The alterations in pathogenicity and immunogenicity of a Kenya sheep and goat pox virus on serial passage in bovine foetal muscle cell cultures.

A Kenyan sheep and goat pox virus was attenuated by serial passage in bovine foetal muscle cell cultures. The pathogenicity of the strain was lost between the 15th and 20th passages. Serum-neutralizing antibody developed after inoculation with passages tested up to the 50th. These passages appeared to protect animals against laboratory challenge by intra-dermal titration. The 18th passage was successfully and extensively used to control the disease under field conditions.