Sequential development of the liver lesions in new-born lambs infected with Rift Valley fever virus. II. Ultrastructural findings.

The macroscopic and microscopic lesions in livers of new-born lambs experimentally infected with Rift Valley fever virus and killed at various intervals between 6-53 h after inoculation, were described in a previous paper. This communication gives an overview of the ultrastructural changes affecting hepatocytes, sinusoids and spaces of Disse, biliary tree and portal triads as well as observations on the morphology and morphogenesis of the virus. Hepatocytes were those primarily affected, while inflammatory and architectural changes were secondary. The changes included prominent nuclear alterations, fragmentation or disintegration of necrotic hepatocytes, focal cytoplasmic degradation and sequestration, and the presence of acidophilic bodies. The ultrastructure and origin of the intranuclear inclusions are discussed.