Attenuated Live Bluetongue Virus 8 Vaccine Protects Sheep from Challenge with the European BTV-8

An attenuated live bluetongue virus (AL-BTV) serotype 8 vaccine of South African origin was evaluated for its ability to protect sheep against challenge with a European BTV-8 isolated from an outbreak. Two groups of sero-negative sheep were vaccinated with either a single or booster vaccination and challenged subcutaneously 28 days following vaccination. Groups of vaccinated challenged sheep showed no clinical signs typical to Bluetongue disease, as compared to unvacci- nated inoculated sheep of a control group. A clinical reaction index (CRI) of values ranging from 0 to 5 was determined for each of the groups, where vaccinates measured a CRI of less than 1 and the control sheep measured a CRI of at least 4.5. All vaccinated sheep developed high serotype-specific neutralizing antibodies post-vaccination. The results indicated that a single dose of the AL-BTV-8 was sufficient to protect vaccinated sheep against a virulent challenge of the European BTV-8 outbreak isolate.