Attenuated Live Bluetongue Virus 8 Vaccine Protects Sheep from Chal- lenge 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 unvaccinated 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.