Flaviviruses in South Africa: pathogenicity for sheep.

Sheep are susceptible to at least 5 of the 10 flaviviruses known to be present in South Africa. Sheep, 7-9 months of age, injected with Wesselsbron, West Nile, Banzi, Uganda-S and AR 5189 (an unidentified virus related to Banzi and Uganda-S), responded with a moderate febrile reaction, a low grade viraemia of short duration and the production of virus neutralizing antibodies. The most pronounced manifestations of infection were encountered in pregnant ewes. Infection with West Nile, Banzi and AR 5189 resulted in abortion, stillbirth and neonatal death, characterized by congenital abnormalities of the brain.