Evaluation of humoral response and protective efficacy of three inactivated vaccines against bluetongue virus serotype 8 one year after vaccination of sheep and cattle.

The long-term efficacy of three commercially available inactivated vaccines against bluetongue virus serotype 8 (BTV-8) (BLUEVAC) 8, Zulvac 8, and BTVPUR AlSap 8) was evaluated in a seroprevalence study and challenge experiments. Seroprevalences 1 year after vaccination ranged from 75% to 100%. In two infection experiments, groups of vaccinated sheep and cattle selected either randomly or for low antibody levels were challenged with a European BTV-8 strain 12 months after vaccination. With two exceptions, all animals, including those with low antibody levels prior to challenge, were protected from viral replication and clinical disease even at low initial antibody levels. Vaccination of susceptible ruminants in yearly intervals is thus considered an adequate scheme for BTV-8 control in Europe.