Studies on the immunogenic properties of tissue-culture sheep pox virus.

Sheep pox is one of the serious contagious diseases causing heavy mortality and great economic loss in some parts of the world. This is especially true in most Asian countries where the majority of the farmers and almost a1l nomads depend on sheep for their livelihood. Their e::onomy suffers greatly from sheep pox which, in some instances, kills 90% of the lambs, reduces production, causes abortion and mastitis and frequently leaves considerable skin defects. Mass vaccination is the method of choice in checking the spread of the disease. Susceptible animaIs, fertile hen's eggs and cell cultures are in use as sources of virus for preparation of vaccine. In vitro cultivation of sheep pox virus (SPY) began with experiments by BRIDE (3), who suspended small pieces of lamb testis in Drew's medium and infected them with SPV. AGYUN (1) succeeded in cultivating the virus in ovine embryo lung and skin and found that the cultured virus at its l5th passage was safe and immunogenic enough to protect susceptible animaIs l'rom natural infection or challenge. BOUE et al. (2) reported the multiplication of SPV in ovine kidney and skin cells. Great progress has been made in the produ::tion of virus using tissue-culture methods since PLOWRIGHT and FERRIS (5) and CILLI and BALDELLI (4) successfully adapted the virus to different cell cultures and studied its characteristics in vitro. This report deals with the work carrie:.l out at this institüte on the largescale production of virus in lamb testis (L. T.) cell cultures and active immunization of sheep using a vaccine prepared l'rom this virus.