Bluetongue virus grown in BHK cells was shown to be inactivated in concentrations of betapropiolactone (BPL) higher than 0-15 per cent. When the virus, inactivated with 0-2 per cent BPL and prepared as a double emulsion vaccine, was injected into Cypriot sheep, no untoward reactions were observed and neutralising antibodies developed. The antibody titre reached a high level and persisted for at least a year. After re-vaccination, a secondary response was observed. A bivalent vaccine elicited a response to both virus types incorporated. The possibilities of using a polyvalent inactivated vaccine are discussed.
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