International Journal of Virology1816-4900xxxx-xxxxAcademic Journals Inc.10.3923/ijv.2021.1.7AmmarA.A. SakrS.F. Abdel WahabA.M. AhmedA.A. EladweyM.M. NageebT.M. 12021171Background and Objective: Nile tilapia is the main cultured species in Egypt. Mass mortalities in cultured freshwater fishes especially Nile tilapia assumed as an annual outbreak in last ten years during summer period. The aim of the present study was viral investigation of devastating mortality. Materials and Methods: Samples were collected from different semi-intensive polyculture fish farm. The average body weight of affected fish ranged from 200-300 g. The most common lesion by external examination was a red circle on one or both fish sides. The common postmortem lesion was hypertrophy with necrotic areas distributed all over the liver surface. The collected prepared samples were gone through three blind passages using an established cell line. Results: Cytopathic changes were showed in a cell that’s include cells rounding, aggregation in the scattered area which was clear in between the 5th and 7th days post inoculation. Transmission electron microscopy visualization of cell line harvest revealed presence of virus-like particles, enveloped icosahedrons measuring 60-70 nm in diameter. Conclusion: It can be concluded that virus-like particles present in summer mortality outbreaks in Nile tilapia in Egypt may be one of the cause. Further studies are needed to identify the isolate and other causes of these outbreaks.]]>Cerezuela, R., J. Meseguer and M.A. Esteban,20112011El-Sayed, S.A.A., S.A. Yousef and N.A. Rashied,2014Oreochromis niloticus).]]>42230Eltholth, M., K. Fornace, D. Grace, J. Rushton and B. Hasler,201551131143Bigarré, L., J. Cabon, M. Baud, M. Heimann, A. Body, F. Lieffrig and J. Castric,2009Oreochromis niloticus (L.), in fresh water.]]>32667673Soliman, N.F. and D.M.M. Yacout,20162412011227El-Deen, A.N., H.M. Osman, M.S. Zaki and H.A. Abo-State,2018Oreochromis niloticus in Kafr El-Sheikh province, Egypt due to saprolegniosis with emphasis on treatment trials.]]>183945Ahmed, E., N. Yehia, M. Elkemary and H. Soliman,201931725Fathi, M., C. Dickson, M. Dickson, W. Leschen and J. Baily et al.,2017473430432Darweesh, S.I., T.T. Saad and S.T. Atallah,20162016Amlacher, E., 1970Pages: 302Pages: 302OIE,20034th Edn.,Pages: 358Pages: 358Dorson, M., E. Quillet, M.G. Hollebecq, C. Torhy and B. Chevassus,1995Haemorrhagic septicaemia virus and transmission of resistance by gynogenesis.]]>26361368Abdel-Wahab, A.M., A.M. Ali and M.M. El-Adwey,2016Oreochromis niloticus).]]>6114Bols, N.C., A. Barlian, M. Chirino-Trejo, S.J. Caldwell, P. Goegan and L.E.J. Lee,1994Oncorhynchus mykiss (Walbaum), gills.]]>17601611Fields, B.N., D.M. Knipe, P.M. Howley, R.M. Chanock and J.L. Melnick et al.,20014th Edn.,pp:1395pp:1395Reynolds, E.S.,196317208212Wassif, I.M.,2018573239Dahdouh, B., O. Basha, S. Khalil and M. Tanekhy,2016Aeromonas hydrophila from fresh, brackish and marine fishes.]]>484653Omar, A.E.D., E.M. Moustafa and M.M. Zayed,2016Aeromonas hydrophila strains.]]>6185192Wen, C.M., C.C. Ku and C.S. Wang,2013Trachinotus blochii (Lacépède).]]>36657667Erni, R., M.D. Rossell, C. Kisielowski and U. Dahmen,200910296101