An inactivated vaccine for the control of bluetongue virus serotype 16 infection in sheep in Italy

Because no suitable products are at the moment available to safely control the spread of BTV-16 in Europe, an inactivated vaccine was produced from the reference field isolate of bluetongue virus serotype 16. One group of six sheep was vaccinated subcutaneously with the inactivated vaccine twice, on days 0 and 28, whereas a second group of eight sheep was inoculated with saline solution and used as mock-vaccinated control animals. Seventy-eight days after the first vaccination, all sheep were inoculated subcutaneously with a suspension containing 106.3 TCID50 of a virulent reference BTV-16 isolate. Apart from a transient inflammatory reaction at the injection site, no adverse effects were reported following vaccination. All vaccinated animals developed high titres (7.3–9.3 log2(ED50%/50 μl)) of virus-specific neutralising antibodies and were resistant to challenge with BTV-16. Conversely, following challenge, control animals developed hyperthermia and long lasting high-titre viraemia.