Attempts to Vaccinate Foals with Living Tissue Culture Adapted Horse Sickness Virus

It is weil known that horses may be vaccinated successfully with mouseadapted types of Horse Sickness virus (HSV), as described by Alexander (1). During the recent outbreak of African Horse Sickness in the MiddleEast region, the Razi Institute, Iran was able to produce, with the collaboration of Onderstepoort Laboratory and under the auspices of F.A.O., large amounts of polyvalent ll1ouse-adapted virus-vaccine to combat the disease in the region (9). It was feh, however, that the imll1unization schedule might be simplified by using a ll10dified tissue culture-adapted virus, if a long-term mass vaccinalion programll1e were to be carried out in the infected countries. This paper gives an account of the techniques developed for the production of living attenuated vaccine in tissue culture.