Adaptation and cultivation of the Perego strain of ovine smallpox virus in tissue culture and an evaluation of its immunogenic properties

: The strain Perego of the sheep pox virus, used for the production of the ovinized vaccine in this country, was adapted and cultured in tissue cultures of lamb testes. A total of ten passages in succession of the virus were performed with the manifestation of a characteristic cytopathic effect in the cultures. The titer of the virus was found to be within the range of 10(3.5)CPE50, for the initial passages, to 10(4.5)CPE50, for the final passages. The activity and harmlessness of the virus was tested on sheep. The inoculated 14 sheep with one vaccinal dose each, containing 100 CPE50, and two sheep treated with tenfold higher dose of the virus showed that sheep in general tolerate well the rates at which the virus was applied within the range cited. The general state of the sheep did not exhibit deviations, however, the animals' body temperature rose, and there were reactions at the site of the inoculation. Serum-neutralizing antibodies were established in the blood of sheep one month following vaccination.