Electron microscopy of a herpes virus associated with the agent of Marek's disease in cell culture.

Propagation of the agent of Marek's disease and production of a cytopathic effect in duck embryo fibroblast monolayer cultures was reported recently (21). A good correlation was obtained (14) between the occurrence of this cytopathic ef fect, the presence of herpes virus-like particles in infected cells, and the ability of these cells to reproduce Marek's disease in susceptible birds. Similar results have also been obtained with kidney cell cultures derived from Marek's disease-infected birds (5, R. L. Witter, unpublished data). The circumstantial evidence relating this virus to Marek's disease and similarities of the virus to the disease agent strongly suggested the implica tion of the virus in the etiology of Marek's disease (14). This report further describes ultrastructural studies of duck embryo fibroblast cultures infected with Marek's disease agent and describes some of the characteristics of the herpes-type virus seen in these cultures.