Morphology and development of bovine ephemeral fever virus.

The development of the virus of bovine ephemeral fever in mouse brain has been studied by electron microscopy. The virus particles are bullet-shaped, 70 by 145 nm, and slightly tapered toward the rounded end. The outer envelope is closely apposed to an electron-dense shell, about 12 nm thick, but no other internal structure is visible. The virus strains studied bud from the marginal membranes of neurones, but intracytoplasmic development, possibly aberrant, was also observed with one strain. Ephemeral fever virus is thus obviously a rhabdovirus, with points of resemblance to vesicular stomatitis, Flanders-Hart Park, and Kern Canyon viruses on the one hand, and to rabies virus on the other, but is structurally distinct from any of these.