The growth of four viruses isolated from lizards in Brazil (Marco, Chaco, and Timbo viruses) and Australia (Almpiwar virus) was studied in a variety of continuous cell lines of mammalian, reptilian, amphibian, and piscine origin. Although replication was found in certain cell lines derived from the coldblooded species, cytopathic effect (CPE) was absent or minimal and growth was less than or equal to that in mammalian cells. These observations appear to limit the value of poikilothermic cells for primary isolation of viruses from field-collected, coldblooded vertebrates or arthropods that feed upon them. The four reptilian viruses were found to be naturally occurring temperature sensitive agents, with optima for growth of approximately 30° C. Electron microscope studies showed three of the viruses (Marco, Chaco, and Timbo) to be new members of the family Rhabdoviridae. Marco virus particles were conically shaped and resembled bovine ephemeral fever virus, and two lyssaviruses (Kotonkan and Obodhiang). Chaco and Timbo viruses were cylindrical viruses resembling other rhabdoviruses with particle lengths longer than the prototype VSV. No serologic relationships were found in cross complement fixation tests between these viruses, Marco virus, and 34 other rhabdoviruses.
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