Sensitivity of infectious bovine rhinotracheitis virus to ether

Identification of a novel RNA virus lethal to tilapia

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.

Contamination of primary embryonic bovine kidney cell cultures with parainfluenza type 2 simian virus 5 and infectious bovine rhinotracheitis virus

Two different viruses were isolated from bovine embryonic cell cultures after two subcultures from the primary cells. One virus was identified as parainfluenza type 2 simian virus 5 (SV-5), and the other was identified as infectious bovine rhinotracheitis virus. Six months later, stock cultures of pig kidney (PK-15) cells were found to be contaminated with SV-5 virus. We believe that the source of the SV-5 virus in the bovine cells was a cross-contamination from monkey kidneys during preparation of the cell cultures. The infectious bovine rhinotracheitis contamination was probably of endogenous origin. The bovine embryonic cell cultures were the probable source of contamination of the PK-15 cells with SV-5 virus.