title: Identification of a novel RNA virus lethal to tilapia.
abstract: Tilapines are important for the sustainability of ecological systems and serve as the second most important group of farmed fish worldwide. Significant mortality of wild and cultured tilapia has been observed recently in Israel. The etiological agent of this disease, a novel RNA virus, is described here, and procedures allowing its isolation and detection are revealed. The virus, denominated tilapia lake virus (TiLV), was propagated in primary tilapia brain cells or in an E-11 cell line, and it induced a cytopathic effect at 5 to 10 days postinfection. Electron microscopy revealed enveloped icosahedral particles of 55 to 75 nm. Low-passage TiLV, injected intraperitoneally in tilapia, induced a disease resembling the natural disease, which typically presents with lethargy, ocular alterations, and skin erosions, with >80% mortality. Histological changes included congestion of the internal organs (kidneys and brain) with foci of gliosis and perivascular cuffing of lymphocytes in the brain cortex; ocular inflammation included endophthalmitis and cataractous changes of the lens. The cohabitation of healthy and diseased fish demonstrated that the disease is contagious and that mortalities (80 to 100%) occur within a few days. Fish surviving the initial mortality were immune to further TiLV infections, suggesting the mounting of a protective immune response. Screening cDNA libraries identified a TiLV-specific sequence, allowing the design of a PCR-based diagnostic test. This test enables the specific identification of TiLV in tilapines and should help control the spread of this virus worldwide.
authors.affiliation: Department of Poultry and Fish Diseases, The Kimron Veterinary Institute, Bet Dagan, Israel.
authors.forename: Marina
authors.initials: M
authors.lastname: Eyngor
authors.affiliation: Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Rachel
authors.initials: R
authors.lastname: Zamostiano
authors.affiliation: Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Japhette Esther
authors.initials: JE
authors.lastname: Kembou Tsofack
authors.affiliation: Department of Poultry and Fish Diseases, The Kimron Veterinary Institute, Bet Dagan, Israel.
authors.forename: Asaf
authors.initials: A
authors.lastname: Berkowitz
authors.affiliation: The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: Hillel
authors.initials: H
authors.lastname: Bercovier
authors.affiliation: Department of Animal Facility, Faculty of Life Sciences, Bar Ilan University, Ramat Gan, Israel.
authors.forename: Simon
authors.initials: S
authors.lastname: Tinman
authors.affiliation: Ein Gev Fisheries, Kibbutz Ein Gev, Israel.
authors.forename: Menachem
authors.initials: M
authors.lastname: Lev
authors.affiliation: Dan Fish Farms, Kibbutz Dan, Upper Galilee, Israel.
authors.forename: Avshalom
authors.initials: A
authors.lastname: Hurvitz
authors.affiliation: Department of Food Science, Section of Veterinary Pathology, University of Udine, Udine, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Galeotti
authors.affiliation: Department of Cell Research and Immunology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel eranbac@post.tau.ac.il.
authors.forename: Eran
authors.initials: E
authors.lastname: Bacharach
authors.affiliation: Department of Poultry and Fish Diseases, The Kimron Veterinary Institute, Bet Dagan, Israel.
authors.forename: Avi
authors.initials: A
authors.lastname: Eldar
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology; D002478:Cells, Cultured; D003588:Cytopathogenic Effect, Viral; D005123:Eye / Q000473:pathology; D005347:Fibroblasts / Q000821:virology; D007557:Israel; D007668:Kidney / Q000473:pathology; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D012327:RNA Virus Infections / Q000473:pathology / Q000635:transmission / Q000662:veterinary* / Q000821:virology; D012328:RNA Viruses / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D012367:RNA, Viral / Q000235:genetics; D017422:Sequence Analysis, DNA; D016019:Survival Analysis; D017210:Tilapia / Q000821:virology*; D014771:Virion / Q000648:ultrastructure; D014776:Virus Cultivation
chemical_list: D012367:RNA, Viral