Growth and Characterization of the Virus of Bovine Malignant Catarrhal Fever in East Africa

Abstract

A strain of bovine malignant catarrhal fever virus (MCF) recovered from the blood of a blue wildebeest was developed by passage in vitro to a stage where it could be propagated serially in primary thyroid cell cultures by inoculation of cell-free fluids. Released virus titres ranged from 103.8 to 105.8 50% tissue culture infectious doses/ml. This virus still caused fatal disease when inoculated to cattle, and was neutralized by antibody that appeared in the sera of cattle recovering from experimental infection. The principal cytopathic effects of the virus were the development of DNA containing intranuclear inclusions and syncytia; the inclusions became increasingly basophilic as they matured. The cytopathic effects were inhibited in the presence of 5-iodo-2[image]-deoxyuri-dine (IUDR), and infectivity of the virus was abolished by treatment with ether or chloroform. Electron microscopy of inoculated cell cultures showed intranuclear, cytoplasmic and extracellular herpes-like virus particles. Suspension of cell-free virus examined by negative-stain electron microscopy contained some particles of diameter 140m[mu]-220 m[mu], comprising an outer envelope and a central body or capsid; others consisted of only a naded capsid about 100 m[mu] in diameter. MCF virus is evidently a member of the herpes group, and has particular affinities to a subgroup which contains the agents of varicella, herpes zoster and the cytomegaloviruses.