common carp injected with 1 ml X 10-3 of viral dilution / fish , respectively. Moreover, the mortality rate decreased steadily from the 1st week to the 4th week and the mortality rate increased with the increasing level of the injected virus.
The PM leasins in the form of reddness, haemorrhage and congestion of all internal organs. The nervous manifestations which appeared in the infected fish may be attributed to the destructive effect of VHS on brain cells.
This results confirmed through histopathological finding as the liver was congested and dilated sinusoid , congested pancreas infiltration of RBCs, fibrosis of kidney glumeruli , vacuolated cytoplasm of nerve cells, necrosis of retina and destructive optic nerve.
The kidney showed, dilatation of blood capillary, fibrosis of glomeruli, hyaline droplet degeneration, atrophy with shrunken and thickening of Bowman’s capsules and its basal lamina. Necrosis and fibrosis of haemtobiotic tissues, hyperplesia of bodocyte of endothelial cells cloudy swelling of tubular cells were noticed.
The muscles showed hyaline degeneration, swelling with basophilic nucleus and disappeared striation with oedema of myofibrilar boundle with pale eosinophilic clour. All, of that mainly due to destructive effect of virus on cells of these organs as well as the diffuse reflects of the fish against virus. Our results indicate that our virus have destructive effects .
Electron microscopical observation confirmed the presence of the virus in tissue culture , results were in the form of cellular vaculation appeared in ovary cell culture within 3 – 4 days post-infection.
The E.M results confirmed the VHS infection in O. niloticus and Common carp fish and consider as one of the most important tools for identification and diagnosis of VHS in case of acute form of infectious dropsy in Carp fish the virus appeared as bullet like bodies in infected tissues..